Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Nonfood Industrial Wastes INTRODUCTION The intent of this chapter is to examine the type, quantity, and quality of nonfood industrial wastes that are available in North America and to describe the status of available processing technology suitable for con- verting such industrial wastes to nutritive animal feeds. Typically, nonfood industrial wastes are not used as feedstuffs and as such fall into the category of underutilized resources. While a few nonfood industrial wastes are suitable for direct animal feeding, most are not and require some pro- cessing. This processing is needed to (1) achieve nutritional enrichment through synthesis of protein; (2J increase the availability of nutrients through hydrolysis of large-molecular-weight components; (3) change the physical form by concentration, dilution, or entrapment; (4) convert nonutilizable organics to nutritionally useful materials, such as carbohydrates, fats, and fatty acids; or (5) remove or destroy toxic components. The nonfood industrial wastes to be covered are those derived primarily from the organic chemical and fermentation industries, with some con- sideration of municipal solid waste. Note will be made of cases in which wastes are currently being used for animal feed, but the focus will be on underutilized materials. In order for an underutilized waste to be utilizable, it must (1) be nontoxic or capable of being detoxified completely; (2) be available in sufficient quantity at each source to allow for economic recovery; (3) have some nutritive value either before or after processing. 46
Nonfood Industrial Wastes 47 ORGANIC CHEMICAL INDUSTRY Quantity The chemical industry in the United States is large and highly diversified. In 1979 the top 50 chemicals produced totalled about 2.56 billion tons and displayed a typical growth rate of about 7.6 percent per year. Of this total, 86 million tons were synthetic organic chemicals, and the remainder were inorganics (Anonymous, 19801. There is relatively little waste uti- lizable as a feedstuff, either directly or with processing. Most organic waste is burned to provide process heat. When the waste is too dilute to be burned, it is usually too dilute for useful recovery. The organic chemical industry traditionally has utilized coal, natural gas, and petroleum as primary feedstocks, with heavy reliance on the latter two. However, as a consequence of the rapidly increasing prices of these commodities and the trend to use indigenous energy resources, changes are occurring in the organic chemical industry (Dasher, 1976~. These changes are important to consider because they have direct impact on the types and quantities of wastes generated. Increased use of coal and shale oil, which are likely to be processed via gasification or liquefaction, will lead to increased availability of aromatic and fatty acid compounds. Jahnig and Bertrand (1977) described the environmental problems produced by a coal gasification plant with a capacity of 16,000 tons/day that would generate 6,000 tons water/day containing 2.0 to 4.0 g phenolics/liter, 0.5 to 1.5 g fatty acids/liter, and 8.0 to 11.0 g ammonia/liter. This translates to about 18 tons phenolics, 6 tons fatty acids-, and 57 tons ammonia/day. If all of the organic carbon could be converted to microbial single-cell protein having a protein content of 60 percent (Cooney et al., 1980), then about 5,000 tons single-cell protein/year could be produced from a coal gasification plant. Similarly, if coal liquefaction were used, then waste- water generation would be 13,000 tons/day with a composition similar to that from a gasification plant (Magee et al., 19771. While such plants do not exist in the United States today, they are anticipated, and it is clear that major changes in primary energy feedstock will change the availability of a potentially important nonfood industrial waste. Current technology for processing and refining natural gas and petroleum produces little waste. Another possible change in primary feedstocks in the chemical industry is a shift to using cellulosic biomass, such as crop residue, forest by- products, or animal waste, as a source of chemicals and fuels. A change from using traditional liquid or gaseous hydrocarbon feedstocks to using solid lignocellulosic feedstocks will cause a major change in waste prod- ucts. Lignocellulosic biomass is primarily a mixture of cellulose, hemi
48 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS cellulose, and lignin, with some ash, protein, fats, and other minor components. In fermentation processes for converting the biomass to chemicals and fuels, only the cellulose and hemicellulose are consumed, while lignin, along with the other materials, remains as a residue. As the use of biomass develops, there will be increased availability of these residual materials. In addition, there will be large amounts of microbial cell mass associated with the residues. While the cell mass is likely to be used as much as possible as an animal feed, its use will not be without major difficulty because most of the microorganisms that will be produced are not approved for use as feed materials. Analyses of the wastes gen- erated through these changes in technology are, to a large extent, presented in the sections of this report that focus on forest by-products, food pro- cessing by-products, and animal waste. The availability and use of wastes from coal, shale oil, and cellulosic biomass processing will not be dealt with further, since these are not currently underutilized materials, though they may be in the future. Physical Characteristics The major organic chemicals derived from primary feedstocks are meth ane, ethylene, propylene, and aromatics. In 1973 the chemical industry was analyzed by the U.S. Environmental Protection Agency (1973) for the purpose of developing effluent limitations for the industry. The EPA report separates the various chemical products into four processing cate- gories, which are useful for understanding the nature of the wastes from nonfood industries. These categories are (l) continuous nonaqueous pro- cesses, (2) continuous vapor-base processes, (3) continuous liquid-phase reaction systems, and (4) batch processes. The processes of interest are primarily those of continuous liquid-phase reaction systems, because these are most likely to involve organic chemical wastes that can be processed to achieve nutritional enrichment. The continuous liquid-phase processes are summarized in Table 3. Batch processes are mostly run on a smaller scale and produce fewer wastes. Nonaqueous as well as vapor-phase wastes are more commonly recovered as an energy source by direct burning. Aqueous wastes are frequently too dilute for burning. To place the chemical industry and its potential waste in perspective, the list of chemicals and processes in Table 3 is compared with the top 50 organic chemicals (Anonymous, 1980), which represent, in total, about 80 million tons or 93 percent of organic chemicals manufactured. Only those chemicals that are in both category 3, liquid-phase reaction systems, and the top 50 (as noted in Table 3) are considered further. This list provides an indication of those processes that use technology likely to
