Enzymes involved in carbohydrate metabolism and their role on exopolysaccharide production in Streptococcus thermophilus

Abstract

The role of the enzymes uridine‐5′‐diphospho‐(UDP) glucose pyrophosphorylase and UDP galactose 4‐epimerase in exopolysaccharide production of Gal− ropy and non‐ropy strains of Streptococcus thermophilus in a batch culture was investigated. Growth of the ropy and non‐ropy strains was accompanied by total release of the galactose moiety from lactose hydrolysis in modified Bellinker broth with lactose as the only carbon source. This was associated with a greater exopolysaccharide production by the ropy strain. The polymer produced by both strains in cultures with lactose or glucose as carbon sources contained glucose, galactose and rhamnose, indicating that glucose was used as a carbon source for bacterial growth and for exopolysaccharide formation. UDP‐glucose pyrophosphorylase activity was associated with polysaccharide production during the first 12 h in a 20 h culture in the ropy strain, but not in the non‐ropy strain. UDP‐galactose 4‐epimerase was not associated with exopolysaccharide synthesis in any strain. The evidence presented suggests that the glucose moiety from lactose hydrolysis is the source of sugar for heteropolysaccharide synthesis, due to a high UDP‐glucose pyrophosphorylase activity.

Correlation of Activities of the Enzymes α-Phosphoglucomutase, UDP-Galactose 4-Epimerase, and UDP-Glucose Pyrophosphorylase with Exopolysaccharide Biosynthesis by Streptococcus thermophilus LY03

“…The main reasons are most likely analytical artifacts encountered during composition analysis and carbohydrate quantification (11). Our results are in agreement with those of Escalante et al, who did not observe any variation in monomeric composition when using either lactose or glucose as an energy source for S. thermophilus (14).…”

“…Our results clearly showed that none of the S. thermophilus strains displayed ␤-phosphoglucomutase activity. The correlation that we observed between the amount of EPS and the activity of UDP-glucose pyrophosphorylase was also reported by Escalante et al (14). They observed that UDP-glucose pyrophosphorylase was correlated with EPS production in a ropy S. thermophilus strain but not in a nonropy strain.…”

“…Some authors have reported the specific activities of enzymes involved in the biosynthesis of EPS from lactic acid bacteria (14,16,19,27,31). A relationship between EPS biosynthesis and the activity of the enzyme ␤-phosphoglucomutase was reported for L. lactis (31).…”

“…This was reflected in the activities of the enzymes involved, namely, UDP-glucose pyrophosphorylase, dTDP-glucose pyrophosphorylase, and the rhamnose nucleotide synthetic enzyme system. Escalante et al found that UDP-glucose pyrophosphorylase was correlated with EPS production in a ropy strain of S. thermophilus but not, although the enzyme was present, in a nonropy strain and that the Leloir enzyme UDP-galactose 4-epimerase was not correlated with EPS biosynthesis in any strain (14). We need more knowledge of the nutritional factors influencing the activities of the enzymes involved in the biosynthetic pathway of EPS and the regulation of the energy and carbon flows between the Embden-Meyerhof-Parnas (EMP) pathway and the biosynthesis of EPS.…”

Textura instrumental e avaliação sensorial de queijo fresco cremoso simbiótico: implicações da adição de Lactobacillus paracasei e inulina

“…No entanto, a presença de inulina nos queijos T2 não foi o fator que contribuiu para o baixo pH desse queijo, uma vez que este ingrediente foi adicionado em etapa posterior à fabricação das massas-base. Por outro lado, as espécies Lactobacillus paracasei (nos queijos T1 e T2) e Streptococcus thermophilus (em T1, T2 e T3), podem realmente diferir quanto ao tipo e à proporção de ácidos produzidos (Stiles, Holzapfel, 1997;Escalante et al, 1998;Kristo et al, 2003;Buriti et al, 2007). Do mesmo modo, existe a possibilidade de Lactobacillus paracasei ter produzido outros tipos de compostos que também influem no sabor do queijo, como peptídeos, cetonas ou aldeídos.…”