Production of 1,3-Propanediol from Pure and Crude Glycerol Using Immobilized Clostridium butyricum

The present study describes the production of the value-added chemical 1,3-propanediol (1,3-PD) from crude glycerol, a waste by-product formed during biodiesel production. The efficiency, robustness, and stability of the process were improved by immobilization of the anaerobic bacterium Clostridium butyricum into a polyvinyl alcohol (PVA) hydrogel. The highest average productivity, 6.8 +/- 0.2 g/(L<bold>h</bold>), was achieved in 10 consecutive, repeated batch fermentations, with an initial concentration of pure glycerol 45.5 +/- 0.7 g/L, after 2.5 h. The highest final concentration and yield of 1,3-PD, 28.3 +/- 0.6 g/L, and 0.42 +/- 0.01 g/g, respectively, were achieved in eleven repeated batch fermentations, after increasing the initial pure glycerol concentration to 70.4 +/- 1.9 g/L. Two different types of crude glycerol, produced from used cooking oil (UCO) and rapeseed oil (RO), were tested in repeated batch fermentations, with an average productivity achieved of 2.3 +/- 0.1 and 3.5 +/- 0.3 g/(L<bold>h</bold>), respectively. The highest final concentration and yield of 1,3-PD, 12.6 +/- 0.9 g/L, and 0.35 +/- 0.02 g/g, respectively, were observed in fifteen repeated batch fermentations with RO crude glycerol. An excellent stability of the immobilized anaerobic bacteria and increase of productivity in fermentation of crude glycerol was demonstrated.