Capsular and slime-polysaccharide production by Lactobacillus rhamnosus JAAS8 isolated from Chinese sauerkraut: Potential application in fermented milk products

Exopolysaccharides (EPSs) produced by lactic acid bacteria (LAB) play an important role in the improvement of the physical properties of fermented dairy products. To find EPS-producing LAB strains with potential industrial applications, a Lactobacillus rhamnosus strain, L. rhamnosus JAAS8, that is capable of producing two forms of EPS when grown in MRS broth or semi-defined medium with glucose as a carbon source was isolated and identified from Chinese sauerkraut. The capsular-polysaccharide (CPS) present surrounding the bacterial surface of L. rhamnosus JAAS8 was observed by both optical microscopy and transmission electron microscopy. The slime-polysaccharide (SPS) present in the growth medium was produced mainly during the exponential growth phase, while the CPS was produced only in fermentation. Monosaccharide analysis of the purified polysaccharide samples showed that the CPS was composed of galactose and N-acetylglucosamine in a molar ratio of 5:1, and the SPS was composed of galactose, glucose and N-acetylglucosamine in a molar ratio of 4:1:1. The use of L. rhamnosus JAAS8 could be considered for potential applications in the dairy industry to improve the rheological properties of fermented milk products by increasing their water-holding capacity and viscosity.     

Effect of buckwheat flour and oat bran on growth and cell viability of the probiotic strains Lactobacillus rhamnosus IMC 501®, Lactobacillus paracasei IMC 502® and their combination SYNBIO®, in synbiotic fermented milk

Fermented foods have a great significance since they provide and preserve large quantities of nutritious foods in a wide diversity of flavors, aromas and texture, which enrich the human diet. Originally fermented milks were developed as a means of preserving nutrients and are the most representatives of the category. The first aim of this study was to screen the effect of buckwheat flour and oat bran as prebiotics on the production of probiotic fiber-enriched fermented milks, by investigating the kinetics of acidification of buckwheat flour- and oat bran-supplemented milk fermented by Lactobacillus rhamnosus IMC 501®, Lactobacillus paracasei IMC 502® and their 1:1 combination named SYNBIO®. The probiotic strains viability, pH and sensory characteristics of the fermented fiber-enriched milk products, stored at 4 °C for 28 days were also monitored. The results showed that supplementation of whole milk with the tested probiotic strains and the two vegetable substrates results in a significant faster lowering of the pH. Also, the stability of L. rhamnosus IMC 501®, L. paracasei IMC 502® and SYNBIO® during storage at 4 °C for 28 days in buckwheat flour- and oat bran-supplemented samples was remarkably enhanced. The second aim of the study was to develop a new synbiotic product using the best combination of probiotics and prebiotics by promoting better growth and survival and be acceptable to the consumers with high concentration of probiotic strain. This new product was used to conduct a human feeding trial to validate the fermented milk as a carrier for transporting bacterial cells into the human gastrointestinal tract. The probiotic strains were recovered from fecal samples in 40 out of 40 volunteers fed for 4 weeks one portion per day of synbiotic fermented milk carrying about 10⁹ viable cells.     

Phenotypic and genotypic characterization of non-starter Lactobacillus species diversity in Indian Cheddar cheese

A total of 243 non-starter lactobacilli were isolated from 12 premium quality Indian Cheddar cheese samples ripened for different periods and in different plant conditions. They were classified up to species level using mainly sugar fermentation assay and PCR. Based upon phenotypes, a maximum of 46.50% were classified as Lactobacillus paracasei, followed by 34.98% isolates as Lactobacillus plantarum. Only 3.29% were classified as Lactobacillus rhamnosus and 4.12% as Lactobacillus delbrueckii species, while 22 (9.05%) isolates (of which 16 L. plantarum/Lactobacillus paraplantarum and 6 Lactobacillus delbrueckii ssp. lactis/Lactobacillus crispatus) could not be designated to a single species. One isolate of Lactobacillus coryniformis ssp. coryniformis was isolated for the first time from Cheddar cheese (0.41%) while 1.65% isolates remained unidentified. Mostly, the tentative characterization based on phenotype, could be confirmed by PCR targeting rRNA. Those isolate groups which could not be tested in PCR, or resembled with more than one species in their phenotypic traits, could be resolved by the BLAST homology analysis of the partial tuf gene sequences of few representative isolates.     

