Two-stage pH control fermentation Based on the results obtained in the different fermentation conditions presented so far,
a two-stage pH control fermentationwas performed to improve the desirable pigments content and to further investigate the effect of pH and nitrogen sources on pigments composition (Figs. 5 and 6). The spectrophotometric and TLC analyses revealed that the pigments composition at 96 h (Figs. 5 and 6) was very close to that observed after 132 h (Figs. 1 and 4) regardless the nitrogen source employed. After the pH was changed to 6.5, the pigments compositions showed remarkable changes. Regardless the nitrogen source employed the intracellular extracts obtained after 156 h of fermentation showed a marked decrease of the absorbance at 470 nm relatively to the absorbance at 410 nm and
510 nm, indicating a relative loss of orange components. In particular, when ammonium and peptone were used as nitrogen sources, the intracellular orange pigments almost disappeared (Fig. 6B, line 2 and 6) and concurrently the intracellular red pigments increased. When peptone was the nitrogen source, the amount of polar red pigments derivatives in the intracellular extract increased significantly, and were retained at the loading point of the TLC plate (Fig. 6A, line 6). When nitrate was used as nitrogen source, the absorption spectrum of the intracellular extract at 156 h showed a shoulder at around 400 nm (Fig. 5B3),probably resulting from the contribution of the newly generated
red pigments (Fig. 6A, line 4), that were not present at 96 h. In terms of yield, considering the fermentations performed with ammonium and peptone, the two-stage fermentation approach increased about two-fold (according to the absorbance at 410 nm) the amount of intracellular pigments obtained (Fig. 5A2 and C2).
Two-stage pH control fermentation Based on the results obtained in the different fermentation conditions presented so far,a two-stage pH control fermentationwas performed to improve the desirable pigments content and to further investigate the effect of pH and nitrogen sources on pigments composition (Figs. 5 and 6). The spectrophotometric and TLC analyses revealed that the pigments composition at 96 h (Figs. 5 and 6) was very close to that observed after 132 h (Figs. 1 and 4) regardless the nitrogen source employed. After the pH was changed to 6.5, the pigments compositions showed remarkable changes. Regardless the nitrogen source employed the intracellular extracts obtained after 156 h of fermentation showed a marked decrease of the absorbance at 470 nm relatively to the absorbance at 410 nm and510 nm, indicating a relative loss of orange components. In particular, when ammonium and peptone were used as nitrogen sources, the intracellular orange pigments almost disappeared (Fig. 6B, line 2 and 6) and concurrently the intracellular red pigments increased. When peptone was the nitrogen source, the amount of polar red pigments derivatives in the intracellular extract increased significantly, and were retained at the loading point of the TLC plate (Fig. 6A, line 6). When nitrate was used as nitrogen source, the absorption spectrum of the intracellular extract at 156 h showed a shoulder at around 400 nm (Fig. 5B3),probably resulting from the contribution of the newly generatedred pigments (Fig. 6A, line 4), that were not present at 96 h. In terms of yield, considering the fermentations performed with ammonium and peptone, the two-stage fermentation approach increased about two-fold (according to the absorbance at 410 nm) the amount of intracellular pigments obtained (Fig. 5A2 and C2).
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