Protein-mediated degradation of aflatoxin B₁ by Pseudomonas putida

Degradation or the removal of aflatoxin B₁ from agriculture commodities is very important because of its acute toxicity and economic loss due to rejection of about 25% contaminated agri produce. The present study aimed at using Pseudomonas putida for the aflatoxin B₁ (AFB₁) degradation and to understand the mechanism involved. AFB₁ degradation was studied with P. putida culture, culture supernatant, cell lysate, cell lysate in the presence of protease inhibitor, and heat-inactivated cell lysate. The remaining AFB₁ was qualitatively and quantitatively measured by thin-layer chromatography and HPLC with a UV detector. P. putida culture and culture supernatant showed 80% reduction in AFB₁ within 24 h of incubation. Cell lysate and the lysate in the presence of protease inhibitor showed the same reduction in 6 and 4 h respectively. The protease-inhibited lysate showed greater thermostability, broad pH range, and tolerance to some of the solvents and detergents in terms of aflatoxin B₁ degrading activity. The heat-inactivated lysate showed only 20% reduction in 24 h of incubation indicating loss of activity on heating. As cell-free supernatant and cell lysate are capable of reducing AFB₁ effectively, actively growing cells are not necessary for degradation. The active principle for degradation might be proteinaceous; therefore, heat-inactivated lysate is ineffective for reducing the AFB₁. These results showed that degradation of aflatoxin B₁ by P. putida might be an enzymatic process and could be used in a broad range of conditions.