Abstract
The presence of lignin and its derivatives in pulp effluent increases the pollution load on the environment. With an aim of better degradation and decolourization of wastewater, this study proposes the utilization of different ligninolytic enzymes from novel bacterial strains. Four novel bacterial strains of Klebsiellapneumoniae (K. pneumoniae strains NITW715076, NITW715076_1, NITW715076_2 and NITW715076_3) were isolated and identified. The ligninolytic enzymes were characterized by plate assay method. For the optimization of various process parameters of effluent sample, different approaches were used like one factor at a time and statistical optimization through response surface methodology (RSM). Further to validate the above data, enzyme activity, total phenolic concentration, GC–MS analysis and seed germination test were also performed. The ligninolytic enzymes produced were characterized as laccase and Manganese peroxidase (MnP). In lignin degradation and decolourization studies, consortia 1 (K. pneumoniae NITW715076_2 + K. pneumoniae NITW715076_1) (82.31%) was found more effective when compared to axenic culture (K. pneumoniae NITW715076_2) (74.1%). In RSM studies, Laccase and MnP activities were increased by 20% and 18%, respectively, as compared to one factor at a time optimization method. In addition, the enzyme activity for laccase and MnP after prediction by RSM was found 53338 IU/L and 147900 IU/L, respectively. The R2 values for both the enzymes were found to be significant. Further, GC–MS analysis also showed the degradation of different organic pollutants in effluent. Lastly, the seed germination test using consortia 1 corroborated the evidence of detoxification of industrial effluent. Effluent treated by consortia 1 showed better results in degradation and decolourization of lignin and their derivatives. Therefore, consortia 1 can be used for various industrial purposes like fruit juice clarification, diagnostic purposes and enhanced bioethanol production.
Highlights
Pulp and paper industries utilize lignocellulosic components of plants and chemicals during the process of manufacturing and cause environmental pollution due to discharge of waste material into the environment
This work completely focused on bacterial isolates as it does not require solid medium and can withstand extreme pH and temperature conditions(de Gonzalo et al 2016)
Out of 25 bacterial strains which were isolated from effluent sample, four strains have displayed the positive response for the degradation of ligninolytic enzymes
Summary
Pulp and paper industries utilize lignocellulosic components of plants and chemicals during the process of manufacturing and cause environmental pollution due to discharge of waste material into the environment. Applied Water Science (2018) 8:111 such as respiratory effects, oxidative stress, liver damage and genotoxicity (Hubbe et al 2016). Conventional treatment methods such as lignin precipitation by acids followed by burning are in use, but they are very costly, inefficient and produce huge amount of sludge which is difficult to handle. Pulp and paper industries 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)
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