Special Issue: Probiotic Potential of Isolated Cultures from Spontaneously or Naturally Fermented Food Products.

Fermentation is probably the oldest ancient tradition used by indigenous inhabitants for the preservation of food [...].

Comparing Business, Innovation, and Platform Ecosystems: A Systematic Review of the Literature.

In recent decades, the term "ecosystem" has garnered substantial attention in scholarly and managerial discourse, featuring prominently in academic and applied contexts. While individual scholars have made significant contributions to the study of various types of ecosystem, there appears to be a research gap marked by a lack of comprehensive synthesis and refinement of findings across diverse ecosystems. This paper systematically addresses this gap through a hybrid methodology, employing bibliometric and content analyses to systematically review the literature from 1993 to 2023. The primary research aim is to critically examine theoretical studies on different ecosystem types, specifically focusing on business, innovation, and platform ecosystems. The methodology of this study involves a content review of the identified literature, combining quantitative bibliometric analyses to differentiate patterns and content analysis for in-depth exploration. The core findings center on refining and summarizing the definitions of business, innovation, and platform ecosystems, shedding light on both commonalities and distinctions. Notably, the research unveils shared characteristics such as openness and diversity across these ecosystems while highlighting significant differences in terms of participants and objectives. Furthermore, the paper delves into the interconnections within these three ecosystem types, offering insights into their dynamics and paving the way for discussions on future research directions. This comprehensive examination not only advances our understanding of business, innovation, and platform ecosystems but also lays the groundwork for future scholarly inquiries in this dynamic and evolving field.

Evaluation of the probiotic potential of yeast isolated from kombucha in New Zealand.

The current study investigated the in vitro probiotic potential of yeast isolated from kombucha, a tea beverage fermented with a symbiotic culture of acetic acid bacteria and yeast. A total of 62 yeast strains were previously isolated from four different commercial kombucha samples sold in New Zealand. Fifteen representative isolates belonging to eight different species were evaluated for their growth under different conditions (temperature, low pH, concentrations of bile salts, and NaCl). Cell surface characteristics, functional and enzymatic activities of the selected strains were also studied in triplicate experiments. Results showed that six strains (Dekkera bruxellensis LBY1, Sachizosaccharomyces pombe LBY5, Hanseniaspora valbyensis DOY1, Brettanomyces anomalus DOY8, Pichia kudraivzevii GBY1, and Saccharomyces cerevisiae GBY2) were able to grow under low-acid conditions (at pH 2 and pH 3) and in the presence of bile salts. This suggests their potential to survive passage through the human gut. All 15 strains exhibited negative enzymatic activity reactions (haemolytic, gelatinase, phospholipase, and protease activities), and thus, they can be considered safe to consume. Notably, two of the fifteen strains (Pichia kudraivzevii GBY1 and Saccharomyces cerevisiae GBY2) exhibited desirable cell surface hydrophobicity (64.60-83.87%), auto-aggregation (>98%), co-aggregation, resistance to eight tested antibiotics (ampicillin, chloramphenicol, colistin sulphate, kanamycin, nalidixic acid, nitrofurantoin, streptomycin, and tetracycline), and high levels of antioxidant activities (>90%). Together, our data reveal the probiotic activities of two yeast strains GBY1 and GBY2 and their potential application in functional food production.

Microbiological and Physico-Chemical Characteristics of Black Tea Kombucha Fermented with a New Zealand Starter Culture.

Kombucha is a popular sparkling sugared tea, fermented by a symbiotic culture of acetic acid bacteria (AAB) and yeast. The demand for kombucha continues to increase worldwide, mainly due to its perceived health benefits and appealing sensory properties. This study isolated and characterised the dominant AAB and yeast from a starter culture and kombucha broth after 0, 1, 3, 5, 7, 9, 11, and 14 days of fermentation at ambient temperature (22 °C). Yeast and AAB were isolated from the Kombucha samples using glucose yeast extract mannitol ethanol acetic acid (GYMEA) and yeast extract glucose chloramphenicol (YGC) media, respectively. The phenotypic and taxonomic identification of AAB and yeast were determined by morphological and biochemical characterisation, followed by a sequence analysis of the ribosomal RNA gene (16S rRNA for AAB and ITS for yeast). The changes in the microbial composition were associated with variations in the physico-chemical characteristics of kombucha tea, such as pH, titratable acidity, and total soluble solids (TSS). During fermentation, the acidity increased and the TSS decreased. The yield, moisture content, and water activity of the cellulosic pellicles which had developed at the end of fermentation were attributed to the presence of AAB. The dominant AAB species in the cellulosic pellicles and kombucha broth were identified as Komagataeibacter rhaeticus. The yeast isolates belonged to Debaryomyces prosopidis and Zygosaccharomyces lentus.

