Chen He, Chen Shiwei, Chen Hongli, Wu Yanyan, Shu Guowei
College of Life Science and Engineering, Shaanxi University of Science and Technology, Xi&#;an, China.
Xinjiang Shihezi Garden Dairy Co., Shihezi, China.
Acta Sci Pol Technol Aliment. 2015 Apr-Jun;14(2):117-124. doi: 10.17306/J.AFS.2015.2.13.
Lactobacillus bulgaricus LB6 is a bacterium which was selected in the commercial yoghurt with high angiotensin converting enzyme (ACE) inhibitory activity. Preparation of concentrated starter cultures via freeze drying is of practical importance to dairy and food industries.
We optimized the optimal sugar alcohol and proteins for Lactobacillus bulgaricus LB6 during the process of freeze drying using a Plackett-Burman design. In our initial tests survival rate and the number of viable cells were associated with the type of lyoprotectant used and so our optimization protocol focused on increasing survival rate. Substances that had previously had a protective effect during freeze drying were investigated, for example: mannitol, sorbitol, xylitol, meso-erythritol, lactitol, whey protein isolate 90, bovine serum albumin, and whey protein concentrate 80 and soy protein isolate 70.
We found that the optimum sugar alcohol and proteins for survival of Lactobacillus bulgaricus LB6 were whey protein concentrate (p = 0.0040 for survival rate), xylitol (p = 0.0067 for survival rate) and sorbitol (p = 0.0073 for survival rate), they showed positive effect (whey protein concentrate and sorbitol) or negative effect (xylitol).
The effectiveness of three chosen sugar alcohols and protein implied that they could be used as lyoprotectant for Lactobacillus bulgaricus LB6 in the further research, the optimal composition of sugar alcohol and protein for the lyoprotectant use must be established.
保加利亚乳杆菌LB6是从具有高血管紧张素转换酶（ACE）抑制活性的商业酸奶中筛选出的一种细菌。通过冷冻干燥制备浓缩发酵剂对乳制品和食品工业具有实际意义。
我们使用Plackett-Burman设计优化了保加利亚乳杆菌LB6在冷冻干燥过程中的最佳糖醇和蛋白质。在我们的初步试验中，存活率和活细胞数量与所用冻干保护剂的类型有关，因此我们的优化方案侧重于提高存活率。研究了以前在冷冻干燥过程中具有保护作用的物质，例如：甘露醇、山梨醇、木糖醇、内消旋赤藓醇、乳糖醇、90%乳清蛋白分离物、牛血清白蛋白、80%乳清蛋白浓缩物和70%大豆蛋白分离物。
我们发现，对保加利亚乳杆菌LB6存活的最佳糖醇和蛋白质是乳清蛋白浓缩物（存活率p = 0.0040）、木糖醇（存活率p = 0.0067）和山梨醇（存活率p = 0.0073），它们显示出积极作用（乳清蛋白浓缩物和山梨醇）或消极作用（木糖醇）。
三种选定的糖醇和蛋白质的有效性表明，它们可在进一步研究中用作保加利亚乳杆菌LB6的冻干保护剂，必须确定冻干保护剂使用的糖醇和蛋白质的最佳组成。
