Bioconversion of crude glycerol to polyhydroxyalkanoate by Bacillus thuringiensis under non-limiting nitrogen conditions

Abstract

Glycerol has emerged as a cheap waste material due to blooming biodiesel manufacturing units worldwide. The need is to exploit the crude glycerol (CG) to produce useful products such as polyhydroxyalkanoate (PHA). Bacillus thuringiensis EGU45 was found to produce 1.5-3.5 gP HA L(-1) from feed containing 1-10% CG (vv(-1)) and nutrient broth (NB, 125 mL) without any acclimatization. B. thuringiensis EGU45 could produce PHA at the rate of 1.54-1.83 g L(-1), from 1% CG (vv(-1)) on media having high nitrogen contents: (i) NB, (ii) NB+0.5% NH4Cl (wv(-1)), and (iii) peptone+yeast extract+0.5% NH4Cl (wv(-1)). B. thuringiensis EGU45 was able to produce co-polymer of P(3HB-co-3HV) with 13.4% 3HV content on high N containing feed supplemented with propionic acid. This is the first report demonstrating the abilities of B. thuringiensis to convert CG into PHA co-polymer under non-limiting N conditions.

Keywords: Co-polymer; Glycerol; Precursor substrate.