Bioprocessing of sweet sorghum with in situ-produced enzymes.

Enzyme-assisted ensiling (ENLAC), using in situ-produced enzymes from Gliocladium sp. TUB-F-498, preserved 80% of the sugar content of sweet sorghum, and facilitated its extraction by countercurrent diffusion. The in situ enzyme was produced on the extracted sweet sorghum pulp by an 8-d solid substrate fermentation (SSF) with a yield of 4.6 cellulase and 400 IU/g dry wt xylanase. Two percent of the fermented substrate had cellulase and xylanase levels equivalent or superior to levels found in the commercial enzymes Celluclast and Viscozyme Novo at the 0.025% application level in ENLAC. The in situ-production of enzymes on recyclable substrates may reduce bioprocessing costs significantly. In this ENLAC process, the cost of the in situ enzymes is estimated to be about $0.12/MT substrate, compared to $9.5/metric ton (MT) for the commercial enzymes, a cost reduction of nearly 80-fold.