Isolation and characterization of alkalotolerant bacteria and optimization of process parameters for decolorization and detoxification of pulp and paper mill effluent by Taguchi approach

Abstract

Four different bacterial strains were isolated from pulp and paper mill sludge in which one alkalotolerant isolate (LP1) having higher capability to remove color and lignin, was identified as Bacillus sp. by 16S RNA sequencing. Optimization of process parameters for decolorization was initially performed to select growth factors which were further substantiated by Taguchi approach in which seven factors, % carbon, % black liquor, duration, pH, temperature, stirring and inoculum size, at two levels, applying L-8 orthogonal array were taken. Maximum color was removed at pH 8, temperature 35°C, stirring 200 rpm, sucrose (2.5%), 48 h, 5% (w/v) inoculum size and 10% black liquor. After optimization 2-fold increase in color and lignin removal from 25-69% and 28-53%, respectively, indicated significance of Taguchi approach in decolorization and delignification of lignin in pulp and paper mill effluent. Enzymes involved in the process of decolorization of effluent were found to be xylanase (54 U/ml) and manganese peroxidase (28 U/ml). Treated effluent was also evaluated for toxicity by Comet assay using Saccharomyces cerevisiae MTCC 36 as model organism, which indicated 58% reduction after treatment by bacterium.

Review of Molecular Techniques for the Identification of Bacterial Communities in Biological Effluent Treatment Facilities at Pulp and Paper Mills

“…Mishra and Thakur (2010) conducted a related study with four bacterial strains isolated from pulp and paper mill sludge having higher capability to remove color and lignin. One of them was identified as Bacillus sp.…”

Extraction of ligninolytic enzymes from novel Klebsiella pneumoniae strains and its application in wastewater treatment

“…In another finding, Citrobacter freundii and Serratia marcescens showed the maximum decolourization at pH 8.2, temperature 34 °C and agitation speed 140 rpm (Abhishek et al 2017). Mishra and Thakur did similar work with Bacillus sp., and they observed the optimum decolourization and detoxification of pulp and paper mill effluent at pH 8.0, temperature 35 °C, agitation speed 200 rpm, sucrose-2.5% w/v, inoculum size 5%(w/v) and 10% black liquor (Mishra and Thakur 2010). From the literature review, it is confirmed that the optimum conditions such as pH, temperature, agitation speed, inoculum volume, carbon source and nitrogen source for lignin degradation and ligninolytic enzyme production in effluent differ greatly from one bacterial strain to another.…”

“…Colour of black liquor is mainly due to the presence of lignin and its derivatives and polymerized tannins. These compounds are recalcitrant in nature because of the presence of carbon-carbon biphenyl linkage (Lindholm-Lehto et al 2015;Mishra and Thakur 2010). Comprehensive treatment technology is required for decolourization and detoxification of pulp and paper mill effluent as it causes detrimental effects on human 1 3 111 Page 2 of 17 such as respiratory effects, oxidative stress, liver damage and genotoxicity (Hubbe et al 2016).…”

“…Generally, pulp and paper industries also use recovery boilers to recover and burn black liquor which is produced during delignification process of paper. Use of biological methods such as utilization of lignin-degrading microorganisms and their enzymes has become attractive because of their economical approach to treat black liquor and making it suitable for discharge in eco-friendly way, which migrates the negative impact on environment (Mishra and Thakur 2010).…”

“…Citrobacter freundii and Serratia marcescens were found to be effective in removing lignin from pulp and paper industry wastewater (Abhishek et al 2017). The importance of ligninolytic bacteria rose because of the role of bacteria in degrading lignin in aquatic ecosystem as wood-degrading bacteria have wider tolerance of pH, temperature and oxygen limitation than fungi (Mishra and Thakur 2010). Studies have been reported, wherein bacteria utilizes lignin oligomers as a sole carbon source and energy that produces enzymes and cleave inter-monomeric linkages of lignin (Rinaldi et al 2016).…”