Microbial lipid production systems

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. 

Figure 2. A diagrammatic presentation of a fermentation system for the production of a singie cell oil. The main fermenter is inoculated from a smaller vessel at about 10% (v/v). Additional nutrients, including glucose, may be added to the microbial culture within the fermenter during growth. The process operates in a batch mode so that when the cells reach their highest lipid contents (see Figure 3), the fermenter is emptied, the cells are removed from the broth, and then finally they are spray-dried. In this form, the oil within the cells is stable and can be extracted by solvents whenever, and wherever, is convenient. (From 50, with kind permission of the author. Dr. David J. Kyle, and the publishers.)...

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