ON THE STEREOSPECIFIC PERMEABILITY OF THE CELLS OF LACTOBACILLI TO D- AND L-LACTIC ACIDS

Abstract

1) The activities of D- and L-lactic dehydrogenases were measured by the decolorization of 2, 4-dichlorophenol indophenol. The activities of these lactic dehydrogenases of intact cells of lactic acid bacteria differ much from those of these sonic lysate. For example, in Lactobacillus delbrückii (D(-)-lactic acid former) activity of L-enzyme is markedly increased by lysis, but D-enzyme shows scarecely any change. And contrary, in L(+)-acid former (L. thermophilus or L. bulgaricus) D-enzyme is activated.
2) By the addition of cetyl trimethyl ammonium bromide (CTAB) or cetyl pyridinium chloride, known as surface active agents which have an effect on the permeability of intact bacterial cells, or by treatment with toluol, similar changes in the enzyme activity is obtained. And under the electron microscope the swelling of the cell surface in these treated cells is quite distinct. From these facts we suggest that the intact cells should have stereospecific permeability to lactic acid, and discussed the permeability of the cell in relation to the inoculation time as well as to the optical property of the lactic acid.
3) Investigating the mode of action of CTAB, it was supposed that CTAB bind tightly with the cells, changing the character of cell surface.
4) Unlike with the β-galactoside permease of E. coil reported by MONOD, the transport of lactic acid was not inhibited by azide, fluoride, monojodoacetic acid and 2, 4-dinitrophenol.