Process optimization for biodegradation of black liquor by immobilized novel bacterial consortium

Abstract

Present investigation deals with the optimization of biodegradation process of black liquor (BL) performed by novel bacterial consortium which consist of two indigenous bacterial strains viz., Bacillus megaterium ETLB-1 and Pseudomonas plecoglossicida ETLB-3. During the process, dextrose as carbon; sodium nitrate as nitrogen; C:N ratio (2.5:1); temperature (35°C); pH (8.0); and agitation rate (160 rpm) were observed as optimum conditions for bacterial consortium. Further, these conditions were assessed for the performance of immobilized consortium that exhibit conspicuous reduction in color (96.1%), lignin (91.5%), biological oxygen demand (96.7%), and chemical oxygen demand (86.4%) of black liquor. A maximum percent reduction of 90.7% in chlorophenols (up to 10.03 mg/L) with highest release of chloride ions i.e. 1,233 mg/L was recorded under optimum conditions. Bioligninolytic activities with the presence of lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase (LAC) was observed as 6.94 U/ml, 9.35, and 8.96 U/ml at different time intervals viz. 120, 144, and 96 h, respectively, during the biodegradation study. Further, gas chromatography/mass spectroscopy revealed presence of certain organic acids, degradation of majority of the toxic compounds, and generation of certain high-value compounds.

Keywords:

• Biodegradation
• Black liquor
• Bacterial consortium
• Parameters optimization
• Cell immobilization

Acknowledgements

AIRF, Jawaharlal Nehru University, New Delhi are thankfully acknowledged for assistance with GC/MS analysis. The authors also sincerely appreciate other laboratory facilities received from G.B. Pant University of Agriculture and Technology, Pantnagar. The authors declare that they have no conflict of interest.