Improvement of aflatoxin B1 degradation ability by Bacillus licheniformis CotA-laccase Q441A mutant

Yanrong Liu; Yongpeng Guo; Limeng Liu; Yu Tang; Yanan Wang; Qiugang Ma; Lihong Zhao

doi:10.1016/j.heliyon.2023.e22388

Improvement of aflatoxin B₁ degradation ability by Bacillus licheniformis CotA-laccase Q441A mutant

Heliyon. 2023 Nov 13;9(11):e22388. doi: 10.1016/j.heliyon.2023.e22388. eCollection 2023 Nov.

Authors

Yanrong Liu¹, Yongpeng Guo², Limeng Liu¹, Yu Tang¹, Yanan Wang¹, Qiugang Ma¹, Lihong Zhao¹

Affiliations

¹ State Key Laboratory of Animal Nutrition and Feeding, Poultry Nutrition and Feed Technology Innovation Team, College of Animal Science and Technology, China Agricultural University, Beijing, 100193, PR China.
² College of Animal Science and Technology, Henan Agricultural University, Zhengzhou, 450046, PR China.

Abstract

Aflatoxin B₁ (AFB₁) contamination seriously threatens nutritional safety and common health. Bacterial CotA-laccases have great potential to degrade AFB₁ without redox mediators. However, CotA-laccases are limited because of the low catalytic activity as the spore-bound nature. The AFB₁ degradation ability of CotA-laccase from Bacillus licheniformis ANSB821 has been reported by a previous study in our laboratory. In this study, a Q441A mutant was constructed to enhance the activity of CotA-laccase to degrade AFB₁. After the site-directed mutation, the mutant Q441A showed a 1.73-fold higher catalytic efficiency (k_cat/K_m) towards AFB₁ than the wild-type CotA-laccase did. The degradation rate of AFB₁ by Q441A mutant was higher than that by wild-type CotA-laccase in the pH range from 5.0 to 9.0. In addition, the thermostability was improved after mutation. Based on the structure analysis of CotA-laccase, the higher catalytic efficiency of Q441A for AFB₁ may be due to the smaller steric hindrance of Ala441 than Gln441. This is the first research to enhance the degradation efficiency of AFB₁ by CotA-laccase with site-directed mutagenesis. In summary, the mutant Q441A will be a suitable candidate for highly effective detoxification of AFB₁ in the future.

Keywords: Aflatoxin B1; Bacillus licheniformis; CotA-laccase; Site-directed mutagenesis.