Studies On Process Engineering Of 1,3-Propanediol Synthesis By Bioconversion

1,3-Propanediol (1,3-PD) as an important chemical product can be used as chainextender for the synthesis of lubricant, solvent and precursor in the chemical andpharmaceutical industries, in particular as a monomer for polycondensations to producepolyesters (PTT), polyethers and polyurethanes. 1,3-PD is produced by two methods:chemical synthesis and microbial conversion. Bioconversion is particularly attractive inthat they typically use renewable feedstock and do not generate toxic byproducts. In thispaper, preparation of enzyme, process of enzymatic synthesis and design of nonchargedultrafiltration membrane reactor were studied with the object of designing a newbiosynthesis method for 1,3-PD production by glycerol dehydrogenase (GDH) and1,3-propanediol oxidoreductase ( PDOR) from Klebsiella pneumoniae.The methods of cell disruption and determination of key enzyme activity of 1,3-PDproduction were established under aerobic conditions. After optimizations of medium bymethods of uniform design, artificial neural networks and genetic algorithms andfermentation conditions, the activities of GDH and PDOR were 3700 and 3840U/L. GDHand PDOR were purified by ion-exchange and affinity chromatography two-stepsprocedure simultaneously under aerobic conditions.When cells of Klebsiella pneumoniae were cultured in buffer supplementedsemicarbazide and glycerol, aerobic conversion of glycerol to 3-hydroxypropionaldehyde(3-HPA) realized. A method based on HPLC for the analysis of glycerol, 3-HPA, 1,3-PDand dihydroxyacetone (DHA) simultaneously was established.Studies on the initial velocity and product inhibition of GDH and PDOR wereconsistent with an ordered BiBi mechanism and the kinetic models of GDH and PDORwere established, respectively. Under aerobic batch operation condition, coupled reactionwith NAD(H) regeneration for production of 1,3-PD and DHA was possible. Optimumretention of native NAD(H) in noncharged ultrafiltration membrane reactor wasinvestigated. The production of 1,3-PD by Klebsiella pneumoniae in NaCS-PDMDAACmicrocapsules was studied. The encapsulated cells were fermented sequentially 10batches in shaking flasks, the maximum 1,3-propanediol productivity was 0.60g/L/h,which was 1.56 times higher than that of free cells.