Dias Carla, Silva Corália, Freitas Claudia, Reis Alberto, da Silva Teresa Lopes
Laboratório Nacional de Energia e Geologia, Estrada do Paço do Lumiar, 22, 1649-038, Lisboa, Portugal.
Appl Biochem Biotechnol. 2016 Jul;179(5):776-87. doi: 10.1007/s12010-016-2030-y. Epub 2016 Mar 5.
The effect of the culture medium pH (3.5-6.0) on the carotenoid and lipid (as fatty acids) production by the yeast Rhodosporidium toruloides NCYC 921 was studied. Flow cytometry was used to evaluate the yeast's physiological response to different culture medium pH values. The yeast biomass concentration and lipid content were maxima at pH 4.0 (5.90 g/L and 21.85 % w/w, respectively), while the maximum carotenoid content (63.37 μg/g) was obtained at pH 5.0. At the exponential phase, the yeast cell size and internal complexity were similar, at different medium pH. At the stationary phase, the yeast cell size and internal complexity decreased as the medium pH increased. At the exponential phase, the proportion of cells with polarized membranes was always high (>80 %) but at the stationary phase, the proportion of yeast cells with depolarized membranes was dominant (>65 %) and increased with the medium pH increase. The results here reported may contribute for yeast bioprocesses optimization. For the first time, multiparameter flow cytometry was used to evaluate the impact of medium pH changes on the yeast cell physiological status, specifically on the yeast membrane potential, membrane integrity, cell size and internal complexity.
研究了培养基pH值（3.5 - 6.0）对酵母红冬孢酵母NCYC 921产类胡萝卜素和脂质（以脂肪酸计）的影响。采用流式细胞术评估酵母对不同培养基pH值的生理反应。酵母生物量浓度和脂质含量在pH 4.0时达到最大值（分别为5.90 g/L和21.85% w/w），而在pH 5.0时获得最大类胡萝卜素含量（63.37 μg/g）。在指数生长期，不同培养基pH值下酵母细胞大小和内部复杂性相似。在稳定期，酵母细胞大小和内部复杂性随培养基pH值升高而降低。在指数生长期，具有极化膜的细胞比例始终很高（>80%），但在稳定期，具有去极化膜的酵母细胞比例占主导（>65%），并随培养基pH值升高而增加。本文报道的结果可能有助于酵母生物过程的优化。首次使用多参数流式细胞术评估培养基pH值变化对酵母细胞生理状态的影响，特别是对酵母膜电位、膜完整性、细胞大小和内部复杂性的影响。
