Effect of decortication and protease treatment on the kinetics of liquefaction, saccharification, and ethanol production from sorghum

BACKGROUND: This study analyzes the effect of decortication and protease treatment on the kinetics of liquefaction, saccharification and ethanol production from sorghum kernels. In general, bioethanol yields from sorghum are lower than those from maize. This has been attributed to reduced access of starch-degrading enzymes due to the crosslinked protein net in the sorghum kernels. RESULTS: Liquefaction is described as a zero order kinetics process, with reaction rates enhanced by protease treatment. The use of protease almost doubled the liquefaction rate in both whole and decorticated sorghum, compared with untreated kernels. During saccharification of decorticated sorghum, protease treatment significantly affected the glucose/starch yield and the glucose concentration profile over time. When compared with maize, protease treatment of decorticated sorghum resulted in superior ethanol production rates. Specific ethanol yields during fermentation were statistically comparable with those for maize. CONCLUSION: Protease treatment of decorticated sorghum kernels can impart substantial economic benefits in terms of improvement of bioethanol yield (13% over whole sorghum) and in reduced fermentation time (approximately 50% with respect to maize). (C) 2010 Society of Chemical Industry