Inhibition of Staphylococcus aureus in vitro by bacteriocinogenic Lactococcus lactis KTH0-1S isolated from Thai fermented shrimp (Kung-som) and safety evaluation.

Lactococcus lactis KTH0-1S isolated from Thai traditional fermented shrimp (Kung-som) is able to produce heat-stable bacteriocin and inhibits food spoilage bacteria and food-borne pathogens. The inhibitory effect of bacteriocin remained intact after treatment with different pHs and after heating, but was sensitive to some proteolytic enzymes. Addition of bacteriocin KTH0-1S to Staphylococcus aureus cultures decreased viable cell counts by 2.8 log CFU/ml, demonstrating a bactericidal mode of action. Furthermore, the growth of S. aureus decreased significantly after 12-h co-cultivation with bacteriocinogenic strain. The molecular mass of bacteriocin KTH0-1S was found to be 3.346 kDa after ammonium sulfate precipitation, reversed phase (C8 Sep-Pak), cation-exchange chromatography, RP-HPLC on C8 column and mass spectrometry (MS/MS) analysis. Bacteriocin KTH0-1S was identified as nisin Z using PCR amplification and sequencing. The majority of tested virulence factors were absent, confirming the safety. Evidenced inhibitory effect of this strain, the absence of virulence factors creates the possibility for its application as protective culture to inhibit pathogenic bacteria in the several fermented seafood products.

ß-lactoglobulin as a vector for ß-carotene food fortification.

Food fortification is a strategy to overcome vitamin A deficiency in developing countries. Our aim was to investigate the involvement of the bovine milk protein ß-lactoglobulin (ß-Lg), a potential retinoid carrier, in vitamin A absorption. In vivo experiments were conducted by force-feeding mice with retinol or ß-carotene associated with either ß-Lg or oil-in-water emulsion, with subsequent determination of both vitamin A intestinal mucosa and plasma contents. Caco-2 cells were then used to investigate the mechanisms of vitamin A uptake when delivered by either ß-Lg or mixed micelles. We showed that ß-Lg was as efficient as emulsion to promote ß-carotene, but not retinol, absorption in mice. Similar results were obtained in vitro. Interestingly, an inhibitor of the Scavenger Receptor Class B Type I significantly decreased the uptake of micellar ß-carotene but not that of ß-carotene bound to ß-Lg. Overall, we showed that ß-Lg would be a good vector for ß-carotene food fortification.

Interlocking of ß-carotene in beta-lactoglobulin aggregates produced under high pressure.

Vitamin A deficiency is one of the major causes of mortality and morbidity in the developing World. This deficiency can be prevented by alimentary or pharmaceutical supplementation. However, both vitamin A oxidation and isomerization should be prevented, as these phenomenons result in loss of nutritional efficacy. The aim of this study was to investigate the effect of a food protein matrix, ß-lactoglobulin (ß-Lg) aggregates produced by high pressure (HP), on the stabilization of ß-carotene during storage and gastro-duodenal digestion and therefore on its bioavailability. In vitro gastro-duodenal digestion of ß-Lg aggregates entrapping ß-carotene showed that up to 12% and 33% of total ß-carotene was released after peptic and pancreatic digestion, respectively. Overall, our study showed that ß-Lg aggregates are efficient for caging and stabilization of ß-carotene during storage and digestion. Hence, it may be an interesting approach for the protection and the delivery of vitamin A.