Bergmaier D, Champagne C P, Lacroix C
Dairy Research Centre STELA, Pavillon Paul Comtois, Université Laval, Québec, PQ, Canada.
J Appl Microbiol. 2005;98(2):272-84. doi: 10.1111/j.1365-2672.2004.02462.x.
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). 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.
目的：研究了在乳清渗透液培养基中，使用鼠李糖乳杆菌RW - 9595M的游离细胞和固定在固体多孔载体（ImmobaSil）上的细胞进行恒化器培养时的生物量和胞外多糖（EPS）产量。 方法与结果：在添加酵母提取物（YE）/矿物质的乳清渗透液中，以0.3至0.8 h⁻¹的稀释率（D）对游离细胞进行连续培养9天。在低稀释率0.3 h⁻¹时，获得了最大EPS产量（1808 mg l⁻¹）和体积产率（542.6 mg l⁻¹ h⁻¹）。在一个两级生物反应器系统中进行连续发酵，该系统由第一阶段的固定化细胞和第二阶段接种在第一反应器中产生的游离细胞组成，持续进行了32天。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。仅发现了一个关于乳酸产量的具有统计学意义的模型。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，且平均可溶性EPS产量较低（138 mg l⁻¹）。在不同的发酵条件和时间下，两级系统的聚集体体积产率在5.7至49.5 g l⁻¹ h⁻¹之间变化。聚集体含有非常高的生物量浓度，通过氮分析估计占聚集体干重的74%，通过DNA提取方法测定为4.3×10¹² CFU g⁻¹，并且含有高含量的不溶性多糖（14.2%）。在培养24天时，不溶性EPS浓度和体积产率分别为1250 mg l⁻¹和2240 mg l⁻¹ h⁻¹。当细胞在连续三个批次培养中孵育时，生理变化显示是可逆的。 结论：使用鼠李糖乳杆菌RW - 9595M进行连续游离细胞恒化器培养期间的EPS产量和体积产率是文献中报道的乳酸菌的最高值之一。固定化和连续培养导致鼠李糖乳杆菌RW - 9595M的可溶性EPS产量较低，以及较大的形态和生理变化，形成了主要由生物量和不溶性EPS组成的宏观聚集体。 研究的意义和影响：这是第一项关于固定化乳酸菌连续生产EPS的研究。固定化和培养时间诱导细胞聚集，可用于生产具有非常高活细胞和EPS浓度的新型合生元产品。
Meded Rijksuniv Gent Fak Landbouwkd Toegep Biol Wet. 2001
Int J Food Microbiol. 2006-3-15
Biotechnol Bioeng. 1995-3-5
Appl Microbiol Biotechnol. 2002-10
Front Microbiol. 2015-9-11
Appl Environ Microbiol. 2006-12
Zotero 插件