Survival of Lactic Acid Bacteria and Their Lactases under Acidic Conditions

In vitro probiotic potential of lactic acid bacteria isolated from the intestines of Muscovy ducks

The current study was conducted to isolate, test and characterize molecularly and physiologically lactic acid bacteria from the intestines of Muscovy ducks to evaluate their probiotic potential for poultry farming. Three hundred lactic acid bacteria from the gastrointestinal tract of Muscovy ducks were isolated. The strains were phenotypically characterized by observing cell morphology, performing Gram staining, catalase production, and testing their ability to grow in MRS broth at different temperatures, pH values, NaCl concentrations, bile concentration, and in compatibility tests between strains. Nine strains were selected based on their resilience. Eight strains were identified using molecular techniques. These strains exhibited significant tolerance to acidic pH, bile salts, and NaCl, essential for probiotic function. All isolates inhibited the growth of Salmonella enterica serotype Typhimurium (DT104) and Enteropathogenic Escherichia coli serotype O86:H34 (EPEC), showcasing their antimicrobial potential. Antibiotic susceptibility testing revealed 100% resistance to clindamycin and erythromycin but high susceptibility to ampicillin and vancomycin. Growth was observed at various temperatures, indicating mesophilic characteristics. Compatibility tests confirmed their suitability for probiotic formulations. Genomic analysis identified the strains primarily as Enterococcus. Conclusively, the study identified eight out of nine selected lactic acid bacteria strains from Muscovy ducks as autochthonous probiotics, showing resilience to treatments and compatibility for consortium formulation. These strains are suitable for in vivo testing for potential poultry farming applications. Further research on their molecular mechanisms and in vivo effects is needed.

Lactic acid bacteria isolated from women' breast milk and infants' faeces have appreciable immunogenic and probiotic potentials against diarrheagenic E. coli strains

Diarrheal diseases remain the leading cause of high mortality among the infants, particularly in the developing countries; Probiotic intervention for diarrhea has been an ongoing novel approach to diarrheal prevention and treatment. This study aims to characterize immunogenic and probiotic properties of lactic acid bacteria (LAB) isolated from human breast milk and neonates' faeces. The LAB isolates from 16 mothers' breast milk and 13 infants' faeces were screened and identified by 16 S rRNA gene partial sequencing. Their antimicrobial activities against 5 strains of diarrheagenic Escherichia coli were tested. Organic acids production was quantified by HPLC, and antibiotic resistance pattern were determined by VITEK®. Autoaggregation, co-aggregation and hydrophobicity properties were assessed by UV spectrophotometry and immunomodulatory effect was determined in mouse model. Ninety-three LAB of five genera were identified. The most abundant species was Lactiplantibacillus plantarum with inhibition zones ranged from 8.0 to 25.0 ± 1 mm. Lacticaseibacillus rhamnosus A012 had 76.8 mg/mL lactic acid, (the highest concentration), was susceptible to all antibiotics tested. L. plantarum A011 and L. rhamnosus A012 were highly resistance to gastrointestinal conditions. L. rhamnosus A012 produced hydrophobicity of 25.01% (n-hexadecane), 15.4% (xylene) and its autoaggregation was 32.52%. L. rhamnosus A012 and L. plantarum A011 exert immunomodulatory effects on the cyclophosphamide-treated mice by upregulating anti-inflammatory cytokine and downregulating proinflammatory cytokines. Lactobacillus sp. demonstrated good probiotic and immunomodulatory properties. Further works are ongoing on the practical use of the strains.