Nonfood Industrial Wastes 49 TABLE 3 Major Chem icals Produced in Liquid-Phase Reaction Systems Product Manufacturing Process Ethanola Isopropanola Acetonea Phenola Oxo-chemicals Includes: N-butyl alcohol Isobutyl alcohol 2-ethylhexanol Isooctyl alcohols Decyl alcohols Acetaldehyde Acetic acida Methyl ethyl ketonea Methyl methacrylate Ethylene oxidea Acrylonitrilea Ethylene glycola Acrylic acid Ethyl acrylate Styrene monomera Adipic acid Terephthalic acida Dimethyl terephthalatea Para-cresol Cresylic acida Anilinea Sulfuric acid hydrolysis of ethylene Sulfuric acid hydrolysis of propylene Cumene oxidation with cleavage of hydroperoxide in sulfuric acid Raschig process, chlorobenzene process Sulfonation process Cumene oxidation with cleavage of hydroperoxide in sulfuric acid Oxo-process (carbonylation and condensation) - Ethylene oxidation via Wacker process Oxidation of LPG (butane) Oxidation of acetaldehyde Carbonylation of methanol Sulfuric acid hydrolysis of butene-2, dehydrogenation of sec-butanol Oxidation of LPG (butane) by-product of acetic acid manufacture Acetone cyanohydrin process Chlorohydrin process Acetylene-HCN process Sulfuric acid catalyzed hydration of ethylene oxide CO synthesis with acetylene Acetylene and ethanol in presence of nickel carbonyl catalyst Oxidation of propylene to acrylic acid followed by esterification Reaction of ketone with formaldehyde followed by esterification Alkylation of benzene with ethylene, dehydrogenation of ethylbenzene with steam Oxidation of cyclohexane/cyclohexanol/ cyclohexanone Direct oxidation of cyclohexane with air Oxidation of para-xylene with nitric acid Catalytic oxidation of para-xylene Esterification of TPA with methanol and sulfuric acid Vapor phase methylation of phenol Oxidation of para-cymene with cleavage in sulfuric acid Caustic extraction from cracked naphtha Nitration of benzene with nitric acid (L.P.), hydrogenation of nitrobenzene
50 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS TABLE 3 (continued Product Chloroprene Bis-phenol-aU Propylene oxidea Propylene glycola Vinyl acetatea Anthraquinone Beta naphthol Caprolactam`' Toluene di-isocyanate Silicones Naphthemic acids Ethyl cellulosea Cellulose acetatea Chlorobenzene Chlorophenol Chlorotoluene Hydroquinone Naphthosulfonic acids Nitrobenzene Amyl acetate Amyl alcohol Ethyl ether Ethyl butyrate Ethyl formate Tetraethyl lead Formic acid Methyl isobutyl ketone Naphthol Manufacturing Process . Dimerization of acetylene to vinyl acetylene followed by hydrochlorination Vapor phase chlorination of butadiene followed by isomerization and reaction Condensation of phenol and acetone in presence of HC1 Addition of propylene and CO2 to aqueous calcium hypochlorite Liquid phase oxidation of isobutane followed by liquid phase epoxidation Hydration of propylene oxide catalyzed by dilute H2SO4 Liquid phase ethylene and acetic acid process Catalytic air oxidation of anthracene Naphthalene sulfonation and caustic fusion Hydroxyl amine production, cyclohexanone production, cyclohexanone oximation, oxamine rearrangement, purification, and ammonium sulfate recovery Toluene nitrification, toluene diamine production, HC1 electrolysis, phosgene production, TD1 production, purification Reaction of silicon metal with methyl chloride From gas-oil fraction of petroleum by extraction with caustic soda solution and acidification From alkali cellulose and ethyl chloride or sulfate Acetylation of cellulose with acetic acid (followed by saponification with sulfuric acid for diacetate) Raschig process Direct chlorination of phenol From chloroaniline through diazonium salt Catalytic chlorination of toluene Oxidation of aniline to quinone followed by hydrogenation Sulfonation of ,B-naphthol Caustic fusion of naphthalene sulfonic acid Benzene and HNO3 in presence of sulfuric acid Esterification of amyl alcohol with acetic acid Pentane chlorination and alkalin hydrolysis Dehydration of ethyl alcohol by sulfuric acid Esterification of ethyl alcohol with butyric acid Esterification of ethyl alcohol with formic acid Reduction of ethyl chloride with amalgam of Na and Pb Sodium hydroxide and carbon monoxide Dehydration of acetone alcohol to mesityl oxide followed by hydrogenation of double bond High-temperature sulfonation of naphthalene followed by hydrolysis to p-naphthol
Nonfood Industrial Wastes 51 TABLE 3 (continued Product Pentachlorophenol Sodium pentachlorophenate Toluidines Hydrazine Oxalic acid Oxalates Sebacic acid Glycerol Diethylene glycol diethyl ether Dichloro-diphenyl-trichloroethane (DDT) Pentachloroethylene Methylene chloride" Pentaerythritolt' Chloral (trichloroacetic aldehyde) Triphenyl phosphate Tridecyl alcohol Tricresyl phosphate Amyl alcohol Acrylamide Higher alcohols Synthetic amino acids Organic esters Trialkylacetic acids Fatty acids Lauric acid esters Oleic acid esters Acetophenone Acrolein Ethyl acetate a Propyl acetate Acetin (glyceryl monoacetate) Propionic acid Fatty alcohol Manufacturing Process Chlorination by phenol Reaction of caustic soda with pentachlorophenol Reduction of nitrotoluenes with Fe and H2SO4 Indirect oxidation of ammonia with sodium hypochlorite Sodium formate process Sodium formate process Caustic hydrolysis of ricinoleic acid (castor oil) Acrolein epoxidation/reduction followed by hydration Propylene oxide to allyl alcohol followed by chlorination Ethylene glycol and ethyl alcohol condensation dehydration Monochlorobenzene and chloral in presence of sulfuric acid Chlorination of acetylene Methane chlorination Methanol esterification followed by chlorination Acetaldehyde and formalydehyde in presence of basic catalyst Chlorination of acetaldehyde Phenol and phosphorous oxychloride From propylene tetramer Cresylic acid and phosphorus oxychloride Chlorination of pentanes and hydrolysis of amyl chlorides Acrylonitrile hydrolysis with H2SO4 Sodium reduction process Acrolein and mercaptan followed by treatment with Na2CO~; and NaCN Alcohol and organic acid, H2SO4 catalyst Olefins and CO followed by hydrolysis Batch or continuous hydrolysis Esterification of lauric acid Esterification of oleic acid By-product of phenol by cumene peroxidation Condensation of acetaldehyde with formaldehyde Acetic acid and ethyl alcohol in presence of sulfuric acid Acetic acid and propyl alcohol in presence of sulfuric acid Glycerol and acetic acid Carbonylation of ethyl alcohol with CO at high pressure Oxidation of propionaldehyde Reduction of fatty acid with sodium metal High pressure catalytic hydrogenation of fatty acids
