Abstract
BackgroundTraditional submerged fermentation mainly accumulates intracellular orange pigments with absorption maxima at 470 nm, whereas extractive fermentation of Monascus spp. with Triton X-100 can promote the export of intracellular pigments to extracellular broth, mainly obtaining extracellular yellow pigments with absorption maxima at approximately 410 nm. In this study, a strain of Monascus (M. anka GIM 3.592) that produces high yields of pigments was employed to investigate the differences in pigment fingerprint profiles between submerged and extractive fermentations.ResultsUsing extractive fermentation with this high-yield strain, the extracellular pigments exhibited an absorption maximum at 430 nm, not 410 nm, as previously observed. By comparing the pigment fingerprint profiles between submerged and extractive fermentations, extractive fermentation was found to not only export intracellular pigments to the extracellular broth, but also to form four other yellow pigments (Y1-Y4) that accounted for a large proportion of the extracellular pigments and that were not produced in submerged fermentation. The yields of Y1-Y4 were closely related to the concentration and feeding time point of Triton X-100. Y1-Y4 presented identical UV-Vis spectra with absorption maxima at 430 nm and fluorescence spectra with absorption maxima (emission) at 565 nm. HPLC-MS and the spectral analysis showed that the four pigments (Y1-Y4) had not been previously reported. The results indicated that these pigments may rely on the bioconversion of orange pigments (rubropunctatin and monascorubrin).ConclusionsUsing extractive fermentation with M. anka led to a high yield of extracellular yellow pigments (AU410 nm = 114), and the pigment fingerprint profile significantly differed compared to the results of traditional submerged fermentation. These results provide information and a detailed view of the composition and variation of pigments in extractive fermentation and could also contribute to characterizing pigment metabolism during extractive fermentation.
Highlights
Traditional submerged fermentation mainly accumulates intracellular orange pigments with absorption maxima at 470 nm, whereas extractive fermentation of Monascus spp. with Triton X-100 can promote the export of intracellular pigments to extracellular broth, mainly obtaining extracellular yellow pigments with absorption maxima at approximately 410 nm
Cell growth and pigment production during extractive fermentation (EF) (50 g/L Triton X-100) showed notable differences compared to Submerged fermentation (SF) in the beginning (Fig. 1c and d)
The highest production of intracellular pigments were obtained on the 4th day when the absorbance units (AU) at 470 nm reached 123
Summary
Traditional submerged fermentation mainly accumulates intracellular orange pigments with absorption maxima at 470 nm, whereas extractive fermentation of Monascus spp. with Triton X-100 can promote the export of intracellular pigments to extracellular broth, mainly obtaining extracellular yellow pigments with absorption maxima at approximately 410 nm. The Monascus pigment composition mainly consists of two yellow pigments (monascin and ankaflavin), two orange pigments (rubropunctatin and Submerged fermentation (SF) at a low pH can rapidly accumulate a large amount of intracellular orange pigments (rubropunctatin and monascorubrin), independent of the nitrogen sources that are employed [15, 16]. Yellow pigments (monascin and ankaflavin) were found to dominate both the intracellular and extracellular pigments, which had the same absorption maxima at 410 nm throughout the EF This phenomenon was due to the export of intracellular yellow pigments and the subsequent blockage of yellow pigment conversion to orange pigments [21]
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