title: Effects of sugar alcohol and proteins on the survival of Lactobacillus bulgaricus LB6 during freeze drying.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: College of Life Science and Engineering, Shaanxi University of Science and Technology, Xi&#;an, China.
authors.forename: He
authors.initials: H
authors.lastname: Chen
authors.affiliation: College of Life Science and Engineering, Shaanxi University of Science and Technology, Xi&#;an, China.
authors.forename: Shiwei
authors.initials: S
authors.lastname: Chen
authors.affiliation: Xinjiang Shihezi Garden Dairy Co., Shihezi, China.
authors.forename: Hongli
authors.initials: H
authors.lastname: Chen
authors.affiliation: Xinjiang Shihezi Garden Dairy Co., Shihezi, China.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Wu
authors.affiliation: College of Life Science and Engineering, Shaanxi University of Science and Technology, Xi&#;an, China.
authors.forename: Guowei
authors.initials: G
authors.lastname: Shu
mesh_terms: D000818:Animals; D002417:Cattle; D002681:China; D015925:Cryopreservation; D003451:Cryoprotective Agents / Q000737:chemistry*; D004896:Erythritol / Q000737:chemistry; D005503:Food Additives / Q000737:chemistry; D005612:Freeze Drying; D048668:Lactobacillus delbrueckii / Q000254:growth & development*; D008353:Mannitol / Q000737:chemistry; D050296:Microbial Viability; D015203:Reproducibility of Results; D012710:Serum Albumin, Bovine / Q000737:chemistry; D013012:Sorbitol / Q000737:chemistry*; D030262:Soybean Proteins / Q000737:chemistry; D013402:Sugar Alcohols / Q000737:chemistry; D000067816:Whey Proteins / Q000737:chemistry*; D014993:Xylitol / Q000737:chemistry*; D015014:Yogurt / Q000382:microbiology
chemical_list: D003451:Cryoprotective Agents; D005503:Food Additives; D030262:Soybean Proteins; D013402:Sugar Alcohols; D000067816:Whey Proteins; D012710:Serum Albumin, Bovine; D008353:Mannitol; D013012:Sorbitol; C014635:lactitol; D004896:Erythritol; D014993:Xylitol
keywords: Lactobacillus bulgaricus; bacteria survival rate; freeze drying; lyoprotectant; sugar alcohol