Mutagenesis of Pachysolen tannophilus and its protoplast fusion with Saccharomyces cerevisiae for ethanol production

摘要

The study deals with mutagenesis of P. tannophilus MTCC1077 and protoplast fusion between S. cerevisiae G and P. tannophilus MTCC1077 to obtain variants and fusants capable of ethanol production from xylose. A total of 103 and 102 ethanol negative variants were selected from mutagenesis with UV and EMS respectively. The parent P. tannophilus MTCC1077 gave maximum ethanol yield of 0.339g/g with a corresponding fermentation efficiency of 66.47% from 20g/l xylose when fermentation was carried out for 120hr at 30^ at a pH of 5.0 with 6% v/v inoculum and aeration of lOOrpm. Two ethanol negative mutants UVmut 62 and UVmut 41 gave ethanol yields 0.347 g/g and 0.350g/g respectively. Three ethanol negative mutants EMSmutU, EMSmuf39 and EMSmu￡26 gave ethanolyield of 0.346g/g 0.350g/g, 0.364g/g respectively. S.cerevisiae G gave ethanol yield of 0.430g/g with a fermentation efficiency of 84.21 %. Protoplast fusion between S. cerevisiae G and P. tannophilus MTCC1077 yielded two stable fusants FUS1 and FUS2 which gave yield of 0.244g/g and 0.273g/g respectively from a mixture of glucose and xylose after 72hrs of fermentation. Scanning electron microscopy (SEM) study of parent strains and fusants revealed differences in the cell surface and also in budding pattern as compared to that seen with either of the individual parent strains. DNA contents of the two fusants were larger than that of any single parental strains, suggesting that these fusants have inherited genetic material from both parental strains.