Probiotic Characteristics of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus as Influenced by Carao (Cassia grandis)

Carao is considered a functional ingredient since its bioactive compounds are meaningful in nutritional, pharmacological, and medicinal applications. The objective of this study was to determine the effects of carao pulp powder on the bacterial viability, acid tolerance, bile tolerance, and protease activity of S. thermophilus STI-06 and L. bulgaricus LB-12. M17 broth with 0.5% lactose and MRS broth were used for S. thermophilus and L. bulgaricus, respectively, for determining bacterial viability, acid tolerance, and bile tolerance. Skim milk was used to study the protease activity of both bacteria. The carao was added at 0 (control), 1.3, 2.6, and 5.3 (g/L) into the broths and skim milk. The broths were enumerated for bacterial viability (every 2 h), bile tolerance (every 4 h), and acid tolerance (every 30 min), and the skim milk was analyzed for protease activity (every 12 h). The General Linear Model (PROC GLM) was used to analyze the data. The 2.6 g/L and 5.3 g/L usage level of carao improved the acid tolerance of S. thermophilus. Carao did not affect the acid tolerance of L. bulgaricus. The usage of 5.3 g/L of carao significantly improved the bile tolerance and protease activity of both bacteria. However, carao did not affect the viability of either bacteria. Overall, 5.3 g/L of carao with these probiotics could be recommended in fermentation processes.

Purified lactases versus whole-cell lactases-the winner takes it all

Lactose-free dairy products are in great demand worldwide due to the high prevalence of lactose intolerance. To make lactose-free dairy products, commercially available β-galactosidase enzymes, also termed lactases, are used to break down lactose to its constituent monosaccharides, glucose and galactose. In this mini-review, the characteristics of lactase enzymes, their origin, and ways of use are discussed in light of their potential for hydrolyzing lactose. We also discuss whole-cell lactase catalysts, which appear to have great potential in terms of cost reduction and convenience, and which are more natural alternatives to purified enzymes. Lactic acid bacteria (LAB) already used in food fermentations seem to be optimal candidates for whole-cell lactases. However, they have not been industrially exploited yet due to technical hurdles. For whole-cell lactases to be efficient, the lactase enzymes inside the cells must be made available for lactose hydrolysis, and thus, cells need to be permeabilized or disrupted prior to use. Here we review state-of-the-art approaches for disrupting or permeabilizing microorganisms. Lastly, based on recent scientific achievements, we propose a novel, resource-efficient, and low-cost scenario for achieving lactose hydrolysis at a dairy plant using a LAB whole-cell lactase.Key points• Lactases (β-galactosidase) are essential for producing lactose-free dairy products• Novel permeabilization techniques facilitate the use of LAB lactases• Whole-cell lactase catalysts have great potential for reducing costs and resources Graphical abstract.

Characteristics of Nutraceutical Chewing Candy Formulations Based on Fermented Milk Permeate, Psyllium Husk, and Apple By-Products

The aim of this study was to develop nutraceutical chewing candy (CCN) formulations based on fermented milk permeate (MP) (source of galactooligosaccharides (GOS) and viable lactic acid bacteria (LAB)), psyllium husk (source of desirable hydrocolloids), and apple by-products (source of phenolic compounds). For CCN preparation, gelatin (Gel) and agar were tested; also, to provide CCN prepared using agar with a desirable hard texture, citric acid (cit) was changed to ascorbic acid. To select the optimal quantities of the ingredients, overall acceptability (OA) and emotions (EMs) induced in consumers by different CCN formulations were evaluated. Furthermore, viable LAB count during storage, texture, colour, and antioxidant characteristics were analysed. The highest OA (score 8.5) was shown for samples consisting of MP, psyllium husk (Ph), apple by-products (App), cit and xylitol (Xy); a very strong correlation was found between OA and the EM “happy” (r = 0.907**). After 14 days of storage, Gel+MP+Ph+App+cit samples showed a LAB count higher than 6.0 log₁₀ CFU g⁻¹; however, better antioxidant properties were found for the CCN prepared with agar. Finally, it can be stated that fermented MP, Ph, and App can be used for preparation of added-value CCN in a sustainable manner, and the recommended formulation is Gel+ MP+Ph+App+cit+Xy.

