Valorization of glycerol into polyhydroxyalkanoates by sludge isolated bacillus sp. RER002: Experimental and modeling studies

Abstract

In this study, the feasibility of glycerol valorization into homo- and hetero-polymers of polyhydroxyalkanoates by a sludge isolated Bacillus sp. RER002 in a 3 L bioreactor was investigated. A mathematical model including logistic, Luedeking-Piret, and Luedeking-Piret-like equations that simulated the active residual biomass growth, P(3HB) synthesis, and glycerol consumption, respectively, was developed. In order to describe the dynamics of batch P(3HB) production, the model kinetic parameters viz., μmax, K1, K2, α, β, and KN were optimized using the stochastic search-based genetic algorithm. The synthesis of P(3HB) wasobserved to be highly growth associated and partially non-growth associated as reflected in a significant higher values of K1 (0.2435-0.5477) than K2 (2.2 × 10-6 to 9.1 × 10-3) within the glycerol concentration range of 10-40 g/L. Besides, the maximum 3.2g/L of copolymer [P(3HAscl-co-3HAmcl)] was observed at 30 g/L of glycerol concentration in synthetic crude glycerol medium with a yield coefficient (YP/S) of 0.16 g/g. Furthermore, the analyses of chemical and thermal properties of copolymer P(3HAscl-co-3HAmcl) revealed its enhanced material properties which make it suitable for various applications.