Affiliation:
1. Unité de Chimie des Interfaces, Université Catholique de Louvain, Louvain-la-Neuve, Belgium
Abstract
ABSTRACT
The surface chemical composition and physicochemical properties (hydrophobicity and zeta potential) of two lactic acid bacteria,
Lactococcus lactis
subsp.
lactis
bv. diacetilactis and
Lactobacillus helveticus
, have been investigated using cells harvested in exponential or stationary growth phase. The surface composition determined by X-ray photoelectron spectroscopy (XPS) was converted into a molecular composition in terms of proteins, polysaccharides, and hydrocarbonlike compounds. The concentration of the last was always below 15% (wt/wt), which is related to the hydrophilic character revealed by water contact angles of less than 30°. The surfaces of
L. lactis
cells had a polysaccharide concentration about twice that of proteins. The S-layer of
L. helveticus
was either interrupted or crossed by polysaccharide-rich compounds; the concentration of the latter was higher in the stationary growth phase than in the exponential growth phase. Further progress was made in the interpretation of XPS data in terms of chemical functions by showing that the oxygen component at 531.2 eV contains a contribution of phosphate in addition to the main contribution of the peptide link. The isoelectric points were around 2 and 3, and the electrophoretic mobilities above pH 5 (ionic strength, 1 mM) were about −3.0 × 10
−8
and −0.6 × 10
−8
m
2
s
−1
V
−1
for
L. lactis
and
L. helveticus
, respectively. The electrokinetic properties of the latter reveal the influence of carboxyl groups, while the difference between the two strains is related to a difference between N/P surface concentration ratios, reflecting the relative exposure of proteins and phosphate groups at the surface.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
180 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献