The use of plant cell wall-degrading enzymes from newly isolated Penicillium ochrochloron Biourge for viscosity reduction in ethanol production with fresh sweet potato tubers as feedstock.

Penicillium ochrochloron Biourge, which was isolated from rotten sweet potato, can produce plant cell wall-degrading enzymes (PCWDEs) with high viscosity reducing capability for ethanol production using fresh sweet potato tubers as feedstock. The enzyme preparation was characterized by a broad enzyme spectrum including 13 kinds of enzymes with the activity to hydrolyze cellulose, hemicellulose, pectin, starch, and protein. The maximum viscosity-reducing capability was observed when the enzyme preparation was obtained after 5 days of fermentation using 20 g/L corncob as a sole carbon source, 4.5 g/L NH4 NO3 as a sole nitrogen source, and an initial medium pH of 6.5. The sweet potato mash treated with the enzyme preparation exhibited much higher fermentation efficiency (92.58%) compared with commercial cellulase (88.06%) and control (83.5%). The enzyme production was then scaled up to 0.5, 5, and 100 L, and the viscosity-reducing rates were found to be 85%, 90%, and 91%, respectively. Thus, P. ochrochloron Biourge displays potential viscosity-reducing capability for ethanol production.