Purification and characteristics of an aflatoxin B1 degradation enzyme isolated from Pseudomonas aeruginosa

Aflatoxin is a highly toxic mycotoxin produced by Aspergillus flavus and Aspergillusparasiticus fungus. Since it contaminates food and grain widely, it has seriously endanger the health of human beings and animals. Some microorganisms that exist in nature can degrade aflatoxin. In this paper, the biological AFB1 (aflatoxin B1)-degradation by Pseudomonas aeruginosa M19 was evaluated. We found that the culture supernatant of P. aeruginosa M19 added with proteinase K (Prok), SDS and heating significantly decreased degradation capacity. Pseudomonas AFB1-degrading enzyme (PADE) was purified from P. aeruginosa M19 by a three-step procedure including ammonium sulfate fractional precipitation and ion exchange chromatography and gel filtration chromatography. PADE was purified 175-fold with a recovery of 35%, and an ultimate specific activity of 6.1 × 104 U/mg was achieved. The molecular weight of PADE estimated by SDS-PAGE is about 48 kDa. PADE displayed the highest degradation activity for AFB1 at 65°C and pH 6.0. Cu2+ and Fe3+ strongly enhanced the activity, whereas Ca2+ and Zn2+ strongly inhibited the activity. These findings indicate that PADE from P. aeruginosa M19 is a promising candidate for AFB1 biodegradation.