Survival of Bifidobacterium longum immobilized in calcium alginate beads in simulated gastric juices and bile salt solution

Use of whey protein beads as a new carrier system for recombinant yeasts in human digestive tract

A new immobilizing protocol using whey protein isolates was developed to entrap recombinant Saccharomyces cerevisiae. The model yeast strain expresses the heterologous P45073A1 that converts trans-cinnamic acid into p-coumaric acid. Beads resulted from a cold-induced gelation of a whey protein solution (10%) containing yeasts (7.5 x 10(7)cells ml(-1)) into 0.1M CaCl(2). The viability and growth capability of yeasts were not altered by our entrapment process. The release and activity of immobilized yeasts were studied in simulated human gastric conditions. During the first 60 min of digestion, 2.2+/-0.9% (n=3) of initial entrapped yeasts were recovered in the gastric medium suggesting that beads should cross the gastric barrier in human. The P45073A1 activity of entrapped yeasts remained significantly higher (p<0.05) than that of free ones throughout digestion (trans-cinnamic acid conversion rate of 63.4+/-1.6% versus 51.5+/-1.8% (n=3) at 120 min). The protein matrix seemed to create a microenvironment favoring the activity of yeasts in the stringent gastric conditions. These results open up new opportunities for the development of drug delivery system using recombinant yeasts entrapped in whey protein beads. The main potential medical applications include biodetoxication or the correction of digestive enzyme deficiencies.

Effect of additives on the viability of bifidobacteria loaded in alginate poly-l-lysine microparticles during the freeze-drying process

Bifidobacteria-loaded alginate poly-l-lysine microparticles (bap microparticles) were prepared using an air atomization method and then freeze-dried. The viability of the bap microparticles was investigated as a function of the amount of the bifidobacteria cultures, and the addition of a yeast extract, cryoprotectants, antioxidants and neutralizer. The size of the bap microparticles with and without the bifidobacteria was 84.8 +/- 28.5 microm (mean +/- standard deviation) and 113.1 +/- 38.5 microm, respectively. The surface morphology was slightly ellipsoid and wrinkled regardless of the incorporating bifidobacteria. The viability gradually decreased with increasing freeze-drying time. Free-flowing powdered bap microparticles were obtained at least 12 h after freeze-drying the wetted slurry of bap microparticles. However, the particles tended to aggregate when either lactose or ascorbic acid was added. The addition of a yeast extract, cryoprotectants (glycerol and lactose), antioxidants (NaHSO3 and ascorbic acid) and neutralizer (Mg3(PO4)2) resulted in a significantly higher viability of the bifidobacteria in the bap microparticles after freeze-drying (0.34-1.84 log) compared with the culture alone.

Challenges in the addition of probiotic cultures to foods

Probiotic cultures are increasingly being added to foods in order to develop products with health-promoting properties. Although the literature is abundant on the beneficial effects of bifidobacteria and Lactobacillus acidophilus on health, little information is available on the challenges industry faces in adding these probiotic cultures to food products. The aim of this article is to examine seven issues that should be addressed when developing functional foods: 1) type or form of probiotic that should be used; 2) addition level required to have a beneficial effect; 3) toxicity; 4) effect of the processing steps on viability; 5) determination, in the product, of the cell populations added; 6) stability during storage; 7) changes in sensory properties of the foods.

Synbiotic microcapsules that enhance microbial viability during nonrefrigerated storage and gastrointestinal transit

A Bifidobacterium infantis strain was microencapsulated within a film-forming protein-carbohydrate-oil emulsion. This novel encapsulant incorporated prebiotics and substantially protected the bacterium during nonrefrigerated storage and gastrointestinal transit. The dried microcapsules were small (15 to 20 microm), had low water activity (0.2 to 0.3), and rapidly released the bacteria in simulated intestinal fluid.

Study of adhesion and survival of lactobacilli and bifidobacteria on table olives with the aim of formulating a new probiotic food

With the aim of developing new functional foods, a traditional product, the table olive, was used as a vehicle for incorporating probiotic bacterial species. Survival on table olives of Lactobacillus rhamnosus (three strains), Lactobacillus paracasei (two strains), Bifidobacterium bifidum (one strain), and Bifidobacterium longum (one strain) at room temperature was investigated. The results obtained using a selected olive sample demonstrated that bifidobacteria and one strain of L. rhamnosus (Lactobacillus GG) showed a good survival rate, with a recovery of about 10(6) CFU g(-1) after 30 days. The Lactobacillus GG population remained unvaried until the end of the experiment, while a slight decline (to about 10(5) CFU g(-1)) was observed for bifidobacteria. High viability, with more than 10(7) CFU g(-1), was observed throughout the 3-month experiment for L. paracasei IMPC2.1. This strain, selected for its potential probiotic characteristics and for its lengthy survival on olives, was used to validate table olives as a carrier for transporting bacterial cells into the human gastrointestinal tract. L. paracasei IMPC2.1 was recovered from fecal samples in four out of five volunteers fed 10 to 15 olives per day carrying about 10(9) to 10(10) viable cells for 10 days.