Bioactive Yoghurt Containing Curcumin and Chlorogenic Acid Reduces Inflammation in Postmenopausal Women.

Menopause is marked by a gradual and permanent decrease of estrogen from the ovaries, leading to metabolic and physiological changes in the body. Combined with increased body mass index, postmenopausal women have elevated systemic inflammation and metabolic disturbances leading to increased risk of developing chronic diseases. A bioactive coconut yoghurt containing curcumin and chlorogenic acid was developed with the potential to target inflammatory processes. In this randomized crossover study, healthy postmenopausal women with a BMI of 25-40 were recruited to consume 125 g of either the bioactive or placebo yoghurt. Blood samples were collected at baseline, 30 min, and 1, 2, 3 and 4 h postprandially. Plasma inflammatory markers (TNFα and IL6) and metabolic markers (triglycerides, insulin and glucose) were measured. Participants had significantly lower plasma TNFα Cmax after consumption of the bioactive yoghurt compared to placebo (mean difference = 0.3 pg/mL; p = 0.04). Additionally, plasma TNFα was significantly lower postprandially compared to baseline after consumption of the bioactive yogurt but not the placebo. No differences were observed in the metabolic markers measured. Conclusions: The bioactive yoghurt fortified with curcumin and chlorogenic acid has the potential to reduce inflammatory mediators; however, a larger and longer-term study is required to confirm these findings.

Kombucha: Production and Microbiological Research.

Kombucha is a sparkling sugared tea commonly prepared using a sugared tea infusion and fermented at ambient temperature for several days using a cellulose pellicle also called tea fungus that is comprised of acetic acid bacteria and yeast. Consumption of Kombucha has been reported as early as 220 B.C. with various reported potential health benefits and appealing sensory properties. During Kombucha fermentation, sucrose is hydrolysed by yeast cells into fructose and glucose, which are then metabolised to ethanol. The ethanol is then oxidised by acetic acid bacteria (AAB) to produce acetic acid which is responsible for the reduction of the pH and also contributes to the sour taste of Kombucha. Characterisation of the AAB and yeast in the Kombucha starter culture can provide a better understanding of the fermentation process. This knowledge can potentially aid in the production of higher quality products as these microorganisms affect the production of metabolites such as organic acids which are associated with potential health benefits, as well as sensory properties. This review presents recent advances in the isolation, enumeration, biochemical characteristics, conventional phenotypic identification system, and modern genetic identification techniques of AAB and yeast present in Kombucha to gain a better understanding of the microbial diversity of the beverage.

Phenotypic and genotypic characterisation of Lactobacillus and yeast isolates from a traditional New Zealand Maori potato starter culture.

Pararoa Rewena is a traditional Maori sourdough produced by fermentation using a potato starter culture. The microbial composition of the starter culture is not well characterised, despite the long history of this product. The morphological, physiological, biochemical and genetic tests were conducted to characterise 26 lactic acid bacteria (LAB) and 15 yeast isolates from a Pararoa Rewena potato starter culture. The results of sugar fermentation tests, API 50 CHL tests, and API ID 32 C tests suggest the presence of four different LAB phenotypes and five different yeast phenotypes. 16S rRNA and 26S rRNA sequencing identified the LAB as Lacticaseibacillus paracasei and the yeast isolates as Saccharomyces cerevisiae, respectively. Multilocus sequence typing (MLST) of the L. paracasei isolates indicated that they had identical genotypes at the MLST loci, to L. paracasei subsp. paracasei IBB 3423 or L. paracasei subsp. paracasei F19. This study provides new insights into the microbial composition of the traditional sourdough Pararoa Rewena starter culture.

Isolation and characterisation of dominant acetic acid bacteria and yeast isolated from Kombucha samples at point of sale in New Zealand.

