Molecular and Biochemical Analysis of the Galactose Phenotype of Dairy
            <i>Streptococcus thermophilus</i>
            Strains Reveals Four Different Fermentation Profiles

Vin, Filip De; Rådström, Peter; Herman, Lieve; Vuyst, Luc De

doi:10.1128/aem.71.7.3659-3667.2005

Cited by 69 publications

(55 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Most strains of S. thermophilus, including St1-WT and St2-WT, are unable to ferment galactose despite having intact galKTEM genes encoding the required enzymes for the Leloir pathway (19,20) (Table 2). The most likely reason for this phenotype is insufficient transcription due to a defective promoter (19).…”

Section: Discussionmentioning

confidence: 99%

Enhancing the Sweetness of Yoghurt through Metabolic Remodeling of Carbohydrate Metabolism in Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus

Sørensen

Curic-Bawden²,

Junge

et al. 2016

Appl Environ Microbiol

View full text Add to dashboard Cite

Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus are used in the fermentation of milk to produce yoghurt. These species normally metabolize only the glucose moiety of lactose, secreting galactose and producing lactic acid as the main metabolic end product. We used multiple serial selection steps to isolate spontaneous mutants of industrial strains of S. thermophilus and L. delbrueckii subsp. bulgaricus that secreted glucose rather than galactose when utilizing lactose as a carbon source. Sequencing revealed that the S. thermophilus strains had mutations in the galKTEM promoter, the glucokinase gene, and genes encoding elements of the glucose/mannose phosphotransferase system (PTS). These strains metabolize galactose but are unable to phosphorylate glucose internally or via the PTS. The L. delbrueckii subsp. bulgaricus mutants had mutations in genes of the glucose/mannose PTS and in the pyruvate kinase gene. These strains cannot grow on exogenous glucose but are proficient at metabolizing internal glucose released from lactose by ␤-galactosidase. The resulting strains can be combined to ferment milk, producing yoghurt with no detectable lactose, moderate levels of galactose, and high levels of glucose. Since glucose tastes considerably sweeter than either lactose or galactose, the sweetness of the yoghurt is perceptibly enhanced. These strains were produced without the use of recombinant DNA technology and can be used for the industrial production of yoghurt with enhanced intrinsic sweetness and low residual levels of lactose. IMPORTANCEBased on a good understanding of the physiology of the lactic acid bacteria Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, we were able, by selecting spontaneously occurring mutants, to change dramatically the metabolic products secreted into the growth medium. These mutants consume substantially more of the lactose, metabolize some of the galactose, and secrete the remaining galactose and most of the glucose back into the milk. This allows production of yoghurt with very low lactose levels and enhanced natural sweetness, because humans perceive glucose as sweeter than either lactose or galactose. Modern yoghurt production begins with pasteurization of milk, followed by inoculation and fermentation by commercially prepared starter cultures containing strains of the lactic acid bacteria Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus (1). In order to satisfy consumer demands regarding appearance, sweetness, texture, and flavor, a number of additional ingredients may be added, including natural or artificial colors, sucrose or artificial sweeteners, texturizing agents, and fruit preparations (2). Today, yoghurt may contain 5 to 12% (wt/vol) added sucrose in addition to the natural sugars (lactose and galactose) already present, resulting in sugar contents that rival those of soft drinks and tarnishing the image of yoghurt as a healthy food. In addition, the potential for gastrointestinal discom...

show abstract

Section: Discussionmentioning

confidence: 99%

Enhancing the Sweetness of Yoghurt through Metabolic Remodeling of Carbohydrate Metabolism in Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus

Sørensen

Curic-Bawden²,

Junge

et al. 2016

Appl Environ Microbiol

View full text Add to dashboard Cite

show abstract

“…A similar accumulation of galactose in the culture medium is observed when S. thermophilus is grown on lactose, albeit for a different reason. In contrast to L. bulgaricus, S. thermophilus does possess the necessary genes to direct catabolism of galactose, but these genes are generally repressed in the presence of lactose (36).…”

Section: Regulatory Functions: Two Siga Homologues and Relatively Fewmentioning

confidence: 99%

The complete genome sequence ofLactobacillus bulgaricusreveals extensive and ongoing reductive evolution

