Lactic acid bacteria, such as those of the Lactobacillus genus, naturally reside within the microbiota of the human body and have long been used as starter cultures and probiotic enhancers in fermented foods, such as fermented drinks, yoghurts and cheeses. Many of the beneficial qualities of these bacteria have traditionally been associated with the bacteria themselves, however, a recent spate of studies have demonstrated a wide variety of biological effects exhibited by lactobacilli-produced exopolysaccharides which could, theoretically, confer a range of local and systemic health benefits upon the host. In this review, we discuss the production of exopolysaccharides within the Lactobacillus genus and explore their potential as beneficial bioactive compounds.

Metabolic syndrome is a leading medical concern that affects one billion people worldwide. Metabolic syndrome is defined by a clustering of risk factors that predispose an individual to cardiovascular disease, diabetes and stroke. In recent years, the apparent role of the gut microbiota in metabolic syndrome has drawn attention to microbiome-engineered therapeutics. Specifically, lactic acid bacteria (LAB) harbors beneficial metabolic characteristics, including the production of exopolysaccharides and other microbial byproducts. We recently isolated a novel fructophilic lactic acid bacterium (FLAB), Apilactobacillus waqarii strain HBW1, from honeybee gut and found it produces a dextran-type exopolysaccharide (EPS). The objective of this study was to explore the therapeutic potential of the new dextran in relation to metabolic syndrome. Findings revealed the dextran’s ability to improve the viability of damaged HT-29 intestinal epithelial cells and exhibit antioxidant properties. In vivo analyses demonstrated reductions in body weight gain and serum cholesterol levels in mice supplemented with the dextran, compared to control (5% and 17.2%, respectively). Additionally, blood glucose levels decreased by 16.26% following dextran supplementation, while increasing by 15.2% in non-treated mice. Overall, this study displays biotherapeutic potential of a novel EPS to improve metabolic syndrome and its individual components, warranting further investigation.

Exopolysaccharides (EPSs) are metabolites synthesized and excreted by a variety of microorganisms, including lactic acid bacteria (LAB). EPS serve several biological functions such as interactions between bacteria and their environments, protection against hostile conditions including dehydration, the alleviation of the action of toxic compounds (bile salts, hydrolyzing enzymes, lysozyme, gastric, and pancreatic enzymes, metal ions, antibiotics), and stresses (changing pH, osmolarity), and evasion of the immune response and phage attack. Bacterial EPSs are considered valuable by the food, pharmaceutical, and nutraceutical industries, owing to their health-promoting benefits and rheological impacts. Numerous studies have reported the unusual antimicrobial activities of various EPS against a wide variety of pathogenic microbes (bacteria, virus, and fungi). This review aims to provide a comprehensive examination of the in vitro and in vivo antimicrobial activities of different EPSs, mainly against foodborne bacterial, fungal, and viral pathogens. The mechanism of EPS action against these pathogens as well as the methods used to measure antimicrobial activities are critically reviewed.

Exopolysaccharides (EPS) are one of the classes of extracellular biopolymers synthesized by bacteria. Some strains of lactic acid bacteria (LAB) used in the dairy industry are able to synthesize EPS (EPS(+) strains). EPS may be secreted by a cell in the form of capsule or slime. Our review describes the factors influencing the activity of EPS production by LAB, the impact of the use of EPS(+) strains on the quality of fermented milk products (yoghurt, cheeses, etc.) and pro-health properties of EPS produced by LAB. The capability to synthesize EPS by LAB depends on many factors, e.g., affiliation to species and characteristics of strain, growth stage, composition of culture medium (type of carbon and nitrogen sources, and presence of other nutrients), temperature, pH, and presence of adjuvant microflora. The presence of EPS synthesized by LAB strains has a significant effect on changes in various properties of dairy products, including: yoghurt, kefir and many other fermented milk drinks, sour cream and cheeses. The EPS act as thickening, emulsifying and gelling agents, hence the use of EPS(+) strains may become a certain alternative to the use of thickeners in, e.g., fermented milks. During formation of a casein milk curd, EPS are able to bind water and thus reduce syneresis. The high water holding capacity of EPS has a positive effect on increasing viscosity and improving texture of low-fat cheeses. EPS are claimed to have health-promoting properties, like: anticarcinogenic, antioxidative, immunomodulatory and reducing blood cholesterol.

