Lignocellulose processing: a current challenge

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Lignocellulosic biomass containing polymers of fermentable hexoses and pentoses is renewable and sustainable, however its utilization in second generation biofuels and chemicals is not yet commercially feasible. Suitable pretreatments have not been developed and this is impeding the progress in commercializing biomass processing technologies. Lignin utilization still remains unexplored and hence its processing to form value added products, either by bio-based or chemical processes, is essential to achieve complete utilization of biomass. Suitable biomass degrading enzymes could be developed with the help of designer cellulosome technology which is capable of degrading untreated biomass efficiently. Signicant reduction of enzyme cost is also needed since high cost is prohibitive for the conversion of tougher substrates. Enzymes acting on the surface of chitin which introduce breaks in the chain, thereby generating oxidized chain ends, have been described.42 These oxidized chain ends are further degraded by chitinases. Similar enzymes producing oxidized cellulose chain ends exist, thus promoting further degradation of cellulose by cellulase. The discovery of these unknown enzymes may provide new avenues for the efficient degradation of lignocellulosic biomass. Development of robust organisms using advanced genetic and metabolic tools is necessary for the production of biofuels and chemicals from biomass. In addition, construction of CBP organisms capable of converting lignocellulosic biomass into biofuels in a single step could be the ideal strategy for commercializing biomass conversion technology. The rapid advances in plant, microbial and enzyme engineering, concentrating more on non-traditional approaches of cell engineering, are likely to provide major breakthroughs which will ease the biomass processing into second generation biofuels and chemicals. Thus biotechnological routes for the synthesis of bio-based chemicals may replace the chemically derived methods and lead to much greener processes.

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