Abstract
The batch fermentation of 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae SU6 at different crude glycerol concentration (40-100 g l(-1)), pH (6.5-7.5) and temperature (31-40 degrees C) combined with two-phase pH-controlled strategy was investigated. Effect of feeding rate (0.10-0.15 L h(-1)) was studied in fed-batch fermentation. In batch fermentation, the optimal condition was 60 g l(-1) crude glycerol, pH control at 6.5 and cultivation temperature at 37 degrees C. The maximum 1,3-PD of 20 g l(-1), the yield of 0.34 g 1,3-PD g(-1) glycerol consumed and the productivity of 1.25 g l(-1) h(-1) were achieved at 16 hrs cultivation. The by-products were acetic acid and succinic acid at 2.7 and 1.1 g l(-1), respectively. Two-phase pH-controlled strategy gave better results (24.95 g l(-1) 1,3-PD and 1.78 g l(-1) h(-1) productivity) than constant pH-controlled strategy (20 g l(-1) and 1.25 g l(-1) h(-1), respectively) at 16 hrs incubation. In fed-batch fermentation, the maximum 1,3-PD of 45.35 g l(-1) was achieved at constant feeding rate of 0.1 L h(-1). The yield and productivity were 0.44 g g(-1) and 1.94 g l(-1) h(-1), respectively. The fed-batch fermentation with constant feeding at 0.1 L h(-1) with two-phase pH-controlled strategy gave 2.2 folds higher 1,3 PD concentration than the batch fermentation with two-phase pH-controlled strategy. This demonstrated the great impact of combination of pH control and feeding strategies in fed-batch fermentation on enhancing 1,3-propanediol production.
