Phylogenetic diversity and prevalence of mycoflora in ready-to-eat supermarket and roadside-vended peanuts

摘要

Little is known of the mycobiota present in ready-to-eat peanuts consumed in Southern Africa. Knowledge of the mycobiota and aflatoxigenic species can elucidate potential health risks associated with consumption of ready-to-eat peanuts sold by supermarkets and roadside vendors. We investigated the culturable mycobiota diversity in supermarket and roadside-vended peanuts as well as the presence of five aflatoxin biosynthesis pathway-related genes (aflR, aflJ, aflM, aflD, andaflP) in 15 suspected aflatoxigenic isolates, with a focus on Mafikeng, South Africa. Mean colony-forming unit (CFU) counts of 288.7 and 619.7 CFU/g were observed in supermarket and roadside-vended peanuts, respectively. A total of 145 fungal isolates comprising 26 distinct taxa (based on 97% internal transcribed spacer region [ITS1-5.8S-ITS2] sequence similarity) were obtained, including strains representingAspergillus, Acremonium, Alternaria, Bipolaris, Chaetomium, Ectophoma, Epicoccum, Hamigera, Leancillium, Monascus, Penicillium, Periconia, Talaromyces, andTrichoderma. Phylogenetic analyses of concatenated sequences of the ITS1-5.8S-ITS2, beta-tubulin, and calmodulin genes delineated the species of Aspergillus, which includedA. flavus, A. fumigatus, A. hiratsukae, A. niger, andA. parasiticus. Higher species richness was obtained from supermarket peanuts compared with roadside-vended peanuts, with eight species common to both sources. Across supermarket or roadside-vended peanuts,A. fumigatus, A. niger, andA. flavuswere prevalent (>40% incidence). In contrast, strains related to or representingEctophoma multirostata, Aspergillus hiratsukae, Bipolaris zeae, Chaetomium bostrychodes, Epicoccum nigrum, Hamigera paravellanea, Lecanicillium aphanocladii, Monascus ruber, Periconia macrospinosa, Periconia lateralis, Talaromyces funiculosus, Talaromyces minioluteus, Talaromyces wortmannii, Talaromycesspp., andTrichodermasp. were detected in either supermarket or roadside-vended peanuts. Among the five aflatoxin biosynthesis pathway-related genes,aflDandaflMwere more prevalent (87%) andaflRwas the least prevalent (40%). Findings suggest that roasted peanuts meant for human consumption and sold at supermarkets and by roadside vendors are contaminated with potential toxin-producing fungi. Hence, proper processing and packaging of peanuts before vending is recommended.