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Tian H.,Massey University | Tian H.,Bioactives Research New Zealand | Maddox I.S.,Massey University | Ferguson L.R.,University of Auckland | Shu Q.,Bioactives Research New Zealand
BioMetals | Year: 2010

This study investigated the effects of bovine lactoferrin (BLf) on the growth of different groups of bacteria in vitro. BLf showed a significant inhibitory effect on the growth of selected pathogens but not probiotics. BLf, in combination with probiotics, has the potential to influence the composition of the gut microflora via inhibition of intestinal pathogens with no significant effect on probiotic bacteria. © 2010 Springer Science+Business Media, LLC.

Chen S.,University of Auckland | Cao Y.,AsureQuality | Ferguson L.R.,University of Auckland | Shu Q.,Bioactives Research New Zealand | Garg S.,University of Auckland
Applied Microbiology and Biotechnology | Year: 2012

The aim of this study was to apply flow cytometric (FCM) analysis to assess the use of sucrose and lecithin vesicles for the protection of probiotic lactic acid bacteria in response to the challenge of gastric acidity and bile salts. FCM analysis in combination with fluorescent probes carboxyfluorescein (cF) and propidium iodide was used to reveal the physiological heterogeneity in the stressed bacteria population. Three subpopulations (intact, stressed, and damaged) were differentiated by FCM in all six examined strains. Significant changes were observed in the presence of the selected protectants. The addition of 20 mM sucrose in the simulated gastric fluid substantially increased the number of intact cells over 20 folds and reduced the damaged subpopulation by half. The presence of 2 % (w/v) lecithin vesicles was shown to protect 50 % more intact cells from the challenge of bile salts. The improved survival as evaluated by FCM analysis was further assessed for the proliferation capacity by sorting a number of cells from each subpopulation on nutrient agar plate. The result confirmed conformity between the proliferation-based cultivability and the probeindicated viability in the samples of the intact and the damaged subpopulations. However, it also revealed the complexities of the stressed (injured) subpopulation. In conclusion, FCM analysis confirmed that the selected protectants could improve the survival of the probiotic strains in the simulated GI environments. The FCM analysis also proved to be a useful analytical tool for the probiotics research. © Springer-Verlag 2012.

Chen S.,University of Auckland | Ferguson L.R.,University of Auckland | Shu Q.,Bioactives Research New Zealand | Garg S.,University of Auckland
LWT - Food Science and Technology | Year: 2011

In this study, we applied flow cytometric (FCM) analyses to characterize the resistance of a probiotic strain Lactobacillus reuteri DPC16 (DPC16) against diverse stresses. Two fluorescent probes, propidium iodide (PI) and carboxylfluorescein diacetate (cFDA), were combined to the FCM method to reveal multiple cellular statuses of DPC16. The FCM results confirmed that the DPC16 strain had probiotic potential in respect of acid tolerance and bile acid resistance, whereby more than 60% of DPC16 bacteria remained intact after 1 h exposure to pH 2.0, and over half of DPC16 bacteria were unaffected by the presence of bile salts at a concentration of 0.2 g/100 mL for 1 h even without nutrient supply. In addition, the comparison among a number of lyo-preservatives for the DPC16 strain confirmed that lactose was able to maintain over 60% viable DPC16 bacteria after the lyophilization and subsequent storage period, outperforming all the other selected sugars. To conclude, the superior stress resistance of the novel DPC16 strain was confirmed by the FCM analyses in this study. The FCM technique also proved to be readily incorporated into probiotics research, and capable of providing insightful information. © 2011 Elsevier Ltd.

Chen S.,University of Auckland | Cao Y.,AsureQuality | Ferguson L.R.,University of Auckland | Shu Q.,Bioactives Research New Zealand | Garg S.,University of Auckland
World Journal of Microbiology and Biotechnology | Year: 2012

The aim of this study was to evaluate whether immobilizing a probiotic strain Lactobacillus reuteri DPC16 in chitosan-coated alginate microcapsules affected their inhibitory performance against food-borne pathogens. The probiotic strain was encapsulated in sub-100 μm alginate microspheres which were further coated with chitosan. This type of probiotic microcapsules was investigated in a co-culture model for its effect against two food-borne pathogenic bacteria. The results confirmed the comparable inhibitory performances between the planktonic and the microencapsulated DPC16 in terms of the medium acidification and the reuterin production in the presence of sufficient nutrients. However, if an infertile condition was present, in which energy source was limited, the planktonic DPC16 tended to instantly accumulate a higher concentration of reuterin but at the cost of substantial viability loss, whereas immobilization in the chitosan-coated alginate microcapsules extended the survival of DPC16, albeit with a significantly lower reuterin production. In conclusion, no attenuated antimicrobial effect was observed for the immobilized DPC16 in the co-culture model. Microencapsulation rendered an enhanced protection on the embedded probiotics, but it may also induce an altered availability of substrates to those microorganisms. © 2012 Springer Science+Business Media B.V.

Zhao Q.,Massey University | Maddox I.S.,Massey University | Mutukumira A.,Massey University | Lee S.J.,Massey University | Shu Q.,Bioactives Research New Zealand
World Journal of Microbiology and Biotechnology | Year: 2012

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. © 2012 Springer Science+Business Media B.V.

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