Biorefining Polyvinyl Alcohol (PVA) by Enterobacter cloacae and its Polyhydroxy Butyrate (PHB) Production Ability

Polyvinyl alcohol (PVA) is a synthetic polymer widely used for industrial applications and having negative impacts on the environment. In this work, we present a novel, potent PVA degrader, MBB8, isolated from the Gulf of Mannar. MBB8 was identified as Enterobacter cloacae based molecular analysis using 16S rRNA gene sequence as well as biochemical and evolutionary distance analysis. This is the first report of a PVA degrader from the Enterobacter genus. The results showed 83% of the PVA present in the culture medium was degraded by E. cloacae MBB8 after 48 h of incubation with 30°C at 145 rpm agitation. The results obtained from FTIR showed notable differences in PVA-degradation stretches (3,000 to 3,300 cm−1 and 2,500 to 3,000 cm−1) at 24 and 48 h, respectively, compared with control (before degradation of PVA). The effects of carbon and nitrogen sources for PVA degradation were also identified. The results revealed nitrogen sources significantly increase PVA-degrading enzyme production (83 U/mL enzyme activity). Furthermore, culturing E. cloacae MBB8 in M9 minimal medium containing 1% PVA accumulated polyhydroxyl butyrate (PHB) inside the cell. The PHB was purified and characterized by UV-spectroscopy. Further, the PHB was chemically converted into monomer and studied using gas chromatography coupled mass spectrometry (GC-MS). Overall, our results suggest that E. cloacae MBB8 is capable of degrading PVA and accumulate PHB that could be exploited industrially.