Isolation, Screening and Optimization of Laccase-Producing Endophytic Fungi from Euphorbia milii

Abstract

The diverse group of endophytic fungi was isolated from Euphorbia milii, an ornamental plant, plated on lignin-based potato dextrose agar. The laccase-producing fungi were screened with alpha-naphthol. Initially, one variable at a time method was used for optimization of the low-cost media for laccase production, and the following parameters were used: carbon source (glucose), nitrogen source (sodium nitrate), pH (7), agitation (120 rpm), amount of mineral solution (2 mL), incubation period ( $$28\,^{\circ }\hbox {C}$$ ) and duration (5 days). The efficiency of media for laccase production was statistically analysed. The optimized laccase production in response surface model was predicted using an artificial neural network with net regression value of 0.98. The final optimum media conditions for laccase production were as follows: carbon source (sodium potassium tartrate (1.4 g/L)), nitrogen source (sodium nitrate (1 g/L)), mineral solution (1 mL), inducer (copper sulphate 0.1 g/L and potassium chloride 0.5/L), pH (5), incubation (120 rpm), temperature ( $$28\,^{\circ }\hbox {C}$$ ) and duration (7 days). The lowest laccase production in response surface model was 38.25 U/L and the highest laccase production was 122 U/L on the 7th day.