The demand for Kombucha, a sparkling sugared tea beverage fermented by a symbiotic culture of acetic acid bacteria (AAB) and yeast is increasing worldwide. Despite the popularity of the beverage which is mainly due to its perceived health benefits and appealing sensory properties, the microbial composition of the products at the time of consumption is unknown. Such information is important to both manufacturers and consumers. Therefore, this study characterised the dominant AAB and yeast present in six commercial Kombucha samples sold in New Zealand which comprised of three domestic and three imported samples. Acetic acid bacteria and yeast were isolated from the Kombucha samples using glucose yeast extract peptone mannitol (GYPM) and yeast extract glucose chloramphenicol (YGC) media, respectively. Phenotypic and taxonomic identification of AAB and yeast were achieved by morphological and biochemical characterisation, followed by sequence analysis of ribosomal RNA genes (16S rRNA for AAB and 26S rRNA for yeast). Viable AAB and yeast were only found in domestically produced Kombucha samples and not in the imported products. The dominant AAB species were identified as Acetobacter musti and Gluconobacter potus. The yeast isolates belonged to Dekkera bruxelensis, Schizosaccharomyces pombes, Hanseniaspora valbyensis, Brettanomyces anamalus, Pichia kudriavzevii, Starmerella vitis and Saccharomyces cerevisiae. The yeast communities were more complex and variable than the AAB communities in the analysed Kombucha samples.

Enterotoxigenicity and genetic relatedness of Staphylococcus aureus in a commercial poultry plant and poultry farm.

Raw (fresh) and frozen poultry products are frequently associated with Staphylococcus aureus contamination. New Zealand is among the developed countries with high incidences of staphylococcal food poisoning. The study investigated the S. aureus isolates obtained from various stages of poultry production, to determine the primary source of contamination. Viable cell counts of S. aureus were enumerated using Petrifilm™ Staph Express Count Plates, and the isolates were confirmed by Gram-stain and coagulase-positive test. Sixty S. aureus isolates were further confirmed by PCR. The PCR analysis used primers that specifically amplifies a fragment of the femA gene, unique to S. aureus. The confirmed S. aureus strains were further examined for enterotoxigenicity by PCR. Multilocus Sequence Typing (MLST) was then used to identify sequence types (STs) of the sixty isolates of S. aureus. The relatedness of the sequence types was investigated by eBURST. In this study, it was observed that all samples from the processing plant and live chickens at the farm were contaminated by S. aureus. Fifty-nine (59) of the 60 isolates were enterotoxigenic carrying enterotoxin genes: seg, sei, seh, sek, sel, sem, sen, or seo. The sixty isolates were categorised into six different sequence types: ST5, ST2594, ST101, ST83, ST398, ST1; where ST5, ST83 and ST2594 belonged to the Clonal Complex (CC) 5 with ST5 being the clonal ancestor. The sources of S. aureus contamination in the final poultry products were linked to fresh mechanically separated meat, fresh skin, fresh skin-on-breast fillet, rubber fingers on mechanical pluckers, and live chickens at the farm. The skin of live chickens at the farm was most likely the origin of S. aureus contamination on equipment and final products. Not all identified S. aureus strains at the farm were observed in the final products. Therefore, further investigation on other potential contamination sources such as gloves and knives used at the processing plant, and feeders and drinkers at the farm level is recommended.

Food safety knowledge, attitudes, and eating behavior in the advent of the global coronavirus pandemic.

The objective of this study was to evaluate the relationships of food safety knowledge, attitude and eating behavior of consumers during national lockdowns in the advent of the COVID-19 pandemic. A total of 157 respondents completed the online survey using a structured questionnaire worldwide. Overall, the respondents exhibited good attitude and good knowledge towards public health including food safety especially on the importance of social distancing, mask wearing, well-balanced diet, physical exercise and personal hygiene, such as hand washing during the pandemic lockdowns. A Structural Equation Modeling (SEM) was used to test the relationships among food safety knowledge, attitude and behavior under the pandemic conditions. Results showed that attitude towards food safety under the coronavirus pandemic and lockdowns positively affected the eating behavior of the respondents, which exhibited a high ß (0.686) among the variables tested (p<0.05). Food safety knowledge was apparently not affected by the food safety behavior of the respondents.

Identification of dominant lactic acid bacteria and yeast in rice sourdough produced in New Zealand.

This study characterised a commercial New Zealand gluten free (GF) rice sourdough and its starter culture composition. Acidity of the mother sourdough, dough before proofing and dough after proofing was determined during the production of rice sourdough bread, and colour was measured for the baked bread. Yeast and lactic acid bacteria (LAB) were enumerated in the rice sourdough samples and representative colonies characterised using API kits and sequenced by the Internal Transcribed Spacer and 16 S rRNA region. Sourdough LAB isolates were identified as Lactobacillus (L.) papraplantarum DSM 10667 and L. fermentarum CIP 102980 and the yeast isolates as Saccharomyces (S.) cerevisiae CBS 1171. Dough acidity increased significantly (p < 0.05) during fermentation due to the metabolic activities of the sourdough cultures. After baking, the colour of the rice sourdough bread crust was similar to that of unleavened wheat bread (golden brown). The improved colour of the rice sourdough bread crust may be a result of combined use of sourdough technique and optimal baking conditions. The results of this study may allow bakers to improve the overall quality of GF rice sourdough baked bread by selecting suitable fermentation and baking parameters.