Exopolysaccharides (EPS) are complex molecules produced by some microorganisms and used in foods as texturizers and stabilizers, their properties depending on their chemical structure. In this work, three different lactic acid bacteria (LAB), were tested for their ability to produce EPS, by using five different mono- and disaccharides as their sole carbon source. The growth and acidifying ability were analysed, the EPSs were quantified by the official method AOAC 991.43, and their chemical structure was investigated. The amount of EPS varied from 0.71 g/L to 2.38 g/L, and maltose was the best sugar for EPS production by Lacticaseibacillus paracasei 2333. Lacticaseibacillus rhamnosus 1019 produced the highest amount when fed with lactose, whereas the EPS amount of Lactobacillus bulgaricus 1932 was not significantly different depending on the sugar type. The EPS chains consisted of fructose, galactose, glucose, mannose, ribose, glucosamine, galactosamine, and in some cases rhamnose in different proportions, depending on the strain and carbon source. The molecular weight of EPS ranged from <10 KDa to >500 KDa and was again highly dependent on the strain and the sugar used, suggesting the possibility of growing different strains under different conditions to obtain EPS with different potential applications in the food system.

Phenol-sulfuric acid method is one of the most common methods applied to the analysis of total sugar content during polysaccharides study. However, it was found that the results obtained from the phenol-sulfuric acid method was generally lower than the real total sugar content, especially when acidic monosaccharides were contained in the polysaccharides samples. Therefore, the present study focused to unveil the proposed problem. Based on the optimization of colorimetric conditions, such as optimal wave length of absorption, linearity range, color reaction time and temperature, it indicated that the phenol-sulfuric acid method was a convenient and accurate way for the total sugar content analysis. In addition, the color-rendering capabilities of 10 common monosaccharides were systematically analyzed to obtain a relative correction factor for each monosaccharide relative to glucose, which was proved to be the main reason for the deviation in the detection of total sugar content. Moreover, the key points during the application of phenol-sulfuric acid method were suggested. This study provides a scientific theoretical basis and a reliable experimental research method for the accurate determination of total sugar content by the phenol-sulfuric acid method, and which will also promote the application of this convenient method in the polysaccharides study.

为提高戊糖乳杆菌YY112 胞外多糖的产量,本研究结合单因素试验、正交试验、Box-Behnken响应面试验设计,对该菌株产多糖的营养条件和发酵工艺进行优化。结果表明:在本次研究的范围内,MRS培养基为适宜的基础培养基;蔗糖为适宜碳源,添加量为质量体积比3%;大豆蛋白胨为适宜氮源,添加量为质量体积比1%;酵母粉能够提高菌株的多糖产量,适宜添加量为质量体积比2%;培养基初始pH值为6.0,菌株接种量为体积比4%,适宜培养温度29.5 ℃,此时培养24.5 h胞外多糖产量最高。在此优化培养条件下,YY112胞外多糖产量达到(380.97±0.45)mg·L^-1,与响应面分析预测值基本吻合,较优化前增加了46.52%。

为获得高产胞外多糖的乳酸菌,采用菌落拉丝法和硫酸-苯酚法相结合的手段筛选获得1株高产胞外多糖的乳酸菌LPC-1,初步鉴定为Lactobacillus plantarum。以胞外多糖产量为指标,采用单因素和响应面实验对发酵工艺进行优化。优化的培养条件为:蔗糖30 g/L、大豆蛋白胨10 g/L、发酵时间24 h、温度30 ℃、初始pH值6.5、接种量4%(体积分数)。通过Plackett-Burman实验确定温度、pH、柠檬酸氢二铵为显著因子,结合中心组合实验及响应面分析,确定最优发酵工艺条件为温度32 ℃、pH值6.7、柠檬酸氢二铵3 g/L,在此条件下发酵测得实际产量为2 064.69 mg/L,与预测值基本吻合,与优化前相比增加了48.64%,为乳酸菌胞外多糖的规模化生产提供了依据。

通过观察乳酸菌菌落拉丝状况并测定其胞外多糖（exopolysaccharide，EPS）的产量，筛选出1 株所产EPS黏性好、产量高的乳酸菌AR307，经鉴定为植物乳杆菌。为得到更多的胞外多糖，对植物乳杆菌AR307的发酵条件进行优化，确定其在发酵温度32 ℃、发酵时间20 h条件下的产糖量为389 mg/L。在体外实验中，所得胞外多糖具有抑制HT-29肿瘤细胞活性、降低血糖水平的作用。