Use of wild yeasts as a biocontrol agent against toxigenic fungi and OTA production

ABSTRACT. This study evaluated the antagonistic potential of 32 wild yeast isolates from coffee and cocoa bean fermentation. These yeasts were inoculated in co-cultivation with Aspergillus carbonarius (CCDCA 10608 and CCDCA 10408) and Aspergillus ochraceus (CCDCA 10612) isolated from grapes and coffee beans. The mycelial growth and ochratoxin A (OTA) production were evaluated, and the spores were counted after cultivation at 28°C for seven days. The yeasts presented higher inhibitory effects (53% in relation to the control) over the mycelial growth of the isolated A. ochraceus (CCDCA10612). Pichia anomala CCMA0148 and Saccharomyces cerevisiae CCMA0159 provided the greatest inhibition of the growth of all fungal strains. All Pichia species presented the highest inhibitory effects on the production of spores, and S. cerevisiae CCMA 0159 at concentrations of both 104 and 107 mL-1 cells inhibited the production of spores by 100%. Rhodotorula mucilaginosa was effective at inhibiting OTA production by the three isolates of Aspergillus. S. cerevisiae CCMA0159 and Pichia anomala CCMA0148 showed high potential as biocontrol agents in the conditions tested.

摘要
本研究评估了32株分离自咖啡与可可豆发酵过程的野生酵母分离株的拮抗潜力。将上述酵母与分离自葡萄及咖啡豆的炭黑曲霉（Aspergillus carbonarius，CCDCA 10608、CCDCA 10408）和赭曲霉（Aspergillus ochraceus，CCDCA 10612）进行共培养。于28℃培养7天后，检测供试菌株的菌丝生长、赭曲霉毒素A（ochratoxin A，OTA）产生情况，并对孢子进行计数。
结果表明，受试酵母对赭曲霉CCDCA10612的菌丝生长抑制效果最为显著，较对照组提升53%。异常毕赤酵母（Pichia anomala）CCMA0148与酿酒酵母（Saccharomyces cerevisiae）CCMA0159对所有供试真菌菌株的生长抑制效果最优。所有毕赤酵母属（Pichia）菌株对孢子生成的抑制活性最高，其中酿酒酵母CCMA0159在10⁴与10⁷个·mL⁻¹的细胞浓度下，可完全抑制孢子产生（抑制率达100%）。黏红酵母（Rhodotorula mucilaginosa）可有效抑制3株曲霉的OTA合成。在本次试验条件下，酿酒酵母CCMA0159与异常毕赤酵母CCMA0148展现出极高的生防菌应用潜力。