Improved Viability of Microencapsulated Probiotics in a Freeze-Dried Banana Powder During Storage and Under Simulated Gastrointestinal Tract

Freeze-dried banana powder represents an ideal source of nutrients and has not yet been used for probiotic incorporation. In this study, microencapsulation by freeze drying of probiotics Lactobacillus acidophilus and Lactobacillus casei was made using whey protein isolate (WPI), fructooligosaccharides (FOS), and their combination (WPI + FOS) at ratio (1:1). Higher encapsulation yield was found for (WPI + FOS) microspheres (98%). Further, microcapsules of (WPI + FOS) were used to produce a freeze-dried banana powder which was analyzed for bacterial viability under simulated gastrointestinal fluid (SGIF), stability during storage at 4 °C and 25 °C, and chemical and sensory properties. Results revealed that (WPI + FOS) microcapsules significantly increased bacteria stability in the product over 30 days of storage at 4 °C averaging (≥ 8.57 log CFU/g) for L. acidophilus and (≥ 7.61 log CFU/g) for L. Casei as compared to free cells. Bacteria encapsulated in microspheres (WPI + FOS) were not significantly affected by the SGIF, remaining stable up to 7.05 ± 0.1 log CFU/g for L.acidophilus and 5.48 ± 0.1 log CFU/g for L.casei after 90 min of incubation at pH 2 compared to free cells which showed minimal survival. Overall, encapsulated probiotics enriched freeze-dried banana powders received good sensory scores; they can therefore serve as safe probiotics food carriers.

Pectin-microfibrillated cellulose microgel: Effects on survival of lactic acid bacteria in a simulated gastrointestinal tract

Using high pressure microfluidization, we prepared micro-fibrillated soybean cellulose (MFSC) and analyzed its morphology and structure. MFSC was then incorporated into low-methoxyl pectin (PC) to coat lactic acid bacteria (LAB) by ionotropic gelation, and the effects of PC-MFSC microgel on LAB survival in a simulated gastrointestinal tract were investigated. Particle size analysis showed that the MFSC particle size decreased significantly with increasing jet pressure. Transmission electron microscopy analysis indicated that many cellulosic microfibers appeared at 150 MPa. Infrared spectroscopy and X-ray diffraction analysis revealed that the crystal structure changed from β-cellulose I type to II type with increasing jet pressure, but excessive pressure (200 MPa) damaged the crystalline structure of MFSC. Scanning microscopy indicated that cellulosic microfibers not only promoted a compact pectin gel morphology but also adhered to and coated the LAB in the pectin gel. MFSC-150 stabilized the pectin gel network, preventing the weakening of the gel under low pH conditions. Compared with other PC-MFSCs, PC-MFSC-150 microgel significantly decreased LAB susceptibility to gastrointestinal juice and increased the viability of LAB.

Phytochemicals and syneresis of osmo-dried mulberry incorporated yoghurt

The research was aimed to study the effect of the addition of Osmo-air-dried mulberry (TSS 29.33%) in yoghurt on syneresis and a bioactive component of yoghurt. Two types of yoghurts, with or without Osmo-dried mulberry, were developed using standard culture (Streptococcus thermophilus and Lactobacillus bulgaricus), and changes at refrigerated temperature (<5°C) were studied. Fruit yoghurt showed high total soluble solids (TSSs) and low-fat content (dry basis) (17.67% and 11.84%) compared with normal yoghurt (9.5% and 17.21%). The addition of fruits increased the ascorbic acid (0.77 to 5.96 mg/100 g yoghurt), anthocyanins content (0 to 7.9 mg/100 g yoghurt), total phenol content (TPC) (6.63 to 68.03 mg GAE/100 g yoghurt), and antioxidant activity (20.73% to 47.6% radical scavenging activity) in yoghurt. During 18 days of storage at refrigerated condition (<5°C), the acidity of all samples increased, while pH decreased. Syneresis increased with a storage period in control samples while fruit incorporated yoghurt showed decreased syneresis with time. The viability of lactic acid bacteria (LAB) count went on decreasing at similar rates for both with and without the Osmo-dried mulberry incorporated yoghurt. There is an ample opportunity for utilization of Osmo-air-dried mulberry in yoghurt to prevent syneresis during storage with increased bioactive components.

