Kwon S, Yoo I K, Lee W G, Chang H N, Chang Y K
Department of Chemical Engineering and BioProcess Engineering Research Center, Korea Advanced Institute of Science and Technology, 373-1 Kusong-dong, Yusong-gu, Taejon 305-701, South Korea.
Biotechnol Bioeng. 2001 Apr 5;73(1):25-34. doi: 10.1002/1097-0290(20010405)73:1<25::aid-bit1033>3.0.co;2-n.
It is important to produce L(+)-lactic acid at the lowest cost possible for lactic acid to become a candidate monomer material for promising biodegradable polylactic acid. In an effort to develop a high-rate bioreactor that provides high productivity along with a high concentration of lactic acid, the performance of membrane cell-recycle bioreactor (MCRB) was investigated via experimental studies and simulation optimization. Due to greatly increased cell density, high lactic acid productivity, 21.6 g L(-1) h(-1), was obtained in the reactor. The lactic acid concentration, however, could not be increased higher than 83 g/L. When an additional continuous stirred tank reactor (CSTR) was attached next to the MCRB a higher lactic acid concentration of 87 g/L was produced at significant productivity expense. When the two MCRBs were connected in series, 92 g/L lactic acid could be produced with a productivity of 57 g L(-1) h(-1), the highest productivity among the reports of L(+)-lactic acid that obtained lactic acid concentration higher than 85 g/L using glucose substrate. Additionally, the investigation of lactic acid fermentation kinetics resulted in a successful model that represents the characteristics of lactic acid fermentation by Lactobacillus rhamnosus. The model was found to be applicable to most of the existing data with MCRBs and was in good agreement with Levenspiel's product-inhibition model, and the Luedeking-Piret equation for product-formation kinetics appeared to be effective in representing the fermentation kinetics. There was a distinctive difference in the production potential of cells (cell-density-related parameter in Luedeking-Piret equation) as lactic acid concentration increases over 55 g/L, and this finding led to a more precise estimation of bioreactor performance.
为了使乳酸成为有前景的可生物降解聚乳酸的候选单体材料，以尽可能低的成本生产L(+)-乳酸至关重要。为了开发一种能够实现高生产率以及高乳酸浓度的高速生物反应器，通过实验研究和模拟优化对膜细胞循环生物反应器（MCRB）的性能进行了研究。由于细胞密度大幅增加，该反应器获得了较高的乳酸生产率，为21.6 g L(-1) h(-1)。然而，乳酸浓度无法提高到高于83 g/L。当在MCRB旁边附加一个连续搅拌釜式反应器（CSTR）时，在显著牺牲生产率的情况下产生了更高的乳酸浓度，为87 g/L。当两个MCRB串联连接时，可以生产出92 g/L的乳酸，生产率为57 g L(-1) h(-1)，这是使用葡萄糖底物获得高于85 g/L乳酸浓度的L(+)-乳酸报道中最高的生产率。此外，对乳酸发酵动力学的研究得出了一个成功的模型，该模型代表了鼠李糖乳杆菌乳酸发酵的特性。发现该模型适用于大多数现有的MCRB数据，并且与Levenspiel的产物抑制模型吻合良好，Luedeking-Piret产物形成动力学方程似乎有效地代表了发酵动力学。随着乳酸浓度超过55 g/L，细胞的生产潜力（Luedeking-Piret方程中与细胞密度相关的参数）存在明显差异，这一发现导致对生物反应器性能的估计更加精确。
