Ethanol production from sweet sorghum juice in repeated-batch fermentation by Saccharomyces cerevisiae immobilized on corncob

Ethanol fermentation from sweet sorghum juice containing 240 g/l of total sugar by Saccharomyces cerevisiae TISTR 5048 and S. cerevisiae NP 01 immobilized on low-cost support materials, corncob pieces, was investigated. In batch fermentation, S. cerevisiae TISTR 5048 immobilized on 6 x 6 x 6 mm(3) corncobs gave higher ethanol production than those immobilized on 12 x 12 x 12 mm(3) corncobs in terms of ethanol concentration (P), yield (Y (p/s) ) and productivity (Q (p) ) with the values of 102.39 +/- A 1.11 g/l, 0.48 +/- A 0.01 and 2.13 +/- A 0.02 g/l h, respectively. In repeated-batch fermentation, the yeasts immobilized on the 6 x 6 x 6 mm(3) corncobs could be used at least eight successive cycles with the average P, Y (p/s) and Q (p) of 97.19 +/- A 5.02 g/l, 0.48 +/- A 0.02 and 2.02 +/- A 0.11 g/l h, respectively. Under the same immobilization and repeated-batch fermentation conditions, P (90.75 +/- A 3.05 g/l) and Q (p) (1.89 +/- A 0.06 g/l h) obtained from S. cerevisiae NP 01 were significantly lower than those from S. cerevisiae TISTR 5048 (P < 0.05), while Y (p/s) from both strains were not different. S. cerevisiae TISTR 5048 immobilized on the corncobs also gave significantly higher P, Y (p/s) and Q (p) than those immobilized on calcium alginate beads (P < 0.05).