Response surface methodology optimization of polyhydroxyalkanoate by recombinant bacillus megaterium pPSPHAR1/1 strain using fish processing waste production

Abstract

Polyhydroxyalkanoates (PHAs) are biomaterials that are accumulated intracellularly by bacterial cells in response to nutrient imbalances under environmental stress. Polyhydroxybutyrate (PHB) is a bioplastic that is of interest to research to find an alternative to fossil-derived plastics. The optimal physical and nutritional conditions for PHB production were investigated by varying one variable at a time. To achieve maximum PHA production, the culture conditions for B. megaterium pPSPHAR1/1 were optimized through response surface methodology (RSM). The final optimum fermentation conditions included: 13.34 (g/L) glucose; 7.28 (g/L) Na2HPO4; 4.45 (g/L) K2HPO4; MgSO4 0.2; 2 (g/L) (NH4)2SO4; NH4Fe(III) citrate 0.005 %; acid citric 0.1 %; 2 Ml of trace minerals, 3 (%w/v) fish oil; 1.3 (%v/v) fish extract; inoculum size, 10 % (v/v)and temperature of 37 oC for 72 h. Using the optimal medium, the PHB production of this recombinant strain accumulated a PHB content of about 76.2 % per cell dry weight in a 5 L stirred bioreactor.