Department of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu 641003, India; School of Biology and Environment Science, Earth Institute, University College Dublin, Science Centre East, Belfield, Dublin 4, Ireland.
Department of Agricultural Microbiology, Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu 641003, India.
Microbiol Res. 2022 Oct;263:127150. doi: 10.1016/j.micres.2022.127150. Epub 2022 Jul 30.
Minimizing Aspergillus flavus growth is an effective strategy to mitigate aflatoxin contamination in food and agricultural products. In the present investigation, we attempted to utilize soil-associated yeasts from the Western and Eastern Ghats of India against A. flavus to reduce aflatoxin contamination. Forty-five yeast isolates were screened against A. flavus using overlay and dual plate assays. Among them, 12 isolates effectively inhibited the growth of A. flavus. The 18S rDNA gene sequence analysis identified the twelve antagonistic isolates as belonging to Saccharomyces cerevisiae, Suhomyces xylopsoci, Pichia kudriavzevii, and Candida tropicalis. From the isolated yeasts, S. cerevisiae strains were selected for further evaluation based on the potential antagonistic activity. Volatiles of S. cerevisiae effectively suppressed the mycelial growth of A. flavus (P < 0.05) up to 92.1 % at 7 DAI. Scanning electron microscopic images of the fungus exposed to volatiles showed hyphal deformity and mycelial damage. Aflatoxin B (AFB) production was drastically reduced up to 99.0 % in the volatile-exposed fungus compared to the control. The yeast strain YKK1 showed consistent Aspergillus flavus growth inhibition (80.7 %) and AFB production (98.1 %) for 14 days. Gas chromatography-mass spectrophotometry analysis of the yeast volatiles revealed the presence of antimicrobial compounds, including 1-pentanol, 1-propanol, ethyl hexanol, ethanol, 2-methyl-1-butanol, ethyl acetate, dimethyl trisulfide, p-xylene, styrene, and 1,4-pentadiene. The evaluated compounds of yeast volatiles, including ethyl acetate, hexanal, 1-propanol, 1-heptanol, 1-butanol, and benzothiazole, inhibited the fungal growth and AFB production of Aspergillus flavus when applied as pure chemicals. Benzothiazole at 5 mM was responsible for a high level of growth inhibition (23.6 %) and reduction of AFB synthesis (93.5 %). Hence, volatile compounds produced by soil yeast strains could be a potential biocontrol mechanism against aflatoxin contamination.
抑制黄曲霉生长是减轻食品和农产品中黄曲霉毒素污染的有效策略。在本研究中，我们试图利用来自印度西高止山脉和东高止山脉的土壤相关酵母来抑制黄曲霉，以减少黄曲霉毒素污染。使用覆盖和双板测定法筛选了 45 株酵母分离株以对抗黄曲霉。其中，有 12 株分离株有效地抑制了黄曲霉的生长。18S rDNA 基因序列分析将 12 株拮抗分离株鉴定为酿酒酵母、苏霍酵母、毕赤酵母和热带假丝酵母。从分离的酵母中，根据潜在的拮抗活性选择酿酒酵母菌株进行进一步评估。酿酒酵母的挥发物有效抑制了黄曲霉的菌丝生长（P < 0.05），在第 7 天达到 92.1%。暴露于挥发物的真菌的扫描电子显微镜图像显示出菌丝畸形和菌丝损伤。与对照相比，挥发性物质暴露的真菌中黄曲霉毒素 B（AFB）的产量降低了 99.0%。酵母菌株 YKK1 对黄曲霉的生长抑制率（80.7%）和 AFB 产量（98.1%）在 14 天内保持一致。酵母挥发物的气相色谱-质谱分析显示存在抗菌化合物，包括 1-戊醇、1-丙醇、乙基己醇、乙醇、2-甲基-1-丁醇、乙酸乙酯、二甲基三硫化物、对二甲苯、苯乙烯和 1,4-戊二烯。酵母挥发物的评估化合物，包括乙酸乙酯、己醛、1-丙醇、1-庚醇、1-丁醇和苯并噻唑，当作为纯化学品应用时，抑制了黄曲霉的生长和 AFB 的产生。5mM 的苯并噻唑可导致高水平的生长抑制（23.6%）和 AFB 合成减少（93.5%）。因此，土壤酵母菌株产生的挥发性化合物可能是一种潜在的防治黄曲霉毒素污染的生物防治机制。