52 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS TABLE 3 (continued Product Manufacturing Process Butyl acetate sec-butyl alcohol N-butyl alcohol N-butyl propionate Chloroacetic acid Sodium chloracetate Chloropicr~n (nitrotr~chloromethane CC13NO2) Thioglycolic acid Adiponitr~le Sodium benzoate Sodium sulfoxalate formaldehyde Sodium acetate Tartary acid Ester~fication of acetic acid and butyl alcohol in presence of sulfuric acid Hydrolysis of butylene (in H2SO4) with steam Condensation of acetaldehyde to crotonaldehyde followed by hydrogenation Esterification of propionic acid with butyl alcohol (H2SO4) Chlorination of acetic acid Esterification of chloroacetic acid Picr~c acid and calcium hypochlor~te Nitr~fication of chlorinated hydrocarbons Monochloroacetic acid and H2S followed by . . neutra 1zatlon Adipic acid and ammonia Benzoic acid neutralized with sodium bicarbonate Zinc hydrosulfite, formaldehyde and caustic soda Neutralization of acetic acid with caustic soda Maleic anhydride and hydrogen peroxide aDenotes those chemicals listed in the top 50 organic chemicals (Anonymous, 1980). SOURCE: U.S. Environmental Protection Agency (1973). generate substantial wastes. It is possible to further reduce this list to meaningful terms by examining (1) the raw materials used in manufacture of the major product, (2) the processes, and (3) the products themselves in order to identify waste streams that contain organics suitable for nu- tritional enrichment by fermentation. A basic premise in this analysis is that none of the wastes from the organic chemical industry will be suitable for direct animal feeding and that fermentation will be required to nutri- tionally enrich the waste via protein synthesis. At the same time, easily metabolizable compounds will convert the chemicals to a more metabol- ically usable form and allow conversion of dilute waste streams to solid material (biological cell mass) that is readily recovered. Nutritive Value From the brief description of manufacturing processes identified as pro- viding potential underutilized waste (see Table 3), an analysis of process effluents (U.S. Environmental Protection Agency, 1973) and of process flow sheets (Lowenheim and Moran, 1975) was made and is summarized in Table 4.
Nonfood Industrial Wastes 53 TABLE 4 Processes Identified as Possibly Having Underutilized NFI Waste Product Process Possible Usable Components in Effluent Ethanol Ester~fication and hydrolysis of ethylene Ethanol Catalytic hydration Isopropanol Esterification and hydrolysis of Isopropanol, other alcohols propylene Acetone Dehydrogenation of isopropanol Acetone, isopropanol Phenol Cumene peroxidation Phenol, acetone, cumene Acetic acid Acetaldehyde oxidation Acetic acid, formic acid Methanol carboxylation Acetic acid, methanol, propionic acid Butane oxidation Terephthalic acid Propylene oxide Propylene glycol Oxidation of p-xylene via propylene chlorohydrin Oxidation of isobutane Hydration of propylene oxide Vinyl acetate Ethylene and acetic acid Cellulose acetate Acetylation Methylene chloride Methanol esterification Pentaerythritol Catalytic Ethylacetate Catalytic Acetic acid, acetone, methanol, formic acid, methylethyl ketone Acetic acid, xylene Propionaldehyde, propylene glycol t-butylalcohol, isopentanols Propylene glycol Dipropylene glycol Acetic acid, acetaldehyde Acetic acid, cellulose Methanol Acetaldehyde, formaldehyde, formic acid, erythritols Ethanol, acetic acid, esters From the list of organic chemicals, relatively few materials can be called potentially underutilized wastes. These wastes, which generally are in dilute solution (total organic carbon less than 2 percent), are not suitable for direct animal feeding. Furthermore, they require concentration prior to fermentation processing. Some wastes will contain toxic metals and organics that will preclude their use for feeding or make their detoxification difficult. An alternative to the production of single-cell protein is production of carbohydrates or fat materials for use as a calorie source in animal feeding. Such technology was used during World War II. The process technology is similar for production of single cells for either a protein or calorie source. However, attention here will focus on protein production. It should be kept in mind that processing for calorie production also could be a useful approach.
54 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS Processing Single-cell protein is a generic term for crude or refined sources of protein whose origin is bacteria, yeast, molds, and algae. There have been a number of reviews published on this subject (Davis, 1974; Pirie, 1975), but the most comprehensive treatments of organisms, processes, and nu- tritional and food technological aspects of utilization are the books based upon two conferences devoted to single-cell protein (Mateles and Tan- nenbaum, 1968; Tannenbaum and Wang, 19751. The need for and use of single-cell protein as a protein supplement is well established, and research and development on microbial protein pro- duction has been intense for over a decade. There are a number of large plants in operation and several more under construction. It is interesting that microbial protein produced from nonagricultural raw materials, such as organic chemical wastes, is not dependent on agricultural sources. It is a synthetic yet complete source of food whose composition can be controlled (Cooney et al., 1980) and contains nu- merous nutrients in addition to protein. Some forms of single-cell protein have been used as human food for millenia. All fermented foods contain significant quantities of cellular mass as diverse as bacteria, yeast, and fungi. Thus, the use of such organisms as a basic protein food is a logical extension of previous ex- perience. There is also good scientific evidence that various types of single-cell protein can be useful as additional protein and vitamin sources in animal diets. During the last few years, much data have accumulated about nu- tritive value and safety of different kinds of yeasts and bacteria grown on chemicals such as n-alkanes and methanol. Technological processes have been developed for industrial production of these products and good es- timates for their application are available. These processes consider eco- nomic aspects and the safety of single-cell protein use for feeding swine, broilers, and calves. Amino acid patterns, content of nucleic acid and lipids, and data on possible toxic substances have been studied (Tannen- baum and Wang, 1975~. A complete description of individual processes is outside the scope of this chapter. However, it is important to note that single-cell protein production is carried out in intensive processes that permit high-volume production of protein. A typical process flow may appear as shown in Figure 1. There are several problems in adapting this technology to organic chem- ical wastes. The first is the need to concentrate the organic waste to levels of 4 to 8 percent usable carbon. The capital investment for a single-cell
