传统干酪中一株产IIa类细菌素乳酸菌的分离与鉴定

从内蒙古传统干酪中分离到一株产抑菌活性物质的乳酸菌M-2，其对单核细胞增生李斯特氏菌、金黄色葡萄球菌等食品中常见致病菌和腐败菌都有抑制作用。排除有机酸、H202等的干扰后，仍有抑菌活性：进一步硫酸铵沉淀、透析及浓缩处理后，其抑菌活性显著增强；用蛋白酶K处理后，其抑菌活性消失，因此确定该抑菌活性物质为蛋白类物质，进而确定乳酸菌M-2为细菌素产生菌。通过生理生化实验和16SrRNA基因序列分析对该菌株进行了鉴定。PCR扩增得到1675bp的16SrRNA序列，并将其通过BLAST软件在NCBI网站中进行同源性比，同时，通过Bioedit7．0和Treedrawing软件绘制系统发育树。结果显示，M-2的16SrRNA序列和数据库中的屎肠球菌SF菌株的序列的同源性为99．87％。在细菌系统发育分类学上，M-2菌株归属屎肠球菌（Enterococcus faecium）。这与生理生化实验初步鉴定结果一致。根据细菌素的分类原则，将该细菌素归类为IIa类细菌素。     

Changes in Soya Bean Lipid Profiles during Kinema Production

The influence of processing on soya bean lipids during kinema production was studied. The crude lipid (CL), free fatty acid (FFA) and phytosterol contents of raw beans were 121 g, 6·9 g and 0·8 g kg⁻¹ dry matter, respectively. After soaking and cooking the moisture content of beans increased significantly from 121 to 749 g kg⁻¹, whilst the lipid contents were unchanged. During a 2 day fermentation at 37°C, the lipid contents increased significantly as indicated by capillary column gas chromatography (GC) analysis of petroleum ether extracts of lyophilised samples of unfermented and fermented beans. The fatty acids, palmitic (C16:0), stearic (C18:0), oleic (C18:1), linoleic (C18:2), linolenic (C18:3) and arachidic (C20:0) acids were identified. The major fatty acid present in all samples was the essential fatty acid, linoleic acid. All of the aforementioned fatty acids (except arachidic) were liberated during fermentation by microbial lipases, yielding approximately the same proportion of fatty acids found in unfermented beans. The unsaponifiable soya bean lipids identified by GC were campesterol, stigmasterol and β-sitosterol (ratio 1·2:1:3·4). Levels of these increased during fermentation by 50–61%, but remained in approximately the same proportions.     

Development of a novel fermented soymilk product with potential probiotic properties

 The study was carried out to test the ability of Enterococcus faecium, Lactobacillus acidophilus, L. jugurti, Streptococcus thermophilus and L. delbrueckii ssp bulgaricus to decrease cholesterol in vitro and to grow in the presence of bile salts. Both properties were dependent on the species under study. The cultures were also inoculated into soymilk fortified with dry milk whey powder as single or mixed starters. The physicochemical and sensory evaluations of the fermented products showed that E. faecium plus L. jugurti (ratio 1 : 1) is the best combination, and this mixture also produces a 43% decrease in cholesterol. Received: 14 October 1998 / Revised version: 5 February 1999