Batch ethanol fermentations from sweet sorghum juice by
Saccharomyces cerevisiae
NP 01 were carried out in a 500 ml air-locked Erlenmeyer flask under very high gravity (VHG) and static conditions. The maximum ethanol production efficiency was obtained when 9 g l
-1 of yeast extract was supplemented to the juice. The ethanol concentration (
P), productivity (
Qp) and yield (Yp/s) were 120.24 ± 1.35 g l
-1, 3.01 ± 0.08 g l
-1 h
-1 and 0.49 ± 0.01, respectively. Scale up ethanol fermentation in a 5-litre bioreactor at an agitation rate of 100 rev min-1 revealed that
P,
Qp and Yp/s were 139.51 ± 0.11 g l
-1, 3.49 ± 0.00 g l
-1 h
-1 and 0.49 ± 0.01, respectively, whereas lower
P (119.53 ± 0.20 g l
-1) and
Qp (2.13 ± 0.01 g l
-1 h
-1) were obtained in a 50-litre bioreactor. In the repeated-batch fermentation in the 5-litre bioreactor with fill and drain volume of 50% of the working volume, lower
P and
Qp were observed in the subsequent batches.
P in batch 2 to 8 ranged from 103.37 ± 0.28 to 109.53 ± 1.06 g l
-1.