Nonfood industrial Wastes s5 Water Minerals (K, P. Mg, S. etc.) Nitrogen Source (NH3) Carbon Source (Sugar or Hydrocarbon) l ~ _ Medium Mixer L Sterilizer (Optional ) Coolant con | Spent Air Cells Spent Medium Separator (Centrifuge or Other Harvesti ng Devices) Wash 1 it' To Recycle or Disposal Air h Air Filter Heat Removal ~- Air (O2) U . _ Dryer Washed Dried Cells Product (50% Protein Dry Cells Weight Basis) FIGURE ~ Simplified flowsheet of production of single-cell protein. SOURCE: Cooney et al. (1980). protein manufacturing facility is usually high and it is necessary to max- imize both the process productivity and the conversion of organic carbon to cell mass (Cooney, 19751. Second, unlike most single-cell protein fermentations where the substrates are pure, these are variable mixtures of organics. Limited research has been done on the use of mixed substrate fermentation (Silver and Mateles, 1969; Wilcox et al., 1978~. Choosing a process, including the organism and the substrate, is extremely complex, and there are many potential processes. In fact, flexibility in process design is an important attribute of single-cell protein. Some important factors, however, will be considered here. Raw Materials One of the major advantages of single-cell protein production is the flex- ibility in being able to choose a variety of organisms able to utilize many
56 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS different substrates. A brief summary of some substrates considered is presented in Table 5, along with an indication of the typical conversion efficiencies to cell mass. The choice of a carbon source in the design of a process usually depends on factors such as availability, purity, cost, acceptability, and lack of toxicity. In the case of nonfood industrial wastes, the carbon sourceLs) is fixed by the particular chemical process (see Table 41. It is useful to consider some of the general characteristics of several classes of organic chemicals that serve as substrates for single-cell protein production. Paraffin Hydrocarbons Paraffin hydrocarbons with 4 to 24 carbons have been of particular interest for microbial protein production. In the pro- duction of diesel fuel, it is important to remove the paraffinic fraction to lower the pour point of the oil. Since gas-oil contains approximately 10- 40 percent paraffins (the only fraction readily used as a carbon source), it is possible to use microorganisms to dewax the gas-oil. Typically, 1 g of cell mass (dry basis) is produced per gram of paraffin consumed. However, a large unutilized portion of gas-oil passes through the fer- mentor, creating problems in cell recovery and in removal of residual hydrocarbons from the cells. The removal of residual hydrocarbon is a significant problem in the use of petroleum fractions as carbon sources and requires that the final cell mass be washed extensively with detergent TABLE 5 Cell Conversion Yields on Various Substrates Cell Yield Temperature (g Cell/g Carbon Source Organism (°C) Substrate) Reference N-paraffins Pseudomonas 30 1.07 Wodzinski and spp. Johnson (1968) Nocardia spp. 30 0.98 Wodzinski and Johnson (1968) Candida 30 0.83 Miller and Johnson intermedia (1967) Methane Mixed bacteria 40 0.62 Sheehan and Johnson (1971) Methanol C. boidinii 28 0.29 Sahm and Wagner (1972) Hansenula 37 0.37 Levine and Cooney polymorpha ( 1973) Mixed bacteria 56 0.42 Snedecor and Cooney (1974) Pseudomonas 32 0.54 Goldberg et al. (1976) Ethanol C. utilis 30 0.68 Johnson (1969) Glucose C. utilis 30 0.51 Johnson (1969)
Nonfood Industrial Wastes 57 solution, and preferably with organic solvents such as hexane and lower- boiling alcohols. Comprehensive reviews of technology applied to hydro- carbons are provided by Davis (1974), Gutcho (1973), and Rockwell (19761. Alcohols Alcohols, particularly methanol and ethanol, are readily used by bacteria and yeast for microbial protein production (Cooney and Levine, 1972; Kihlberg, 19721. These substrates are water soluble, and leave no residues associated with the cell mass after drying. Since the lower-mo- lecular-weight alcohols have some of the advantages of both hydrocarbon and carbohydrate fermentations, they have significant potential for single- cell protein processes, and are particularly attractive when considered as a food protein source (Cooney, 19751. Higher alcohols are less well used. The cell yield (g cell mass/g alcohol) is typically 0.5 to 0.7 for methanol and ethanol, respectively. Carbohydrates A variety of carbohydrates can serve as substrates for single-cell protein processes (Tannenbaum and Wang, 1975~. Some, such as sulfite liquor and dairy whey, are being used. In addition, it is possible to utilize starch and molasses to produce protein by conventional fermen- tation technology. The cell yield on carbohydrates is 0.5 g cell mass/g carbohydrate. Organisms Bacteria, yeasts, and fungi are all being considered for com- mercial-scale single-cell protein processes; each has advantages and dis- advantages. A comparison of protein content of some microorganisms considered for single-cell protein production is provided in Table 6. The most common organisms used for human food are yeasts (Reed and Peppier, 19731. They are used in foods as vitamin additives and flavoring agents. Their protein concentration is high and they are easier to recover from the fermentation broth than are bacteria. They also have the advantage of availability in the open market and of being produced from a variety of carbohydrate substrates that are themselves recognized as sources of food. Three yeasts, Saccharomyces cerevisiae, Klavaro- mycesfragilis, and Candida mills are considered food yeast. Bacteria have some advanages over other organisms, particularly for animal diets. They have higher levels of protein that is rich in sulfur amino acids. A major technical and economic problem is the high cost of cell recovery because of smaller cell size. However, bacteria are a good long- range prospect because of the potential economic advantage they offer. Until recently the higher fungi have received relatively little attention in industrial-scale projects (Anderson et al., 1975; Imrie and Vlitos, 19751. The possibility exists for their production in continuous culture on very
