拟干酪乳杆菌发酵生产L-乳酸过程中在线生理参数CER和RQ用于指导发酵过程优化

Optimization of L- lactic acid fermentation process in Lactobacillus paracasei through on- line physiological parameter CER and RQ

生理参数二氧化碳释放速率(CER)和呼吸商(RQ)对于深入理解生物过程的变化具有非常重要的意义。本研究以拟干酪乳杆菌发酵生产L-乳酸过程为研究对象,解析了发酵过程中CER和RQ变化与细胞生长和代谢之间关系,结果表明,CER与细胞生长速率密切相关,能够有效表征菌体的生长状态,而RQ值能很好地反映过程中代谢途径的变化。将CER和RQ作为在线指导参数,通过分阶段氮源添加策略,使得L-乳酸产率和转化率较原始发酵工艺分别提高了5.9%和3.0%,而且副产物乙酸和乙偶姻的浓度分别下降了31.3%和24.7%。因此,通过生理参数CER和RQ的变化对发酵过程进行优化,能够有效地提高L-乳酸的发酵产量和质量。

Carbon dioxide evolution rate（ CER） and respiratory quotient（ RQ） are two important physiological parameters for deep understanding of bioprocesses. In this study,on the basis of L- lactic acid production by Lactobacillus paracasei,the relationships of CER and RQ with cell growth and metabolism were investigated. The results indicated that CER was closely related to cell growth rate,and it could characterize the cell growth status effectively.Furthermore,during the fermentation,intracellular metabolic pathway change could be well reflected by macroscopical RQ level.Through adoption of CER and RQ as online indicative parameters,and applying rational step wise nitrogen source addition strategy,overall L- lactic acid productivity and yield improved by 5.9% and3.0%,respectively,while the primary byproducts acetic acid and acetoin decreased by 31.3% and 24.7%. On the basis of these results,both of L- lactic acid quantity and quality could be efficiently improved through on- line monitoring physiological parameters CER and RQ.