Department of Agricultural, Food and Environmental Sciences, University of Perugia, Borgo XX Giugno 74, 06121 Perugia, Italy.
Centre for Analytical Chemistry, Department of Agrobiotechnology (IFA-Tulln), University of Natural Resources and Life Sciences (BOKU), Vienna, Konrad Lorenz Strasse 20, A-3430 Tulln, Austria.
Int J Food Microbiol. 2018 May 20;273:33-42. doi: 10.1016/j.ijfoodmicro.2018.03.005. Epub 2018 Mar 12.
In recent years, due to the negative impact of toxigenic mycobiota and of the accumulation of their secondary metabolites in malting barley grains, monitoring the evolution of fungal communities in a certain cultivation area as well as detecting the different mycotoxins present in the raw material prior to malting and brewing processes have become increasingly important. In this study, a survey was carried out on malting barley samples collected after their harvest in the Umbria region (central Italy). Samples were analyzed to determine the composition of the fungal community, to identify the isolated Fusarium species, to quantify fungal secondary metabolites in the grains and to characterize the in vitro mycotoxigenic profile of a subset of the isolated Fusarium strains. The fungal community of barley grains was mainly composed of microorganisms belonging to the genus Alternaria (77%), followed by those belonging to the genus Fusarium (27%). The Fusarium head blight (FHB) complex was represented by nine species with the predominance of Fusarium poae (37%), followed by Fusarium avenaceum (23%), Fusarium graminearum (22%) and Fusarium tricinctum (7%). Secondary metabolites biosynthesized by Alternaria and Fusarium species were present in the analyzed grains. Among those biosynthesized by Fusarium species, nivalenol and enniatins were the most prevalent ones. Type A trichothecenes (T-2 and HT-2 toxins) as well as beauvericin were also present with a high incidence. Conversely, the number of samples contaminated with deoxynivalenol was low. Conjugated forms, such as deoxynivalenol-3-glucoside and HT-2-glucoside, were detected for the first time in malting barley grains cultivated in the surveyed area. In addition, strains of F. avenaceum and F. tricinctum showed the ability to biosynthesize in vitro high concentrations of enniatins. The analysis of fungal secondary metabolites, both in the grains and in vitro, revealed also the presence of other compounds, for which further investigations will be required. The combination of microbiological analyses, of molecular biology assays and of multi-mycotoxin screening shed light on the complexity of the fungal community and its secondary metabolites released in malting barley.
近年来，由于产毒真菌菌群及其在麦芽大麦谷物中次生代谢物的积累所带来的负面影响，对特定种植区域内真菌群落的演变进行监测以及在酿造前检测原料中存在的不同霉菌毒素变得越来越重要。在本研究中，对意大利中部翁布里亚地区收获后的麦芽大麦样本进行了调查。对样本进行了分析，以确定真菌群落的组成、鉴定分离出的镰刀菌物种、量化谷物中的真菌次生代谢物，并描述分离出的部分镰刀菌菌株的体外产毒特征。大麦籽粒中的真菌群落主要由属于链格孢属（Alternaria）的微生物（77%）组成，其次是属于镰刀菌属（Fusarium）的微生物（27%）。赤霉病（FHB）复合体由 9 个种组成，其中禾谷镰刀菌（Fusarium poae）占优势（37%），其次是燕麦镰刀菌（Fusarium avenaceum）（23%）、禾谷镰刀菌（Fusarium graminearum）（22%）和三线镰刀菌（Fusarium tricinctum）（7%）。在所分析的谷物中存在由链格孢属和镰刀菌属物种合成的次生代谢物。在由镰刀菌物种合成的次生代谢物中，最为常见的是雪腐镰刀菌烯醇和恩镰孢菌素。A型单端孢霉烯族化合物（T-2 和 HT-2 毒素）以及 beauvericin 的含量也很高。相反，受脱氧雪腐镰刀菌烯醇污染的样本数量较少。在调查区域种植的麦芽大麦中，首次检测到结合态形式的脱氧雪腐镰刀菌烯醇-3-葡萄糖苷和 HT-2-葡萄糖苷。此外，F. avenaceum 和 F. tricinctum 菌株表现出体外合成高浓度恩镰孢菌素的能力。对谷物和体外真菌次生代谢物的分析还揭示了其他化合物的存在，需要进一步研究。微生物分析、分子生物学检测和多毒素筛查的结合，揭示了真菌群落及其在麦芽大麦中释放的次生代谢物的复杂性。
