丙酮酸分批发酵的供氧控制模式

以一株光滑球拟酵母的多重维生素营养缺陷型为研究菌株,考察了分批发酵中不同体积传氧系数(KL_a)对其产丙酮酸性能的影响.高KL_a(450 h^-1)下,丙酮酸产率较高(0.797 g·g^-1),但葡萄糖消耗速度较慢(1.14 g·L^-1·h^-1);低KL_a(200 h^-1)下,葡萄糖消耗速度快(1.97 g·L^-1·h^-1),然而丙酮酸产率(0.483 g·g^-1)却明显下降.根据发酵过程主要参数和碳流分配的变化特性提出了发酵前16h控制KL_a为450h^-1、16h后控制KL_a为200 h^-1的分阶段供氧控制模式,结果实现了高产量(69.4 g·L^-1)、高产率(0.636 g·g^-1)和高葡萄糖消耗速度(1.95g·L^-1·h^-1)的相对统一,丙酮酸生产强度(1.24g·L^-1·h^-1)比控制KL_a恒定为450、300和200h^-1的过程分别提高了36％、23％和31％.实验数据表明,供氧良好状态下细胞产丙酮酸性能出现的差异可能是由维生素处于亚适量水平时酵解产生的NADH去路不同,导致细胞处于不同的能量水平而引起的.

OXYGEN- SUPPLY CONTROL MODE FOR EFFICIENT PRODUCTION OF PYRUVATE IN BATCH PROCESS

The effect of volumetric oxygen transfer coefficient (kL_a), on the performance of producing pyruvate by a multi - vitamin - auxotrophic yeast of Torulopsis glabrata , was investigated in batch fermentation process. High yield of pyruvate to glucose (0.797 g·g^-1) was achieved at higher kL_a (450 h^-1), while the glucose consumption rate was low (1.14 g·L^-1·h^-1). Glucose consumption was enhanced at lower kLa (200 h^-1), however, the yield of pyruvate to glucose decreased to 0.483 g·g^-1. Based on the characteristics of process parameters and carbon flux distribution, a two - stage oxygen supply control mode, in which kL_a was controlled at 450 h in the first 16 h then switched to 200 h after 16 h, was proposed and experimentally verified. Relative high concentration of pyruvate (69.4 g·L^-1), high yield of pyruvate to glucose (0.636 g· g^-1), and high glucose consumption rate (1.95 g·L^-1·h^-1) was achieved by applying this mode. The productivity (1.24g·L^-1·h^-1) was improved by 36% , 23% and 31% than the cases of constant KL_a (450 h^-1, 300 h^-1 and 200 h^-1), respectively. Experimental results indicate that the difference between the performance of producing pyruvate under favorable state of oxygen- supply was caused by the different energy state of cell, which may be due to the different regenerated pathways of NADH generated from glycolysis.