Impact of engineered Streptococcus thermophilus trains overexpressing glyA gene on folic acid and acetaldehyde production in fermented milk

• Published in: Brazilian journal of microbiology Vol. 34; no. S1; pp. 114 - 117
• Main Authors: Chaves, Ana Carolina Sampaio Dória, Ruas-Madiedo, Patrícia, Starrenburg, Marjo, Hugenholtz, Jeroen, Lerayer, Alda Luiza Santos
• Format: Journal Article
• Language: English
• Published: São Paulo Springer Nature B.V 01-11-2003; Sociedade Brasileira de Microbiologia
• Subjects: MICROBIOLOGY; Streptococcus thermophilus; Acetaldeído; Streptococcus thermophilus; serina hidroximetil transferase (SHMT); gene glyA e ácido fólico; serine hydroxymethyltransferase and folic acid; acetaldehyde; glyA gene
• ISSN: 1517-8382; 1678-4405; 1678-4405
• DOI: 10.1590/S1517-83822003000500039

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.