Effect of glucose and olive oil as potential carbon sources on production of PHAs copolymer and tercopolymer by Bacillus cereus FA11.

Abstract

In this study, the influence of different physicochemical parameters on the yield of polyhydroxyalkanoates (PHAs) produced by Bacillus cereus FA11 is investigated. The physicochemical factors include pH, temperature, time, inoculum size and its age, agitation speed and composition of the glucose rich peptone deficient (GRPD) medium. During two-stage fermentation, B. cereus FA11 produced a significantly high (p<0.05) yield (80.59% w/w) of PHAs copolymer using GRPD medium containing glucose (15g/L) and peptone (2g/L) at pH 7, 30°C and 150rpm after 48h of incubation. On the other hand, the presence of olive oil (1% v/v) and peptone (2g/L) in the GRPD medium resulted in biosynthesis of tercopolymer during two-stage fermentation and the yield of tercopolymer was 60.31% (w/w). The purified PHAs was characterized by Fourier transform infrared spectroscopy and proton resonance magnetic analysis. Proton resonance magnetic analysis confirmed that the tercopolymer was comprised of three different monomeric subunits, i.e., 3-hydroxybutyrate, 3-hydroxyvalerate and 6-hydroxyhexanoate.