Effect of Warming Process on the Survival of Cryopreserved Human Peripheral Blood Mononuclear Cells.

It is well known that the warming process is a critical step in cell cryopreservation, affecting the survival rate of the cryopreserved cells. However, there is a lack of understanding and optimization of the warming process for the cryopreserved human peripheral blood mononuclear cells (PBMCs) that are greatly needed for the cellular/immune therapies worldwide. In this study, the effect of the warming process on cryosurvival of the PBMCs was investigated, resulting in a recommendation of an optimal warming method. In the experiments, all PBMC samples were cooled by a fixed slow cooling process and stored in a liquid nitrogen tank. The frozen samples were then warmed in water baths with stirring at various temperatures, 37°C, 42°C, and 65°C, respectively. After thawing, PBMC's viability as well as phenotypic and functional analyses were performed and evaluated. It was shown that a relatively rapid warming process at 65°C in a water bath with stirring generated a significant improvement of cell viability, recovery, and functionality of the cryopreserved PBMCs. In addition, interferon-γ and interleukin-2 secretion were much higher in PBMCs thawed at 65°C than that in 42°C and 37°C, respectively. This study suggests that a rapid warming process at 65°C in a water bath should be used to replace the current conventional warming approach at 37°C.

Optimization of Initial Cation Concentrations for L-Lactic Acid Production from Fructose by Lactobacillus pentosus Cells.

In this study, Box-Behnken design was applied to optimize the initial concentrations of 4 cations for L-lactic acid production from fructose by homologous batch fermentation of Lactobacillus pentosus cells. The optimum initial cation concentrations were obtained as 6.542 mM Mg2+, 3.765 mM Mn2+, 2.397 mM Cu2+, and 3.912 mM Fe2+, respectively. The highest L-lactic acid yield and productivity were obtained as 0.935 ± 0.005 g/g fructose and 1.363 ± 0.021 g/(L × h), respectively, with a maximum biomass concentration of 7.97 ± 0.17 g/L. The effectiveness of the optimization by Box-Behnken design was confirmed based on the small errors between predicted results and experimental results shown as 0.3%, - 0.2%, and - 1.2%, respectively. The quadratic models with high accuracy and reliability can be applied to mathematically forecasted the fermentation performance. After the optimization, the lactic acid yield and productivity were significantly improved by 3.7% and 21.0%, respectively.

L-Lactic acid production from fructose by chitosan film-coated sodium alginate-polyvinyl alcohol immobilized Lactobacillus pentosus cells and its kinetic analysis.

Under the optimal conditions of immobilization and fermentation, the highest LA yield of 0.966 ± 0.006 g/g fructose and production rate of 2.426 ± 0.018 g/(L × h) with an error of -0.5% and -0.2% to the predicted results were obtained from batch fermentation by the CS film-coated SA-PVA immobilized L. pentosus cells. The LA yield and production rate of these immobilized cells were 2.7% and 10.1% higher than that of normal SA-PVA immobilized cells respectively, and they were 5.7% and 48.4% higher than that of free cells, respectively. The effect of temperature on different types of immobilized cells and free cells was significantly different, but the effect of pH on different types of cells was not much different. The kinetic models could effectively describe the different fermentation performances of three types of cells. The immobilized cells have excellent reusability to conduct 9 runs of repeated batch fermentation.