Comparative genomic analysis of Lactobacillus plantarum GB-LP4 and identification of evolutionarily divergent genes in high-osmolarity environment

Lactobacillus plantarum is one of the widely-used probiotics and there have been a large number of advanced researches on the effectiveness of this species. However, the difference between previously reported plantarum strains, and the source of genomic variation among the strains were not clearly specified. In order to understand further on the molecular basis of L. plantarum on Korean traditional fermentation, we isolated the L. plantarum GB-LP4 from Korean fermented vegetable and conducted whole genome assembly. With comparative genomics approach, we identified the candidate genes that are expected to have undergone evolutionary acceleration. These genes have been reported to associate with the maintaining homeostasis, which are generally known to overcome instability in external environment including low pH or high osmotic pressure. Here, our results provide an evolutionary relationship between L. plantarum species and elucidate the candidate genes that play a pivotal role in evolutionary acceleration of GB-LP4 in high osmolarity environment. This study may provide guidance for further studies on L. plantarum.

Preparation and characterization of alginate and gelatin microcapsules containing Lactobacillus rhamnosus

This paper describes the preparation and characterization of alginate beads coated with gelatin and containing Lactobacillus rhamnosus. Capsules were obtained by extrusion method using CaCl2 as cross linker. An experimental design was performed using alginate and gelatin concentrations as the variables investigated, while the response variable was the concentration of viable cells. Beads were characterized in terms of size, morphology, scanning electron microscopy (SEM), moisture content, Fourier Transform Infrared Spectrometry (FTIR), thermal behavior and cell viability during storage. The results showed that the highest concentration of viable cells (4.2 x 109 CFU/g) was obtained for 1 % w/v of alginate and 0.1 % w/v of gelatin. Capsules were predominantly spherical with a rough surface, a narrow size distribution ranging from 1.53 to 1.90 mm and a moisture content of 97.70 ± 0.03 %. Furthermore, FTIR and thermogravimetric analysis indicated an interaction between alginate-gelatin. Cell concentration of alginate/gelatin microcapsules was 105 CFU/g after 4 months of storage at 8 oC.

Survival of Microencapsulated Probiotic Bacteria after Processing and during Storage: A Review

The use of live probiotic bacteria as food supplement has become popular. Capability of probiotic bacteria to be kept at room temperature becomes necessary for customer's convenience and manufacturer's cost reduction. Hence, production of dried form of probiotic bacteria is important. Two common drying methods commonly used for microencapsulation are freeze drying and spray drying. In spite of their benefits, both methods have adverse effects on cell membrane integrity and protein structures resulting in decrease in bacterial viability. Microencapsulation of probiotic bacteria has been a promising technology to ensure bacterial stability during the drying process and to preserve their viability during storage without significantly losing their functional properties such acid tolerance, bile tolerance, surface hydrophobicity, and enzyme activities. Storage at room temperatures instead of freezing or low temperature storage is preferable for minimizing costs of handling, transportation, and storage. Concepts of water activity and glass transition become important in terms of determination of bacterial survival during the storage. The effectiveness of microencapsulation is also affected by microcapsule materials. Carbohydrate- and protein-based microencapsulants and their combination are discussed in terms of their protecting effect on probiotic bacteria during dehydration, during exposure to harsh gastrointestinal transit and small intestine transit and during storage.

Microencapsulation of Lactobacillus rhamnosus GG by Transglutaminase Cross-Linked Soy Protein Isolate to Improve Survival in Simulated Gastrointestinal Conditions and Yoghurt

Microencapsulation is an effective way to improve the survival of probiotics in simulated gastrointestinal (GI) conditions and yoghurt. In this study, microencapsulation of Lactobacillus rhamnosus GG (LGG) was prepared by first cross-linking of soy protein isolate (SPI) using transglutaminase (TGase), followed by embedding the bacteria in cross-linked SPI, and then freeze-drying. The survival of microencapsulated LGG was evaluated in simulated GI conditions and yoghurt. The results showed that a high microencapsulation yield of 67.4% was obtained. The diameter of the microencapsulated LGG was in the range of 52.83 to 275.16 μm. Water activity did not differ between free and microencapsulated LGG after freeze-drying. The survival of microencapsulated LGG under simulated gastric juice (pH 2.5 and 3.6), intestinal juice (0.3% and 2% bile salt) and storage at 4 °C were significantly higher than that of free cells. The survival of LGG in TGase cross-linked SPI microcapsules was also improved to 14.5 ± 0.5% during storage in yoghurt. The microencapsulation of probiotics by TGase-treated SPI can be a suitable alternative to polysaccharide gelation technologies.