Effect of exopolysaccharides (EPSs) produced by Lactobacillus delbrueckii subsp. bulgaricus strains to bacteriophage and nisin sensitivity of the bacteria

Lactobacillus strains used in this study were isolated from village-type yogurt and raw milk. The isolates were identified as Lactobacillus delbrueckii subsp. bulgaricus by 16 s rDNA sequence analysis and API 50 CHL identification systems. The exopolysaccharide (EPS) production of the strains growth in skim milk were investigated. In addition sensitivity and insensitivity of these strains against domestic bacteriophages and nisin were examined. It was deduced that those strains which had relatively high EPS-producing capacity were insensitive against phages and nisin. Linear relationships were determined between EPS production of the bacteria and bacteriophage and nisin insensitivity of the bacteria.There was a negative correlation between EPS production quantity and phage and nisin sensitivity of the bacteria. Of all the strains, L. delbrueckii subsp bulgaricus B3 produced the highest EPS quantity, and it was insensitive against phages and nisin. Based on these results, it is suggested that L. delbrueckii subsp bulgaricus B3 can be used with the starter culture in dairy industry for stable and high-quality yogurt production.     

Microbial transformation of tectoridin from Pueraria flos by Lactobacillus and bifidobacteria

Tectoridin could be hydrolyzed to tectorigenin by β-glucosidase-producing intestinal bacteria. In this study, nine strains of Lactobacillus and bifidobacteria were screened for high levels of β-glucosidase activity. We investigated their ability to transform tectoridin from Pueraria flos to tectorigenin. Lactobacillus reuteri DSM20016 showed the highest cell-envelope associated β-glucosidase activity, whereas the intracellular β-glucosidase activity from Bifidobacterium adolescentis ATCC15703 was higher than the other screened bacterial strains. L. reuteri DSM20016, Lactobacillus rhamnosus GGB41031 and B. adolescentis ATCC15703 showed high bioconversion rate of tectoridin. L. reuteri DSM20016 showed the highest bioconversion efficiency of tectoridin, 100% tectoridin was hydrolyzed and there was an approximate 185-fold increase in the concentration of tectorigenin after 24 h. The present study suggests that L. reuteri DSM20016, L. rhamnosus GGB41031 and B. adolescentis ATCC15703 have great potential for converting tectoridin from Pueraria flos to more bioactive tectorigenin.     

Lactobacillus pentosus dominates spontaneous fermentation of Italian table olives

Culture-dependent and -independent approaches were applied to identify the bacterial species involved in Italian table olive fermentation. Bacterial identification showed that Lactobacillus pentosus was the dominant species although the presence of Lactobacillus plantarum, Lactobacillus casei, Enterococcus durans, Lactobacillus fermentum and Lactobacillus helveticus was observed. Rep-PCR allowed to obtain strain-specific profiles and to establish a correlation with table olive environment. PCR-DGGE (Denaturing Gradient Gel Electrophoresis) confirmed the heterogeneity of bacterial community structure in fermented table olives as well as the prevalence of L. pentosus. The strains were characterized on the basis of technological properties (NaCl tolerance, β-glucosidase activity and the ability to grow in synthetic brine and in presence of 1 g/100 mL oleuropein). L. pentosus showed a high capacity of adaptation to the different conditions characterizing the olive ecosystem. This species showed the highest percentage of strains able to grow in presence of 10 g/100 mL NaCl, oleuropein and in the synthetic brine. Moreover, all the strains belonging to L. pentosus and L. plantarum species showed a β-glucosidase activity. This study allowed both to identify the main species and strains associated to Italian table olives and to obtain a lactic acid bacteria collection to apply as starter culture in the process of olive fermentation.     

