Optimization of Process Parameters for Production of Poly(3-hydroxybutyrate) by Bacillus pumilus AHSD 04, a Seed Borne Endophyte of Oleaginous Plant Arachis hypogaea L.

Abstract

Endophytic bacteria, which thrive inside the plants, synthesize and accumulate intracellular biopolymer polyhydroxyalkanoates (PHAs) to strive against the hostile plant environment. The present study is focused on enhancing the production of poly(3-hydroxybutyrate) [P(3HB)], the most common PHA by the seed endophytic bacterium Bacillus pumilus AHSD 04 (GenBank accession number KY038573; MCC accession number 3573) isolated from the oleaginous plant Arachis hypogaea L. Interactions among the three most important influencing variables, glucose, tryptose, and initial pH affecting growth and P(3HB) production were studied using the central composite design (CCD) of response surface methodology (RSM). A 3.94-fold enhancement of P(3HB) production (5.36 g/L) was achieved over that of the 'one variable at a time' method. The isolate also produced co-polymers of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) [P(3HB-co-3HV)] with the incorporation of 4.98 mol% 3HV during dual-step cultivation using glucose and valeric acid as co-substrate. The polymers, P(3HB) and P(3HB-co-3HV), so produced have been validated and characterized by Fourier transform infrared (FTIR) and 1H nuclear magnetic resonance (1H NMR) spectroscopic analysis. It is apparent that RSM has been successfully established as a promising tool to increase P(3HB) yield by the seed endophyte B. pumilus AHSD 04, which can further be utilized to scale up the production of these biodegradable polymers of industrial importance.