Guchte

Penaud

Grimaldi

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

376

300

View full text Add to dashboard Cite

Lactobacillus delbrueckii ssp. bulgaricus (L. bulgaricus) is a representative of the group of lactic acid-producing bacteria, mainly known for its worldwide application in yogurt production. The genome sequence of this bacterium has been determined and shows the signs of ongoing specialization, with a substantial number of pseudogenes and incomplete metabolic pathways and relatively few regulatory functions. Several unique features of the L. bulgaricus genome support the hypothesis that the genome is in a phase of rapid evolution. (i) Exceptionally high numbers of rRNA and tRNA genes with regard to genome size may indicate that the L. bulgaricus genome has known a recent phase of important size reduction, in agreement with the observed high frequency of gene inactivation and elimination; (ii) a much higher GC content at codon position 3 than expected on the basis of the overall GC content suggests that the composition of the genome is evolving toward a higher GC content; and (iii) the presence of a 47.5-kbp inverted repeat in the replication termination region, an extremely rare feature in bacterial genomes, may be interpreted as a transient stage in genome evolution. The results indicate the adaptation of L. bulgaricus from a plant-associated habitat to the stable protein and lactose-rich milk environment through the loss of superfluous functions and protocooperation with Streptococcus thermophilus.bulgaricus) is one of the economically most important representatives of the heterogeneous group of lactic acid bacteria, with a worldwide application in yogurt production. Yogurt has long been recognized as a nutritious, natural, and safe component of a healthy diet and is at the basis of the concept of probiotics (1, 2). A well documented health benefit of the consumption of yogurt containing live L. bulgaricus and Streptococcus thermophilus is an attenuation of lactose intolerance (3). In addition, immune modulation and diarrhea-alleviating effects have been reported (4), and both L. bulgaricus and S. thermophilus have been implicated in these effects (3,5). During yogurt fermentations protocooperation between these two bacteria results in an accelerated acidification, but the mechanisms involved are not completely understood (6).Among the lactic acid bacteria, L. bulgaricus belongs to the acidophilus complex, a group of lactobacilli related to Lactobacillus acidophilus, Lactobacillus johnsonii, and Lactobacillus gasseri, which have been used as probiotic cultures. Although within this group L. bulgaricus is considered unique because of its atypical GC content, until recently the lack of tools for genetic manipulation has severely hampered a more detailed analysis of this organism (7, 8, † †).Here we present the genome sequence of L. bulgaricus strain ATCC11842, originally isolated from bulgarian yogurt by S. OrlaJensen in 1919 (unpublished work). The analysis of this genome and comparison to other members of the acidophilus complex and S. thermophilus (9) have contributed to a more complete understanding of its p...

show abstract

“…bulgaricus and S. thermophilus that are traditionally used together in starter culture mixes. However, it has been shown that many S. thermophilus strains metabolize only glucose, but not galactose [12,13,21,30]. During growth of L. delbrueckii ssp.…”

Section: Introductionmentioning

confidence: 99%

Pediocin production in milk by Pediococcus acidilactici in co-culture with Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus

Somkuti

Steinberg

2009

J Ind Microbiol Biotechnol

View full text Add to dashboard Cite

The production of pediocin in milk by Pediococcus acidilactici was evaluated in co-culture with the dairy fermentation cultures Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus. The cultures were tested singly and in different combinations in milk (0 or 2% fat content) during incubation at 40 degrees C for up to 10 h. Cell-free milk samples taken every 60 min were tested for bacteriocin activity against Listeria monocytogenes. Pediocin activity was not detectable when P. acidilactici was inoculated into milk as a monoculture. When P. acidilactici was grown in combination with the yogurt starter cultures S. thermophilus and Lb. delbrueckii ssp. bulgaricus, pediocin concentration reached 3,200-6,400 units ml(-1) after 8 h of incubation. The results showed that pediocin producing pediococci may be useful adjunct components in mixed cultures of S. thermophilus and Lb. delbrueckii ssp. bulgaricus to amplify the bioprotective properties of fermented dairy foods against Listeria contamination.

show abstract

Molecular and Biochemical Analysis of the Galactose Phenotype of Dairy Streptococcus thermophilus Strains Reveals Four Different Fermentation Profiles

Cited by 69 publications

References 28 publications

Enhancing the Sweetness of Yoghurt through Metabolic Remodeling of Carbohydrate Metabolism in Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus

Enhancing the Sweetness of Yoghurt through Metabolic Remodeling of Carbohydrate Metabolism in Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus

The complete genome sequence ofLactobacillus bulgaricusreveals extensive and ongoing reductive evolution

Pediocin production in milk by Pediococcus acidilactici in co-culture with Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus

Contact Info

Product

Resources

About