Spontaneous sauerkraut fermentation was performed at industrial scale in "Prehrana Inc.", Varaždin, in order to select autochthonous lactic acid bacteria (LAB) which were evaluated according probiotic criteria and tested for their capacity as probiotic starter cultures. At the end of the spontaneous sauerkraut fermentation, total LAB counts reached 9.0×10(5) CFU/ml. This underlines that the need for addition of the well characterised probiotic cultures, in appropriate viable cell counts, would be valuable in probiotic sauerkraut production. Phenotypic characterisation through API 50 CHL and SDS-PAGE of cell protein patterns revealed that Lactobacillus plantarum is predominant LAB strain in homofermentative phase of fermentation. Autochthonous LAB isolates SF1, SF2, SF4, SF9 and SF15 were selected based on the survival in in vitro gastrointestinal tract conditions. RAPD fingerprints indicated that the selected autochthonous LAB were distinct from one another. All of the strains efficiently inhibited the growth of indicator strains and satisfied technological properties such as acidification rate, tolerance to NaCl and viability during freeze-drying. Strains Lb. paraplantarum SF9 and Lb. brevis SF15, identified by AFLP DNA fingerprints, have shown the best properties to be applied as probiotic starter cultures, because of their highest adhesion to Caco-2 cells and expression of specific, protective S-layer proteins of 45 kDa in size. With addition of these strains, probiotic attribute of the sauerkraut will be achieved, including health promoting, nutritional, technological and economic advantages in large scale industrial sauerkraut production.

The objective of this study was the characterisation of the S-layer protein (SlpA) and its functional role in the probiotic activity of Lactobacillus helveticus M92. SlpA was isolated and identified by SDS-PAGE LC-MS/MS analysis. The slpA gene encoding the SlpA from L. helveticus M92 was sequenced and compared with other well characterised slpA genes. Sequence similarity searches revealed high homology with the SlpA of Lactobacillus strains. Purified SlpA showed significantly better immunomodulatory effects in orally immunised mice than L. helveticus M92 cells after SlpA removal. SlpA is involved in the autoaggregation of L. helveticus M92 cells and coaggregation of L. helveticus M92 with S. Typhimurium FP1 as these processes were negatively affected after SlpA removal from the cell surface. Therefore, the influence of oral treatment with L. helveticus M92 on an oral infection of mice by S. Typhimurium FP1 was investigated. Following the oral immunization of mice, with viable L. helveticus M92 and S. Typhimurium FP1 cells, the concentration in the luminal contents of total S-IgA and specific anti-Salmonella S-IgA antibodies, from all immunized mice was significantly higher compared to the control group or a group of mice infected only with S. Typhimurium FP1. These results demonstrate that the observed reduced infection by S. Typhimurium FP1 in mice with L. helveticus M92 is associated with competitive exclusion in the intestinal tract and enhanced immune protection conferred by the L. helveticus M92 and its SlpA.

The results of this research could be applied in the production of fermented cabbage heads with added functional (probiotic) value and with lower NaCl concentration with expected shortened fermentation time. This could not only be of economic but also of ecological importance.

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