Degradation of aflatoxin B1 from naturally contaminated maize using the edible fungus Pleurotus ostreatus

Abstract

Aflatoxins are highly carcinogenic secondary metabolites that can contaminate approximately 25% of crops and that cause or exacerbate multiple adverse health conditions, especially in Sub-Saharan Africa and South and Southeast Asia. Regulation and decontamination of aflatoxins in high exposure areas is lacking. Biological detoxification methods are promising because they are assumed to be cheaper and more environmentally friendly compared to chemical alternatives. White-rot fungi produce non-specific enzymes that are known to degrade aflatoxin in in situ and ex situ experiments. The aims of this study were to (1) decontaminate aflatoxin B1 (AFB1) in naturally contaminated maize with the edible, white-rot fungus Pleurotus ostreatus (oyster mushroom) using a solid-state fermentation system that followed standard cultivation techniques, and to (2) and to assess the risk of mutagenicity in the resulting breakdown products and mushrooms. Vegetative growth and yield characteristics of P. ostreatus were not inhibited by the presence of AFB1. AFB1 was degraded by up to 94% by the Blue strain. No aflatoxin could be detected in P. ostreatus mushrooms produced from AFB1-contaminated maize. Moreover, the mutagenicity of breakdown products from the maize substrate, and reversion of breakdown products to the parent compound, were minimal. These results suggest that P. ostreatus significantly degrades AFB1 in naturally contaminated maize under standard cultivation techniques to levels that are acceptable for some livestock fodder, and that using P. ostreatus to bioconvert crops into mushrooms can reduce AFB1-related losses.

Structure Elucidation and Toxicity Analysis of the Byproducts Formed after Biodegradation of Aflatoxins B1 and B2 Using Extracts of Mentha arvensis

“…A total of 28% of these compounds were formed due to the modification of the lactone ring. The lactone ring is responsible for the toxicity, carcinogenicity and fluorescence of aflatoxin B1 [35]. Modification in the lactone ring of AFB1 results in the loss of these properties, as observed in this study.…”

“…Plant extracts were incubated with toxins at 25,30,35,40,45,50, 55 and 60 • C for 3, 6, 12, 24, 48 and 72 h. The toxin content in various reaction mixtures was estimated using high-performance liquid chromatography.…”

Worldwide aflatoxin contamination of agricultural products and foods: From occurrence to control

“…High degradation levels have been observed from certain fungi species. For instance, Jackson and Pryor (2017) reported a 94% degradation of aflatoxin B1 in naturally contaminated maize using the fungal strain white‐rot fungus Pleurotus ostreatus (oyster mushroom) as a degrading agent. A study by Zhang et al.…”

Mycoremediation in Soil

“…Many works on the edible mushroom P. ostreatus have been published. The biodegradation of the carcinogenic secondary metabolite aflatoxin B 1 (AFB 1 ), produced by Aspergillus flavus on rice straw [90] and on maize [91], was reported for this species. The mycoremediation of heavy metal-contaminated soils by means of different Pleurotus species was also reviewed in the work of [92].…”