58 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS TABLE 6 Protein Content of Various Microorganisms Protein Content (gig Dry Cell Microorganism Weight) Reference Bacteria Pseudomonas methylotropha 0. 83 Cow et al. (1975) Nethylomonas methanolica 0.82 Dostalek and Molin (1975) Yeast Hansenula polymorpha 0.50 Levine and Cooney (1973) Candida spp. 0.71 Laine and Chaffaut (1975) Molds Aspergillus niger 0.35 Imrie and Vlitos (1975) A. oryzoe 0.41 Rolz (1974) Fusarium graminearum 0.66 Anderson et al. (1975) Algae - Spirulina 0.64-0.70 Clement (1975) inexpensive waste carbohydrate sources. The molds might be of consid- erable interest because of ease of harvesting from fermentation media and their mycelial nature, which provides natural texture. Utilization Systems Experimental A wide variety of experimental systems utilizing microorganisms to con- vert a chemical to single-cell protein have been examined (Tannenbaum and Wang, 19751. However, these studies have focused more on low-cost methods of protein production than on utilization of chemical wastes. Purified chemicals such as methanol, ethanol, acetic acid, n-alkanes, etc. have been used for production of microorganisms to be used in animal feeding studies. Shacklady (1974) reviewed the response of livestock and poultry to yeast and bacterial single-cell protein. Animal feeding trials with microfungi were described by Duthie (19751. Despite the success of these efforts, microbial protein has remained too expensive in comparison to soybean meal and has not been commercialized to a major extent. Industrial The industrial production of single-cell protein from chemicals is limited to a few examples. Amoco Foods has a plant to produce 5,000 to 10,000 ton/year of the food yeast Candida utilis from ethanol. Imperial Chemical Industries Ltd. has a 70,000 ton/year plant in England for the production of bacteria on methanol. There are also several large plants producing
Nonfood industrial Wastes 59 yeast from paraffins in the USSR. In all cases, the product is utilized as a nutritional supplement. As a consequence, the pricing must be such that it can compete with alternative protein commodities. Animal and Human Health Pathogens Unprocessed organic chemical waste is not likely to contain pathogenic microorganisms. However, the processing by fermentation can introduce pathogens. For this reason, guidelines for single-cell protein used in the feeding of animals have been recommended by the International Union of Pure and Applied Chemistry with regard to limits on enterobacteriaceae, salmonella, Staphylococcus aureus, clostridia (total), Clostridium per- fringens, and Lancefield Group D streptococci (Hoogerheide et al., 19791. In addition, guidelines for preclinical and clinical trials for single-cell protein for human consumption have been published by the United Nations Protein Advisory Group (see appendix in Tannenbaum and Wang  for a summary of these guidelines). Harmful Substances A major problem in the utilization of organic chemical waste is the pres- ence of toxic organic chemicals and heavy metals; both can concentrate in microorganisms used for conversion of waste to animal feed. In the production of single-cell protein from alkanes containing aromatic com- pounds, the single-cell protein is solvent-extracted in order to remove any accumulated or residual material prior to animal feeding. FERMENTATION INDUSTRY The fermentation industry can be divided into three broad categories: (1) antibiotics and other therapeutic compounds, (2) chemical catalysts (en- zymes), and (3) beverages such as wine, beer, and distilled spirits. Wine industry waste is considered in Chapter 2. Quantity The antibiotics industry in the United States has annual sales of about $1 billion, and the total amount of antibiotics produced is 10,000 to 20,000 tons/year (U.S. Tariff Commission, 1970~. A summary of all the anti- biotics produced was presented by Perlman (1978), showing that there are a large number of different products and hence an expected diversity of
60 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS waste. However, the major fermentation antibiotics, penicillin, cephalo- sporin, tetracycline, erythromycin, and the aminoglycosides, account for most of the production and produce most of the pharmaceutical fermen- tation waste. In the United States there are approximately 25 fermentation plants producing antibiotics and organic acids; most of these are located in the Midwest, the Middle Atlantic region, and Puerto Rico. The primary waste from this industry is the spent mycelia. Unlike chemical industry wastes, pharmaceutical waste is collected in a highly concentrated form, with a high protein content. Estimating a total antibiotics production of 15,000 ton/year and a ratio of 2.5 kg waste/kg antibiotic, it is possible to estimate the yearly production of waste mycelium at 38,000 tons dry material/ year. Currently, these wastes are primarily burned, treated in waste treat- ment systems, or used as fertilizer. The alcoholic beverage industry (wine, beer, and distilled spirits) is large and produces substantial waste. About 5.5 kg dry brewers grains are recovered for each 117 liters (31 gallon barrel) of beer brewed (Anon- ymous, 1977a). This means that about 1 million ton/year were available from 5.5 billion liters (176 million barrels) in 1978 for use in animal feeds (U.S. Department of Commerce, 19801. The distilling industry produces about 1 billion liters of distilled spirits at 50 percent ethanol per year (U.S. Department of Commerce, 1980) and in the process generates an estimated 360,000 tons of waste per year. Essentially all of the brewers and distillers wastes are currently utilized for animal feeding and do not represent underutilized materials. Physical Characteristics Most of the waste from antibiotic manufacture is the fungal mycelia that is removed from the fermentation broth by filtration. It will typically have a solids content of about 15 percent. Even with 85 percent moisture, the material is a nonflowing cake. Mycelia contains 20-50 percent protein, about 10-30 percent ash (depending on how much fiber aid is used in filtration), and has a C/N ratio of about 10 (on a dry basis). Nutritive Value There are very few published data on the nutritive value of antibiotic- producing organisms, primarily because of the low incentive for industry to develop a feed market for its waste mycelia. However, it is possible to compare some of the data available with information on other fungi and attempt to draw some general conclusions. In Appendix 1, Tables 1 through 3, information on several fungi and actinomycetes is presented.
