Developing Organisms for Consolidated Bioprocessing of Biomass to Ethanol

Abstract

Lignocellulosic biomass is an abundant, renewable feedstock for sustainable production of biofuels and chemicals. The main technological barrier that impedes widespread utilizationof this resource for production of fuels and other commodity products is the lack of low-costtechnologies to overcome the recalcitrance of lignocellulose. Organisms that hydrolyse thecellulose and hemicelluloses in biomass and produce a commodity product such as ethanolat a high rate and titre would significantly reduce the costs of biomass conversion. Thiswould allow steps that are currently accomplished in different reactors, often by differentorganisms, to be combined in a consolidated bioprocess (CBP). While there is still no idealorganism to use in one-step biomass conversion, several candidates have been identifiedthat are in various stages of development for establishment of a cellulolytic system and/orimprovement of product-forming attributes. This chapter assesses the status quo for CBPorganismal development either by enabling non-cellulolytic organisms to grow on cellulosicsubstrates or by improving product forming abilities of native cellulose utilizing organisms.The authors also discuss feedstocks that are available for the production of biofuels using CBPand assess how process integrations can make CBP economically feasible in the near future.The increasing demand for oil coupled to the premium many governments place on greaterenergy security and environmental concerns have led to the development of an activebiofuels industry (Van Zyl et al., 2011). First generation biofuels such as ethanol from starch