title: Effects of cryoprotectants on viability of Lactobacillus reuteri CICC6226.
abstract: Freeze-drying is commonly used to preserve probiotics, but it could cause cell damage and loss of viability. The cryoprotectants play an important role in the conservation of viability during freeze-drying. In this study, we investigated the survival rates of Lactobacillus reuteri CICC6226 in the presence of cryoprotectants such as sucrose, trehalose, and reconstituted skim milk (RSM). In addition, we determined the activities of hexokinase (HK), pyruvate kinase (PK), lactate dehydrogenase (LDH), and ATPases immediately following the freeze-drying. The results showed that the differences in HK and PK activities with and without the cryoprotectants during freeze-drying were not significant, but cell viability and activities of LDH and ATPase were significantly different (P<0.01) prior to and after freeze-drying. Meanwhile, the results showed that the maintenance of the membrane integrity and fluidity was improved in the presence of the 10% trehalose or 10% RSM than other treatments during freeze-drying. These results have provided direct biochemical and metabolic evidence of injured cell during freeze-drying. Freeze-drying damaged membrane structure and function of cell and inactivated enzymes (LDH and ATPases). The results imply that LDH and ATPases are key markers and could be used to evaluate the effect of cryoprotectants on viability and metabolic activities of L. reuteri CICC6226 during freeze-drying.
authors.affiliation: State Key Laboratory of Food Science and Technology, School of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, People's Republic of China.
authors.forename: Baokun
authors.initials: B
authors.lastname: Li
authors.forename: Fengwei
authors.initials: F
authors.lastname: Tian
authors.forename: Xiaoming
authors.initials: X
authors.lastname: Liu
authors.forename: Jianxin
authors.initials: J
authors.lastname: Zhao
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002462:Cell Membrane / Q000502:physiology; D003451:Cryoprotective Agents / Q000378:metabolism*; D005612:Freeze Drying / Q000379:methods*; D006593:Hexokinase / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D052200:Limosilactobacillus reuteri / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology / Q000528:radiation effects*; D008560:Membrane Fluidity / Q000187:drug effects / Q000528:radiation effects; D050296:Microbial Viability / Q000187:drug effects* / Q000528:radiation effects*; D008892:Milk; D011770:Pyruvate Kinase / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism; D014199:Trehalose / Q000378:metabolism
chemical_list: D003451:Cryoprotective Agents; D013395:Sucrose; D014199:Trehalose; D007770:L-Lactate Dehydrogenase; D006593:Hexokinase; D011770:Pyruvate Kinase; D000251:Adenosine Triphosphatases