Co-metabolism of substrates by Bacillus thuringiensis regulates polyhydroxyalkanoate co-polymer composition

Polyhydroxyalkanoate (PHA) production by Bacillus thuringiensis EGU45 was studied by co-metabolism of crude glycerol (CG) (1%, v/v), glucose (0.05-0.5%, w/v) and propionic acid (0.05-0.5%, v/v) under batch (shake flask) culture conditions. Glycerol + PA combination resulted in 15-100 mg/L PHA co-polymers with a HV content of 33-81 mol%. The addition of NH4Cl (0.5%, w/v) to CG + PA enhanced PHA production by 1.55-fold, with a HV content of 58-70 mol%. The time period of incubation of PA to the feed: CG + glucose was optimized to be 3 h after initiation of fermentation. The PHA contents were found to be stable at 1900-2050 mg/L up scaling from 0.4 to 2.0 L feed material. Biochemical characterization through GC-MS of PHA co-polymer revealed the presence of 3-hydroxydecanoate (3-HDD), 3-hydroxyoctadecanoate (3HOD), 3-hydroxyhexadecanoate (3HHD).