Purification and characterization of polyhydroxyalkanoate (PHA) from a Bacillus megaterium strain using various dehydration techniques

BACKGROUND Polyhydroxyalkanoates (PHAs) are natural biodegradable polymers synthesized by several microorganisms. Poly(3‐hydroxybutyrate) (PHB) is the most well‐characterized biopolymer produced abundantly by Bacillus species. In order to get a better PHA recovery, efficient pretreatment steps, especially dehydration, have a large impact on PHA purification from microbial PHA‐rich biomass. In this study, we have described the effects of lyophilization (‐L), microwave‐assisted drying (‐M) and ethanol/heat‐treatment (‐E) dehydration techniques on PHA production by B. megaterium NRRL B‐14308 strain. RESULTS After 66 h of batch cultivation, cells reached the maximum PHA accumulation (PHA‐L: 1.36 g L –1 , PHA‐E: 1.55 g L –1 , PHA‐M: 2.08 g L –1 ). The highest overall volumetric productivity for PHA was obtained as 0.226 g L –1 h ‐1 for PHA‐M, which was 1.5‐fold higher than PHA‐L. Structural and thermal properties of PHA were characterized by GC–MS, FT‐IR, 1 H‐NMR, TGA and DSC analyses. Analyses of the accumulated PHA by GC–MS, FT‐IR and 1 H‐NMR revealed that the biopolymer was made up of 3‐hydroxybutyrate (3HB) and 3‐hydroxyvalerate(3 HV) monomers, irrespective of the dehydration technique. CONCLUSION The present study offers an alternative biomass drying technique (microwave‐assisted drying) to conventional drying techniques that is favorable in terms of energy efficiency and processing times, and should help to enhance biopolymer production processes.