Levan-Producing Leuconostoc citreum Strain BD1707 and Its Growth in Tomato Juice Supplemented with Sucrose

A levan-producing strain, BD1707, was isolated from Tibetan kefir and identified as Leuconostoc citreum. The effects of carbon sources on the growth of L. citreum BD1707 and levan production in tomato juice were measured. The changes in pH, viable cell count, sugar content, and levan yield in the cultured tomato juice supplemented with 15% (wt/vol) sucrose were also assayed. L. citreum BD1707 could synthesize more than 28 g/liter of levan in the tomato juice-sucrose medium when cultured at 30°C for 96 h. Based on the monosaccharide composition, molecular mass distribution, Fourier transform infrared (FTIR) spectra, and nuclear magnetic resonance (NMR) spectra, the levan synthesized by L. citreum BD1707 was composed of a linear backbone consisting of consecutive β-(2→6) linked d-fructofuranosyl units, with an estimated average molecular mass of 4.3 × 10(6) Da.

Dextran synthesized by Leuconostoc mesenteroides BD1710 in tomato juice supplemented with sucrose

The characteristics of the growth of Leuconostoc mesenteroides BD1710 and the synthesis of dextran in tomato juice supplemented with 15% sucrose were assayed. L. mesenteroides BD1710 could synthesize approximately 32 g L(-1) dextran in the tomato-juice-sucrose medium when cultured at 28 °C for 48 h, which was on the same level as the dextran yield in a chemically defined medium. The viscosity of the cultured tomato-juice-sucrose medium with various dextran contents was also measured. The results of the monosaccharide composition, molecular-weight distribution, Fourier transform infrared spectra (FTIR) and nuclear magnetic resonance spectra (NMR) showed that the polysaccharide synthesized by L. mesenteroides BD1710 in the tomato-juice-sucrose medium was dextran with a peak molecular weight of 6.35 × 10(5)Da, a linear backbone composed of consecutive α-(1 → 6)-linked d-glucopyranosyl units and approximately 6% α-(1 → 3) branches.

Novel intestinal-targeted Ca-alginate-based carrier for pH-responsive protection and release of lactic acid bacteria

A novel intestinal-targeted carrier for pH-responsive protection of lactic acid bacteria in stomach and rapid release of lactic acid bacteria in small intestine is successfully developed. The proposed carrier is composed of a Ca-alginate/protamine (CAP) composite shell and a Lactobacillus-casei-encapsulated Ca-alginate (CA) core. The carriers are prepared simply by a coextrusion minifluidic and subsequent adsorption method. The CAP composite shell offers not only improved protection for Lactobacillus casei to guarantee the endurance and survival in the stomach but also satisfactory intestinal-targeted characteristics to guarantee the rapid release of Lactobacillus casei in the small intestine. In the stomach, where there is an acidic environment, the diffusion channels delineated by the CA networks in the CAP composite shell of the carriers are choked with protamine molecules; as a result, it is hard for the gastric acid to diffuse across the CAP composite shell and thus the encapsulated Lactobacillus casei inside carriers can be efficiently protected. However, when they come to the small intestine, where there is a neutral environment, the carriers dissolve rapidly because of the cooperation between protamine and trypsin; consequently, the encapsulated Lactobacillus casei can be quickly released. The proposed CAP composite carrier provides a novel mode for developing efficient protection systems, responsive controlled-release systems, and intestinal-targeted drug delivery systems.

