PubMed · 5951484
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F L Soper. 1966. Smallpox--world changes and implications for eradication.. https://doi.org/10.2105/ajph.56.10.1652
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Maintaining the viability of lactic acid bacteria during dehydration and subsequent storage remains a significant challenge. Here, we employed single-cell RNA sequencing to reveal the heterogeneous stress responses of Lactobacillus delbrueckii subsp. bulgaricus, identifying seven distinct transcriptional clusters across the liquid culture, freeze-drying, and storage phases. The dominant clusters in the freeze-drying and storage were not completely consistent, showing significant functional differentiation. Genomic stability may be important for survival during freeze-drying and storage, while intracellular energy homeostasis appears important for viability during storage. The magnesium transporter mgtB was highly expressed in clusters tolerant to freeze-drying and storage, suggesting a critical role for Mg2+ homeostasis. Further experimental validation confirmed that Mg2+ treatment significantly bolstered stress resistance, increasing immediate post-freeze-drying survival by over 2-fold (up to 92.90%) and post-storage survival by over 5-fold (up to 5.98%). Proteomic data indicated that Mg2+ supplementation correlated with the maintenance of several biological functions potentially relevant to bacterial survival during freeze-drying and storage, including DNA repair, translation, and central carbon metabolism. These findings provide a map of microbial stress resistance through population heterogeneity and offer a potential strategy that may be adapted for enhancing the stability of other industrial lactic acid bacteria products.
To preserve the size and transfection potential of polymer-plasmid complexes. Freeze-drying and freeze-thawing were used for stabilization of these complexes. The concentration of the sugars is an important factor affecting both the size and transfection capability of the complexes after freeze-drying and freeze-thawing. However, the type of lyoprotectant (sugar) used is of minor importance. It is also shown that when damage to polymer-plasmid complexes occurs, it results from the drying process but is not due to the freezing step.
In this work we describe the structural investigation of the model protein recombinant human growth hormone (rhGH) under conditions relevant to polymeric sustained-delivery depots, including the dried protein entrapped in a film of poly(DL-lactic-co-glycolic)acid. At each step of the procedure, dehydration of rhGH by lyophilization, suspension in methylene chloride, and drying from that suspension, the structure of rhGH was probed noninvasively using Fourier transform infrared (FTIR) spectroscopy. We found that the structure of rhGH was significantly changed by the dehydration process as indicated by a marked drop in the alpha-helix content and increase in the beta-sheet content. Subsequent suspension of this powder in methylene chloride, drying from that suspension, and drying from a methylene chloride/PLGA solution introduced only minor additional structural changes when using appropriate conditions. This result is likely due to the limited molecular mobility of proteins in nonprotein-dissolving organic solvents. Finally, when rhGH was co-lyophilized with the lyoprotectant trehalose, which preserves the secondary structure, the rhGH entrapped in the PLGA matrix also had a nativelike secondary structure.