Abstract

Polyhydroxyalkalonates (PHAs) are biodegradable thermoplastics that are receiving immense attention as an alternative to petroleum derived plastics. The present study aimed to produce PHA using cheap and ecofriendly biodiesel waste glycerol as a substrate. Several PHA–producing bacterial isolates were isolated from different environmental samples and their efficacy for PHA production was assessed. Isolate Azu-IN1 showed the highest PHA production and was identified as Zobellella taiwanensis Azu-IN1 using 16S rRNA gene sequence and biochemical characterization. Factors affecting PHA production were optimized in batch fermentations. Supplementation of ammonium chloride as nitrogen source, methanol as an auxiliary carbon source, and agitation rate are the main limiting factors affecting PHA production. Maximum PHA production of 2.65 g/L at recovery yield of 50.3 (%), (w/w) was achieved after 36 h in batch fermentation using optimized medium. Enhanced PHA production of 3.73 g/L with recovery yield of 61.7 % (w/w) was obtained in fed batch fermentation. The characteristics of extracted PHA was analyzed using Fourier Transform Infrared Spectroscopy (FTIR) and proton and carbon Nuclear Magnetic Resonance (NMR) spectroscopy. This is the first report on accumulation of PHA by Zobellella taiwanensis using glycerol as the sole carbon source.

Key words: Bioplastic; PHA-production; fed-batch fermentation, glycerol; Zobellella taiwanensis.