Chlorogenic Acid Potentiates the Anti-Inflammatory Activity of Curcumin in LPS-Stimulated THP-1 Cells.

The anti-inflammatory effects of curcumin are well documented. However, the bioavailability of curcumin is a major barrier to its biological efficacy. Low-dose combination of complimentary bioactives appears to be an attractive strategy for limiting barriers to efficacy of bioactive compounds. In this study, the anti-inflammatory potential of curcumin in combination with chlorogenic acid (CGA), was investigated using human THP-1 macrophages stimulated with lipopolysaccharide (LPS). Curcumin alone suppressed TNF-α production in a dose-dependent manner with a decrease in cell viability at higher doses. Although treatment with CGA alone had no effect on TNF-α production, it however enhanced cell viability and co-administration with curcumin at a 1:1 ratio caused a synergistic reduction in TNF-α production with no impact on cell viability. Furthermore, an qRT-PCR analysis of NF-κB pathway components and inflammatory biomarkers indicated that CGA alone was not effective in reducing the mRNA expression of any of the tested inflammatory marker genes, except TLR-4. However, co-administration of CGA with curcumin, potentiated the anti-inflammatory effects of curcumin. Curcumin and CGA together reduced the mRNA expression of pro-inflammatory cytokines [TNF-α (~88%) and IL-6 (~99%)], and COX-2 (~92%), possibly by suppression of NF-κB (~78%), IκB-ß-kinase (~60%) and TLR-4 receptor (~72%) at the mRNA level. Overall, co-administration with CGA improved the inflammation-lowering effects of curcumin in THP-1 cells.

Gynura bicolor DC. (Okinawa spinach): A comprehensive review on nutritional constituents, phytochemical compounds, utilization, health benefits, and toxicological evaluation.

Functional food plants are nature's gift to human beings to help them battle against various ailments for thousands of years. With the global pursuit of improving the quality of life, there is an increasing demand for functional plants in the world's diet. There is a long history of using Gyruna bicolor not only as a vegetable but also as a medicinal herb in East and Southeast Asia. It has been found in G. bicolor that there is a broad spectrum of nutrients and plant bioactives. G. bicolor has been acknowledged by local people as a useful source of medicine for several therapeutic treatments. This paper provides a comprehensive review of G. bicolor from updated research literature. Botanical characteristics, cultivation information, traditional uses, phytochemistry, nutrient values, as well as biological activities are discussed. The storage, processes, proposals for product development, and toxic assessment of G. bicolor are also covered. It is expected that the paper will encourage further research thereby contributing to open avenues for scientific applications of G. bicolor as a valuable plant with multiple health benefits.

Persistent contamination of Salmonella, Campylobacter, Escherichia coli, and Staphylococcus aureus at a broiler farm in New Zealand.

Intensive poultry production due to public demand raises the risk of contamination, creating potential foodborne hazards to consumers. The prevalence and microbial load of the pathogens Campylobacter, Salmonella, Staphylococcus aureus, and Escherichia coli was determined by standard methods at the farm level. After disinfection, swab samples collected from wall crevices, drinkers, and vents were heavily contaminated, as accumulated organic matter and dust likely protected the pathogens from the disinfectants used. The annex floor also showed high microbial concentrations, suggesting the introduction of pathogens from external environments, highlighting the importance of erecting hygiene barriers at the entrance of the main shed. Therefore, pathogen control measures and proper application of disinfectants are recommended as intervention strategies. Additionally, quantitative polymerase chain reaction (qPCR) was evaluated as a quantification tool. qPCR showed limitations with samples containing low microbial counts because of the low detection limit of the method. Thus, bacterial pre-enrichment of test samples may be necessary to improve the detection of pathogens by qPCR.

Food safety governance in China: From supervision to coregulation.

