Abstract
Background: The paper and pulp industry is a capital and resource-intensive industry that contributes to ecosystem toxicity and affects human beings.
Objective: The study aimed to appraise the potential of xylanases, laccases and manganese peroxidase for the bio-bleaching of paper pulp and to highlight the role of these enzymes as a promising substitute for chlorine-based chemical methods in the bleaching process.
Methods: The ligninolytic enzymes including xylanase, laccase and manganese peroxidase isolated from white rot fungi were used for pre-bleaching and bleaching of oven-dried wheat straw pulp.
Results: During the sequential enzymatic treatment of oven-dried pulp the brightness was improved and kappa number was reduced by 3.1% and 3.1 points respectively after xylanase treatment, 0.3% and 0.4 points after laccase treatment and 3% and 0.2 points after MnP treatment. During separate treatment of pulp samples with individual enzymes, brightness and kappa number improved by 8% and 3 points respectively after xylanase treatment, by 5% and 1.7 points after laccase treatment and 5% and 1.8 points after treatment with MnP. During subsequent treatment with 4% sodium hypochlorite, the brightness was further improved by 27.9 % for xylanase treated pulp and 29% for the laccase and MnP treated pulp. The xylanase was found most efficient in comparison to laccase and MnP in reduction of kappa number and improvement of brightness.
Conclusion: These results clearly indicate the role of laccase, MnP and xylanase from white rot fungi as effective bio-bleaching agents. Therefore, these enzymes can facilitate the bleaching process without threat to environment.
Keywords: Xylanase, laccase, manganese peroxidase, biobleaching, paper pulp, white rot fungi.
Graphical Abstract
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