Lignite, leonardite, or subbituminous coal is ground to a size ranging from 8 mesh to 200 mesh and extracted with distilled or tap water to obtain a nutrient useful in the cultivation of microbes for the production of protein. The extractant water temperature is 25 deg-125 deg c and the coal/water weight ratio is 1:1 to 1:100. After separation from residual solids and sterilization, the water- extract is inoculated with candida tropicalis, c. Lipolytica, c. Pulcherrima, c. Utilis [torulopsis utilis], t. Colliscubsa [t. Colliculosa], hansenula anomala, pseudomonas aeruginosa, rhodotorulia gracilis, and culture is carried out at optimum environmental conditions for the microorganism's growth. The production of viable cells is increased 10-fold by the addition of 0.5-10.0 Vol pct (based on the total volume) of liquid animal nitrogenous wastes to the extract nutrient and is increased further by the addition of 0.1-10.0 G/100 ml of glucose to the urine-treated extract.
U.S. Pat. 3,540,983; Nov. 17, 1970; Chem. Abstr. 74:52,309E