Influence of synthetic carbon grade on the monomeric constitution of polyhydroxyalkanoate produced by Bacillus cereus AAR-1

Abstract

Three synthetic sucrose samples with varying manufacturing purity levels were selected as carbon substrates to synthesize diverse polyhydroxyalkanoates (PHAs) using a wild-type Bacillus cereus AAR-1. Comparative analyses of the extracted biopolymers were characterized using Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (1H and 13C NMR), gas chromatography-mass spectrometry (GC-MS), Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), CHNS/O elemental analysis, and X-ray diffraction (XRD). The biopolymers identified include Poly(3-hydroxytetradecanoate) (P3HTD), Poly(3-hydroxybutyrate-co-2-hydroxytetradecanoate) [P(3HB-co-2HTD)], and Poly(3-hydroxybutyrate) (P3HB). The carbon content of the biopolymers ranged from 39-53%, with no nitrogen element detected. The thermal decomposition temperature of [P(3HB-co-2HTD)] was 279 °C, surpassing the corresponding values for the other two biopolymers. Notably, the homopolymer P3HTD exhibited an increased melting temperature of 172.4 °C and a reduced crystallinity percentage (Xc %= 20%), crucial properties for bioplastics and medical sector applications. The results suggest that different carbon purity grades influenced homopolymer accumulated in Bacillus cereus AAR-1.