Discrimination of dairy industry isolates of the Lactobacillus casei group

Lactobacilli are a major part of the microflora of the gut and of many fermented dairy products, and are found in a variety of environments. Lactobacillus casei, Lactobacillus paracasei, Lactobacillus rhamnosus, and Lactobacillus zeae form a closely related taxonomic group within the facultatively heterofermentative lactobacilli. The classification and nomenclature of these bacteria are controversial. In this study, relationships between these species were investigated using type strains and dairy industry isolates examined with DNA-based techniques and conventional carbohydrate use tests. Carbohydrate use patterns gave poor discrimination of some species, but DNA PCR using specific primers targeted to sequences of the 16S rRNA gene discriminated 4 types consistent with the currently recognized species. Pulsed-field agarose gel electrophoresis of chromosomal NotI restriction fragments identified 18 different band patterns from 21 independent Lactobacillus isolates and confirmed the identity of L. casei strains from 2 culture collections (CSCC 5203 and ASCC 290), both representing the type strain of L. casei. Some isolates were reclassified as L. rhamnosus, suggesting that the prevalence of L. rhamnosus as a natural component of the microflora of dairy foods and dairy environments has previously been underestimated. These methods can provide a practical basis for discrimination of the species and identification of individual industrial strains.     

Short communication: Survival of the characteristic microbiota in probiotic fermented camel,cow, goat,and sheep milks during refrigerated storage

The objective of this study was to monitor the viability during storage of Lactobacillus acidophilus LA-5 (A), Bifidobacterium animalis ssp. lactis BB-12 (B), and Streptococcus thermophilus CHCC 742/2130 (T) in probiotic cultured dairy foods made from pasteurized camel, cow, goat, and sheep milks fermented by an ABT-type culture. The products manufactured were stored at 4°C for 42 d. Microbiological analyses were performed at weekly intervals. Streptococcus thermophilus CHCC 742/2130 was the most numerous culture component in all 4 products both at the beginning and at the end of storage. The viable counts of streptococci showed no significant decline in fermented camel milk throughout the entire storage period. The initial numbers of Lb. acidophilus LA-5 were over 2 orders of magnitude lower than those of Strep. thermophilus CHCC 742/2130. With the progress of time, a slow and constant decrease was observed in lactobacilli counts; however, the final viability percentages of this organism did not differ significantly in the probiotic fermented milks tested. The cultured dairy foods made from cow, sheep, and goat milks had comparable B. animalis ssp. lactis BB-12 counts on d 0, exceeding by approximately 0.5 log₁₀ cycle those in the camel milk-based product. No significant losses occurred in viability of bifidobacteria in fermented camel, cow, and sheep milks during 6 wk of refrigerated storage. In conclusion, all 4 varieties of milk proved to be suitable raw materials for the manufacture of ABT-type fermented dairy products that were microbiologically safe and beneficial for human consumption. It was suggested that milk from small ruminants be increasingly used to produce probiotic fermented dairy foods. The development of camel milk-based probiotic cultured milks appears to be even more promising because new markets could thus be conquered. It must be emphasized, however, that further microbiological and sensory studies, technology development activities, and market research are needed before such food products can be successfully commercialized.     

Antioxidant and antibacterial activities of exopolysaccharides from Bifidobacterium bifidum WBIN03 and Lactobacillus plantarum R315

The objective of this study was to investigate the antioxidant and antibacterial activities of exopolysaccharide (EPS) from Bifidobacterium bifidum WBIN03 (B-EPS) and Lactobacillus plantarum R315 (L-EPS). The 1,1-diphenyl-2-picrylhydrazyl (DPPH)-radical scavenging, hydroxyl radical-scavenging, and superoxide radical-scavenging abilities were measured to evaluate antioxidant activity. Inhibition of erythrocyte hemolysis and lipid peroxidation was also measured. Both B-EPS and L-EPS had strong scavenging ability against DPPH and superoxide radicals at high concentration. The inhibitory effect of B-EPS on erythrocyte hemolysis was stronger than that of L-EPS in a concentration range from 0.30 to 1.00 mg/mL, whereas the hydroxyl scavenging ability of L-EPS (39.15 ± 0.58%) was significantly higher than that of 0.15 mg/mL ascorbic acid (24.33 ± 1.17%) and B-EPS (17.89 ± 3.30%) at 0.10 mg/mL. The inhibition of lipid peroxidation of 0.50 mg/mL B-EPS and L-EPS was 13.48 ± 1.74% and 12.43 ± 0.51%, respectively, values lower than that of ascorbic acid at the same concentration (23.20 ± 1.41%). Furthermore, all these abilities were enhanced in a concentration-dependent manner. Agar diffusion assay showed that both EPS exhibited antibacterial activities against tested pathogens such as Cronobacter sakazakii, Escherichia coli, Listeria monocytogenes, Staphyloccocus aureus, Candida albicans, Bacillus cereus, Salmonella typhimurium, and Shigella sonnei at 300 μg/mL. In conclusion, both EPS have antimicrobial and antioxidant activities and could have applications in the food industry.     

