Abstract:
This study aims at developing the kinetic model of Clostridium butyricum DSM 5431 for 1,3-propanediol production from glycerol in fed-batch fermenter. The first part of the study was to investigate effects of initial glycerol concentration (60-120 g/l) on 1,3-propanediol production and cell growth in 1 litre batch fermenter under 33 °C and pH 7.0. The maximum 1,3-propanediol concentration (44.75 g/l) with the production yield of 0.77 (mol/mol) was obtained from fermentation at optimal initial glycerol concentration of 80 g/l. The inhibition effect of glycerol was observed at concentration equaled to or higher than 100 g/l. Experimental results under the same fermentation conditions in a 15 litre batch fermenter revealed the maximum 1,3-propanediol concentration of 42.89 g/l with the production yield of 0.71 (mol/mol). The proposed cell model developed using MATLAB program (version 2007a) indicated multiple inhibition effects of glycerol, 1,3-propanediol, and butyric acid on Clostridium butyricum DSM 5431 growth as the following equation: Constant feeding was found by mathematical simulation to be the most suitable strategy for 1,3-propanediol productivity in fed-batch fermentation. Fed-batch experiment with 80 g/l of initial glycerol concentration and 120 g/l of glycerol concentration in feed with a constant feed rate of 0.353 l/hr was carried out to test the model accuracy. The deviation between simulated and experimental results of 2.77% was obtained demonstrating high model accuracy. The highest 1,3-propanediol concentration obtained in 15 litre fed-batch fermenter was 52.29 g/l. Fed-batch fermentation apparently gave 1,3-propanediol concentration 39.27% higher than batch fermentation. This proved that production of 1,3-propanediol is more favorable in fed-batch than batch fermentation.
