Collins Jonathan, Grund Marcel, Brandenbusch Christoph, Sadowski Gabriele, Schmid Andreas, Bühler Bruno
Laboratory of Chemical Biotechnology, TU Dortmund University, Emil-Figge-Str. 66, 44227, Dortmund, Germany.
J Ind Microbiol Biotechnol. 2015 Jul;42(7):1011-26. doi: 10.1007/s10295-015-1621-x. Epub 2015 Apr 28.
Emulsion stability plays a crucial role for mass transfer and downstream processing in organic-aqueous bioprocesses based on whole microbial cells. In this study, emulsion stability dynamics and the factors determining them during two-liquid phase biotransformation were investigated for stereoselective styrene epoxidation catalyzed by recombinant Escherichia coli. Upon organic phase addition, emulsion stability rapidly increased correlating with a loss of solubilized protein from the aqueous cultivation broth and the emergence of a hydrophobic cell fraction associated with the organic-aqueous interface. A novel phase inversion-based method was developed to isolate and analyze cellular material from the interface. In cell-free experiments, a similar loss of aqueous protein did not correlate with high emulsion stability, indicating that the observed particle-based emulsions arise from a convergence of factors related to cell density, protein adsorption, and bioreactor conditions. During styrene epoxidation, emulsion destabilization occurred correlating with product-induced cell toxification. For biphasic whole-cell biotransformations, this study indicates that control of aqueous protein concentrations and selective toxification of cells enables emulsion destabilization and emphasizes that biological factors and related dynamics must be considered in the design and modeling of respective upstream and especially downstream processes.
乳液稳定性在基于全微生物细胞的有机-水生物过程中的传质和下游加工中起着至关重要的作用。在本研究中，针对重组大肠杆菌催化的立体选择性苯乙烯环氧化反应，研究了双液相生物转化过程中的乳液稳定性动态及其决定因素。加入有机相后，乳液稳定性迅速增加，这与水相培养液中溶解蛋白的损失以及与有机-水界面相关的疏水细胞部分的出现有关。开发了一种基于相转变的新方法来从界面分离和分析细胞物质。在无细胞实验中，水相蛋白的类似损失与高乳液稳定性无关，这表明观察到的基于颗粒的乳液是由与细胞密度、蛋白吸附和生物反应器条件相关的多种因素共同作用产生的。在苯乙烯环氧化过程中，乳液失稳与产物诱导的细胞毒性相关。对于双相全细胞生物转化，本研究表明控制水相蛋白浓度和细胞的选择性毒性可实现乳液失稳，并强调在各自上游尤其是下游过程的设计和建模中必须考虑生物学因素及相关动态。
