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4.8 Adhesive properties
4.8.1 Microbial adhesion to solvents
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Chapter IV: Results
The use of three solvents allowed the evaluation of the hydrophobic/hydrophilic cell
surface properties of Lactobacilli and their Lewis acid-base (electron donor and acceptor)
characteristics (Pelletier et al., 1997; Briandet et al., 1999). As shown in Table 4.19, strains
of L. delbrueckii and L. helveticus had a low partitioning percentage in the apolar solvent n-
hexadecane, indicating that these strains possess a hydrophilic surface. All L. casei, and L.
fermentum strains were characterised by a high affinity to n-hexadecane, indicating the
hydrophobic nature of their surfaces (Table 4.19).
In order to measure the Lewis acid-base properties of the bacterial surface, two solvents
(chloroform and ethyl acetate) with the same van der Waals properties as n-hexadecane
(Pelletier et al., 1997) were used in order to be sure that the affinity for each solvent tested
was not due to van der Waals forces. The results of the microbial adhesion to chloroform
showed that L. delbrueckii and L. helveticus strains (LKH-2, LKH-3 and LKH-5) had a low
affinity for this acidic solvent, whereas all other strains had a strong affinity for it. When
ethyl acetate, an electron donor, was employed for determining the microbial adhesion to
solvents, adhesion values were noticeably high (ranging from 16.8 to 67.8%) for L.
delbruckeii and L. fermentum strains, indicating that these bacteria also have an acidic surface
character. L. casei LAM-1 strains also showed relatively good adherence value (30%) to
ethyl acetate.