Decolorization of Distillery Effluent by the Novel Bacterial Strain Bacillus nitratireducens (B2)

Abstract

As sugarcane molasses is converted into ethanol, a sizable volume of effluent with high biochemical oxygen demand (BOD) and chemical oxygen demand(COD) is generated. This effluent contains melanoidin. Melanodin is a chemical broken down by certain bacteria and can produce peroxidases, phenoxidases, laccases, and mono- and dioxygenases. The primary function of these bacteria is to break down complex hydrocarbons, including aromatics such as coloring pigments. This study aimed to identify melanoidin-decolorizing microorganisms in natural resources that are thermally resistant and have the potential to be used in industrial-scale distillery treatment for effluent applications. A total of 55 distinct isolates were tested on a solid medium, including molasses pigments. Three thermotolerant bacterial isolates were identified as melanoidin-decolorizing agents: Bacillus nitratireducens (B2), Bacillus paramycoides (B1), and Brucellatritici (B3). These isolates under went additional optimization for decolorization under various physicochemical and nutritional conditions. At 40°C, B. nitratireducens (B2) exhibited the highest degree of decolorization (86%) among the three species while using 0.5% glucose(w/v), 0.5% peptone(w/v), 0.05% MgSO4, and 0.01% KH2PO4 at a pH of 6.0 over 40 h of incubation under static conditions. In submerged fermentation, the B2 strain of B.nitratireducens can withstand higher temperatures and requires only a small amount of carbon (0.5%, [w/v]) and nitrogen sources (0.5%, [w/v]). Therefore, it is feasible to use melanoidin on an industrial scale to decolorize distilled effluents.