title: Fed-batch optimization of alpha-amylase and protease-producing Bacillus subtilis using Markov chain methods.
abstract: A stoichiometry-based model for the fed-batch culture of the recombinant bacterium Bacillus subtilis ATCC 6051a, producing extracellular alpha-amylase as a desirable product and proteases as undesirable products, was developed and verified. The model was then used for optimizing the feeding schedule in fed-batch culture. To handle higher-order model equations (14 state variables), an optimization methodology for the dual-enzyme system is proposed by integrating Pontryagin's optimum principle with fermentation measurements. Markov chain Monte Carlo (MCMC) procedures were appropriate for model parameter and decision variable estimation by using a priori parameter distributions reflecting the experimental results. Using a simplified Metropolis-Hastings algorithm, the specific productivity of alpha-amylase was maximized and the optimum path was confirmed by experimentation. The optimization process predicted a further 14% improvement of alpha-amylase productivity that could not be realized because of the onset of sporulation. Among the decision variables, the switching time from batch to fed-batch operation (t(s)) was the most sensitive decision variable.
authors.affiliation: Department of Chemical Engineering, University of Waterloo, N2L 3G1 Canada. swanwisa@engr.tu.ac.th
authors.forename: Wanwisa
authors.initials: W
authors.lastname: Skolpap
authors.forename: J M
authors.initials: JM
authors.lastname: Scharer
authors.forename: P L
authors.initials: PL
authors.lastname: Douglas
authors.forename: M
authors.initials: M
authors.lastname: Moo-Young
mesh_terms: D000465:Algorithms; D001412:Bacillus subtilis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D018533:Biomass; D019149:Bioreactors; D018929:Cell Culture Techniques / Q000379:methods*; D002849:Chromatography, Gas; D003470:Culture Media; D004591:Electrophoresis, Polyacrylamide Gel; D010450:Endopeptidases / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D005240:Feasibility Studies; D008390:Markov Chains; D015233:Models, Statistical; D009010:Monte Carlo Method; D015203:Reproducibility of Results; D000516:alpha-Amylases / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D003470:Culture Media; D000516:alpha-Amylases; D010450:Endopeptidases