The objectives of this study were to determine the efficacy of metabolites of a Streptomyces strain AS1 on (a) spore germination, (b) mycelial growth, (c) control of mycotoxins produced by Penicillium verrucosum (ochratoxin A, OTA), Fusarium verticillioides (fumonisins, FUMs) and Aspergillus fumigatus (gliotoxin) and (d) identify the predominant metabolites involved in control. Initial screening showed that the Streptomyces AS1 strain was able to inhibit the mycelial growth of the three species at a distance, due to the release of secondary metabolites. A macroscopic screening system showed that the overall Index of Dominance against all three toxigenic fungi was inhibition at a distance. Subsequent studies showed that the metabolite mixture from the Streptomyces AS1 strain was very effective at inhibiting conidial germination of P. verrucosum, but less so against conidia of A. fumigatus and F. verticillioides. The efficacy was confirmed in studies on a conducive semi-solid YES medium in BioScreen C assays. Using the BioScreen C and the criteria of Time to Detection (TTD) at an OD = 0.1 showed good efficacy against P. verrucosum when treated with the Streptomyces AS1 extract at 0.95 and 0.99 water activity (a_w) when compared to the other two species tested, indicating good efficacy. The effective dose for 50% control of growth (ED₅₀) at 0.95 and 0.99 a_w were approx. 0.005 ng/ml and 0.15 μg/ml, respectively, with the minimum inhibitory concentration (MIC) at both a_w levels requiring > 40 μg/ml. In addition, OTA production was completely inhibited by 2.5 μg/ml AS1 extract at both a_w levels in the in vitro assays. Ten metabolites were identified with four of these being predominant in concentrations > 2 μg/g dry weight biomass. These were identified as valinomycin, cyclo(L-Pro-L-Tyr), cyclo(L-Pro-L-Val) and brevianamide F.

中文翻译：

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链霉菌菌株（AS1）的代谢产物在培养中控制疣状青霉，轮状镰刀菌和烟曲霉的生长和霉菌毒素产生的功效。

这项研究的目的是确定链霉菌菌株AS1的代谢产物对（a）孢子萌发，（b）菌丝生长，（c）防治由疣状青霉菌（ra曲霉毒素A，OTA），镰孢镰刀菌产生的霉菌毒素（烟曲霉毒素（FUM）和烟曲霉（gliotoxin）和（d）确定了与控制有关的主要代谢产物。初步筛选显示链霉菌由于次级代谢产物的释放，AS1菌株能够在远距离抑制这三种菌丝体的生长。宏观筛选系统显示，针对所有三种产毒真菌的总体优势指数在一定距离上均受到抑制。随后的研究表明，链霉菌AS1菌株的代谢产物混合物在抑制疣形疣孢子的孢子萌发方面非常有效，但对烟曲霉和拟螺旋藻的分生孢子的抑制作用较小。在BioScreen C分析中对有益的半固体YES培养基进行的研究证实了疗效。使用BioScreen C和OD = 0.1的检测时间标准（TTD）显示出对疣状假单胞菌的良好疗效当用链霉菌AS1提取物以0.95和0.99的水活度（a _w）处理时，与其他两个受试物种相比，表明具有良好的功效。的有效剂量为50％生长控制（ED ₅₀为0.95和0.99）一_瓦特为约 0.005纳克/毫升和0.15微克/毫升，分别与在两个最小抑制浓度（MIC）一_瓦特的水平，需要> 40微克/毫升。此外，OTA生产完全被2.5微克/毫升AS1提取物在两个抑制一_瓦特体外测定中的水平。鉴定出十种代谢物，其中四种以浓度> 2μg/ g干重生物质为主。这些被鉴定为缬氨霉素，环（L-Pro-L-Tyr），环（L-Pro-L-Val）和brevianamideF。