Fermentative Production Of 1,3-Propanediol From Industrial Glycerol And Its Pervaporative Enrichment From Aqueous Mixture

A paradigm shift towards renewable feedstocks has given rise to a fast growing global market for biorenewable chemicals, of which, glycerin is a major platform chemical. Industrial glycerol production as a byproduct of the biodiesel and other industries has led to an over capacity with issues related to its disposal. Fermentation of this crude glycerol to 1,3-propanediol as a value added product may provide a recourse to capitalizing on the current over capacity. This thesis explores the fermentative production of 1,3-propanediol from industrial glycerol using a soil based bacterial inoculum and the development of several families of polymers as pervaporation membranes for enriching 1,3-propanediol from dilute aqueous broths. The first part of the thesis studies and optimizes the yield of 1,3-propanediol from industrial glycerol using an organic soil based inoculum with various process parameters. The optimized parameters are used to run CSTR experiments wherein the specific 1,3-propanediol productivity is shown to increase with dilution rate. In addition to substrate, the real process bottleneck in fermentative 1,3-propanediol production lies in high energy costs of concentration enrichment. While pervaporation is energetically advantageous, the proximity of the solubility parameters of 1,3-propanediol with those of water preclude the usage of conventional membrane materials for enrichment from dilute aqueous broths. The second part of the thesis concerns development of three polymer families– cyclohexylamine functionalized siloxanes, cyclohexylamine based methacrylates and imidazolium dibutylphosphate ionic liquid based methacrylates - with progressively increasing separation factors and good price–performance trade off. The final part of the thesis explores their performance with batch and continuous pervaporation to enrich 1,3-propanediol from simulated broths of compositions replicated from the CSTR fermentations. The imidazolium ionic liquid based methacrylates not only enrich 1,3-propanediol from water with highest efficiency, but also from other broth components while striking the best possible cost – performance balance. The development and fine tuning of such materials present themselves as steps towards possible membrane module fabrication for continuous pervaporation and hence establishment of commercially viable and energy efficient alternatives to conventional purification processes