Nonfood Industrial Wastes 61 The protein content of the antibiotic producer is generally low (Pfizer, Inc., Groton, Conn., personal communication); it is diluted by a high ash level resulting from use of insoluble inorganic materials for pH control and as a filtration aid. Doctor and Kerur ( 1968) conducted rat feeding studies with Penicillium chrysogenum in which mycelia was used in combination with peanut meal to provide the total protein in the diet. It was necessary to supplement mycelia with peanut meal in order to make the feed palatable to the rats. These results demonstrated the usefulness of the mycelia in supplementing lysine and threonine, two amino acids which are low in concentration in peanut meal. In addition, the authors refer to unpublished data on the use of mycelia in chick feeding. Earlier studies by Pathak and Seshadri (1965) and Yakinov et al. (1960) also examined P. chrysogenum as a protein feed for animals. There is a substantial amount of knowledge and experience in the use of fermentation wastes from the brewing and distilling industry, and the composition and nutritive value of these by-products is well defined. A recent study of the feeding value of by-products from ethanol production has also been published (National Research Council, 1981) and represents a good source of relevant information. Processing Technology One of the limitations in the use of fungi and other mycelial organisms for animal feed is the problem of digestibility. When waste mycelia is processed to allow reuse as a complex nutrient in fermentation, the problem of digestion may be overcome by acid or enzymatic hydrolysis to solubilize the mycelia. This process has the further advantage of permitting the organic material to be concentrated by evaporation to a molasses-like product (Cooney, unpublished results). The digestion of fungal cell walls has typically been performed using fermentation broth containing extracellular enzymes. It has most often been observed that treated cells are harder to decompose than cell wall suspensions; viable cells are still harder to digest (Kawakami et al., 1972; Matsuo et al., 1967; Okazaki, 1972; Tabata and Terui, 19631. There are a number of enzymes involved in degrading cell walls since the mycelial cell wall is composed of a mixture of polymers including chitins, 3-glucans, lamarins, and peptides; in addition, many of these polymers are cross-linked. Microbial digestion of cell walls was reported by Sonoda and Ono (1965~; they examined the mycelial cake obtained from kanamycin, strep- tomycin, and penicillin fermentations. They also used the digest from these mycelia to produce methane in an anaerobic digestor.
62 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS Utilization Systems Experimental Utilization of antibiotic waste has been examined by blending it with other feed components and incorporating it directly into animal diets. However, there are palatability problems (Doctor and Kerur, 1968~. The high in- organic content often precludes its direct use in concentrated form. Deg- radation of the mycelial cell wall to facilitate dehydration has been examined by Ackerman (19751. It was shown that over 50 percent solubilization of the mycelial solids could be accomplished with less than 20 percent loss to carbon dioxide during aerobic treatment. This material was much easier to dehydrate than the whole mycelia. Industrial While antibiotic fermentation waste is not used as animal feeds, the dried by-products from the brewing and distilling industries are used widely for animal feeds. Experience with these materials will facilitate the evaluation and utilization of other fermentation residues if they become available. Health Considerations One major problem with the use of mycelia from antibiotics manufacturing is the presence of residual antibiotics. In the case of antibiotics used in animal feed (e.g., tetracycline, bacitracin) the whole broth frequently contains cells plus antibiotics that are both dried and fed. In this situation, there is no waste. However, with wastes from processes for antibiotics destined for human use, it is important that residual antibiotics in the mycelia are not permitted to be widely dispersed. Otherwise, there will be selection processes favoring drug resistance (Smith, 19771. It is nec- essary to remove traces of some antibiotics from the mycelia before it can be fed to animals. Regulatory Aspects For the antibiotics industry, a major limitation in the utilization of mycelial wastes is the problem of residual antibiotics. It may be necessary to develop processing methods to eliminate antibiotics if mycelia is-to be used for feed. In order to obtain approval from regulatory authorities for use of any feed material, it is necessary to establish standards for the product. This may be very difficult with antibiotic processes because variable raw
Nonfood Industrial Wastes 63 material quality and variable process operation may cause significant changes in the waste product. Since the primary product of the fermentation has such a high value, there is little economic incentive to alter process op- eration to assure routine high-quality mycelia. Thus, establishment of such standards may provide a negative incentive to develop the use of antibiotic mycelia as animal feed. MUNICIPAL SOLID WASTE Quantity Municipal Solid Waste (MSW) is often cited as an important and under- utilized resource. The total municipal solid waste available through col- lection in 1975 in the United States was estimated at 68 million dry tons per year (U.S. Department of Energy, 19791. In Canada, it was estimated by Pequegnat (1975) to be 12.7 million dry tons/year. The availability of municipal solid waste is concentrated in large metropolitan areas, and it is anticipated that large quantities will continue to be available. Compet- itive uses include direct combustion or possible future conversion to al- cohol. Physical Characteristics The physical characteristics of municipal solid waste are quite variable and depend strongly on the source. There are usually substantial quantities of cellulosic materials, metals, glass, plastics, and dirt. Furthermore, there is no control over the source. The quality of the municipal solid waste fraction used for animal feeding will be determined by the ability of the processor to separate out undesired materials. Belyea et al. (1979) have examined the composition of municipal solid waste that had been frac- tionated by several methods. Ash content was quite variable and often above the usual level present in farm animal diets. The bulk density of municipal solid waste is low and, as a consequence, its collection and storage are problems. Not surprisingly, collection costs are a major fraction of the cost of municipal solid waste. Nutritive Value Chemical Composition The composition of shredded and air-classified shredded solid waste is presented in Appendix 1, Tables 1 to 3 (Belyea et al., 1979~. The minerals
