|کد مقاله||کد نشریه||سال انتشار||مقاله انگلیسی||ترجمه فارسی||نسخه تمام متن|
|5740082||1616232||2018||7 صفحه PDF||سفارش دهید||دانلود کنید|
- Folate-producer strains of S.Â thermophilus are selected in folate-free medium.
- Selected strains increased folate content of milk during fermentation.
- The folK and folP genes are differentially expressed during the different stages of growth in milk.
- 5-Met-THF and THF are the main forms of folates produced by S.Â thermophilus in milk.
The ability of folate-producer strains of Streptococcus thermophilus to accumulate folates and the expression of two target genes (folK and folP), involved in the folate biosynthesis, were studied during milk fermentation. An over-expression of folK took place only in the early phase of growth, whereas folP was mainly expressed in the mid log-phase of growth and declined thereafter. The accumulation of total folates, which was quantified by a microbiological assay, was strain-dependent. Two major forms of folates, i.e. tetrahydrofolate (THF) and 5-methyl-tetrahydrofolate (5-Met-THF), were identified and quantified by HPLC. With respect to the level accumulated by a weak folate producer (St 383), used as calibrator in the expression experiments and as control in folate quantification in milk, the strains St 563 and St 399 produced 5-Met-THF in amounts significantly higher than THF. The possibility of using selected folate-producer S.Â thermophilus strains as functional cultures for a bio-fortification of dairy products is discussed.
Journal: Food Microbiology - Volume 69, February 2018, Pages 116-122