Optimization of different culture conditions for enhanced laccase production and its purification from Tricholoma giganteum AGHP

Abstract

Background: In current times, enzyme-catalyzed reactions have gained importance for the development of new chemical processes. These require the production of large quantity of enzyme at low cost. Solid-state fermentation (SSF) is an efficient process because this bioprocess has a potential to convert agro-industrial residues into valuable compounds. Hence, the current study focuses on the optimization of process parameters for the higher production of laccase using a novel basidiomycete fungi Tricholoma giganteum AGHP under solid-state fermentation (SSF). Further, the purification of laccase using column chromatographic technique was performed. Results: Various physico-chemical parameters were evaluated and maximum production obtained was 2.69 × 105 U/g using wheat straw as a dry substrate. Optimum pH was found to be 5.0 and the temperature of 30 °C with 0.3 mM copper as an inducer. The enzyme was purified from the initial protein preparation by two-step column chromatography. A yield of 10.49 % with 3.33-fold purification was obtained using Sephadex G-75 gel permeation chromatography. Further increase in purification (total) was found to be 10.80-fold with a yield of 8.50 % using DEAE Sephadex A-50 ion exchange column chromatography. The purified enzyme was identified as a monomeric protein with a molecular weight of 66 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Conclusion: In view of the results obtained, we can conclude that the extracellular laccase production is governed by various cultural parameters such as pH, temperature, and the composition of culture medium. “One-factor-at-a-time” methodology was capable of establishing the optimum conditions that significantly increases the enzyme production several folds using lignocellulosic substrate. Therefore, laccase from T. giganteum AGHP has a potential in several industrial applications.