کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
2442029 1108160 2005 7 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Use of an α-Galactosidase Gene as a Food-Grade Selection Marker for Streptococcus thermophilus
موضوعات مرتبط
علوم زیستی و بیوفناوری علوم کشاورزی و بیولوژیک علوم دامی و جانورشناسی
پیش نمایش صفحه اول مقاله
Use of an α-Galactosidase Gene as a Food-Grade Selection Marker for Streptococcus thermophilus
چکیده انگلیسی
The α-galactosidase gene (aga) of Lactococcus raffinolactis ATCC 43920 was previously shown to be an efficient food-grade selection marker in Lactococcus lactis and Pediococcus acidilactici but not in Streptococcus thermophilus. In this study, we demonstrated that the α-galactosidase of L. raffinolactis is thermolabile and inoperative at 42°C, the optimal growth temperature of S. thermophilus. An in vitro assay indicated that the activity of this α-galactosidase at 42°C was only 3% of that at 30°C, whereas the enzyme retained 23% of its activity at 37°C. Transformation of Strep. thermophilus RD733 with the shuttle-vector pNZ123 bearing the aga gene of L. raffinolactis (pRAF301) generated transformants that were stable and able to grow on melibiose and raffinose at 37°C or below. The transformed cells possessed 6-fold more α-galactosidase activity after growth on melibiose than cells grown on lactose. Slot-blot analyses of aga mRNA indicated that repression by lactose occurred at the transcriptional level. The presence of pRAF301 did not interfere with the lactic acid production when the transformed cells of Strep. thermophilus were grown at the optimal temperature in milk. Using the recombinant plasmid pRAF301, which carries a chloramphenicol resistance gene in addition to aga, we showed that both markers were equally efficient at differentiating transformed from nontransformed cells. The aga gene of L. raffinolactis can be used as a highly efficient selection marker in Strep. thermophilus.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Dairy Science - Volume 88, Issue 7, July 2005, Pages 2341-2347
نویسندگان
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