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This study describes a strategy to select and isolate spontaneous riboflavin-overproducing strains …


Home » Biology Articles » Microbiology » Food Microbiology » A general method for selection of riboflavin-overproducing food grade micro-organisms » Figures

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- A general method for selection of riboflavin-overproducing food grade micro-organisms

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Figure 1 Riboflavin produced by roseoflavin-resistant Lc. mesenteroides NCDO2028 mutants. The riboflavin concentration was determined in the cell free supernatant as the cells entered stationary phase. The various patterns indicate different mutations.

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Figure 2Alignment of the rib operon regulatory region of Lc. mesenteroides NCDO2028 and seven different mutants isolated. The mutations are shaded. The predicted -10 and -35 recognition sequences and ribosomal binding site are boxed. The ribG start codon is boxed with dashed lines. The RFN element predicted by RFAM is indicated by the arrows below the sequence.

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Figure 3 (A) Growth of Lb. plantarum NCDO 1752 (black lines with circles) and Lb. plantarum WCFS1 (red lines with triangles) in CDM (solid lines, closed symbols) or CDM + 5 μM riboflavin (dashed lines, open symbols) (B) Amplification of the region from lp_1345 to the C terminal of ribB from Lb. plantarum strains chromosomal DNA. Lane 1: Molecular weight marker; Lane 2: Lb. plantarum WCFS1; Lane 3: Lb. plantarum NCDO 1752; Lane 4: negative control (H2O). The size of the marker bands are indicated to the left of the picture. (C) Schematic diagram of the deleted region in Lb. plantarum WCFS1 in comparison to Lb. plantarum NCDO 1752.

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Figure 4 Riboflavin produced by roseoflavin-resistant Lb. plantarum NCDO1752 mutants. The riboflavin concentration was determined in the cell free supernatant after the cells entered stationary phase. The two shades represent the two mutants isolated.

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Figure 5 Alignment of the rib operon regulatory region of Lb. plantarum NCDO1752 and the two mutants isolated. The mutations are shaded. The predicted -10 and -35 recognition sequences and ribosomal binding site are boxed. The ribG start codon is boxed with dashed lines. The RFN element predicted by RFAM is indicated by the arrows below the sequence.

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Figure 6 Riboflavin produced by roseoflavin-resistant P. freudenreichii B374 mutants. The riboflavin concentration was determined in the cell free supernatant after the cells entered stationary phase. The solid bars represent the levels produced by the roseoflavin-resistant strains, while the open bars represent the wildtype strain concentrations.

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Figure 7 Riboflavin produced by P. freudenreichii B374 and its riboflavin overproducing derivatives B2336 and B374.21 after successive generations in roseoflavin free broth.

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Figure 8 (A) Final pH of yoghurt with various inoculum levels of P. freudenreichii B374 or B2336 either added 24 hours beforehand or simultaneously with the yoghurt starter culture. (B) Final riboflavin levels in yoghurt with various inoculum levels of P. freudenreichii B374 or B2336 either added sequentially or simultaneously with the yoghurt starter culture.

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