Huang Hanjing, Yang Shang-Tian, Ramey David E
Department of Chemical Engineering, The Ohio State University, 140 West 19th Avenue, Columbus, OH 43210, USA.
Appl Biochem Biotechnol. 2004 Spring;113-116:671-88. doi: 10.1385/abab:114:1-3:671.
An energy-efficient hollow-fiber membrane extraction process was successfully developed to separate and recover lactic acid produced in fermentation. Although many fermentation processes have been developed for lactic acid production, an economical method for lactic acid recovery from the fermentation broth is still needed. Continuous extraction of lactic acid from a simulated aqueous stream was achieved by using Alamine 336 in 2-octanol contained in a hollow-fiber membrane extractor. In this process, the extractant was simultaneously regenerated by stripping with NaOH in a second membrane extractor, and the final product is a concentrated lactate salt solution. The extraction rate increased linearly with an increase in the Alamine 336 content in the solvent (from 5 to 40%). Increasing the concentration of the undissociated lactic acid in the feed solution by either increasing the lactate concentration (from 5 to 40 g/L) or decreasing the solution pH (from 5.0 to 4.0) also increased the extraction rate. Based on these observations, a reactive extraction model with a first-order reaction mechanism for both lactic acid and amine concentrations was proposed. The extraction rate also increased with an increase in the feed flow rate, but not the flow rates of solvent and the stripping solution, suggesting that the process was not limited by diffusion in the liquid films or membrane pores. A mathematical model considering both diffusion and chemical reaction in the extractor and back extractor was developed to simulate the process. The model fits the experimental data well and can be used in scale up design of the process.
成功开发了一种节能中空纤维膜萃取工艺，用于分离和回收发酵过程中产生的乳酸。尽管已经开发了许多用于生产乳酸的发酵工艺，但仍需要一种从发酵液中回收乳酸的经济方法。通过在中空纤维膜萃取器中使用2-辛醇中的阿拉明336，实现了从模拟水流中连续萃取乳酸。在此过程中，萃取剂在第二个膜萃取器中用NaOH汽提同时再生，最终产物是浓缩的乳酸盐溶液。萃取率随溶剂中阿拉明336含量的增加（从5%到40%）呈线性增加。通过提高乳酸盐浓度（从5 g/L到40 g/L）或降低溶液pH值（从5.0到4.0）来增加进料溶液中未解离乳酸的浓度，也会提高萃取率。基于这些观察结果，提出了一种针对乳酸和胺浓度均具有一级反应机理的反应萃取模型。萃取率也随进料流速的增加而增加，但不随溶剂和反萃液流速的增加而增加，这表明该过程不受液膜或膜孔中扩散的限制。开发了一个考虑萃取器和反萃取器中扩散和化学反应的数学模型来模拟该过程。该模型与实验数据拟合良好，可用于该过程的放大设计。
