Production of exopolysaccharide by Lactobacillus rhamnosus R and analysis of its enzymatic degradation during prolonged fermentation
Production of exopolysaccharide by Lactobacillus rhamnosus R and analysis of its enzymatic degradation during prolonged fermentation
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DOI：
10.1128/aem.66.6.2302-2310.2000
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发表时间：
2000-06-01
影响因子：
4.4
通讯作者：
Cerning, J
中科院分区：
文献类型：
--
作者：
Pham, PL;Dupont, I;Cerning, J
研究了鼠李糖乳杆菌（Lactobacillus rhamnosus R）在添加葡萄糖或乳糖的基础培养基上生长时产生外多糖（EPS）的潜力。L. rhamnosus R的EPS生产部分与生长有关，两种糖合成的EPS约为每升500 mg。产物产率系数（Y-EPS/S）分别为3.15 (0.0315 g EPS [g乳糖]（-1）和2.88 （0.0288 g EPS [g葡萄糖](-1)）。结果表明，随着发酵时间的延长，EPS的产量明显下降。通过测定EPS的分子量和粘度来评估其在发酵过程中的降解情况。由于这些减少可能对EPS的产量和增粘性能产生负面影响，因此有必要研究与此分解相关的可能原因。在不同的培养时间提取的EPS粘度和分子量的下降使我们怀疑在发酵培养基中存在解聚酶。我们对酶生产谱的研究显示了大量的糖水解酶（α - d -葡萄糖苷酶、β - d -葡萄糖苷酶、α - d -半乳糖糖苷酶、β - d -半乳糖糖苷酶、β - d -葡萄糖醛酸酶和一些α - l -鼠李糖糖苷酶）。这些酶被定位，其中两个（α - d -葡萄糖苷酶和β - d -葡萄糖醛酸酶）被部分纯化和表征。当与EPS孵育时，这些酶能够降低聚合物的粘度并释放一些还原糖。延长孵育时间（27小时）后，粘度损失增加到33%。
The potential of Lactobacillus rhamnosus R for producing exopolysaccharide (EPS) when grown on basal minimum medium supplemented with glucose or lactose was investigated. EPS production by L. rhamnosus R is partially growth associated and about 500 mg of EPS per liter was synthesized with both sugars. The product yield coefficient (Y-EPS/S) was 3.15 (0.0315 g of EPS [g of lactose](-1)) and 2.88 (0.0288 g of EPS [g of glucose](-1)). It was clearly shown that the amount of EPS produced declined upon prolonged fermentation. Degradation of EPS in fermentation processes was also assessed by measuring its molecular weights and viscosities. As these reductions might have a negative effect on the yield and viscosifying properties of EPS, it was essential to examine possible causes related to this breakdown. The decrease in viscosities and molecular weights of EPS withdrawn at different cultivation times permitted us to suspect the presence of a depolymerizing enzyme In the fermentation medium. Our study on enzymatic production profiles showed a large spectrum of glycohydrolases (alpha-D-glucosidase, beta-D-glucosidase, alpha-D-galactosidase, beta-D-galactosidase, beta-D-glucuronidase, and some traces of alpha-L-rhamnosidase). These enzymes were localized, two of them (alpha-D-glucosidase and beta-D-glucuronidase) were partially purified and characterized. When incubated with EPS, these enzymes were capable of lowering the viscosity of the polymer as well as liberating some reducing sugars. Upon prolonged incubation (27 h), the loss of viscosity was increased up to 33%.