树干毕赤酵母酒精发酵碳元素代谢流向分析

实验对树干毕赤酵母（Pichia stipitis）进行了4个阶段共400 h连续恒化培养，在不同阶段以30.0 g/L葡萄糖作为基本碳源，添加30.0或15.0 g/L的木糖，通过控制温度（35±1）℃，进气量100～150mL/min，搅拌转速250～300 r/min。4个阶段共建立4个连续培养的"稳态"。对碳元素进行物料衡算发现，四个阶段碳元素回收率分别为118.0 %、105.6 %、113.5 %和94.7 %。对4个近似"稳态"的碳元素的代谢流向进行分析发现：将近50.0 %左右碳元素流向产物酒精，其次是CO2和酵母细胞；木糖醇浓度与流入底物中木糖浓度有直接关系，在相同发酵条件下流入的木糖浓度越大代谢生成木糖醇浓度也越高；实验所采用的通气条件更适合底物为30.0 g/L葡萄糖和30.0 g/L木糖混合液的连续发酵。

Analysis of carbon metabolic effluence on ethanol fermentation by Pichia stipitis

Abstract The balance computation and metabolism analysis of carbon in xylose/glucose fermentation by Pichia stipitis was studied. A 400 h continuous chemostat culture was divided into 4 phases by adding different sugar concentration during each phase. By controlling temperature of （35±1）℃ and aeration of 100～150mL/min and stirring speed of 250～300 r/min, one steady state was established during each phase. The carbon recovery ratios of the four steady states were 118.0%, 105.6%, 113.5% and 94.7 %, respectively. By analyzing of metabolic effluence of carbon, it was found that approximately 50.0 % carbon from glucose and xylose was mainly turned into ethanol, while carbon was secondly emitted as CO2 and thirdly charged into yeast cells. Xylitol concentration was correlative with substrate xylose concentration. Aeration of 100～150mL/min was appropriate to continuous fermentation with mixture substrate of 30.0 g/L xylose and 30.0 g/L glucose .