Sunday, April 29, 2007

Fungal enzymes and microbial systems for ethanol production

T. de Villiers and W. H. van Zyl. Microbiology, University of Stellenbosch, De Beer Street, Stellenbosch, South Africa

Growing environmental concerns, the need for energy security, utilization of agricultural surpluses and biomass resources, as well as job creation are only a few reasons feeding the initiative of finding a renewable energy source to sustain energy consumption. Biofuels generated from biomass will be able to address climatic change and security of supply and energy. A single step process (Consolidated Bioprocessing (CBP)) where production of cellulolytic enzymes to hydrolyze cellulosic biomass and fermentation of the resulting sugars to ethanol is accomplished via a cellulolytic microorganism or consortium will ensure a commercially feasible process. The key problems identified to execute this process are finding sufficiently active lignocellulose hydrolyzing enzymes and highly reactive substrates. The commercial practice of converting starch to ethanol by comparison has been very successful to date and may serve as platform to test the development of a successful CBP process. The starch to ethanol process however currently employs liquefying and saccharifying enzymes to hydrolyze the starch, with subsequent conversion of the released sugars to ethanol by yeast. This study focuses on generating amylolytic yeast strains, which may serve as model for a CBP process. Recombinant yeast strains producing efficient combinations of fungal amylolytic enzymes have been developed and the concurrent hydrolysis and fermentation of starch will be demonstrated.