Improved viability of bifidobacteria in fermented milk by cocultivation with Lactococcus lactis subspecies lactis

The poor survival of probiotic bacteria in commercial yogurts may limit their potential to exert health benefits in humans. The objective was to improve the survival of bifidobacteria in fermented milk. Cocultivation with some strains of Lactococcus lactis ssp. lactis improved the survival of bifidobacteria in fermented milk during refrigerated storage. Studies on one strain, Lc. lactis ssp. lactis MCC866, showed that the concentrations of dissolved oxygen were kept lower in the cocultivated fermented milk during storage compared with monocultured Bifidobacterium longum BB536 or samples cocultured with another noneffective Lc. lactis ssp. lactis strain. Degradation of genomic DNA was suppressed in the cocultivating system with Lc. lactis ssp. lactis MCC866. Several genes that participated in protection from active oxygen species (e.g., genes coding for alkyl hydroperoxide reductase and Fe(2+) transport system) were expressed at higher levels during refrigerated storage in Lc. lactis ssp. lactis MCC 866 compared with another noneffective Lc. lactis ssp. lactis strain. Concentration of free iron ion was also lower in supernatants of fermented milk cocultivated with B. longum BB536 and Lc. lactis ssp. lactis MCC866. These results suggest that Lc. lactis ssp. lactis MCC 866 is potentially superior in reducing oxygen damage and consequently improves the survival of bifidobacteria in the cocultivating system. This cocultivation system is of industrial interest for producing fermented milk containing viable bifidobacteria with long shelf life.

Improving the stability of probiotic bacteria in model fruit juices using vitamins and antioxidants

This study examined the survival of probiotic bacteria in a model fruit juice system. Three different strains of probiotic bacteria were used in this study: HOWARU Lactobacillus rhamnosus HN001, HOWARU Bifidobacterium lactis HN001, and Lactobacillus paracasei LPC 37. The probiotic bacteria were inoculated into model juice with various vitamins and antioxidants, namely white grape seed extract, green tea extract, vitamin B2, vitamin B3, vitamin B6, vitamin C, and vitamin E. The model juice without any additives was used as a control. Their viability was assessed on a weekly basis using plate count method. The model juice was made with sucrose, sodium citrate, citric acid powder, and distilled water and was pasteurized before use. Our findings showed that probiotic bacteria did not survive well in the harsh environment of the model fruit juice. However, the model juice containing vitamin C, grape extract, and green tea extract showed better survival of probiotic bacteria. The model juice containing grape seed extract, green tea extract, and vitamin C had the same initial population of 8.32 log CFU/mL, and at the end of the 6-wk storage period it had an average viability of 4.29 log CFU/mL, 7.41 log CFU/mL, and 6.44 log CFU/mL, respectively. Juices containing all other ingredients tested had viable counts of <10 CFU/mL at the end of the 6-wk storage period.

An experimental study on ulcerative colitis as a potential target for probiotic therapy by Lactobacillus acidophilus with or without "olsalazine"

Traditional medical treatments for ulcerative colitis (UC) are still compromised by its adverse effects and not potent enough to keep in remission for long-term periods. So, new therapies that are targeted at specific disease mechanisms have the potential to provide more effective and safe treatments for ulcerative colitis. Probiotics is recently introduced as a therapy for ulcerative colitis. In the present study, Lactobacillus acidophilus was selected as a probiotic therapy to investigate its effects in oxazolone-induced colitis model in rats that mimics the picture in human. The rats were grouped (8 rats each) as normal control group (Group I), Group II served as untreated oxazolone-induced colitis, Group III oxazolone-induced colitis treated with probiotic L. acidophilus (1×10(7) colony-forming units (CFU)/mL/day oral for 14 days), Group IV oxazolone-induced colitis treated with olsalazine (60 mg/kg/day oral for 14 days), Group V oxazolone-induced colitis treated with probiotic L. acidophilus and olsalazine in the same doses and duration. Disease activity index (DAI) was recorded, serum levels of C-reactive protein (CRP), tumor necrosis factor-α (TNF-α) and intrleukin-6 (IL-6) was assessed as inflammatory markers and the histopathological picture of the colon of each rat was studied. Disease activity index (DAI) showed significant positive correlation with the elevated serum levels of CRP (r=0.741, p<0.05), TNF-α (r=0.802, p<0.05) and IL-6 (r=0.801, p<0.05). Treatment with either L. acidophilus (group III) or olsalazine (group IV) resulted in significant reduction in serum levels of CRP, TNF-α and IL-6, as well as disease activity index (DAI). Treatment with combination of L. acidophilus and olsalazine (group V) offered more significant reduction in serum levels of CRP, TNF-α, IL-6 and disease activity index (DAI) when compared to either group II (untreated group), group III (treated with L. acidophilus) or group IV (treated with olsalazine). So, it was concluded that L. acidophilus probiotic could be recommended as adjuvant therapy in combination with olsalazine to achieve more effective treatment for ulcerative colitis. For application in human, this needs to be verified in further clinical studies.

