A Review of Research Progress on the Microbial or Enzymatic Degradation and Mechanism of Aflatoxin B1

Abstract

. AFBO can bind to the N 7 position of guanine in DNA, forming an AFB1-N 7guanine adduct, which induces transversion mutations from GC to TC [9,10].This process leads to cellular damage, genetic mutations, and tumor development, making it the most toxic site of AFB1.The second toxic site is the lactone ring within the coumarin nucleus, which is prone to opening in alkaline conditions to form sodium or ammonium salts, thereby reducing its toxicity.The cleavage of the lactone ring in AFB1 results in a nonfluorescent compound, with a 450-fold decrease in mutagenicity and an 18-fold reduction in toxicity [11].The third toxic site is located on the cyclopentenone ring of AFB1, specifically at positions 1, 2, 3, and 14.The detoxification pathway for this site generally involves hydroxylation of the cyclopentenone ring [12].The liver is the primary target organ for AFs, with AFB1 capable of causing hepatitis, liver cancer, and even death.It is a potent carcinogen [13,14].Therefore, different countries and regions have established specific limits for AFB1 in various food products.For example, the European Commission has stipulated that the maximum allowable level of AFB1 in any product intended for direct human consumption is 2 g/kg.Due to the high toxicity and widespread occurrence of AFB1, the prevention and degradation of AFB1 in food are essential.Current preventive strategies mainly involve the application of pesticides and antimicrobial agents before grain harvest, and post-harvest drying, storage, vacuum packaging, preservatives, and pesticide use to reduce the contamination of grains by AFs.However, these preventive measures cannot completely eliminate aflatoxin contamination.Aflatoxins (AFs) are secondary metabolites produced by toxigenic Aspergillus species, which are highly toxic and exhibit carcinogenic, mutagenic, and teratogenic properties, posing a significant threat to human and animal health.Cereals and their products are the primary targets for aflatoxinproducing fungal contamination, causing substantial losses to the livestock and food industries.Due to the high toxicity and widespread contamination of aflatoxin B1 (AFB1), the prevention and degradation of AFs in cereals and their products are essential.This review summarizes the AFB1degrading bacteria, such as Bacillus, Actinomycetes, and -Proteobacteria, as well as fungi, including Aspergillus and Basidiomycota.It also provides an overview and discussion of the chemical structures and toxicity of the degradation products.Additionally, the review delves into the possible oxidative, reductive, and hydrolytic mechanisms of AFB1 enzymatic degradation.The aim of this study is to provide a reference for the biological degradation of AFB1 and to promote further research in this area.

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