Shibasaki-Kitakawa Naomi, Iizuka Yasuhiro, Takahashi Atsushi, Yonemoto Toshikuni
Department of Chemical Engineering, Tohoku University, Sendai, Japan.
Interdisciplinary Research Center for Catalytic Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.
Bioprocess Biosyst Eng. 2017 Feb;40(2):211-219. doi: 10.1007/s00449-016-1688-4. Epub 2016 Oct 3.
As one of the strategies for efficient production of a metabolite from cell cultures, a kinetic model is very useful tool to predict productivity under various culture conditions. In this study, we propose a kinetic model for flavonoid production in tea cell culture based on the cell life cycle and expression of PAL, the gene encoding phenylalanine ammonia-lyase (PAL)-the key enzyme in flavonoid biosynthesis. The flavonoid production rate was considered to be related to the amount of active PAL. Synthesis of PAL was modelled based on a general gene expression/translation mechanism, including the transcription of DNA encoding PAL into mRNA and the translation of PAL mRNA into the PAL protein. The transcription of DNA was assumed to be promoted at high light intensity and suppressed by a feedback regulatory mechanism at high flavonoid concentrations. In the model, mRNA and PAL were considered to self-decompose and to be lost by cell rupture. The model constants were estimated by fitting the experimental results obtained from tea cell cultures under various light intensities. The model accurately described the kinetic behaviors of dry and fresh cell concentrations, glucose concentration, cell viability, PAL specific activity, and flavonoid content under a wide range of light intensities. The model simulated flavonoid productivity per medium under various culture conditions. Therefore, this model will be useful to predict optimum culture conditions for maximum flavonoid productivity in cultured tea cells.
作为从细胞培养物中高效生产代谢物的策略之一，动力学模型是预测各种培养条件下生产率的非常有用的工具。在本研究中，我们基于细胞生命周期以及苯丙氨酸解氨酶（PAL）（黄酮类生物合成中的关键酶）编码基因PAL的表达，提出了一个茶细胞培养中黄酮类化合物生产的动力学模型。黄酮类化合物的生产率被认为与活性PAL的量有关。基于一般的基因表达/翻译机制对PAL的合成进行建模，包括将编码PAL的DNA转录为mRNA以及将PAL mRNA翻译为PAL蛋白。假设DNA转录在高光强度下被促进，而在高黄酮类化合物浓度下通过反馈调节机制被抑制。在该模型中，mRNA和PAL被认为会自我分解并因细胞破裂而损失。通过拟合在各种光强度下从茶细胞培养物获得的实验结果来估计模型常数。该模型准确地描述了在广泛的光强度下干、鲜细胞浓度、葡萄糖浓度、细胞活力、PAL比活性和黄酮类化合物含量的动力学行为。该模型模拟了各种培养条件下每培养基的黄酮类化合物生产率。因此，该模型将有助于预测培养茶细胞中黄酮类化合物最大生产率的最佳培养条件。
