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Impact of engineered Streptococcus thermophilus trains overexpressing glyA gene on folic acid and acetaldehyde production in fermented milk
- Source :
- Scopus-Elsevier, Brazilian Journal of Microbiology v.34 suppl.1 2003, Brazilian Journal of Microbiology, Sociedade Brasileira de Microbiologia (SBM), instacron:SBM, Brazilian Journal of Microbiology, Volume: 34 Supplement 1, Pages: 114-117, Published: NOV 2003
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Abstract
- The typical yogurt flavor is caused by acetaldehyde produced through many different pathways by the yogurt starter bacteria L. bulgaricus and S. thermophilus. The attention was focused on one specific reaction for acetaldehyde and folic acid formation catalyzed by serine hydroxymethyltransferase (SHMT), encoded by the glyA gene. In S. thermophilus, this enzyme SHMT also plays the typical role of the enzyme threonine aldolase (TA) that is the interconvertion of threonine into glycine and acetaldehyde. The behavior of engineered S. thermophilus strains in milk fermentation is described, folic acid and acetaldehyde production were measured and pH and counts were followed. The engineered S. thermophilus strains StA2305 and StB2305, have the glyA gene (encoding the enzyme serine hydroxymethyltransferase) overexpressed. These engineered strains showed normal growth in milk when it was supplemented with Casitione. When they were used in milk fermentation it was observed an increase in folic acid and in acetaldehyde production by StA2305 and for StB2305 it was noticed a significative increase in folic acid formation. O acetaldeído, responsável pelo sabor e aroma característicos de iogurte, é produzido por diferentes vias metabólicas pelas bactérias lácticas: Streptococcus thermophilus (S. thermophilus) e Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus). Neste trabalho, a atenção foi focada especificamente na reação para a formação de acetaldeído e de ácido fólico, catalisada pela enzima serina hidroximetil transferase (SHMT), codificada pelo gene glyA. A enzima SHMT catalisa diversas reações e, no caso da bactéria S. thermophilus, ela exerce também a atividade característica da enzima treonina aldolase (TA), definida como a interconversão do aminoácido treonina em glicina e acetaldeído. Foram construídas linhagens de S. thermophilus (StA2305 e StB2305) com super expressão do gene glyA. Estas linhagens modificadas apresentaram crescimento normal quando o leite foi suplementado com hidrolisado de caseína (Casitione). Quando foram usadas para fermentação de leite, observou-se: aumento na produção de ácido fólico e acetaldeído por StA2305 e aumento significativo na formação de ácido fólico por StB2305.
- Subjects :
- chemistry.chemical_classification
Streptococcus thermophilus
Acetaldeído
biology
gene glyA e ácido fólico
Acetaldehyde
food and beverages
serine hydroxymethyltransferase and folic acid
biology.organism_classification
Microbiology
Threonine aldolase
chemistry.chemical_compound
Enzyme
chemistry
Biochemistry
glyA gene
serina hidroximetil transferase (SHMT)
Serine hydroxymethyltransferase
Glycine
Fermentation
Threonine
acetaldehyde
Subjects
Details
- Database :
- OpenAIRE
- Journal :
- Scopus-Elsevier, Brazilian Journal of Microbiology v.34 suppl.1 2003, Brazilian Journal of Microbiology, Sociedade Brasileira de Microbiologia (SBM), instacron:SBM, Brazilian Journal of Microbiology, Volume: 34 Supplement 1, Pages: 114-117, Published: NOV 2003
- Accession number :
- edsair.doi.dedup.....1c842c4480f3f138bda0fa25e5392d7b