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.

Optimization of Ralstonia solanacearum cell growth using a central composite rotational design for the P(3HB) production: Effect of agitation and aeration

“…Zafar et al (2012) [45] investigated the modeling and optimization of the poly(3-hydroxybutyrate-co-hydroxyvalerate) production from cane molasses using a bioreactor, and the effect of agitation and aeration regime on Azohydromonas lata MTCC 2311 inoculum, at 180 rpm and 30°C for 24 h. The authors reported a higher P(3HB-co-3HV) productivity of 0.163 g.L − 1 .h − 1 , which is similar to the findings of the present study. However, only the inoculum production conditions can be compared with the current study.…”

Microbial biopolymer production byMicrobacteriumWA81 in batch fermentation

“…The inhibition of PHB accumulation in presence of high oxygen could be due to the generated high shear force which was proven to inhibit the PHB biosynthesis by a number of microbes [42,43].…”

Valorization of Glycerol into Polyhydroxyalkanoates by Sludge Isolated Bacillus sp. RER002: Experimental and Modeling Studies

“…The mixture was filtered and treated with 4 volume of cold methanol to precipitate the PHA granules. The precipitates were filtered off and dried at room temperature to get the powder of PHA [32].…”

“…The analysis was carried out in an inert gas atmosphere of nitrogen at a flow rate of 100 mL/min in the temperature range from 25 to 350°C with a heating rate of 10°/min. The temperatures of melting and decomposition were determined as the temperature of corresponding endothermic maxima [32].…”