Lodato P, Se govia de Huergo M, Buera M P
Departamento de Industrias, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina.
Appl Microbiol Biotechnol. 1999 Aug;52(2):215-20. doi: 10.1007/s002530051511.
The viability and thermal stability of a freeze-dried yeast strain were studied in relation to some physical properties of the matrices in which the cells were freeze-dried. Samples of inoculum with solutions of the matrix components [polyvinylpyrrolidone (PVP), maltose, trehalose, maltodextrins, or mixtures of maltodextrin and trehalose] and controls without matrices were freeze-dried and then equilibrated at several relative humidities. Viability was determined before and after freeze-drying and after heat treatment (100 min at 70 degrees C). Freeze-drying with trehalose, PVP, maltose or 1.8-kDa maltodextrin, and mixtures of maltodextrin/trehalose increased viability in comparison with controls. The 3.6-kDa maltodextrin was ineffective at protecting the cells during freeze-drying. The glass transition temperature (Tg), which depends on moisture content, was indicated as a possible factor to determine the stability of labile materials. Protective effects of the excipients during thermal treatment were analysed in relation to the physical changes (collapse or structural shrinkage) which were dependent on the Tg of the systems. The presence of a certain amount of amorphous disaccharides during freeze-drying and heating was found to be a critical factor for ensuring cell viability, which was protected even in rubbery (above Tg) matrices.
研究了冻干酵母菌株的活力和热稳定性与细胞冻干所用基质的一些物理性质之间的关系。将接种物与基质成分[聚乙烯吡咯烷酮（PVP）、麦芽糖、海藻糖、麦芽糊精或麦芽糊精与海藻糖的混合物]的溶液以及不含基质的对照物进行冻干，然后在几种相对湿度下平衡。在冻干前后以及热处理（70℃下100分钟）后测定活力。与对照相比，用海藻糖、PVP、麦芽糖或1.8 kDa麦芽糊精以及麦芽糊精/海藻糖混合物进行冻干可提高活力。3.6 kDa麦芽糊精在冻干过程中对细胞的保护作用无效。取决于水分含量的玻璃化转变温度（Tg）被认为是决定不稳定材料稳定性的一个可能因素。根据系统的Tg所依赖发生的物理变化（塌陷或结构收缩）分析了赋形剂在热处理过程中的保护作用。发现冻干和加热过程中一定量无定形二糖的存在是确保细胞活力的关键因素，即使在橡胶态（高于Tg）基质中细胞也受到保护。
