Growth and 1, 3-propanediol Production on Pre-Treated Sunflower Oil Bio-Diesel Raw Glycerol Using a Strict Anaerobe-Clostridium butyricum

The objectives of the present investigation were to evaluate the pre-treated sunflower oil biodiesel raw glycerol for the growth and 1,3-propanediol (1,3-PD) production by Clostridium butyricum DSM 5431. The growth inhibition percentages of Clostridium butyricum DSM 5431 on grade A (pH, 4.0) and grade B (pH, 5.0) pre-treated sunflower oil biodiesel raw glycerol (SOB-RG) were almost similar to those of pure glycerol at 20 g glycerol L-1 i.e., 18.5±0.707 to 20.5±0.7% inhibition. In grade A raw glycerol, the growth inhibition was reduced from 85.25±0.35 to 32±1.4% (about 53.2% reduction) at 40 g glycerol L-1 by giving a two times washing to grade A raw glycerol with n-hexanol (grade A-2). When two times n-hexane washed grade AH-2 raw glycerol was employed a reduction of 42.9% was observed which is significantly lower as compared to that of grade A-2 raw glycerol. In anaerobic fed-batch cultures, 42 and 45 g L-1 of 1, 3-PD was accumulated in the fermented broth at the expense of 85 and 87.8 g L-1, giving almost similar yields, i.e., 0.51 and 0.49 g 1,3-propanediol per g of pure and grade A-2 raw glycerol, respectively. The kinetic parameters for 1,3-propanediol formation and glycerol consumption in anaerobic fed-batch cultures did not differ significantly, thus suggesting the feasibility of pre-treated sunflower oil bio-diesel raw glycerol fermentation to 1,3-propanediol.