Two Saccharomyces cerevisiae auxotrophic mutants (GT160-34B and XJ133-1B) were fused with two Pichia stiptis auxotrophic mutants, spontaneous mutant M1 and M2 which resulted from a wild type strain (Y-7124) by UV treatment. Growth behavior of 17 hybrid fusant yeast strains and their parents were tested for growth on different carbon sources (xylose, glucose, lactose, cellobiose, raffinose and starch) indicated that hybrid fusants acquired some characters of Pichia stiptis parental strains via intergeneric protoplast fusion technique. Results showed that hybrid fusants and parental strains of Pichia stiptis, M1 and M2 fermented 5% D-xylose, aerobically, at 30°C directly to ethanol within 48 hours. The two parents Saccharomyces cerev/s/ae,GT160-34B and XJ133-1B did not show any xylose fermentation efficiency or ethanol production. The two mutants M1 and M2 were 6% and 12% less than its parent Pichia stiptis (Y-7124), in xylose fermentation efficiency respectively. On the other hand, M1 showed 17% and 12% decrease in ethanol production and conversion coefficient, respectively than its parent, but M2 reached the same amount of ethanol production and showed 11% increase in conversion coefficient than its parent. Results showed that the tested 17 hybrid fusants showed increasing average in xylose fermentation efficiency ranged from 13% to 40% than its active parent M1 or M2. However, results also, showed that ethanol production from xylose sugar varied and 11 hybrid fusants showed increasing average ranged from 5% to 56% more than the active parent, but the other 6 hybrid fusants showed decreasing average in ethanol production ranged from 5% to 21% less than the active parent. On the other hand, most of the tested hybrid fusants showed decrease in conversion coefficient ranged from 2% to 43% of the active parent, but F1, F2 and F16 showed 16%, 16% and 30% .respectively, increase in conversion coefficient than the active parent. Highly significant positive correlation between sugar consummation and ethanol production was indicated at (P>0.01). Keywords: D-xylose, fermentation, ethanol production, protoplast fusion, mutation, UV |
