title: Protective effect of sucrose on the membrane properties of Lactobacillus casei Zhang subjected to freeze-drying.
abstract: The purpose of this research was to investigate the influence of sucrose at 2.0, 4.0, and 8.0% as a protectant during freeze-drying on the viability and membrane properties of Lactobacillus casei Zhang. Membrane properties were determined using zeta potential, hydrophobicity, fluidity, and integrity before and after freeze-drying. Exposing L. casei Zhang to sucrose protected it from drastic changes in cell surface electrophoretic mobility and hydrophobicity in contrast with the untreated condition, and the effect was dose related. Sucrose caused an increase in membrane fluidity compared with the control sample. Moreover, 2.0% sucrose decreased the general polarization values less than 4.0 or 8.0% sucrose, while 4.0% sucrose and 8.0% sucrose had no significant difference in decreasing general polarization values (P < 0.05). L. casei Zhang freeze-dried in the presence of 2.0% sucrose retained up to 23.7% membrane integrity, whereas cells freeze-dried with 4.0 and 8.0% sucrose had 32.4 and 37.6% membrane integrity compared with that of L. casei Zhang before freeze-drying. Correspondingly, the number of survivors of L. casei Zhang, determined by the plate count method, decreased from 8.02 to 0.63 log CFU/ml after freeze-drying in the absence of sucrose. However, in the presence of 2.0, 4.0, and 8.0% sucrose, the numbers of survivors were 2.01, 2.87, and 3.20 log CFU/ml after freeze-drying, respectively. The present work suggested that sucrose was an effective membrane protectant at 2.0, 4.0, or 8.0% on the surface zeta potential, hydrophobicity, fluidity, and integrity of L. casei Zhang.
authors.affiliation: College of Biotechnology and Food Science, Tianjin University of Commerce, Tianjin, People's Republic of China.
authors.forename: Haiping
authors.initials: H
authors.lastname: Li
authors.forename: Meijun
authors.initials: M
authors.lastname: Lu
authors.forename: Hongfang
authors.initials: H
authors.lastname: Guo
authors.forename: Wei
authors.initials: W
authors.lastname: Li
authors.forename: Heping
authors.initials: H
authors.lastname: Zhang
mesh_terms: D002462:Cell Membrane / Q000187:drug effects*; D015169:Colony Count, Microbial; D003451:Cryoprotective Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005516:Food Microbiology; D005612:Freeze Drying; D057927:Hydrophobic and Hydrophilic Interactions; D007780:Lacticaseibacillus casei / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D008560:Membrane Fluidity; D008563:Membrane Lipids; D008564:Membrane Potentials; D050296:Microbial Viability; D019936:Probiotics; D013395:Sucrose / Q000494:pharmacology*
chemical_list: D003451:Cryoprotective Agents; D008563:Membrane Lipids; D013395:Sucrose