Effect of galactose and glucose on the exopolysaccharide production and the activities of biosynthetic enzymes in Lactobacillus casei CRL 87

F. MOZZI; G. ROLLÁN; G. SAVOY DE GIORI; G. FONT DE VALDEZ

JOURNAL OF APPLIED MICROBIOLOGY

Blackwell Publishing

Lugar: Oxford, Inglaterra; Año: 2001 vol. 91 p. 160 - 167

1364-5072

Aims: The objective of this work was to study the in¯uence of the sugar source on exopolysaccharide (EPS) production and the activities of the enzymes involved in the synthesis of sugar nucleotides in Lactobacillus casei CRL 87. The relationship between these enzymes and EPS formation was determined.The objective of this work was to study the in¯uence of the sugar source on exopolysaccharide (EPS) production and the activities of the enzymes involved in the synthesis of sugar nucleotides in Lactobacillus casei CRL 87. The relationship between these enzymes and EPS formation was determined.Lactobacillus casei CRL 87. The relationship between these enzymes and EPS formation was determined. Methods and Results: The concentration of EPS was estimated by the phenol/sulphuric acid method while the chemical composition of puri®ed EPS was investigated using gas-liquid chromatography. Biosynthetic enzyme activities were determined spectrophotometrically by measuring the formation or disappearance of NAD(P)H at 340 nm. Polysaccharide production by Lb. casei CRL 87 was 1á7 times greater on galactose than on glucose. The isolated polymer was composed of rhamnose, glucose and galactose. The activities of uridine-diphosphate (UDP)-glucose-pyrophosphorylase, thymidine-diphosphate (dTDP)-glucose-pyrophosphorylase and the dTDP-rhamnose-synthetic enzyme system were higher in galactose-grown than in glucose-grown cells. When an EPS) mutant strain was used, galactokinase activity was not detected on galactose, this sugar not being available for the formation of sugar nucleotides for further EPS production. dTDP-glucose-pyrophosphorylase and dTDP-rhamnose-synthetic enzyme system activities were lower than the values found for the wild type strain.The concentration of EPS was estimated by the phenol/sulphuric acid method while the chemical composition of puri®ed EPS was investigated using gas-liquid chromatography. Biosynthetic enzyme activities were determined spectrophotometrically by measuring the formation or disappearance of NAD(P)H at 340 nm. Polysaccharide production by Lb. casei CRL 87 was 1á7 times greater on galactose than on glucose. The isolated polymer was composed of rhamnose, glucose and galactose. The activities of uridine-diphosphate (UDP)-glucose-pyrophosphorylase, thymidine-diphosphate (dTDP)-glucose-pyrophosphorylase and the dTDP-rhamnose-synthetic enzyme system were higher in galactose-grown than in glucose-grown cells. When an EPS) mutant strain was used, galactokinase activity was not detected on galactose, this sugar not being available for the formation of sugar nucleotides for further EPS production. dTDP-glucose-pyrophosphorylase and dTDP-rhamnose-synthetic enzyme system activities were lower than the values found for the wild type strain.Lb. casei CRL 87 was 1á7 times greater on galactose than on glucose. The isolated polymer was composed of rhamnose, glucose and galactose. The activities of uridine-diphosphate (UDP)-glucose-pyrophosphorylase, thymidine-diphosphate (dTDP)-glucose-pyrophosphorylase and the dTDP-rhamnose-synthetic enzyme system were higher in galactose-grown than in glucose-grown cells. When an EPS) mutant strain was used, galactokinase activity was not detected on galactose, this sugar not being available for the formation of sugar nucleotides for further EPS production. dTDP-glucose-pyrophosphorylase and dTDP-rhamnose-synthetic enzyme system activities were lower than the values found for the wild type strain.) mutant strain was used, galactokinase activity was not detected on galactose, this sugar not being available for the formation of sugar nucleotides for further EPS production. dTDP-glucose-pyrophosphorylase and dTDP-rhamnose-synthetic enzyme system activities were lower than the values found for the wild type strain. Conclusions: The carbon source present in the culture medium affects EPS production byThe carbon source present in the culture medium affects EPS production by Lb. casei CRL 87. The greater polymer synthesis by galactose-grown cells is correlated with the higher UDP-glucose-pyrophosphorylase, dTDP-glucose-pyrophosphorylase and dTDPrhamnose- synthetic enzyme system activities. Initial sugar metabolism is also an important step for the synthesis of EPS precursors by this strain.CRL 87. The greater polymer synthesis by galactose-grown cells is correlated with the higher UDP-glucose-pyrophosphorylase, dTDP-glucose-pyrophosphorylase and dTDPrhamnose- synthetic enzyme system activities. Initial sugar metabolism is also an important step for the synthesis of EPS precursors by this strain. Signi®cance and Impact of the Study: Knowledge of the effect of the sugar source on EPS production and the activities of biosynthetic enzymes provides information about the mechanisms of regulation of the synthesis of EPS which can contribute to improving polymer production.Knowledge of the effect of the sugar source on EPS production and the activities of biosynthetic enzymes provides information about the mechanisms of regulation of the synthesis of EPS which can contribute to improving polymer production.