Effect of 3 lactobacilli on immunoregulation and intestinal microbiota in a β-lactoglobulin–induced allergic mouse model

Milk is one of the earliest and most common allergen sources in the world, with β-lactoglobulin representing a major allergen protein. Numerous studies have reported that probiotics exert antiallergic and anti-inflammatory effects. Here, we examined the effects of 3 strains of Lactobacillus on immunomodulatory functions, intestinal barrier functions, and intestinal microbiota through a β-lactoglobulin–induced allergic mouse model. We found that the oral administration of Lactobacillus plantarum ZDY2013 and Lactobacillus rhamnosus GG suppressed allergic response, attenuating serum IgE and relieving anaphylaxis symptoms. The 3 strains of Lactobacillus could induce T helper (Th) 1 or T regulatory cells to differentiate to inhibit the Th2-biased response for regulating Th1/Th2 immune balance. Furthermore, L. plantarum ZDY2013 and L. rhamnosus GG enhanced intestinal barrier function through the regulation of tight junction. We also found that L. plantarum ZDY2013 and L. plantarum WLPL04 could regulate alterations in intestinal microbiota caused by allergies. In particular, Rikenella, Ruminiclostridium, and Lachnospiraceae UCG-006 were considerably reduced after treatment with L. plantarum ZDY2013 and L. plantarum WLPL04. These results suggested that 3 Lactobacillus strains may serve as an effective tool for the treatment of food allergies by regulating immune and gut microbiota.     

Fermentation of commercial soy beverages with lactobacilli and bifidobacteria strains featuring high β-glucosidase activity

An increase of isoflavone aglycone content in soy foods can be attained through fermentation with food-grade bacteria. In this study, two commercial soy beverages with distinctive chemical composition (AS and VS) were fermented by strains of lactobacilli (eight strains) and bifidobacteria (two strains) with a high β-glucosidase activity. Along fermentation, growth of the strains and isoflavone deglycosylation in the soy beverages were monitored. Large differences in growth, aglycone content and chemical parameters in AS and VS beverages fermented by different species and strains were observed. Isoflavone glycosides were completely transformed into their corresponding aglycones by most strains during fermentation of AS beverage, whereas large amounts of undeglycosilated isoflavones were still present in fermented VS. Four strains showing strong deglycosylation activity and appropriate technological properties (Lactobacillus casei LP71, Lactobacillus plantarum E112, Lactobacillus rhamnosus E41 and Bifidobacterium pseudocatenulatum C35) were proposed as industrial starters to improve functionality in soy-based fermented foods.     

Short communication: Viability of culture organisms in honey-enriched acidophilus-bifidus-thermophilus (ABT)-type fermented camel milk

