Abstract
Microbial degradation is an effective and attractive method for eliminating aflatoxin B1 (AFB1), which is severely toxic to humans and animals. In this study, Aspergillus niger RAF106 could effectively degrade AFB1 when cultivated in Sabouraud dextrose broth (SDB) with contents of AFB1 ranging from 0.1 to 4 μg/mL. Treatment with yeast extract as a nitrogen source stimulated the degradation, but treatment with NaNO3 and NaNO2 as nitrogen sources and lactose and sucrose as carbon sources suppressed the degradation. Moreover, A. niger RAF106 still degraded AFB1 at initial pH values that ranged from 4 to 10 and at cultivation temperatures that ranged from 25 to 45 °C. In addition, intracellular enzymes or proteins with excellent thermotolerance were verified as being able to degrade AFB1 into metabolites with low or no mutagenicity. Furthermore, genomic sequence analysis indicated that the fungus was considered to be safe owing to the absence of virulence genes and the gene clusters for the synthesis of mycotoxins. These results indicate that A. niger RAF106 and its intracellular enzymes or proteins have a promising potential to be applied commercially in the processing and industry of food and feed to detoxify AFB1.
Highlights
Mycotoxins, such as aflatoxins, ochratoxin A, fumonisins, deoxynivalenol, and zearalenone, are toxic metabolites that are primarily produced by fungi, including Aspergillus, Penicillium, and Fusarium, and have contaminated approximately 60–80% of the food and feed around the world [1,2]
We found that A. niger RAF106, a catechin-transforming fungus isolated from Pu-erh tea [31], could degrade aflatoxin B1 (AFB1) by 88.59% after 72 h
With regard to the influence of the initial pH on the degradation of AFB1 in A. niger RAF106, we found that the degradation mediated by A. niger RAF106 was unaffected by the initial pH values
Summary
Mycotoxins, such as aflatoxins, ochratoxin A, fumonisins, deoxynivalenol, and zearalenone, are toxic metabolites that are primarily produced by fungi, including Aspergillus, Penicillium, and Fusarium, and have contaminated approximately 60–80% of the food and feed around the world [1,2]. Aflatoxin B1 (AFB1), a bisfuranocoumarin derivative, is the most toxic contaminant and causes carcinogenic, teratogenic, hepatotoxic, and immunosuppressive effects in humans and many types of animals, including poultry, trout, cattle, and rats, with different incidences across species, gender, and age [3,4,5]. Considering the potential hazards to animal and human health, there is an urgent need to lower the content of AFB1 to the established permissible levels in food and feed, which vary from 0 to 50 μg/kg in different countries [13]
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