title: Influence of fermentation conditions on the surface properties and adhesion of Lactobacillus rhamnosus GG.
abstract: BACKGROUND
  The surface properties of probiotic bacteria influence to a large extent their interactions within the gut ecosystem. There is limited amount of information on the effect of the production process on the surface properties of probiotic lactobacilli in relation to the mechanisms of their adhesion to the gastrointestinal mucosa. The aim of this work was to investigate the effect of the fermentation pH and temperature on the surface properties and adhesion ability to Caco-2 cells of the probiotic strain Lactobacillus rhamnosus GG.
  
  
  RESULTS
  The cells were grown at pH 5, 5.5, 6 (temperature 37°C) and at pH 6.5 (temperature 25°C, 30°C and 37°C), and their surfaces analysed by X-ray photoelectron spectrometry (XPS), Fourier transform infrared spectroscopy (FT-IR) and gel-based proteomics. The results indicated that for all the fermentation conditions, with the exception of pH 5, a higher nitrogen to carbon ratio and a lower phosphate content was observed at the surface of the bacteria, which resulted in a lower surface hydrophobicity and reduced adhesion levels to Caco-2 cells as compared to the control fermentation (pH 6.5, 37°C). A number of adhesive proteins, which have been suggested in previous published works to take part in the adhesion of bacteria to the human gastrointestinal tract, were identified by proteomic analysis, with no significant differences between samples however.
  
  
  CONCLUSIONS
  The temperature and the pH of the fermentation influenced the surface composition, hydrophobicity and the levels of adhesion of L. rhamnosus GG to Caco-2 cells. It was deduced from the data that a protein rich surface reduced the adhesion ability of the cells.
authors.affiliation: Food and Nutritional Sciences, University of Reading, PO Box 226, Reading, UK, RG6 6AP.
authors.forename: Gurjot
authors.initials: G
authors.lastname: Deepika
authors.forename: Esther
authors.initials: E
authors.lastname: Karunakaran
authors.forename: Claire R
authors.initials: CR
authors.lastname: Hurley
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Biggs
authors.forename: Dimitris
authors.initials: D
authors.lastname: Charalampopoulos
mesh_terms: D001422:Bacterial Adhesion; D018938:Caco-2 Cells; D005285:Fermentation; D006801:Humans; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D052201:Lacticaseibacillus rhamnosus / Q000737:chemistry / Q000254:growth & development / Q000502:physiology*; D019936:Probiotics / Q000737:chemistry; D013499:Surface Properties; D013696:Temperature