Structural and thermal characterization of PHAs produced by Lysinibacillus sp. through submerged fermentation process

Abstract

In this investigation an attempt has been made to characterize and identify Lysinibacillus sp. 3HHX by 16S-rDNA sequencing. The bacterium exhibited occurrence of PHAs granules on an average 11±1 per cell of 1.0μm length and breadth 0.72μm, revealed from TEM studies. Under optimized condition, 4.006gm/L of PHAs was extracted using hypochlorite digestion and multi-solvent extraction process. PhaC gene of ∼540bp and higher PHA synthase activity was detected at 48h of cultivation. The extracted PHAs was structurally characterized by GC–MS and 1H NMR reported to be P(3HB-co-3HDD-co-3HTD) and amorphous in nature with 112°C melting point, −11.0°C glass transition point and 114.76°C decomposition temperature detected by DSC & TGA respectively. The C/O of biopolymer disc was 1:65 as revealed from C1s and O1s spectra of XPS, that was completely biodegradable within 30 days. This biopolymer was observed to be non-cytotoxic to NIH 3T3 mouse fibroblast cells. The report is of its kind in establishing the abilities of Lysinibacillus sp. 3HHX for non-growth associated PHA co-polymer production. Moreover the biocompatible and biodegradable nature of the biopolymer conferred to its substantial biomedical applications.