64 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS found in major (> l percent) amounts are Si, Al, Ca, Mg, and Fe; in minor (0.01-1 percent) amounts are Na, Zn, Pb, Bo, Cr. Ti, and Cu.; and in trace amounts are An, Ar, Mn, P. Vn, Mo, Ni, Co, and Bi. An examination of potentially harmful elements suggested that six Ba, Sn, Se, Pb, Cr. and Cd may be present in unacceptable levels. Mertens and Van Soest (1971) analyzed a variety of different paper sources; results for the Washington Post are shown in Appendix Tables 1 and 2 for compar- ison. Newspaper is high in indigestible fiber and low in protein and ash. Nutrient Utilization A number of studies have been done on the inclusion of municipal solid waste, more specifically newspaper, into animal diets. Kesler et al. ( 1967) examined the use of waste paper as an absorbent or carrier for molasses in cattle feeding. Compared with controls using corn silage or corn and soybean meal, digestibility of crude fiber was reduced when paper was the absorbent. The addition of newspapers to diets of growing dairy steers was studied by Daniels et al. (19701. Newspaper was evaluated at 8 and 12 percent levels, replacing 8 percent cottonseed bulk in the control diet. They found no significant differences in rates of gain and feed efficiency. Carcass grade was not affected. It appears that newspaper can be added up to 12 percent of the diet with no detrimental effect. When paper was used at the 20 percent level in lactating dairy cows, however, there was a decrease in milk yield (Mertens et al., 19711. Processing An alternative to direct feeding of MSW would be to hydrolyze the cel- lulase faster by acid or enzymes to produce a sugar syrup. This syrup could be used as a carbohydrate feed or further processed by fermentation to produce products such as single-cell protein. The process of hydrolysis, followed by a solid-liquid separation would be useful in removing un- desired materials from the MSW feedstock. Animal and lIuman Health Although municipal solid waste and newspaper have been shown exper- imentally to be usable as fiber sources in animal diets, there are several serious health concerns. Excess amounts of several minerals were mea- sured in St. Louis municipal solid waste. In addition, Belyea et al. (1979) reported dangerous levels of polychlorinated biphenyls and other toxic
Nonfood Industrial Wastes 65 compounds. There is no control over the source of waste, and variable levels of harmful materials may occur. Their removal would be expensive. As a consequence, the use of municipal solid waste for animal feed is not considered viable at this time. RESEARCH NEEDS The major factors limiting the use of underutilized nonfood industrial waste are the need for nutritional upgrading and the need to remove toxic ma- ter~als. Therefore, the research needs relating to the problem of nonfood industrial waste utilization should focus on: 1. Evaluation of nonconventional organisms that will utilize chemical process stream wastes and produce microbial proteins. Such an evaluation should include not only effectiveness of conversion to single-cell protein, but also value of the product for use in animal diets. 2. Development of innovative ways to remove or destroy toxic materials from chemical waste streams, municipal solid wastes, and fermentation industry wastes. SUMMARY An examination of the nonfood industry to identify underutilized wastes that could be used directly or after further processing for animal feeding has identified a number of areas where better utilization might be achieved. However, there are two major limitations to the use of waste from these nonfood industries: the need and hence expense of processing to achieve nutritional upgrading and the need to remove toxic or otherwise harmful materials from the waste. Problems in nutritional upgrading are associated with factors such as dilute chemical waste stream and variable quantity and quality. LITERATURE CITED Ackerman, R. A. 1975. The Degradation of Solid Wastes M.S. thesis. Massachusetts Institute of Technology. Anderson, C., J. Longton, C. Maddix, G. W. Scammell, and G. L. Solomons. 1975. The growth of microfungi on carbohydrates. P. 314 in Single-Cell Protein II, S. R. Tannen- baum and D. I. C. Wang, eds. Cambridge, Mass.: MIT Press. Anonymous. 1977. Animal feeds in the brewing industry. Pp. 5-6 in Proceedings of the U.S. Brewers Association Feed Conference. Anonymous. 1980. Facts and figures for the chemical industry. Chem. Eng. News. 58(23):33 90.
66 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS Belyea, R. L., F. A. Martz, W. McIlroy, and K. E. Keene. 1979. Nutrient composition and contaminants of solid cellulosic waste. J. Animal Sci. 49: 1281 - 1291. Clement, G. 1975. Producing Spirulina with CO2. P. 467 in Single-Cell Protein, II. S. R. Tannenbaum and D. I. C. Wang, eds. Cambridge, Mass.: MIT Press. Cooney, C. L. 1975. In Microbial Utilization of C '-Compounds. Japan: Society for Fer- mentation Technology. 183 pp. Cooney, C. L., and D. W. Levine. 1972. Microbial utilization of methanol. Adv. Appl. Microbiol. 15 :337-365. Cooney, C. L., C. K. Rha, and S. R. Tannenbaum. 1980. Single-cell protein: Engineering, economics and utilization in foods. Adv. Food Res. 26: 1-52. Daniels, L. B., J. R. Campbell, F. A. Martz, and H. B. Hedrick. 1970. An evaluation of newspaper as feed for ruminants. J. Anim. Sci. 30:593-596. Dasher, J. R. 1976. Changing petrochemical feedstocks Causes and effects. Chem. Eng. Prog. 72:15-26. Davis, P. 1974. Single Cell Protein. New York: Academic Press. Doctor, V. M., and L. Kerur. 1968. Penicillium mycelium waste as protein supplement in animals. Appl. Microbiol. 16: 1723- 1726. Dostalek, M., and N. Molin. 1975. Studies of biomass production of methanol-utilizing bacteria. P. 385 in Single-Cell Protein II, S. R. Tannenbaum and D. I. C. Wang, eds. Cambridge, Mass.: MIT Press. Duthie, I. F. 1975. Animal feeding trials with a microfungal protein. P. 505 in Single- Cell Protein II, S. R. Tannenbaum and D. I. C. Wang, eds. Cambridge, Mass.: MIT Press. Goldberg, I., J. S. Rock, A. Ben-Basset, and R. I. Mateles. 1976. Bacterial yields on methanol, methylamine, formaldehyde, and fermate. Biotechnol. Bioeng. 18:1657-1668. Gow, J. S., J. D. Litchailes, S. R. L. Smith, and R. B. Walter. 1975. SCP production from methanol: Bacteria. P. 370 in Single-Cell Protein II, S. R. Tannenbaum and D. I. C. Wang, eds. Cambridge, Mass.: MIT Press. Gutcho, S. 1973. Proteins From Hydrocarbons. Park Ridge, N.J.: Noyes Data Corp. Hoogerheide, J. C., K. Yamada, J. D. Littlehailes, and K. Ohno. 1979. Guidelines for testing of single-cell protein destined as protein source for animal feed II. Proc. Appl. Chem. 51:2537-2560. Imrie, F. K. E., and A. J. Vlitos. 1975. Production of fungal protein from carob. P. 223 in Single-Cell Protein II, S. R. Tannenbaum and D. I. C. Wang, eds. Cambridge, Mass.: MIT Press. Jahnig, C. E., and R. R. Bertrand. 1977. Environmental aspects of coal gasification. Pp. 127-132 in Coal Processing Technology. New York: American Institute of Chemical Engineers. Johnson, M. J. 1969. Microbial cell yields from various hydrocarbons. Pp. 833-842 in Fermentation Advances, D. Perlman, ed. New York: Academic Press. Kawakami, N., H. Kawakami, and T. Sato. 1972. Cell wall disintegration with Physarium enzyme in Sahizosaccharomyces pombe. J. Ferm. Technol. 50:567-711. Kesler, E. M., P. T. Chandler, and A. E. Branding. 1967. Dry molasses product using waste paper as a base for a possible feed for cattle. J. Dairy Sci. 50:1994-1996. Kihlberg, R. 1972. The microbe as a source of food. Ann. Rev. Microbiol. 26:427. Laine, B. M., and J. Chaffaut. 1975. Gas-oil as a substrate for single-cell protein pro- duction. P. 424 in Single-Cell Protein II, S. R. Tannenbaum and D. I. C. Wang, eds. Cambridge, Mass.: MIT Press. Levine, D. W., and C. L. Cooney. 1973. Isolation and characterization of a thermotolerant methanol utilizing yeast. Appl. Microbiol. 26:982-990.
