Metabolic Engineering of Bacteria for Renewable Bioethanol Production from Cellulosic Biomass

Biomass is renewable and most abundant raw material on earth. Technologies have been employed to utilize this vast renewable resource for biofuel production. In recent years, microorganisms have received much attention for biofuel production so that it can replace the non-renewable fossil fuels. They secrete synergistic enzymes for degrading the complex biomass to simple sugars and subsequently fermenting them to alcohol. With the help of recombinant DNA technology and other metabolic engineering, biomass metabolizing enzymes and bioethanol producing microbes have been developed which have been used as consolidated bioprocessing (CBP) reactors. In CBP, both hydrolysis and fermentation are carried out in a single reaction vessel. This review focuses on the recent achievements that have been made in some important industrial bacteria so that they are better capable of scavenging the biomass for bioethanol production. We have concentrated on introduction of heterologous genes and modifications of metabolic pathways in these microbes so that they can ferment a wide variety of sugars and at the same time can overcome the major challenges faced by them during ethanol production.