title: Modeling and optimization of poly(3hydroxybutyrate-co-3hydroxyvalerate) production from cane molasses by Azohydromonas lata MTCC 2311 in a stirred-tank reactor: effect of agitation and aeration regimes.
abstract: The effects of agitation and aeration rates on copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] production by Azohydromonas lata MTCC 2311 using cane molasses supplemented with propionic acid in a bioreactor were investigated. The experiments were conducted in a three-level factorial design by varying the impeller (150-500 rev min(-1)) and aeration (0.5-1.5 vvm) rates. Further, the data were fitted to mathematical models [quadratic polynomial equation and artificial neural network (ANN)] and process variables were optimized by genetic algorithm-coupled models. ANN and hybrid ANN-GA were found superior for modeling and optimization of process variables, respectively. The maximum copolymer concentration of 7.45 g l(-1) with 21.50 mol% of 3HV was predicted at process variables: agitation speed, 287 rev min(-1); and aeration rate, 0.85 vvm, which upon validation gave 7.20 g l(-1) of P(3HB-co-3HV) with 21 mol% of 3HV with the prediction error (%) of 3.38 and 2.32, respectively. Agitation speed established a relative high importance of 72.19% than of aeration rate (27.80%) for copolymer accumulation. The volumetric gas-liquid mass transfer coefficient (k (L) a) was strongly affected by agitation and aeration rates. The highest P(3HB-co-3HV) productivity of 0.163 g l(-1) h(-1) was achieved at 0.17 s(-1) of k (L) a value. During the early phase of copolymer production process, 3HB monomers were accumulated, which were shifted to 3HV units (9-21%) during the cultivation period of 24-42 h. The enhancement of 7.5 and 34% were reported for P(3HB-co-3HV) production and 3HV content, respectively, by hybrid ANN-GA paradigm, which revealed the significant utilization of cane molasses for improved copolymer production.
authors.affiliation: Department of Chemical Engineering, Indian Institute of Technology Roorkee, Roorkee, 247 667, Uttarakhand, India.
authors.forename: Mohd
authors.initials: M
authors.lastname: Zafar
authors.forename: Shashi
authors.initials: S
authors.lastname: Kumar
authors.forename: Surendra
authors.initials: S
authors.lastname: Kumar
authors.forename: Amit K
authors.initials: AK
authors.lastname: Dhiman
mesh_terms: D000421:Alcaligenes / Q000378:metabolism*; D000465:Algorithms; D019149:Bioreactors; D007218:Industrial Microbiology; D008965:Molasses; D011091:Polyesters / Q000378:metabolism*; D054813:Polyhydroxyalkanoates / Q000378:metabolism; D011422:Propionates / Q000378:metabolism; D031786:Saccharum; D000094122:Polyhydroxybutyrates
chemical_list: D011091:Polyesters; D054813:Polyhydroxyalkanoates; D011422:Propionates; C052620:poly(3-hydroxybutyrate)-co-(3-hydroxyvalerate); D000094122:Polyhydroxybutyrates; C029658:propionic acid