Dipartimento di Scienze Agrarie, Alimentari ed Ambientali, Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy.
Food Quality and Nutrition Department (DQAN), Research and Innovation Center, Fondazione Edmund Mach (FEM), via E. Mach 1, 38010 San Michele all'Adige, Italy.
Int J Food Microbiol. 2018 May 2;272:49-60. doi: 10.1016/j.ijfoodmicro.2018.03.001. Epub 2018 Mar 7.
Tenebrio molitor represents one of the most popular species used for the large-scale conversion of plant biomass into protein and is characterized by high nutritional value. In the present laboratory study, the bacterial biota characterizing a pilot production chain of fresh T. molitor larvae was investigated. To this end, different batches of fresh mealworm larvae, their feeding substrate (wheatmeal) and frass were analyzed by viable microbial counts, PCR-DGGE and Illumina sequencing. Moreover, the occurrence of Coxiella burnetii, Pseudomonas aeruginosa and Shiga toxin-producing E. coli (STEC) was assessed through qualitative real-time PCR assays. Microbial viable counts highlighted low microbial contamination of the wheatmeal, whereas larvae and frass were characterized by high loads of Enterobacteriaceae, lactic acid bacteria, and several species of mesophilic aerobes. Spore-forming bacteria were detected to a lesser extent in all the samples. The combined molecular approach used to profile the microbiota confirmed the low microbial contamination of wheatmeal and allowed the detection of Enterobacter spp., Erwinia spp., Enterococcus spp. and Lactococcus spp. as dominant genera in both larvae and frass. Moreover, Klebsiella spp., Pantoea spp., and Xenorhabdus spp. were found to be in the minority. Entomoplasmatales (including Spiroplasma spp.) constituted a major fraction of the microbiota of one batch of larvae. From the real-time PCR assays, no sample was positive for either C. burnetii or STEC, whereas P. aeruginosa was detected in one sample of frass. Based on the overall results, two sources of microbial contamination were hypothesized, namely feeding with wheatmeal and vertical transmission of microorganisms from mother to offspring. Since mealworms are expected to be eaten as a whole, the overall outcomes collected in this laboratory study discourage the consumption of fresh mealworm larvae. Moreover, microbial loads and the absence of potential pathogens known to be associated with this insect species should be carefully assessed in order to reduce the minimum risk for consumers, by identifying the most opportune processing methods (e.g., boiling, frying, drying, etc.).
黄粉虫是将植物生物质大规模转化为蛋白质的最受欢迎的物种之一，其特点是营养价值高。在本实验室研究中，研究了新鲜黄粉虫幼虫生产链中特征的细菌生物群。为此，通过活菌计数、PCR-DGGE 和 Illumina 测序分析了不同批次的新鲜黄粉虫幼虫、它们的饲料（麦麸）和粪便。此外，通过定性实时 PCR 检测评估了考克斯氏体、铜绿假单胞菌和产志贺毒素大肠杆菌（STEC）的发生情况。微生物活菌计数突出了麦麸的低微生物污染，而幼虫和粪便的特征是肠杆菌科、乳酸菌和几种嗜温需氧菌的高负荷。所有样本中都检测到较少的芽孢形成菌。用于分析微生物群的组合分子方法证实了麦麸的低微生物污染，并允许检测到肠杆菌属、欧文氏菌属、肠球菌属和乳球菌属作为幼虫和粪便中的主要属。此外，还发现克雷伯菌属、泛菌属和 Xenorhabdus 属为少数。昆虫质体菌（包括螺旋体属）构成了一批幼虫微生物群的主要部分。从实时 PCR 检测中，没有一个样本对考克斯氏体或 STEC 呈阳性，而在一份粪便样本中检测到铜绿假单胞菌。基于总体结果，假设了两种微生物污染来源，即麦麸喂养和微生物从母亲垂直传播到后代。由于黄粉虫预计将被整个吃掉，因此本实验室研究中收集的总体结果不鼓励食用新鲜黄粉虫幼虫。此外，应该仔细评估微生物负荷和不存在与该昆虫种类相关的潜在病原体，以通过确定最合适的加工方法（例如煮沸、油炸、干燥等）来降低消费者的最低风险。