The aim of this research was to monitor the survival during refrigerated storage of Lactobacillus acidophilus LA-5 (A), Bifidobacterium animalis ssp. lactis BB-12 (B), and Streptococcus thermophilus CHCC 742/2130 (T) in cultured dairy foods made from camel and, for comparison, cow milks supplemented with black locust (Robinia pseudoacacia L.) honey and fermented by an acidophilus-bifidus-thermophilus (ABT)-type culture. Two liters of dromedary camel milk and 2 L of cow milk were heated to 90°C and held for 10 min, then cooled to 40°C. One half of both types of milk was fortified with black locust honey at the rate of 5.0% (wt/vol), whereas the other half was devoid of honey and served as a control. The camel and cow milks with and without honey were subsequently inoculated with ABT-5 culture and were fermented at 37°C until a pH value of 4.6 was reached. Thereafter, the probiotic fermented milks were cooled to 15°C in ice water and were each separated into 18 fractions that were transferred in sterile, tightly capped centrifuge tubes. After 24 h of cooling at 8°C (d 0), the samples were stored at refrigeration temperature (4°C). Three tubes of all 4 products (i.e., fermented camel and cow milks with and without honey) were taken at each sampling time (i.e., following 0, 7, 14, 21, 28, and 35 d of storage), and the counts of characteristic microorganisms and those of certain spoilage microbes (yeasts, molds, coliforms, Escherichia coli) were enumerated. The entire experimental program was repeated twice. The results showed that addition of black locust honey at 5% to heat-treated camel and cow milks did not influence the growth and survival of starter streptococci during production and subsequent refrigerated storage of fermented ABT milks. In contrast, honey improved retention of viability of B. animalis ssp. lactis BB-12 in the camel milk-based product during storage at 4°C up to 5 wk. No spoilage organisms were detected in any of the samples tested in this study. In conclusion, supplementation of cultured dairy foods, especially those made from camel milk, with honey is recommended because honey is a healthy natural sweetener with a variety of beneficial microbiological, nutritional, and sensory properties.     

Short communication: effect of exopolysaccharide isolated from "viili" on the adhesion of probiotics and pathogens to intestinal mucus

The strong ropy character of the Scandinavian fermented milk viili is conferred by the exopolysaccharides (EPS) produced by lactococcal strains. These biopolymers can be responsible for some health benefits. We have assessed the influence of the EPS fraction isolated from commercial viili on the adhesion of some probiotics and pathogens to human intestinal mucus. Concentrations of viili EPS greater than 0.1 mg/mL promoted a decrease in adherence of Bifidobacterium lactis Bb12 and Lactobacillus rhamnosus GG and this effect was dose-dependent. However, no modifications were detected on the adhesion levels of the pathogenic strains tested at a concentration of 1 mg/mL of EPS. Results obtained in the present work should be considered in the design of new probiotic products.     

Selection of Lactobacillus plantarum strains to use as starters in fermented table olives: Oleuropeinase activity and phage sensitivity

Fermented table olives (Olea europaea L.) are largely diffused in the Mediterranean area. Olives are picked at different stages of maturity and after harvesting, processed to eliminate the characteristic bitterness caused by the presence of the oleuropein glucoside and to become suitable for human consumption. The spontaneous fermentation of table olives mainly depends on lactic acid bacteria (LAB), and in particular on Lactobacillus plantarum which plays an important role in the degradation of oleuropein. The hydrolysis of oleuropein is attributed to the β-glucosidase and esterase activities of the indigenous LAB microflora. This study investigated the potential of L. plantarum strains isolated from dairy products and olives to be used as starters for fermented table olives. Forty-nine strains were typed by RAPD-PCR and investigated for the presence of the β-glucosidase (bglH) gene. The full sequence of the bglH gene was carried out. All the 49 L. plantarum strains were also tested for phage resistance. A total of six strains were selected on the basis of genotypic polymorphism, bglH gene sequence analysis, and phage resistance profile. These strains were further characterized to assess the acidifying capability, the growth at different temperatures, the tolerance to different NaCl concentrations, and the oleuropeinolytic activity. Although further characterizations are required, especially concerning the influence on sensory properties, L. plantarum proved to have the potential to be used as a debittering and fermentative agent in starter culture for fermented table olives.     

Fatty acid profile, trans-octadecenoic, α-linolenic and conjugated linoleic acid contents differing in certified organic and conventional probiotic fermented milks

