| Abstract: | An investigation was made to determine the feasibility of utilizing a natural fat (inedible tallow) as a carbon source by microorganisms for single cell protein (SCP) production. Emphasis was placed on the physical-chemical characteristics of inedible tallow, growth characteristics of test microorganisms in media with tallow as source of carbon, and characteristics of the cell product (SCP). Pseudomonas cepacia, Candida utilis, Saccharomycopsis lipolytica, and an unidentified yeast TK-1 were used as test organisms. The optimum growth conditions for each of these test microorganisms was determined. Optimum growth temperature for P.cepacia, C.utilis , and S.lipolytica was at 20-30 C and for the yeast TK-1 at 10-20 C. Optimum pH for growth was as follows: for P.cepacia at pH 6-7, for the yeast TK-1 at pH 6, for C.utilis at pH 4-7, and for S.lipolytica at pH 4-6. The composition of the tallow consisted of monoglycerides and fatty acids in sufficient amounts to provide natural emulsification properties when homogenized with a mineral salts medium. The fatty acid profile of tallow consisted primarily of palmitic, stearic, and oleic acids. Candida utilis and S.lipolytica were selected as principal test organisms because of their lipolytic activity, ability to utilize the major fatty acids of tallow, and recognition as food yeasts. Optimum cell density of the lipolytic yeasts was achieved by growth in a mineral salts medium with 1% tallow for 24 h at 25 C. When the pH of the growth medium in the fermentor was controlled, SCP could be produced more economically than without pH control. The SCP produced from growth of C.utilis and S.lipolytica had an average protein content (24.96%), a high oil yield (23.65%), and a good cell yield per unit substrate (0.76 g /liter per g substrate). The amino acid composition of the SCP produceo with C.utilis and S.lipolytica was comparable to that of commercial yeast products. |
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