Arsenite oxidation in batch reactors with alginate-immobilized ULPAs1 strain

Arsenic is one of the major groundwater contaminants worldwide. It was previously demonstrated that the beta-proteobacterium Cenibacterium arsenoxidans has an efficient As[III] oxidation ability. The present study was conducted to evaluate the performance of alginate-immobilized ULPAs1 in the oxidation of As[III] to As[V] in batch reactors. A two-level full factorial experimental design was applied to investigate the influence of main parameters involved in the oxidation process, i.e., pH (7-8), temperature (4 degrees C-25 degrees C), kind of nutrient media (2%-20% sauerkraut brine), and arsenic concentration (10-100 mg/L). One hundred milligram per liter of As[III] was fully oxidized by calcium-alginate immobilized cells in 1 h. It was found that the temperature as well as the kind of nutrient media used were significant parameters at a 95% confidence interval whereas only temperature was a significant parameter at a 99% confidence interval. The immobilization of the As[III] oxidizing strain in alginate beads offers a promising way to implement new treatment processes in the remediation of arsenic contaminated waters.

Increased stress tolerance of Bifidobacterium longum and Lactococcus lactis produced during continuous mixed-strain immobilized-cell fermentation

AIMS

The effect of immobilization and long-term continuous culture was studied on probiotic and technological characteristics of lactic acid and probiotic bacteria.

METHODS AND RESULTS

A continuous culture in a two-stage system was carried out for 17 days at different temperatures ranging from 32 to 37 degrees C, with a first reactor containing Bifidobacterium longum ATCC 15707 and Lactococcus lactis subsp. lactis biovar. diacetylactis MD immobilized separately in gel beads, and a second reactor operated with free cells released from the first reactor. The tolerance of free cells from both strains produced in the effluent medium of both reactors to hydrogen peroxide, simulated gastric and intestinal juices, antibiotics and nisin, and freeze-drying markedly increased with culture time and was generally higher after 6 days than that of stationary-phase cells produced during free-cell batch fermentations. The reversibility of the acquired tolerance of B. longum, but not L. diacetylactis, to antibiotics was shown during successive free-cell batch cultures.

CONCLUSIONS

Free cells produced from continuous immobilized-cell culture exhibited altered physiology and increased tolerance to various chemical and physico-chemical stresses.

SIGNIFICANCE AND IMPACT OF THE STUDY

Continuous culture with immobilized cells could be used to produce probiotic and lactic acid bacteria with enhanced technological and probiotic characteristics.

Fermentation of banana media by using κ-carrageenan immobilized Lactobacillus acidophilus

Fermentation media were prepared by using banana as the raw material, and cell immobilization of Lactobacillus acidophilus by kappa-carrageenan entrapment was applied to enhance the fermentation efficiency. Gel beads of diameters around 3.0 mm were prepared for the immobilized cells, ripe bananas were used for preparation of media, and both free and immobilized cells were employed to carry out the fermentation for 80 h. Cells leaked out from the gel beads and proliferated in the medium solution during the fermentation of immobilized cells. The final viable cell number reached 10(5) CFU/ml in the medium suspension, over 10(8) CFU/(ml gel) in gel beads for the immobilized cell fermentation and around 10(6) CFU/ml for the free cell fermentation. Immobilized cells withstand the adverse conditions in banana media resulting in better fermentation efficiency compared to free cells. Variation of fructooligosaccharides (FOS) in banana media was not significant in immobilized cell fermentation compared to free cell. Immobilized L. acidophilus fermented banana medium was found to possess synbiotic properties.

