Biodegradation of aflatoxin B1 in contaminated rice straw by Pleurotus ostreatus MTCC 142 and Pleurotus ostreatus GHBBF10 in the presence of metal salts and surfactants

Abstract

Aflatoxin B1 (AFB1) is a highly toxic fungal metabolite having carcinogenic, mutagenic and teratogenic effects on human and animal health. Accidental feeding of aflatoxin-contaminated rice straw may be detrimental for ruminant livestock and can lead to transmission of this toxin or its metabolites into the milk of dairy cattle. White-rot basidiomycetous fungus Pleurotus ostreatus produces ligninolytic enzymes like laccase and manganese peroxidase (MnP). These extracellular enzymes have been reported to degrade many environmentally hazardous compounds. The present study examines the ability of P. ostreatus strains to degrade AFB1 in rice straw in the presence of metal salts and surfactants. Laccase and MnP activities were determined spectrophotometrically. The efficiency of AFB1 degradation was evaluated by high performance liquid chromatography. Highest degradation was recorded for both P. ostreatus MTCC 142 (89.14 %) and P. ostreatus GHBBF10 (91.76 %) at 0.5 µg mL(-1) initial concentration of AFB1. Enhanced degradation was noted for P. ostreatus MTCC 142 in the presence of Cu(2+) and Triton X-100, at toxin concentration of 5 µg mL(-1). P. ostreatus GHBBF10 showed highest degradation in the presence of Zn(2+) and Tween 80. Liquid chromatography-mass spectrometric analysis revealed the formation of hydrated, decarbonylated and O-dealkylated products. The present findings suggested that supplementation of AFB1-contaminated rice straw by certain metal salts and surfactants can improve the enzymatic degradation of this mycotoxin by P. ostreatus strains.

Detoxification of Mycotoxins through Biotransformation

“…(iv) Reduction and oxidation: AFB 1 (1) was converted to AFB 2a (133), which was also called dihydrohydroxyaflatoxin B 1 , by Pleurotus ostreatus GHBBF10. AFB 2a (133) was 200 times less toxic than AFB 1 (1) [108].…”

“…Aflatoxin B 1 (AFB 1 , 1) was converted to dihydrohydroxyaflatoxin B 1 (133), which was also named as aflatoxin B 2a (AFB 2a ), via reduction and oxidation by Pleurotus ostreatus GHBBF10 ( Figure S68) [108]. AFB 1 (1) was detoxified to aflatoxin D 1 (AFD 1 , 134), aflatoxin D 2 (AFD 2 , 135) and aflatoxin D 3 (AFD 3 , 136) through hydrolysis, decarboxylation, and oxidation-reduction by Pseudomonas putida, which was isolated from sugarcane ( Figure S69).…”

Strategies and Methodologies for Developing Microbial Detoxification Systems to Mitigate Mycotoxins

“…A number of studies have evaluated intrinsic factors, including carbon source [26,34], nitrogen source [26,34,88], vitamins [26], metals ions [12,34,46,89,90,91,92,93], enzyme inhibitors and promoters [52,89,90,91,92,93,94], initial concentration of mycotoxins [93,95], initial concentration of cells [53,95] and initial pH value [12,14,17,26,31,34,41,46,54,60,88,89,95,96], as well as extrinsic factors, including temperature [12,14,17,25,26,31,34,38,41,46,52,54,60,88,89,95,96], aeriation (shaking rate) [26], oxygen preference [14], as well as pre-incubation [26] and incubation time [34,97]. The experimental designs and optimized biotransformation conditions are summarized in Table 2.…”

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

“…Wang et al (2011) and Yehia (2014) used manganese peroxidases from Phanerochaete sordida and P. ostreatus , respectively, to degrade AFB 1 in ex situ experiments. In a microcosm study, Das et al (2014) demonstrated enhanced degradation of AFB 1 in rice straw by P. ostreatus in the presence of certain surfactants and metal salts, and identified several potential breakdown products. Two strains of P. ostreatus were also used to degrade AFB 1 in a co-cultivation experiment with Aspergillus flavus on rice straw revealing that one strain demonstrated superior degradation efficiency (Das et al 2015).…”