环境条件对丙酮酸分批发酵的影响

考察了搅拌转速、pH和温度对丙酮酸分批发酵的影响。高转速（500r／min）下，丙酮酸产率较高（71％），但葡萄糖消耗速度较慢（1．23g／（L·h））；低转速（300r／min）下，细胞消耗葡萄糖的速度加快（1．95g/（L·h）），而丙酮酸产率（0．48％）却明显下降。将搅拌转速恒定在400r／min可在一定程度上获得较高的丙酮酸产率（0．62％）和葡萄糖消耗速度（1．66g／（L·h））。CaCO3调节pH时，较多碳流从丙酮酸节点转向α-酮戊二酸节点和细胞生长，最终丙酮酸产量比NaOH调节pH时的发酵结果低38．7％；NH3·H2O调节pH时最终细胞浓度和丙酮酸产量仅为NaOH调节时的77．8％和90．9％。pH5．5时最利于丙酮酸的合成。较高的发酵温度加速T.glabrata积累丙酮酸，但同时会导致α-酮戊二酸的提前积累；而较低的温度下甘油和α-酮戊二酸积累较少，丙酮酸发酵的最适温度为28～30℃。

Effects of environmental conditions on pyruvate production

The effect of stirring speed, pH and temperature on the pyruvate production by T. glabrata CCTCC M202019, was investigated in batch culture process using a 7 L fermentor. High pyruvate yield of 71% was achieved at 500 r/min with slow glucose consumption rate of 1.23 g/（L·h）, and the glucose consumption rate was 1.95 g/（ L·h） at 300 r/min, but the pyruvate yield decreased to 48%. When the stirring speed was controlled at 400 r/min, high pyruvate yield of 62% and high glucose consumption rate of 1.66 g/（L·h） were achieved. The effect of pH-buffer agent on pyruvate production was also studied. It was found that NaOH was better for both cell growth and pyruvate production. When the pH was controlled by CaCO3, the carbon flux was directed to α-ketoglutarate accumulation and pyruvate production was decreased by 40. 9% compared with the correspond value of NaOH. The time courses of the cell growth and the pyruvate production were similar between NaOH and NH3·H2O. However, the final DCW and pyruvate production were only 77.8% and 90. 1% of the former one, respectively. At a range of 5.0 to 6. 0, 5. 5 was the optimal pH for the pyruvate production. The effect of the temperature, from 26 ℃ to 34 ℃, on the pyruvate production in a 7 L stirred fermentor by T. glabrata CCTCC M202019 was investigated. High temperatures fastened the formation of glycerol and α-ketoglutarate, and their concentrations were higher at higher temperature. The optimal temperature for the pyruvate production was 28 ℃ to 30 ℃.