Poly β-hydroxybutyrate production by Bacillus subtilis NG220 using sugar industry waste water

Abstract

The production of poly β-hydroxybutyrate (PHB) by Bacillus subtilis NG220 was observed utilizing the sugar industry waste water supplemented with various carbon and nitrogen sources. At a growth rate of 0.14 g h(-1) L(-1), using sugar industry waste water was supplemented with maltose (1% w/v) and ammonium sulphate (1% w/v); the isolate produced 5.297 g/L of poly β-hydroxybutyrate accumulating 51.8% (w/w) of biomass. The chemical nature of the polymer was confirmed with nuclear magnetic resonance, Fourier transform infrared, and GC-MS spectroscopy whereas thermal properties were monitored with differential scanning calorimetry. In biodegradability study, when PHB film of the polymer (made by traditional solvent casting technique) was subjected to degradation in various natural habitats like soil, compost, and industrial sludge, it was completely degraded after 30 days in the compost having 25% (w/w) moisture. So, the present study gives insight into dual benefits of conversion of a waste material into value added product, PHB, and waste management.

Figure 1

Phylogenetic tree of isolate NG220.

Figure 2

(a) NMR spectra, (b) FTIR spectra, (c) thermogram by DSC analysis, and (d) GC-MS spectra of extracted PHB polymer.

Figure 3

Optimization of cultural conditions for Bacillus subtilis NG220.

Figure 4

Effect of moisture content on PHB degradation in compost.