Growth and exopolysaccharide production during free and immobilized cell chemostat culture of Lactobacillus rhamnosus RW-9595M
Growth and exopolysaccharide production during free and immobilized cell chemostat culture of Lactobacillus rhamnosus RW-9595M
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DOI：
10.1111/j.1365-2672.2004.02462.x
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发表时间：
2005-01-01
影响因子：
4
通讯作者：
Lacroix, C
中科院分区：
文献类型：
--
作者：
Bergmaier, D;Champagne, CP;Lacroix, C
目的：目的：研究鼠李糖乳杆菌rw - 9595m游离细胞和固定在固体多孔载体（ImmobaSil(R)）上的细胞在乳清渗透培养基中的恒化培养过程中生物量和胞外多糖（EPS）的产生。方法和结果：在酵母浸膏(YE)/添加乳清渗透物的矿物质中，以0.3 ~ 0.8 h（-1）的稀释率(D)连续培养游离细胞9天。低D为0.3 h（-1）时，EPS产量最高（1808 mg l(-1)），体积产率最高(542.6 mg l（-1) h(-1)）。在两段生物反应器系统中连续发酵32天，由第一期固定细胞和第二期接种第一期反应器产生的游离细胞组成。研究了YE浓度、温度和稀释率及其相互作用对生物量、EPS和乳酸产量的影响。只有乳酸生成模型具有统计学意义。显著的细胞形态和生理变化导致形成非常大的含细胞聚集体和低平均可溶性EPS产量（138 mg l(-1)）。在不同的发酵条件和时间下，两级体系的总容积率在5.7 ~ 49.5 g l(-1) h（-1）之间变化。团聚体含有非常高的生物量浓度，通过氮分析估计为团聚体干重的74%，通过DNA提取方法估计为4.3 × 10(12) CFU g(-1)，并且不溶性多糖含量高（14.2%）。24日龄时，不溶性EPS浓度为1250 mg l(-1)，体积产率为2240 mg l(-1) h（-1）。当细胞连续三次分批培养时，生理变化是可逆的。结论：鼠李糖乳杆菌RW-9595M连续自由细胞恒化培养的EPS产量和体积生产率是文献报道的乳酸菌中最高的。固定化和连续培养导致鼠李糖RW-9595M可溶性EPS产量低，形态和生理发生较大变化，形成以生物量和不溶性EPS为主的宏观聚集体。研究意义与影响：首次对固定化LAB连续生产EPS进行了研究。固定化和培养时间诱导细胞聚集，可用于生产具有很高活细胞和EPS浓度的新合成产品。
Aims: Aims: Biomass and exopolysaccharide (EPS) production were studied during chemostat cultures in whey permeate medium with Lactobacillus rhamnosus RW-9595M-free cells and cells immobilized on solid porous supports (ImmobaSil(R)).Methods and Results: A continuous culture with free cells was conducted for 9 days at dilution rates (D) between 0.3 and 0.8 h(-1) in yeast extract (YE)/mineral supplemented whey permeate. Maximum EPS production (1808 mg l(-1)) and volumetric productivity (542.6 mg l(-1) h(-1)) were obtained for a low D of 0.3 h(-1). A continuous fermentation in a two-stage bioreactor system, composed of a first stage with immobilized cells and a second stage inoculated with free cells produced in the first reactor, was carried out for 32 days. The influence of YE concentration, temperature and dilution rate, and their interactions on biomass, EPS and lactic acid production was investigated. A statistically significant model was found only for lactic acid production. Marked cell morphological and physiological changes led to the formation of very large cell-containing aggregates and a low mean soluble EPS production (138 mg l(-1)). Aggregate volumetric productivity of the two-stage system varied between 5.7 and 49.5 g l(-1) h(-1) for different fermentation conditions and times. Aggregates contained a very high biomass concentration, estimated at 74% of aggregate dry weight by nitrogen analysis and 4.3 x 10(12) CFU g(-1) by a DNA extraction method and a high nonsoluble polysaccharide content (14.2%). At age 24 days, insoluble EPS concentration and volumetric productivity were 1250 mg l(-1) and 2240 mg l(-1) h(-1) respectively. The physiological changes were shown to be reversible when cells were incubated during three successive batch cultures.Conclusions: EPS production and volumetric productivity during continuous free-cell chemostat cultures with L. rhamnosus RW-9595M are among the highest values reported for lactobacilli in literature. Immobilization and continuous culture resulted in low soluble EPS production and large morphological and physiological changes of L. rhamnosus RW-9595M, with formation of macroscopical aggregates mainly composed of biomass and nonsoluble EPS.Significance and Impact of the Study: This is the first study on continuous EPS production by immobilized LAB. Immobilization and culture time-induced cell aggregation and could be used to produce new synbiotic products with very high viable cell and EPS concentrations.