Abstract
This study investigated the aflatoxin production potentials of selected fungi using a polyphasic approach. Internally transcribed spacer region of the fungi was amplified using the polymerase chain reaction. Forty-five Aspergillus strains were further assessed for aflatoxin production using the conventional methods such as growth on yeast extract sucrose, β-cyclodextrin neutral red desiccated coconut agar (β-CNRDCA); expression of the aflatoxin regulatory genes and the use of both thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). A large proportion (82.22%) of the isolates harbored the Nor-1 gene while 55.56%, 68.89%, and 80% possessed the ver-1, omt-A, and aflR genes, respectively. All 100% the isolates harbored the aflJ gene. Twenty-three isolates were positive for aflatoxin production based on the yeast extract sucrose medium (YES) test; ammonium vapor test (51%), yellow pigment production (75.5%), and β-CNRDCA tests; and blue/green fluorescence (57.7%). Based on TLC detection 42.2% produced aflatoxins while in the HPLC, total aflatoxin (AFTOT) production concentrations ranged from 6.77–71,453 µg/g. Detectable aflatoxin B1 (AFB1) concentrations obtained from the HPLC ranged between 3.76 and 70,288 µg/g; 6.77 and 242.50 µg/g for aflatoxin B2 (AFB2); 1.87 and 745.30 µg/g for aflatoxin G1 (AFG1); and 1.67 and 768.52 µg/g for aflatoxin G2 (AFG2). AFTOT contamination levels were higher than European Union tolerable limits (4 µg/kg). The regression coefficient was one (R2 = 1) while significant differences exist in the aflatoxin concentrations of Aspergillus (p ≤ 0.05). This study reports the potentials of Aspergillus oryzae previously known as a non-aflatoxin producer to produce AFG1, AFG2, AFB1, and AFB2 toxins. Aspergillus species in feedlots of animals reared for food are capable of producing aflatoxins which could pose hazards to health.
Highlights
Fungi are normal flora in the soil, hays, silage, and grains which exercise decay activities when conditions are favorable for growth [1]
This study reports the potentials of Aspergillus oryzae previously known as a non-aflatoxin producer to produce aflatoxin G1 (AFG1), aflatoxin G2 (AFG2), aflatoxin B1 (AFB1), and aflatoxin B2 (AFB2) toxins
Mycotoxin production in food and animal feed is influenced by the type of colonizing fungi, climatic conditions, environmental factors such as pH, type of food, or feed substrate, and types of agronomic practices employed in a specific locality [4,5]
Summary
Fungi are normal flora in the soil, hays, silage, and grains which exercise decay activities when conditions are favorable for growth [1]. Fungal growth on food and feed substrates does not culminate directly into the release of toxins that may persist in the medium even after the death of fungal pathogens but can be triggered by stress factors in the environment [2]. Mycotoxins are secondary metabolites produced by fungi in food and feed substrates [3]. Mycotoxin production in food and animal feed is influenced by the type of colonizing fungi, climatic conditions, environmental factors such as pH, type of food, or feed substrate, and types of agronomic practices employed in a specific locality [4,5]. Specific complications resulting from the consumption of food or feeds contaminated with mycotoxins includes; liver damage, hepatocarcinoma, hepatitis, cirrhosis, and DNA mutations [8,9]. Aflatoxicosis is a disease condition that results from direct or indirect exposure to aflatoxin through food or animals and their related food products [10]
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