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产胞外多糖的嗜热链球菌ST冷冻干燥制剂的研究

吴荣荣1,王立平2,高莉莉2,刘伯衢3,张柏林2*   

  1. 1. 衡水学院生命科学系, 河北 衡水 053000; 2. 北京林业大学生物科学与技术学院, 北京100083; 3. 河北农业大学食品学院, 河北 保定 071001

  • 收稿日期:1900-01-01 修回日期:1900-01-01 出版日期:2006-10-24 发布日期:2006-10-24
  • 通讯作者: 张柏林

Exopolysaccharide production and lyophilization preparation from Streptococcus thermophilus ST

WU Rong-rong1, WANG Li-ping2, GAO Li-li2, LIU Bai-qu3, ZHANG Bo-lin 2*

  

  1. 1. Department of Biological Sciences, Hengshui University, Hengshui 053000, Hebei, China; 2. Department of Food Science, College of Biological Science & Technology, Beijing Forestry University, Beijing 100083, China; 3. School of Food Science & Technology, Hebei Agricultural University, Baoding 071001, Hebei, China

  • Received:1900-01-01 Revised:1900-01-01 Online:2006-10-24 Published:2006-10-24
  • Contact: ZHANG Bo-lin

摘要:

从当地市售的传统酸奶中分离出一株产胞外多糖的链球菌,经生理生化和16S rDNA序列分析,将该菌株确定为嗜热链球菌ST。在补充了20g·L-1的葡萄糖,初始pH7.0的培养基上,40℃,培养24h后,其胞外多糖产量为55.62mg·L-1。进一步的结构分析显示,此多糖的主要单糖组成为葡萄糖。在生产嗜热链球菌ST冷冻干燥制剂时,其最佳的增殖培养基组成为脱脂奶粉100.0g·L-1,酵母膏3.0g·L-1,碳酸钙9.0g·L-1和乳清粉20.0g·L-1,活菌数达到1.05×109CFU·mL-1。由脱脂奶粉160.0g·L-1、甘油30.0g·L-1谷氨酸钠30.0g·L-1和5.0g·L-1吐温80构成的保护剂能明显改善菌体细胞在冷冻干燥条件下的存活能力。发酵温度37℃、搅拌转速90r·min-1和pH5.9的条件下培养,经冷冻干燥获得的直投式发酵剂产品的活菌数量可达1.7×1011CFU·g-1。当采用固形物仅为80.0g·L-1的还原乳做为原料时,与不产胞外多糖的菌株生产的酸乳相比,采用该产品制备成的产品乳清析较少。

关键词: 嗜热链球菌, 冷冻干燥, 保护剂, 增殖, 胞外多糖

Abstract:

ST strain, isolated from yogurt purchased from a local market and identified as Streptococcus thermophilus based on physiological-biochemical characteristics and 16S rDNA sequence, produced 55.62mg·L-1 of exopolysaccharides (EPS). The EPS level produced by strain ST depended upon incubation time (24h), tem(20g·L-1). The major monosaccharide of EPS formed by this strain was confirmed to be glucose. Moreover, data from the lyophilization preparation of strain ST showed that the optimal medium containing NFMS (100.0g·L-1), yeast extract (3.0?g·L-1), CaCO3(9.0g·L-1) and whey powder (20.0g·L-1) promoted its viable cells to a level of 1.05×109CFU·mL-1. The combination of NFMS (160.0g·L-1), glycerol (30.0g·L-1), sodium glutamate (30.0g·L-1) and Tween 80 (5.0g·L-1) was proved to be a good cytoprotectant for the protection of strain ST against the stresses of freeze-drying. Temperature, pH and rotation speed were important factors for gaining high viable counts in pilot-plant production of strain ST lyophilizator. Theoptimal combination including fermentation temperature (37℃), rotation speed (90r·min-1) and pH (5.9), resulted in a direct-vat-inoculation preparation of strain ST that contained viable cells of 1.7×1011CFU·g-1 after lyophilization. Use of lyophilized strain ST preparation to directly ferment 80.0g·L-1 reconstituted skim milk to yogurt produced lower whey separation than that of yogurt made with non-EPS strains used as controls.

Key words: lyophilization.

, cytoprotectant, multiplication, exopolysaccharides (EPS),

Streptococcus thermophilus

中图分类号: 

  • TS252.54
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