中文摘要：

利用荧光染料标记直投式发酵剂菌体细胞并结合流式细胞术快速检测和分析菌体细胞的活力以及生存状态,对科学地评价各种微生物发酵剂的品质具有现实意义。研究选用保加利亚乳杆菌（Lactobacillus bulgaricus）和嗜热链球菌（Streptococcus thermophilus）两种直投式发酵剂以及制备的新鲜菌体细胞和热处理菌体细胞作为分析检测对象,利用流式细胞术结合羧基荧光素双乙酸酯（5-（6）-carboxyfluoresceindiacetate,5（6）-cFDA）和碘化丙啶（两种荧光染料检测了这些菌体的细胞活力。研究结果表明,5（6）-cFDA和PI双染色方法适合检测L.bulgaricus直投式发酵剂中菌体的存活力,该发酵剂中菌体存活率仅为4.7%,活力较低;而利用5（6）-cFDA单染色方法检测S.thermophilus直投式发酵剂中菌体存活力的效果较好,其菌体存活力接近于90%,活力较强;同时,发酵活力验证也得到了相同的结果;另外,研究证实了PI不能很好地区分S.thermophilus的死活细胞。因此,流式细胞术可作为直投式发酵剂生产行业快速检测评价产品质量的可靠方法。

英文摘要：

Direct labeling of starter ceils with the fluorescent dye in combination with flow cytometry for rapid assessment of cell viability and survival status has practical significance for the scientific evaluation of the quality of various microbial fermentation starters. Direct vat set yogurt starter consisting of either Lactobacillus bulgaricus or Streptococcus thermophilus as well as their freshly harvested cells and heat-killed cells were evaluated for their viability using flow cytometry combined with staining with two specific fluorescent dyes, 5（6）-cFDA and propidium iodide （PI）. Double staining with 5（6）-cFDA and PI was suitable for evaluating the cell viability ofL. bulgaricus in direct vat set starter, which was low, only 4.7%, while staining with 5（6）-cFDA alone could more effectively evaluate the viability of S. thermophilus in direct vat set culture, which was almost 90%. Also, the same results were observed in confirmatory experiments. Finally, our results also showed that PI did not give clear live/dead discrimination for S. thermophilus. Consequently, flow cytometry is a reliable tool to rapidly evaluate the viability of direct vat set starter cultures in dairy industry.