Department of Food Science, Cornell University, Ithaca, NY, United States of America.
Department of Chemistry, University of Alberta, Edmonton, AB, Canada.
PLoS One. 2022 Apr 6;17(4):e0266470. doi: 10.1371/journal.pone.0266470. eCollection 2022.
Raw honey contains a diverse microbiota originating from honeybees, plants, and soil. Some gram-positive bacteria isolated from raw honey are known for their ability to produce secondary metabolites that have the potential to be exploited as antimicrobial agents. Currently, there is a high demand for natural, broad-spectrum, and eco-friendly bio-fungicides in the food industry. Naturally occurring antifungal products from food-isolated bacteria are ideal candidates for agricultural applications. To obtain novel antifungals from natural sources, we isolated bacteria from raw clover and orange blossom honey to evaluate their antifungal-producing potential. Two Bacillus velezensis isolates showed strong antifungal activity against food-isolated fungal strains. Antifungal compound production was optimized by adjusting the growth conditions of these bacterial isolates. Extracellular proteinaceous compounds were purified via ammonium sulfate precipitation, solid phase extraction, and RP-HPLC. Antifungal activity of purified products was confirmed by deferred overlay inhibition assay. Mass spectrometry (MS) was performed to determine the molecular weight of the isolated compounds. Whole genome sequencing (WGS) was conducted to predict secondary metabolite gene clusters encoded by the two antifungal-producing strains. Using MS and WGS data, we determined that the main antifungal compound produced by these two Bacillus velezensis isolates was iturin A, a lipopeptide exhibiting broad spectrum antifungal activity.
天然蜂蜜含有源自蜜蜂、植物和土壤的多样化微生物群。从天然蜂蜜中分离出的一些革兰氏阳性细菌以产生具有开发为抗菌剂潜力的次生代谢产物而闻名。目前，食品工业对天然、广谱和环保型生物杀真菌剂的需求很高。从食品分离的细菌中获得的天然来源的抗真菌产品是农业应用的理想候选物。为了从天然来源获得新型抗真菌剂，我们从生苜蓿和橙花蜂蜜中分离细菌，以评估它们的抗真菌产生潜力。两种芽孢杆菌分离株对食品分离的真菌菌株表现出强烈的抗真菌活性。通过调整这些细菌分离株的生长条件来优化抗真菌化合物的生产。通过硫酸铵沉淀、固相萃取和 RP-HPLC 纯化胞外蛋白化合物。通过延迟覆盖抑制测定证实了纯化产物的抗真菌活性。进行质谱 (MS) 以确定分离化合物的分子量。进行全基因组测序 (WGS) 以预测产生两种抗真菌化合物的菌株所编码的次级代谢物基因簇。使用 MS 和 WGS 数据，我们确定这两种芽孢杆菌分离株产生的主要抗真菌化合物是伊枯草菌素 A，一种具有广谱抗真菌活性的脂肽。
