Bioconversion of rapeseed meal for the production of a generic microbial feedstock

Rapeseed meal, a major byproduct from biodiesel production, has been used as a low-cost raw material for the production of a generic microbial feedstock through a consolidated bioconversion process. Solid state fermentation by Aspergillus oryzae led to the production of hydrolytic enzymes that could release free amino nitrogen (FAN), inorganic phosphorus (IP), small amount of glucose, and possibly many other microbial nutrients from rapeseed meal. Suspending the fermented solids in water at elevated temperature resulted in further hydrolysis of the remaining meal components for the production of a feedstock containing 2061.2 mg l−1 FAN, 304 mg l h−1 IP, and 1.8 g l−1 glucose. A three-fold dilution of this feedstock provided all essential nutrients except sufficient carbon source to support the production of 6.85 g l−1 dry Saccharomyces cerevisiae cells in aerobic incubation, while consuming 80.6 g l−1 of the glucose supplement. Comparative yeast incubation confirmed the nutritional similarity between the feedstock and a mixture of commercial peptone and yeast extract.