Screening for Potential Laccase Producers from Trichoderma Strains Isolated from Riau Citrus Rhizosphere and Palm Tree Plant Parts

Abstract

The enzyme laccase has wide biotechnology applications in the textile, pulp, food and pharmaceutical industry. Fungal laccases have higher redox potential than bacterial laccases, therefore are more preferred for industry. This study aimed to screen for potential laccase producers from several Trichoderma strains isolated from citrus rhizosphere and as endophytes of palm trees. Four strains were initially screened in a qualitative colour assay on PDA supplemented with substrate indicators of laccase. The qualitative assay showed that Trichoderma asperelloides LBKURCC2 demonstrated strong laccase activity on PDA supplemented with guaiacol or 2,2'-azino-di-3-ethylbenzotiazol-6-sulfonate (ABTS). Trichoderma virens LBKURCC70, 71 and 85 showed very week laccase activity on media supplemented with guaiacol, and no detectable laccase on media supplemented with ABTS. Quantitative assays for laccase activity were performed on crude enzyme extracts from solid state fermentation systems with rice straw as the laccase inducer, and the test fungal strain as the prospective producer. From the quantitative assays it was found that T. asperelloides LBKURCC2 produced the highest laccase activity (208 ± 76 U/L). Laccase activity produced by T. virens LBKURCC70 was 19 ± 5 U/L, while there were no detectable laccase activities produced by T. virens LBKURCC71 and 85.