Tuesday, April 30, 2013
Exhibit Hall
1,3 propanediol was produced by batch fermentation of pure and industrial glycerin. Yields of up to 0.67 - 0.8mol of 1,3 PD /mol of glycerol were obtained under pH control with a mixed bacterial culture grown from organic farm soils in selective media. The total solvent yield was higher with batches carried out under pH control compared to those with no pH control. While the total solvent production increased at lower pH, there was little or no change in ethanol production. The production of 1,3 propanediol may occur via an oxidative pathway through pyruvate formation and 3-hydroxyprionaldehyde, while the production of ethanol may be part of a reductive pathway via the dihydroxyacetone intermediate. The solvent production patterns of this natural innoculum may be similar to C. butyricum where 1,3 propanediol and ethanol arise from separate pathways, and therefore may not vary concomitantly. The bacterial inoculum also showed good resistance to ~ 6 - 7% by weight of excess phosphates in the glycerol obtained from continuous biodiesel production. The feed nutrient composition had a profound effect on the fermentative behavior of the mixed innoculum. While acetic acid was the dominant product with one composition, it was completely eliminated by using a different nutrient composition in industrial glycerol fermentation. The disparate fermentative results with different nutrient compositions present interesting indications to the presence of different bacterial species.