N Sai

Production of bioethanol from lignocellulosic biomass is gaining much research interest because of its abundant supply. Saccharomyces cerevisiae is The commonly used industrial yeast for ethanol production but it lacks the property to ferment pentose sugars mainly xylose present in lignocellulosic materials. In this study, the hybrid yeast strains are developed by genome shuffling process between the xylose sugar fermenting yeast Pichia stipitis and hexose sugar fermenting yeast Saccharomyces cerevisiae. Lyticase enzyme is used to establish viable protoplasts from both the parental yeast strains. Factors affecting physic chemical properties viz., protoplast isolation, enzyme concentration and incubation time were investigated. The optimal parameter for the protoplast release of S. cerevisiae and P. stipitis include 700 µg/µl Lyticase for 60 min and 700 µg/µL Lyticase for 120 min respectively. The maximum protoplast formation ratios were 98.75% and 82.24% for S. cerevisiae and P. stipitis respectively. The frequency of the protoplast fused hybrids was carried out by using Polyethylene Glycol (PEG) as fusogen. Fused hybrids were produced by use of 35% (w/v) PEG 4000, optimized conditions of protoplasts fusion of S.cerevisiae and P. stipitis genome shuffling was achieved at a rate of 80.90% with fusion of 20 min. Further, these hybrids produced through genome shuffling will be further evaluated for production of bioethanol using lignocellulosic materials.

Lignocellulosic biomass consist of inedible parts of woody grass plants, stalk of sweet sorghum and agricultural residues, are the sources for the 2 nd generation biofuels. Lignocellulosic biomass comprises of many different polysaccharides cellulose, hemicelluloses, phenolic polymer lignin and proteins. The problem of the 2 nd generation feed stock is the extraction of the sugars located inside the lignin and cellulose structure. To convert lignocellulosic biomass to biofuels the complex polysaccharides and lignin must be broken down or hydrolysed into simple sugars. This process of bioconversion of cellulose to ethanol involves pre-treatment, saccharification and fermentation. The other challenges include types of the biomass and their availability round the year, logistics, and production technologies. These challenges take in identification and improvement of energy crops like sweet sorghum, switch grass, miscanthus, alfa alfa, etc., by biotechnological approaches by generating feed stocks with low lignin content and modified traits which can tolerate biotic and abiotic stresses with improved cellulose content. Down regulation of key enzymes involved in lignin biosynthetic pathway may be a promising approach to decrease or alter the hard lignin content in lignocellulosic feed stock materials. With the advent of genetic engineering and crop improvement strategies in energy crops may provide continuous supply of feed stock for the production of biofuels as an alternative source of energy. To benefit the environment and also to meet the global demand of fossil fuels, the biofuels produced from lignocellulosic biomaterial by biotechnological route may help in decreasing the emission of green house gasses and also save our food crops.