Abstract: In recent years, the addition of probiotics to milk powder has gradually become a research focus. In order to ensure the product quality and safety, a microbiological detection method for Lactobacillus fermentum CECT5716 in milk powder has been established. It was found that the population of Lactobacillus fermentum in milk powder could be accurately counted by spreading serial 10-fold dilutions in buffered peptone water (BPW) onto MRS plates and culturing them under anaerobic conditions at (36 ± 1) ℃ for (48 ± 2) h, with clear discrimination from inoculated bifidobacteria. This method was more suitable for counting Lactobacillus fermentum than the Chinese national standard method (GB 4789.35?2016), and had the advantages of high discrimination capacity, short culture time, simple operation, good repeatability, and high accuracy. This method also included 16S rDNA sequence analysis of the strain for its subsequent molecular identification. There was no significant difference in the accuracy of this method versus the national standard method in detecting 20 samples prepared in our laboratory (P = 0.127).

Key words: Lactobacillus fermentum, test method, 16S rDNA sequencing

摘要： 近年来乳粉中添加益生菌逐渐成为研究热点之一，为保证产品质量和安全，建立乳粉中发酵乳杆菌CECT5716的微生物检测方法。结果表明：在以缓冲蛋白胨水为稀释液进行10 倍系列稀释后，采用MRS平板涂布法，（36±1） ℃厌氧培养（48±2） h后，乳粉中发酵乳杆菌可准确计数，且能与乳粉中添加的双歧杆菌属细菌明显区分；该方法较GB 4789.35—2016《食品安全国家标准 食品微生物学检验 乳酸菌检验》方法更适合发酵乳杆菌计数，具有区分度高、培养时间短、操作简单、重复性好、准确性高的优点；该方法增加了菌株16S rDNA序列测定，以进一步对发酵乳杆菌进行分子鉴定；通过对20 份自制样品进行检测评价，表明所建立的方法与国标方法的准确性无显著性差异（P=0.127）。

关键词: 发酵乳杆菌, 检测方法, 16S rDNA序列测定