3.2. Enhancement of T. trogii Berk S0301 laccase production
Production of laccase is affected by many fermentation factors including carbon and nitrogen sources in the medium, metal ions (especially Cu2+), and phenolic and aromatic compounds related to lignin or lignin derivatives (Janusz et al., 2013). In this study, carbon and nitrogen sources and Cu2+ were tested for elevation of enzyme production. Fructose and glucose were found to be optimal among the eight carbon sources tested, with the highest laccase activities of 8.5 and 7.9 U mL−1, respectively (Fig. 1a). The highest laccase activity was 11.1 U mL−1, which was observed in culture medium with 20 g L−1 peptone and yeast extract mixture (1:1), designated medium-N culture (Fig. 1b). Cu2+ exerted an obvious effect on the induction of laccase production with the highest laccase activity of 30.9 U mL−1at the concentration of 1.5 mM relative to the control without Cu2+ (0.893 U mL−1) (Fig. 1c). Among the surfactants tested, CTAB and SDS inhibited laccase activity, but Tween 80 and PEG 4000 had no effect at a concentration of 0.05 g L−1. Furthermore, Tween 80 was tested at various concentrations (0–12 g L−1) and the enzyme activity was enhanced up to 5.6-fold (approx. 68 U mL−1) with the addition of 7 g L−1 Tween 80 (Fig. 1d). In addition, no MnP activity was detected.