Utilization of pulp and paper industrial wastewater for production of polyhydroxybutyrate by Bacillus sonorensis NAM5

Abstract

Given the environmental pollution caused by petroleum-based plastics, finding alternative substitutes for sustainability has become critical. Polyhydroxybutyrate (PHB), a storage food material that is accumulated by several bacteria, is biodegradable, safe, environment friendly and comparable to conventional plastics. However, scale-up is an issue due to high production cost. Substrate replacement using renewable, plentiful, sustainable and low-cost carbon sources derived from industrial waste facilitates waste reduction, while also enabling the synthesis of value-added products. In this context, inexpensive pulp and paper industrial waste as carbon source was exploited for production of PHB by using previously isolated (Source: hot springs of Manikarn, Himachal Pradesh, India) thermophilic bacteria Bacillus sonorensis NAM5 under optimized conditions in a fermenter. Production was done in a fermenter under optimized conditions (72 h of incubation at 50 °C temperature and 7 pH) to enhance the accumulation of PHB. The bacterial strain was able to produce 5.28 ± 0.11 g L⁻¹ after 72 h of growth without any carbon and nitrogen source supplementation to the industrial effluent. The culture accumulated 66% PHB of cell dry weight (CDW). The produced polymer was characterized through FTIR, NMR and TGA. Additionally, bacteria-treated industrial wastewater was used for phytotoxicity assay on agriculturally important crops such as wheat, maize and mung, which exhibited considerable difference in growth parameters.