Acid, bile, and heat tolerance of free and microencapsulated probiotic bacteria

Eight strains of probiotic bacteria, including Lactobacillus rhamnosus, Bifidobacterium longum, L. salivarius, L. plantarum, L. acidophilus, L. paracasei, B. lactis type Bl-O4, and B. lactis type Bi-07, were studied for their acid, bile, and heat tolerance. Microencapsulation in alginate matrix was used to enhance survival of the bacteria in acid and bile as well as a brief exposure to heat. Free probiotic organisms were used as a control. The acid tolerance of probiotic organisms was tested using HCl in MRS broth over a 2-h incubation period. Bile tolerance was tested using 2 types of bile salts, oxgall and taurocholic acid, over an 8-h incubation period. Heat tolerance was tested by exposing the probiotic organisms to 65 degrees C for up to 1 h. Results indicated microencapsulated probiotic bacteria survived better (P < 0.05) than free probiotic bacteria in MRS containing HCl. When free probiotic bacteria were exposed to oxgall, viability was reduced by 6.51-log CFU/mL, whereas only 3.36-log CFU/mL was lost in microencapsulated strains. At 30 min of heat treatment, microencapsulated probiotic bacteria survived with an average loss of only 4.17-log CFU/mL, compared to 6.74-log CFU/mL loss with free probiotic bacteria. However, after 1 h of heating both free and microencapsulated probiotic strains showed similar losses in viability. Overall microencapsulation improved the survival of probiotic bacteria when exposed to acidic conditions, bile salts, and mild heat treatment.

Yoghurt fermented by Lactobacillus delbrueckii subsp. bulgaricus H+-ATPase-defective mutants exhibits enhanced viability of Bifidobacterium breve during storage

Persistent acid production by Lactobacillus delbrueckii subsp. bulgaricus during refrigerated storage is a major cause of reduced viability of probiotic strains such as Bifidobacterium breve in yoghurt. It was established that H+ -ATPase-defective mutants of lactic acid bacteria have reduced growth and metabolism in low pH environments. Therefore, the aim of this study was to evaluate inhibition of post-acidification and maintenance of B. breve viability in yoghurt fermented by L. delbrueckii subsp. bulgaricus mutants with reduced membrane-bound H+ -ATPase activity during refrigerated storage. Spontaneous neomycin mutants of L. delbrueckii subsp. bulgaricus that had a significantly (P < or = 0.05) reduced H+ -ATPase activity were successfully isolated. Yoghurt fermented using L. delbrueckii subsp. bulgaricus SBT0164 No. 55-1 (mutant) starter culture had markedly reduced post-acidification and maintained viability (> or = 10(8) CFU/ml) of both Bifidobacteruim breve JCM 1192(T) and Bifidobacteruim breve JCM 7017 during storage at 10 degrees C for 21 days. These results clearly showed that yoghurt fermented by mutants of L. delbrueckii subsp. bulgaricus with reduced membrane-bound H+ -ATPase activity has reduced post-acidification that prolongs viability of B. breve in yoghurt during refrigerated storage.