An improved method of microencapsulation and its evaluation to protect Lactobacillus spp. in simulated gastric conditions

An improved method of microencapsulation was developed to increase the efficacy of capsules in protecting the encapsulated bacteria under simulated gastric conditions. Lactobacillus acidophilus CSCC 2400 was encapsulated in calcium alginate and tested for its survival in simulated gastric conditions. The effects of different capsule sizes (200, 450, 1000 microm), different sodium alginate concentrations (0.75%, 1%, 1.5%, 1.8% and 2% w/v) and different concentrations of calcium chloride (0.1, 0.2, 1.0 M) on the viability of encapsulated bacteria were investigated. The viability of the cells in the microcapsules increased with an increase in alginate capsule size and gel concentration. There was no significant difference (p>0.05) in the viability of encapsulated cells when the concentration of calcium chloride was increased. Increase in cell load during encapsulation increased the number of bacterial survivors at the end of 3-h incubation in simulated gastric conditions. Hardening the capsule in calcium chloride solution for a longer time (8 h) had no impact on increasing the viability of encapsulated bacteria in a simulated gastric environment. The release of encapsulated cells at different phosphate buffer concentrations was also studied. When encapsulated L. acidophilus CSCC 2400 and L. acidophilus CSCC 2409 were subjected to low pH (pH 2) and high bile concentration (1.0% bile) under optimal encapsulation conditions (1.8% (w/v) alginate, 10(9) CFU/ml, 30 min hardening in 0.1 M CaCl(2) and capsule size 450 microm), there was a significant increase (p<0.05) in viable cell counts, compared to the free cells under similar conditions. Thus the encapsulation method described in this study may be effectively used to protect the lactobacillus from adverse gastric conditions.

Protection of bifidobacteria encapsulated in polysaccharide-protein gel beads against gastric juice and bile

Bifidobacterium cells were encapsulated in a mixed gel composed of alginate, pectin, and whey proteins. Two kinds of capsules were obtained: gel beads without membranes and gel beads with two membranes formed by the transacylation reaction. In vitro studies were carried out to determine the effects of simulated gastric pH and bile salts on the survival of free and encapsulated Bifidobacterium bifidum. The protective effects of gel beads without membranes and gel beads coated with two membranes formed by the transacylation reaction were evaluated. After 1 h in an acidic solution (pH 2.5), the free-cell counts decreased by 4.75 log units, compared with a <1-log decrease for entrapped cells. The free cells did not survive after 2 h of incubation at pH 2.5, while immobilized-cell counts decreased by about 2 log units. After incubation (1 or 3 h) in 2 and 4% bile salt solutions, the bifidobacterium mortality level for membrane-free gel beads (4 to 7 log units) was higher than that for free cells (2 to 3 log units). However, counts of bifidobacteria immobilized in membrane-coated gel beads decreased by <2 log units. Cell encapsulation in membrane-coated protein-polysaccharide gel beads could be used to increase the survival of healthy probiotic bacteria during their transit through the gastrointestinal tract.

Growth and morphology of thermophilic dairy starters in alginate beads

The aim of this research was to produce concentrated biomasses of thermophilic lactic starters using immobilized cell technology (ICT). Fermentations were carried out in milk using pH control with cells microentrapped in alginate beads. In the ICT fermentations, beads represented 17% of the weight. Some assays were carried out with free cells without pH control, in order to compare the ICT populations with those of classical starters. With Streptococcus thermophilus, overall populations in the fermentor were similar, but maximum bead population for (8.2 x 10(9) cfu/g beads) was 13 times higher than that obtained in a traditional starter (4.9 x 10(8) cfu/ml). For both Lactobacillus helveticus strains studied, immobilized-cell populations were about 3 x 10(9) cfu/g beads. Production of immobilized Lb. bulgaricus 210R strain was not possible, since no increases in viable counts occurred in beads. Therefore, production of concentrated cell suspension in alginate beads was more effective for S. thermophilus. Photomicrographs of cells in alginate beads demonstrated that, while the morphology of S. thermophilus remained unchanged during the ICT fermentation, immobilized cells of Lb. helveticus appeared wider. In addition, cells of Lb. bulgaricus were curved and elongated. These morphological changes would also impair the growth of immobilized lactobacilli.

Improved survival of Lactobacillus paracasei NFBC 338 in spray-dried powders containing gum acacia

AIMS

To assess the protective effect of gum acacia (GA) on the performance of Lactobacillus paracasei NFBC 338 during spray-drying, subsequent storage and exposure of the culture to porcine gastric juice.

METHODS AND RESULTS

For these studies, Lact. paracasei NFBC 338 was grown in a mixture of reconstituted skim milk (10% w/v) and GA (10% w/v) to mid log phase and spray-dried at outlet temperatures between 95 and 105 degrees C. On spray drying at the higher air outlet temperature of 100-105 degrees C, the GA-treated culture displayed 10-fold greater survival than control cells. Probiotic lactobacilli in GA-containing powders also survived dramatically better than untreated cultures during storage at 4-30 degrees C for 4 weeks. A 20-fold better survival of the probiotic culture in GA-containing powders was obtained during storage at 4 degrees C while, at 15 and 30 degrees C, greater than 1000-fold higher survival was obtained. Furthermore, the viability of probiotic lactobacilli in GA-containing powders was 100-fold higher when exposed to porcine gastric juice over 120 min compared with the control spray-dried culture.

