Bioethanol production from pentose sugars: Current status and future prospects

The utilization of hemicellulose, the second most abundant polysaccharide, is must for the cost-efficient production of ethanol from second generation feedstocks. Xylan, the major hemicellulose in plant biomass yields mainly xylose as pentose sugars on hydrolysis. The progress in fermentation of pentose sugars has gone on slow pace as there are few microorganisms known, which are capable of pentose metabolism. The future perhaps lies in finding organisms that would ferment high density hydrolysates without purification. This obviously has to use the genetic and metabolic engineering routes. Either a direct or a sequential fermentation system needs to be worked out. This review provides an overview of the current pentose bioconversion processes and future prospects for bioethanol production.