Characterization of the aflatoxin B1 degradation role of laccases in Stenotrophomonas acidaminiphila

Abstract:

[Objective] Characterization of the aflatoxin B1 (AFB1) degradation roles of the laccases screened from Stenotrophomonas acidaminiphila CW117. [Methods] Two laccase genes lc1 and lc2 from strain CW117 genome were screened, and their AFB1 degrading activity was examined in vitro by heterologous expressed proteins of rLC1 and rLC2 in E. coli BL21. On the basis of in vitro test, two laccase-deficient strains CW117^△lc1 and CW117^△lc1-lc2 were constructed by homologous recombination method by using suicide plasmid pK18mobsacB, and the laccases (lc1 and lc2) AFB1 degradation role on strain CW117 was validation in vivo. [Results] Laccase rLC1 showed the AFB1 degradation activity in vitro, but rLC2 did not show degradation activity. Degradation activity of rLC1 was improved by redox mediators of 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid), acetosyringone or syringaldehyde. The degrading activity of mutants CW117^△lc1 and CW117^△lc1-lc2 showed similar degradation activity to the wild-type strain CW117 in most evaluation time-points. [Conclusion] Laccase LC1 from S. acidaminiphila showed AFB1 degradation activity, and the degradation activity could be enhanced by redox mediators as previous study. However, the laccases’ contribution to AFB1 degradation in strain CW117 was minimal, and other degradation pathways existed in the strain.

Key words:detoxification;laccase;aflatoxin B1;degradation gene;mutant