Nonfood Industrial Wastes 67 Lowenheim, F. A., and N. K. Moran. 1975. Industrial Chemicals. New York: John Wiley & Sons. Magee, E. M., C. E. Jahnig, and C. D. Kalfaldas. 1977. The environmental influence of coal liquefaction. Pp. 16-22 in Coal Processing Technology. New York: American Institute of Chemical Engineers. Mateles, R. I., and S. R. Tannenbaum, eds. 1968. Single-Cell Protein. Cambridge, Mass.: MIT Press. Matsuo, M., T. Yasui, and T. Kobayashi. 1967. Cytolytic enzymes from thermophilic microorganisms: I. Cytase production from Thermoinactinomyces vulgaris. J. Ferm. Technol. 49:860-868. Mertens, D. R., J. R. Campbell, F. A. Martz, and E. S. Hildebrand. 1971. Lactational and ruminal response of dairy cows to ten and twenty percent dietary newspaper. J. Dairy Sci. 54:667-672. Mertens, D. R., and P. J. Van Soest. 1971. Paper composition and-estimated nutritive value. Paper presented at National ASAS Meeting. Miller, T. L., and M. J. Johnson. 1967. Utilization of normal alkanes bv yeast. Biotechnol. Bioeng. 8:549-565. At, ~_~. ~ am._ .... . National Research Council. 1981. Feeding Value of Ethanol Production By-Products. Wash- ington, D.C.: National Academy Press. Okazaki, H. 1972. On cell wall lytic activity produced by thermophilic actinomyces. III. Some properties of the components of the lytic enzyme produced by Micropolyspora sp. J. Ferm. Technol. 50:580-591. Okazaki, H., and H. Iizuka. 1972. On cell wall lytic activity produced by thermophilic actinomyces. I. Lysis of intact cells of various yeasts (including hydrocarbon assimilating yeasts), thermophilic fungi, and green algae. J. Ferm. Technol. 50:405-413. Pathak, S. G., and R. Seshadri. 1965. Use of Penicillium chyrogenum mycelium as animal food. Appl. Microbiol. 18:262-266. Pequegnat, C. 1975. Economic feasibility of waste as animal feed. P. 26 in Waste Recycling and Canadian Agriculture. Ottawa: Agricultural Economics Council of Canada. Perlman, D. 1978. The fermentation industries. ASM News. 43(2):82-89. Pirie, N. W. 1975. Food Protein Sources. Cambridge, Eng.: Cambridge University Press. Reed, G., and H. J. Peppler. 1973. Yeast Technology. Westport, Conn.: AVI. Rockwell, P. J. 1976. Single Cell Protein From Cellulose and Hydrocarbons. Park Ridge, N.J.: Noyes Data Corp. Rolz, C. 1974. Utilization of cane and coffee processing by-products as microbial protein substrates. P. 273 in Single-Cell Protein II. S. R. Tannenbaum and D. I. C. Wang, eds. Cambridge, Mass.: MIT Press. Sahm, H., and F. Wagner. 1972. Mikrobielle verwettung von methanol. Arch. Mikrobiol. 84:29-42. Shacklady, C. A. 1974. Response of livestock and poultry to SCP. Pp. 115-128 in Single- Cell Protein, P. Davis, ed. New York: Academic Press. Sheehan, B. T., and M. J. Johnson. 1971. Production of bacterial cells from methane. Appl. Microbiol. 21:511. Silver, R. S., and R. I. Mateles. 1969. Control of mixed-substrate utilization in continuous cultures of Escherichia coli. J. Bacteriol. 97:535-543. Smith, H. W. 1977. Antibiotic resistance in bacteria and associated problems in farm animals before and after the 1969 Swann report. Pp. 344-357 in Antibiotics and Anti- biotics in Agriculture. W. Woodbine, ed. Boston: Butterworths. Snedecor, B., and C. L. Cooney. 1974. Thermophilic mixed culture for bacteria utilizing methanol for growth. Appl. Microbiol. 27: 1112- 1117.
68 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS Sonoda, Y., and H. Ono. 1965. Anaerobic digestion of antibiotic waste water. I. On kanamycin, streptomycin, penicillin waste water and mycelium cake. J. Ferm. Technol. 43(1 1):842-846. Tabata, S., and G. Terui. 1963. Studies on microbial enzyme active in hydrolizing yeast cell wall. III. On the protease fraction of the yeast cell wall-lytic enzyme of Streptomyces albidoflavus. J. Ferm. Technol. 43(10):777-782. Tannenbaum, S. R., and D. I. C. Wang. 1975. Single-Cell Protein II. Cambridge, Mass.: MIT Press. U.S. Department of Commerce. 1980. Statistical Abstract of the United States, 100th ed. Washington, D.C.: U.S. Government Printing Office. U.S. Department of Energy. 1979. The Report of the Alcohol Fuels Policy Review Raw Fuels Availability Reports. Report No. ET-01 14/1. Washington, D.C.: U.S. Government Printing Office. U.S. Environmental Protection Agency. 1973. Development Document for Effluent Lim- itations Guidelines and Standards of Performance. EPA Report for Contract No. 68-01- 1509. Washington, D.C.: U.S. Government Printing Office. U.S. Tariff Commission. 1970. Synthetic Organic Chemicals. United States Production and Sales. TC Publication 327. Washington, D.C.: U.S. Government Printing Office. Wilcox, R. P., L. B. Evans, and D. I. C. Wang. 1978. Experimental behavior and math- ematical modeling of mixed cultures on mixed substrates. AIChE Symp. Ser. 74:236- 240. Wodzinski, R. S., and M. J. Johnson. 1968. Yields of bacterial cells from hydrocarbons. Appl. Microbiol. 16:1886-1891. Yakinov, P. A., O. V. Krusser, and Y. E. Koney. 1960. Investigations of Penicillium chrysogenum mycelium as a possible protein source for feeding domestic animals. I. Leningr. Khim. Farmatsevt. Inst. 9:212-219.