Development of dairy organic probiotic fermented products is of great interest as they associate ecological practices and benefits of probiotic bacteria. As organic management practices of cow milk production allow modification of the fatty acid composition of milk (as compared to conventional milk), we studied the influence of the type of milk on some characteristics of fermented milks, such as acidification kinetics, bacterial counts and fatty acid content. Conventional and organic probiotic fermented milks were produced using Bifidobacterium animalis subsp. lactis HN019 in co-culture with Streptococcus thermophilus TA040 and Lactobacillus delbrueckii subsp. bulgaricus LB340. The use of organic milk led to a higher acidification rate and cultivability of Lactobacillus bulgaricus. Fatty acids profile of organic fermented milks showed higher amounts of trans-octadecenoic acid (C18:1, 1.6 times) and polyunsaturated fatty acids, including cis-9 trans-11, C18:2 conjugated linoleic (CLA-1.4 times), and α-linolenic acids (ALA-1.6 times), as compared to conventional fermented milks. These higher levels were the result of both initial percentage in the milk and increase during acidification, with no further modification during storage. Finally, use of bifidobacteria slightly increased CLA relative content in the conventional fermented milks, after 7 days of storage at 4 °C, whereas no difference was seen in organic fermented milks.     

Comparison of the functionality of exopolysaccharides produced in situ or added as bioingredients on yogurt properties

The effect on yogurt properties of in situ production of exopolysaccharides (EPS) and addition of 2 EPS powders (crude and purified EPS from Lactobacillus rhamnosus RW-9595M fermentation in whey-based medium) at different concentrations was studied. No effect of purified powder addition for EPS concentrations up to 500 mg/L was observed on acidification rate to the difference of milks supplemented with crude EPS, which exhibited longer acidification times. The addition of EPS from 125 to 500 mg/L or the use of EPS-producing cultures resulted in yogurts with lower yield stress and viscoelastic moduli compared with control yogurts without EPS, with no apparent effect of EPS concentration. However, the consistency index was higher for yogurts produced with the commercial EPS-producing culture, and to a lesser extent with the mixed culture containing Lb. rhamnosus RW-9595M, compared with yogurts supplemented with EPS powders, which were not different from that for control yogurts. Our study showed that the mode of EPS incorporation in yogurts has a major effect on the rheological properties of the final product.     

Enhancement of functional characteristics of mixed lactic culture producing nisin z and exopolysaccharides during continuous prefermentation of milk with immobilized cells

Antagonistic phenomena between strains often occur in mixed cultures containing a bacteriocinogenic strain. A nisin Z producer (Lactococcus lactis ssp. lactis biovar. diacetylactis UL719) and 2 nisin-sensitive strains for acidification (Lactococcus lactis ssp. cremoris ATCC19257) and exopolysaccharide (EPS) production (Lactobacillus rhamnosus RW-9595M) were immobilized separately in gel beads and used to continuously preferment milk at different temperatures, with pH controlled at 6.0 by fresh milk addition. The process showed high volumetric productivity, with an increase from 8.0 to 12.5 L of prefermented milk per liter of reactor volume and hour as the temperature was increased from 27 to 35°C. Lactococcus lactis ssp. lactis biovar. diacetylactis UL719 counts in prefermented and fermented (22-h batch fermentation) milks were stable during 3 wk of continuous fermentation (8.1 ± 0.1 and 8.9 ± 0.2 log cfu/mL, respectively). The L. lactis ssp. cremoris population (estimated with real-time quantitative PCR) decreased rapidly during the first week of continuous culture to approximately 4.5 log cfu/mL and remained constant afterward. Lactobacillus rhamnosus counts in prefermented and fermented milks significantly increased with prefermentation time, with no temperature effect. Nisin Z reached high titers in fermented milks (from 177 to 363 IU/mL), with EPS concentration in the range from 43 to 178 mg/L. Immobilization and continuous culture led to important physiological changes, with Lb. rhamnosus becoming much more tolerant to nisin Z, and Lb. rhamnosus and L. lactis ssp. lactis biovar. diacetylactis UL719 exhibiting large increases in milk acidification capacity. Our data showed that continuous milk prefermentation with immobilized cells can stimulate the acidification activity of low-acidifying strains and produce fermented milks with improved and controlled functional properties.     