The food control and regulatory system in China is beset by several challenges. While firms have to reduce their costs in pursuit of benefits, customers are increasingly focusing on safety and quality of food products. Although the Chinese government has developed more stringent regulatory measures, food safety incidents still occur, including abuse of food additives, adulterated products as well as contamination by pathogenic microorganisms, pesticides, veterinary drug residues, and heavy metals, and use of substandard materials. A national food safety strategy has been proposed to assure food safety from "farm to table." This paper begins with the analysis of current food regulatory systems and then discusses cogovernance of food safety management in China. We explore the practice in the city of Shenzhen where government intervention has strengthened food control, thereby creating an opportunity to form a coregulatory system. The review highlights that the current food safety regulatory system of multi-agency structure can inevitably lead to insufficient incentives for business entities. Due to asymmetric information, lack of regulatory resources, and consumer advocacy, coregulation has been developed and is increasingly being promoted as an important instrument of food regulation.

Development of a recombinase polymerase amplification assay for Vibrio parahaemolyticus detection with an internal amplification control.

A novel RPA-IAC assay using recombinase polymerase and an internal amplification control (IAC) for Vibrio parahaemolyticus detection was developed. Specific primers were designed based on the coding sequence for the toxR gene in V. parahaemolyticus. The recombinase polymerase amplification (RPA) reaction was conducted at a constant low temperature of 37 °C for 20 min. Assay specificity was validated by using 63 Vibrio strains and 10 non-Vibrio bacterial species. In addition, a competitive IAC was employed to avoid false-negative results, which co-amplified simultaneously with the target sequence. The sensitivity of the assay was determined as 3 × 103 CFU/mL, which is decidedly more sensitive than the established PCR method. This method was then used to test seafood samples that were collected from local markets. Seven out of 53 different raw seafoods were detected as V. parahaemolyticus-positive, which were consistent with those obtained using traditional culturing method and biochemical assay. This novel RPA-IAC assay provides a rapid, specific, sensitive, and more convenient detection method for V. parahaemolyticus.

Host range and in vitro lysis of Listeria monocytogenes seafood isolates by bacteriophages.

Listeria-infecting bacteriophages (listeriaphages) can be used to control Listeria monocytogenes in the food industry. However, the sensitivity of many of seafood-borne Listeria strains to phages has not been reported. This research investigated the host ranges of three listeriaphages (FWLLm1, FWLLm3 and FWLLm5) by the formation of lytic zones and plaques on host lawns and in vitro lysis kinetics of listeriaphage FWLLm3. The study also predicted the phage titres required to lyse host cells. The host ranges of the phages were determined using 50 L. monocytogenes strains, of which 48 were isolated from the seafood industry and two from clinical cases. Of the 50 strains, 36 were tested at 25 and 30 ℃ and the remainder (14) at 15 and 25 ℃. Based on the formation of either discrete plaques or lytic zones (host kill zones), the host ranges of FWLLm1, FWLLm3 and FWLLm5 were about 87%, 81% and 87%, respectively, at 25 ℃. Six L. monocytogenes strains from the seafood environment were insensitive to all three phages, while the other seafood strains (42) were phage-sensitive. The adsorption rate constant (k value) of listeriaphage FWLLm3 was between 1.2 × 10(-9) and 1.6 × 10(-9 )ml/min across four host strains in tryptic soy broth at 25 ℃. The cultures (at 3-4 log colony-forming unit (CFU/ml) were completely lysed (<1 log CFU/ml) when cultures were infected with FWLLm3 at > 8.7 log phage-forming units (PFU/ml) for 30 min. Re-growth of phage-infected cultures was not detected after 24 h. The effective empirical phage titre was similar to the calculated titre using a kinetic model. Results indicate the potential use of the three phages for controlling L. monocytogenes strains in seafood processing environments.

Effectiveness of phages in the decontamination of Listeria monocytogenes adhered to clean stainless steel, stainless steel coated with fish protein, and as a biofilm.

