(641c) Design Optimization By Response Surface Methodology for Continuous Fermentative Production of 1,3 Propanediol From Waste Glycerol By Product of Biodiesel Processes

The production of ~10 gallons of crude glycerol for every 100 gallons of biodiesel has led to a current glycerol excess of ~2.52Bn pounds per annum by the US biodiesel industry and non biodiesel sources.  The bio-fermentation of crude glycerol to 1, 3-propanediol, an emerging intermediate platform in biorenewable chemicals with a nascent market of $575 million worldwide,  as a value added product gives a recourse to capitalizing on the current over capacity of glycerol. This work presents the design optimization for a green and efficient process for the  batch and continuous production of 1,3 propanediol from industrial waste glycerol using soil based bacterial inoculums. The optimal process parameters for the best possible yield of 1,3 propanediol were determined using a design of experiment by varying paramaters such as pH, glycerol concentration and yeast concentration. Response surface methodology (RSM), an important branch of experimental design, was used to find the relationship between experimental parameters and the yield and biomass growth in order to find the optimal conditions for the process. The optimization of 1,3 propandeiol production, in this way, with several inputs, helps to enhance the conversion in an economic manner. pH was seen to have the most profound effect on the process both in terms of yeild as well as bacterial growth. The optimised conditions were used to run a continous fermentation and arrive at a steady state for a given dilution rate, while the inhibitory solvent effects were mitigated by cycling between acetate and butyrate laced batches. While the addition of acetate enhanced biomass growth, butyrate addition enhanced 1,3 propanediol production with distinct inhibitory effects on the growth of bacteria. The effects were utilized to systematically maximize the survival of the mixed inoculum in a continuous run.