Survival of three Bifidobacterium animalis subsp. lactis strains is related to trans-vaccenic and α-linolenic acids contents in organic fermented milks

This study aims at relating the survival at 4 °C for 28 days in organic and conventional fermented milks of three strains of Bifidobacterium animalis subsp. lactis (BB12, B94 and BL04), in co-culture with Streptococcus thermophilus TA040 and Lactobacillus bulgaricus LB340, to milk fatty acids profile. Cultivability after 28 days of cold storage was improved in organic fermented milks as compared to conventional products, with slight differences among strains. In addition, the poly-unsaturated fatty acids fraction was higher in organic products, as well as the relative trans-vaccenic (TVA) and α-linolenic (ALA) fatty acids contents that were respectively 1.7 and 2.4 times higher in organic than in conventional fermented milks. From these results, it was concluded that elevated levels of TVA and ALA, together with a lower ratio between linoleic acid and α-linolenic acid, as found in organic products, improved the survival of the bifidobacteria during chilled storage.     

Rheological, sensorial, and chemopreventive properties of milk fermented with exopolysaccharide-producing lactic cultures

The objective of this research was to evaluate the rheological, sensorial, and chemopreventive properties of milk fermented with different exopolysaccharide (EPS)-producing lactic cultures. Reconstituted skim milk (11% wt/vol) was fermented with single strains of EPS-producing and non-EPS-producing cultures. Whey that collected on the surface of undisturbed fermented milks and after cutting was measured. All EPS-producing cultures reduced the amount of whey present on the surface of the undisturbed samples, whereas only 3 out of 5 strains reduced syneresis measured after cutting. All EPS-producing cultures except a strain of Lactobacillus delbrueckii ssp. bulgaricus reduced viscoelastic moduli in fermented milk. There was a linear correlation between ropiness and smoothness. In the chemoprevention study, 140 male Fisher rats were divided into 7 groups of 20 each. Rats in 6 groups were fed diets supplemented with fermented milks each made with a single strain of EPS-producing or non-producing cultures, whereas rats in group 7 (control) were fed a diet supplemented with milk acidified with glucono-δ-lactone (GDL). All rats were injected with azoxymethane (15 mg/kg, subcutaneous) at wk 7 and 8 of age to induce tumors and fed their respective diets ad libitum throughout the study. After 30 wk of initiation, all rats were anesthetized with ether, and their intestinal tissues were isolated and washed with cold normal saline. The number and size of tumors in the colon and small intestine were recorded. Rats fed diets supplemented with fermented milk made with 2 EPS-positive and 1 EPS-negative strains had significantly lowered incidence of colon tumor and colon tumor multiplicity. Cyclooxygenase-2 enzyme activity (the enzyme implicated in colon tumor development) was significantly lower in the colon tissue of rats fed diets containing milk fermented with 4 EPS-producing and 1 non-producing cultures than that in rats fed diets supplemented with GDL-acidified milk. Different EPS-positive cultures produced fermented milks with distinct rheological characteristics and levels of ropiness. No relationship was found between rheological properties or level of ropiness of fermented milk and its chemopreventive effect.     

Microbiological,physicochemical and rheological properties of fermented soymilk produced with exopolysaccharide (EPS) producing lactic acid bacteria strains

Growth of Lactobacillus plantarum 70810, Lactobacillus rhamnosus 6005 and a commercial yogurt starter culture in soymilk was investigated in the present study. It was found that the fermented soymilk using L. plantarum 70810 had significantly higher viable cell counts, water holding capacity (WHC, 88.27%), apparent viscosity (1840.35 mPa s) and exopolysaccharide (EPS) amount (832.15 mg/L) than the other two starter cultures in soymilk. Direct observation of microstructure in fermented soymilk indicated that the network structures of EPS-protein could improve the texture of fermented soymilk. Considering that the beneficial effects of L. plantarum 70810 in fermented soymilk, volatile compounds in fermented soymilk were further identified. Then the growth and fermentation characteristics of L. plantarum 70810 including changes in viable cell counts, pH, titratable acidity, apparent viscosity and EPS production during storage were investigated. In comparison to original soymilk base, the concentrations of the characteristic flavor compounds for fermented soymilk using L. plantarum 70810 increased, whereas hexanal, 2-pentylfuran and 2-pentanone in relation to beany flavor of soymilk decreased. In addition, fermented soymilk using L. plantarum 70810 maintained high viable cell count (>10⁸ cfu/mL), apparent viscosity (966.43 mPa s) and amounts of EPS (635.49 mg/mL) during storage at 4 °C for 21 days.