Listeria monocytogenes is a food-borne pathogen which causes listeriosis and is difficult to eradicate from seafood processing environments; therefore, more effective control methods need to be developed. This study investigated the effectiveness of three bacteriophages (LiMN4L, LiMN4p and LiMN17), individually or as a three-phage cocktail at ≈9 log10 PFU/ml, in the lysis of three seafood-borne L. monocytogenes strains (19CO9, 19DO3 and 19EO3) adhered to a fish broth layer on stainless steel coupon (FBSSC) and clean stainless steel coupon (SSC), in 7-day biofilm, and dislodged biofilm cells at 15 ± 1 °C. Single phage treatments (LiMN4L, LiMN4p or LiMN17) decreased bacterial cells adhered to FBSSC and SSC by ≈3-4.5 log units. Phage cocktail reduced the cells on both surfaces (≈3.8-4.5 and 4.6-5.4 log10 CFU/cm², respectively), to less than detectable levels after ≈75 min (detection limit = 0.9 log10 CFU/cm²). The phage cocktail at ≈5.8, 6.5 and 7.5 log10 PFU/cm² eliminated Listeria contamination (≈1.5-1.7 log10 CFU/cm²) on SSC in ≈15 min. One-hour phage treatments (LiMN4p, LiMN4L and cocktail) in three consecutive applications resulted in a decrease of 7-day L. monocytogenes biofilms (≈4 log10 CFU/cm²) by ≈2-3 log units. Single phage treatments reduced dislodged biofilm cells of each L. monocytogenes strain by ≈5 log10 CFU/ml in 1 h. The three phages were effective in controlling L. monocytogenes on stainless steel either clean or soiled with fish proteins which is likely to occur in seafood processing environments. Phages were more effective on biofilm cells dislodged from the surface compared with undisturbed biofilm cells. Therefore, for short-term phage treatments of biofilm it should be considered that some disruption of the biofilm cells from the surface prior to phage application will be required.

Carbohydrate composition, viscosity, solubility, and sensory acceptance of sweetpotato- and maize-based complementary foods.

BACKGROUND: Cereal-based complementary foods from non-malted ingredients form a relatively high viscous porridge. Therefore, excessive dilution, usually with water, is required to reduce the viscosity to be appropriate for infant feeding. The dilution invariably leads to energy and nutrient thinning, that is, the reduction of energy and nutrient densities. Carbohydrate is the major constituent of food that significantly influences viscosity when heated in water. OBJECTIVES: To compare the sweetpotato-based complementary foods (extrusion-cooked ComFa, roller-dried ComFa, and oven-toasted ComFa) and enriched Weanimix (maize-based formulation) regarding their 1) carbohydrate composition, 2) viscosity and water solubility index (WSI), and 3) sensory acceptance evaluated by sub-Sahara African women as model caregivers. METHODS: The level of simple sugars/carbohydrates was analysed by spectrophotometry, total dietary fibre by enzymatic-gravimetric method, and total carbohydrate and starch levels estimated by calculation. A Rapid Visco™ Analyser was used to measure viscosity. WSI was determined gravimetrically. A consumer sensory evaluation was used to evaluate the product acceptance of the roller-dried ComFa, oven-toasted ComFa, and enriched Weanimix. RESULTS: The sweetpotato-based complementary foods were, on average, significantly higher in maltose, sucrose, free glucose and fructose, and total dietary fibre, but they were markedly lower in starch content compared with the levels in the enriched Weanimix. Consequently, the sweetpotato-based complementary foods had relatively low apparent viscosity, and high WSI, than that of enriched Weanimix. The scores of sensory liking given by the caregivers were highest for the roller-dried ComFa, followed by the oven-toasted ComFa, and, finally, the enriched Weanimix. CONCLUSION: The sweetpotato-based formulations have significant advantages as complementary food due to the high level of endogenous sugars and low starch content that reduce the viscosity, increase the solubility, impart desirable sensory characteristics, and potentially avoid excessive energy and nutrient thinning.

The effect of cell immobilization on the antibacterial activity of Lactobacillus reuteri DPC16 cells during passage through a simulated gastrointestinal tract system.

Cell immobilization has the ability to influence the survival and functional characteristics of probiotic bacterial strains in harsh environments. This study investigated the effect of cell immobilization and passage through a simulated gastrointestinal tract (GI) on the antibacterial activity of Lactobacillus reuteri DPC16. Antibacterial activity, reuterin production and diol dehydratase activity were assayed in recovered isolates of L. reuteri that had been immobilized in Ca alginate-skim milk, and incubated in simulated GI fluids. Among all the recovered isolates tested, any that had undergone immobilization followed by immediate recovery of the cells without subsequent incubation in any fluids demonstrated the highest reuterin production, antimicrobial activity and diol dehydratase enzyme activity. L. reuteri DPC16 cells that had been immobilized, incubated in simulated GI fluids, and subsequently recovered from the beads often showed some loss of antimicrobial activity compared to the immobilized cells. The data confirm that the process of immobilization of L. reuteri in Ca alginate-skim milk, rather than the passage through simulated GI fluids, resulted in enhanced antibacterial activity. This is attributed to increased diol dehydratase activity, resulting in increased reuterin production.