Isolation, identification of a laccase-producing fungal strain and enzymatic properties of the laccase.

A new type of thermostable laccase was isolated from sp. GZS18, and its partial enzymatic properties were determined. A strain GZS18 of laccase with high yield was screened from forest soil and identified as sp. GZS18 through morphological characteristics and ITS sequence analysis. The laccase of sp. GZS18 (Lac-P) was obtained through cation-anion exchange chromatography, gel filtration chromatography, and other purification processes. The testing result shows that Lac-P is a single protein of 75 kDa, and the 11 amino acid sequences in the N-terminal are AXVSVASREMT (X was the non-standard protein). The optimum temperature and optimum pH of lac-P activity are substrate-independent. The temperature is in the range of 50-70 °C, and pH has high catalytic efficiency in the acidic range. Lac-P has good stability in the temperature and pH. The half time at 70-60 °C is 1.5 and 4 h, respectively. At pH 6-9 and room temperature, there is more than 80% activity 24 h later. Lac-P is tolerant of most metal ions and low concentrations of inhibitors but is inhibited by Hg, Fe and NaN. The laccase from sp. GZS18 at high temperature and pH 6-9, with strong stability, has better industrial application characteristics.