Protein source, microbial biomass

Most often, the rates for feedstock destruction in anaerobic digestion systems are based upon biogas production or reduction of total solids (TS) or volatile solids (VS) added to the system. Available data for analyses conducted on the specific polymers in the anaerobic digester feed are summarized in Table II. The information indicates a rapid rate of hydrolysis for hemicellulose and lipids. The rates and extent of cellulose degradation vary dramatically and are different with respect to the MSW feedstock based on the source and processing of the paper and cardboard products (42). Rates for protein hydrolysis are particularly difficult to accurately determine due the biotransformation of feed protein into microbial biomass, which is representative of protein in the effluent of the anaerobic digestion system. 

Of the various new sources of nutrients, especially proteins, microbial biomass shows great potential. This applies particularly to yeasts which have a long tradition of successful use as foods, as producers of foods and beverages, and as food ingredients (1,2,3,4,5). The interest in and the supply of yeast and microbial biomass will increase rapidly with the growing activities in biomass conversion (alcohol production, etc.). Microbial biomass can become a significant source of food protein... 

It is evident that natural proteins are not a primary source of large amounts of amino acids, despite the fact that many of the acids are commercially significant chemicals and a few are commodity chemicals. The technical difficulties just alluded to include undesirable distributions of the amino acids in natural proteins, the sensitivity of proteins and amino acids to chemical hydrolysis conditions, racemization, the multiplicity of the product acids and the often low concentration of the desired acid or acids in the hydrolysate, and the consequent separation problems. Microbial synthesis of specific amino acids from biomass substrates or biomass-derived intermediates often has substantial advantages over thermochemical processing methods and is used for the commercial production of several of the amino acids. This is discussed in more detail in the next section. 

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