Department of Chemical Engineering, Chulalongkorn University, Bangkok, 10330, Thailand.
J Microbiol Biotechnol. 2010 Jan;20(1):110-6.
Lactic acid (LA) fermentation by Lactobacillus salivarius ATCC 11741 immobilized on loofa sponge (LS) was evaluated. To increase the surface area of LS for cell immobilization, H2O2 and chitosan were introduced as surface modifying reagents. Four chitosan of different molecular weight were separately coated on LS. All experiments were conducted in shaking flask mode at 100 rpm rotating speed and 37 degrees with 5% CaCO3 as a pH regulating agent. The effects of initial glucose concentration were investigated in the range of 20-100 g L-1 on LA fermentation by free cells. The results indicate that the maximum concentration of LA was produced with 50 g L-1 glucose concentration. The immobilized cell system produced 1.5 times higher concentration than free cells for 24 h of fermentation. Moreover, immobilized cells can shorten the fermentation time by 2 fold compared with free cells at the same level of LA concentration. At 1% w/v chitosan in 2% v/v acetic acid, Yp/s and productivities of various molecular weight of chitosan were insignificantly different. Repeated batch fermentations showed 5 effective recycles with Yp/s and productivity in the range of 0.55-0.85 and 0.90-1.20 g L-1 h-1, respectively. It is evident that immobilization of L. salivarius onto LS permits reuse of the system under these fermentation conditions. Scanning electron micrographs indicated that there were more intact cells on the chitosan-treated LS than on the untreated LS, thus confirming the effectiveness of the LS-chitosan combination when being utilized as a promising immobilization carrier for LA fermentation.
唾液乳杆菌 ATCC 11741 固定在丝瓜络上进行乳酸发酵的评估。为了增加丝瓜络用于细胞固定化的表面积，引入了 H2O2 和壳聚糖作为表面改性试剂。四种不同分子量的壳聚糖分别涂覆在丝瓜络上。所有实验均在 100rpm 转速和 37°C 的摇瓶模式下进行，使用 5% CaCO3 作为 pH 调节剂。研究了初始葡萄糖浓度在 20-100gL-1 范围内对游离细胞乳酸发酵的影响。结果表明，在 50gL-1 葡萄糖浓度下，LA 的最大浓度最高。固定化细胞系统在 24 小时的发酵过程中产生的 LA 浓度比游离细胞高 1.5 倍。此外，与游离细胞相比，固定化细胞可以将发酵时间缩短 2 倍，达到相同的 LA 浓度水平。在 1%w/v 壳聚糖在 2%v/v 乙酸中，各种分子量的壳聚糖的 Yp/s 和产率没有显著差异。分批重复发酵显示，在 Yp/s 和产率分别为 0.55-0.85 和 0.90-1.20gL-1h-1 的范围内，有 5 次有效循环。显然，在这些发酵条件下，将唾液乳杆菌固定在丝瓜络上允许系统重复使用。扫描电子显微镜照片表明，经过壳聚糖处理的丝瓜络上的完整细胞比未经处理的丝瓜络上的更多，从而证实了丝瓜络-壳聚糖组合在作为 LA 发酵有前途的固定化载体时的有效性。
