Characterization of a Novel Laccase-producing Bacillus sp. A4 and its Application in Miscanthus Degradation

Haipeng Guo, Chaoyang Lin, Shihui Wang, Dean Jiang, Bingsong Zheng, Yun Liu, Wensheng Qin

Abstract


Bacillus sp. A4 exhibiting laccase production was isolated from forest soil. Its laccase secreted into a LB medium exhibited a maximum activity of 3.9 U mg-1 protein at the optimal temperature (37 °C) and pH (6.0). The purified laccase of Bacillus sp. A4 demonstrated a low molecular mass of 33 kDa, and its optimal temperature and pH were 40 °C and 4.6, respectively, when using ABTS as a substrate. The activity of the purified laccase was significantly increased in the presence of Cu2+, methanol, and ethanol, but it was totally inhibited by L-cysteine. The laccase production of this strain was markedly stimulated when the strain was incubated with 0.5% different lignocellulosic biomasses. The highest activity of laccase (22.6 U mg-1 protein) was obtained in using algal biomass. This new strain efficiently decreased the lignin content of lignocellulose biomasses after 9 d of incubation at 37 °C, especially lignin from grasses. Further analysis showed that, compared to that of all tested biomasses, the new strain was a more efficient decomposer of the lignin of Miscanthus, which exhibited much more lignin loss and cell wall structure destruction in a short span of time. Therefore, the potential use of this strain could be advantageous for using lignin in Miscanthus for industrial processes.

Keywords


Laccase; Bacillus sp.; Miscanthus; Lignin; Scanning electron microscope

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