Department of Biotechnology and Food Microbiology, Faculty of Food Science, University of Environmental and Life Sciences, Norwida 25/27, Wrocław, 50-375 Wrocław, Poland.
J Biotechnol. 2011 Mar 10;152(1-2):54-7. doi: 10.1016/j.jbiotec.2011.01.007. Epub 2011 Jan 22.
The aim of the study was to examine how the dilution rate and the chemical composition of the production medium impacts on the synthesis of citric acid by the Yarrowia lipolytica strain Wratislavia AWG7 from glycerol in a chemostat culture. The yeast Y. lipolytica Wratislavia AWG7, an acetate (acet(-)) and morphological (fil(-)) mutant, was cultured in a nitrogen- and phosphorus-limited medium at the dilution rate of 0.009-0.031h(-1) in the chemostat. Under steady-state conditions, the increase in the dilution rate was paralleled by the decrease in citric acid concentration (from 86.5 to 51.2gL(-1)), as well as by the increase in the volumetric rate (from 0.78 to 1.59gL(-1)h(-1)) and specific rate (from 0.05 to 0.18gg(-1)h(-1)) of citric acid production. The yield of the production process varied from 0.59 to 0.67gg(-1). In a 550-h continuous culture of the yeast test, at a dilution rate of 0.01h(-1), in a medium with enhanced concentrations of carbon, nitrogen and phosphorus sources, the concentration of citric acid, the concentration of biomass and the volumetric rate of citric acid production were 97.8gL(-1), 22.2gL(-1) and 0.98gL(-1)h(-1), respectively. The yield of the process decreased to 0.49gg(-1). The number of dead cells did not exceed 1% while that of the budding cells accounted for about 20%. Owing to the low content of isocitric acid and polyols, the fermentation process was characterized by a high purity. This study has produced the following finding: the double mutant Y. lipolytica AWG7 is an effective citric acid producer, with the ability to preserve its properties unchanged during the long run of the continuous chemostat process. This is a valued technological feature of such mutants.
本研究旨在考察稀释率和生产培养基的化学成分如何影响脂肪酵母（Yarrowia lipolytica）Wratislavia AWG7 菌株在恒化器培养中从甘油合成柠檬酸。酵母 Y. lipolytica Wratislavia AWG7 是一种乙酸盐（acet(-)）和形态（fil(-)）突变体，在氮磷有限的培养基中，在恒化器中以 0.009-0.031h(-1) 的稀释率培养。在稳态条件下，随着稀释率的增加，柠檬酸浓度（从 86.5 降至 51.2gL(-1)）降低，柠檬酸的比生产速率（从 0.78 升至 1.59gL(-1)h(-1)）和特定生产速率（从 0.05 升至 0.18gg(-1)h(-1)）增加。生产过程的产率从 0.59 至 0.67gg(-1)变化。在酵母试验的 550 小时连续培养中，在稀释率为 0.01h(-1)、碳源、氮源和磷源浓度增强的培养基中，柠檬酸浓度、生物量浓度和柠檬酸比生产速率分别为 97.8gL(-1)、22.2gL(-1)和 0.98gL(-1)h(-1)。过程的产率下降到 0.49gg(-1)。死细胞的数量不超过 1%，而芽殖细胞的数量约占 20%。由于异柠檬酸和多元醇的含量低，发酵过程具有高纯度的特点。本研究得出以下结论：双突变体 Y. lipolytica AWG7 是一种有效的柠檬酸生产菌，在长期的恒化器连续过程中能够保持其特性不变。这是此类突变体的一个有价值的技术特征。
