This research was carried out to evaluate the bio-ethanol production by yeasts. Out of the 7 tested yeast
isolates, only 5 isolates were able to produce bio-ethanol efficiently during the fermentation of sugarcane molasses. It is
worthily to mention that the highest bio-ethanol producers from sugarcane and sugar beet molasses were Saccharomyces
cerevisiae F15 (S. cerevisiae) followed by Candida kefyr EMCC77 (C. kefyr). Therefore, they were selected for further
experiments. Regarding the effect of environmental factors on bio-ethanol yield, the optimum pH values for bioethanol yield were 4.5 and 5 for S. cerevisiae and C. kefyr respectively. Whereas the optimum incubation temperature
for bio-ethanol production for both S. cerevisiae and C. kefyr was 32oC. Maximum production of bio-ethanol by S.
cerevisiae and C. kefyr was optimally obtained after 48hours incubation period. Under all optimum conditions, S.
cerevisiae gave bio-ethanol yield from sugar cane molasses higher than that obtained by C. kefyr and vice versa in case of
sugar beet molasses. Finally, immobilized cell technique showed better results in bio-ethanol production than free cells.
In view of the obtained results, it could be recommended that the S. cerevisiae and C. kefyr can be used for industrial
production of bio-ethanol. |
