P66: Bioethanol production from Lignocellulosic waste by developing new yeast strains

Bioethanol generated from the agricultural or forestry waste is currently being sought as a second generation biofuel. To convert lignocellulosic residues to bioethanol in efficient and economical manner requires an organism that can simultaneously ferment hexose and pentose sugars and is resistant to inhibitors formed during pre-treatments and conditions experienced within industrial fermentors. Inhibitory compounds are generated during the pre-treatment of wheat straw, and these can affect ethanol production during fermentation. S. cerevisiae strains that we have tested can grow in a 1/4X concentration of synthetic inhibitor mimicking pre-treatment conditions. Natural fermentative ecosystems such as agricultural manure and forest floors are potential sources of new yeast strains. We have isolated wild yeasts from these sources and analysed them. Phenotyping of 102 yeast isolates by HPLC has identified pentose utilisers and ethanol producers. Phylogenetic analysis was carried out using D1/D2 and ITS regions of the ribosomal DNA and BLAST searches against all known fungal species for 32 selected isolates from Fermentative ecosystems. The species make up of manure heap and forest ecosystems was found to be diverse. We performed Phenotypic microarrays and microplate reader analysis for the best strains isolated from both ecosystems. The strains were tested in 6% xylose and different concentrations of pre-treatment inhibitor in aerobic and anaerobic conditions. The analysis further confirms the presence of promising strains for xylose and inhibitor tolerance. The mini Fermentation by Co2 weight loss method was tested that confirmed wild yeasts isolated from fermentative ecosystems are capable of producing ethanol under stressed conditions.