Biotransformation of aflatoxin B₁ by Lactobacillus helviticus FAM22155 in wheat bran by solid-state fermentation

Lactobacillus helveticus FAM22155 was the most efficient among five lactic acid bacteria at removing aflatoxin B₁ (AFB₁) during solid-state fermentation on wheat bran substrate. The mechanism of removal was explored by comparing different fermentation modes. Liquid fermentation had little effect on the breakdown of AFB₁. However, a protein extract from the fermented bran was equally effective at degrading aflatoxin B₁ as living cell digestion. After treatment with heat and protease K, the degrading capacity of the protein extract was significantly reduced. Taken together, the observed biotransformation of AFB₁ was mainly associated with proteins produced during bran fermentation. Four products of U-[¹³C₁₇]-AFB₁ were found by mass spectrometry, including Ⅱ-1 (C₁₁H₁₀O₄), Ⅱ-2 (C₁₁H₁₀O₄), III (C₁₅H₁₂O₅), and IV (C₁₄H₁₀O₄). These products all lack the lactone ring indicating lower toxicity than aflatoxin B₁.