CONCLUSIONS

The data indicate that GA has applications in the protection of probiotic cultures during drying, storage and gastric transit.

SIGNIFICANCE AND IMPACT OF THE STUDY

Gum acacia treatment for the manufacture of probiotic-containing powders should result in more efficient probiotic delivery to the host gastrointestinal tract.

Increase of viability of entrapped cells of Lactobacillus delbrueckii ssp. bulgaricus in artificial sesame oil emulsions

A technique was developed to protect lactic acid bacteria (Lactobacillus delbrueckii ssp. bulgaricus) against simulated gastrointestinal conditions by encapsulation of bacterial cells within artificial sesame oil emulsions. Purified sesame oil bodies consisting of approximately 99% oil, 0.5% phospholipid, and 0.5% protein were decomposed by heating at 70 degrees C for 1 h. The bacteria cultured in nonfat milk were encapsulated in artificial oil emulsions constituted with decomposed sesame oil bodies and excess sesame or vegetable cooking oil. Viability of bacteria in storage at 4 degrees C for 16 d was substantially elevated from 0.023 to 5.45% after encapsulation. Compared with free cells, the entrapped bacteria demonstrated a significant increase (approximately 10(4) times) in survival rate when subjected to simulated high acid gastric or bile salt conditions. The results indicate that artificial sesame oil emulsion may serve as an effective biocapsule for encapsulation of bacteria in dairy products.

Evaluation of microencapsulation of a Bifidobacterium strain with starch as an approach to prolonging viability during storage

AIMS

To optimize a spray coating process for the production of encapsulated microspheres containing viable Bifidobacterium cells and to determine whether the readily gelatinized modified starch coating used in this study improved bacterial survival in foods or under acid conditions.

METHODS AND RESULTS

An air inlet temperature of 100 degrees C was demonstrated to be optimal for the spray drying process, as it afforded good drying, low outlet temperatures (45 degrees C) and resulted in less than 1 log reduction in bifidobacteria numbers during drying. Maximum recovery yields of 30% were obtained after optimizing the air aspiration conditions. The average size of the Bifidobacterium PL1-containing starch microparticles was determined by scanning electron microscopy to be of the order of 5 microm. The starch-coated cells did not display any enhanced viability compared with free PL1 cells when exposed to acid conditions for 6 h or in two dry food preparations over 20 d storage at ambient temperature (19-24 degrees C). Determination of 1491 nucleotides of the 16S rRNA gene from PL1 indicated that it shared 97% homology with a previously sequenced Bifidobacterium ruminantium strain.

CONCLUSIONS

Our data demonstrated that, although spray drying is a valuable process for encapsulating bifidobacteria, further work is required to ascertain a more appropriate coating material that will protect this strain against adverse environmental conditions.

SIGNIFICANCE AND IMPACT OF THE STUDY

The production of small, uniformly coated microspheres containing viable bifidobacteria using an affordable and industrially convenient process, such as spray drying, has commercial implications for the production of probiotic products. Although popular for use as a coating polymer by the food industry, this study indicated that modified starches might not be suitable for use as an encapsulating material for probiotic strains.

Encapsulation of probiotic bacteria with alginate-starch and evaluation of survival in simulated gastrointestinal conditions and in yoghurt

A modified method using calcium alginate for the microencapsulation of probiotic bacteria is reported in this study. Incorporation of Hi-Maize starch (a prebiotic) improved encapsulation of viable bacteria as compared to when the bacteria were encapsulated without the starch. Inclusion of glycerol (a cryo-protectant) with alginate mix increased the survival of bacteria when frozen at -20 degrees C. The acidification kinetics of encapsulated bacteria showed that the rate of acid produced was lower than that of free cultures. The encapsulated bacteria, however, did not demonstrate a significant increase in survival when subjected to in vitro high acid and bile salt conditions. A preliminary study was carried out in order to monitor the effects of encapsulation on the survival of Lactobacillus acidophilus and Bifidobacterium spp. in yoghurt over a period of 8 weeks. This study showed that the survival of encapsulated cultures of L. acidophilus and Bifidobacterium spp. showed a decline in viable count of about 0.5 log over a period of 8 weeks while there was a decline of about 1 log in cultures which were incorporated as free cells in yoghurt. The encapsulation method used in this study did not result in uniform bead size, and hence additional experiments need to be designed using uniform bead size in order to assess the role of different encapsulation parameters, such as bead size and alginate concentration, in providing protection to the bacteria.