High production of 1,3-propanediol from industrial glycerol by a newly isolated Clostridium butyricum strain

Batch and continuous cultures of a newly isolated Clostridium butyricum str ain were carried out on industrial glycerol, the major by-product of the bi o-diesel production process. For both types of cultures, the conversion yie ld obtained was around 0.55 g of 1,3-propanediol formed per 1 g of glycerol consumed whereas the highest 1,3-propanediol concentration, achieved durin g the single-stage continuous cultures was 35-48 g l(-1). Moreover, the str ain presented a strong tolerance at the inhibitory effect of the 1,3-propan ediol, even at high concentrations of this substance at the chemostat (e.g. 80 g l(-1)). 1,3-Propanediol was associated with cell growth whereas aceta te and butyrate seemed non growth-associated products. At low and medium di lution rates (until 0.1 h(-1)), butyrate production was favoured, whereas a t higher rates acetate production increased. The maximum 1,3-propanediol vo lumetric productivity obtained was 5.5 g l(-1) h(-1). A two-stage continuou s fermentation was also carried out. The first stage presented high 1,3-pro panediol volumetric productivity, whereas the second stage (with a lower di lution rate) served to further increase the final product concentration. Hi gh 1,3-propanediol concentrations were achieved (41-46 g l(-1)), with a max imum volumetric productivity of 3.4 g l(-1) h(-1). A cell concentration dec rease was reported between the second and the first fermenter. (C) 2000 Els evier Science B.V. All rights reserved.