Fig.3-9 Dry weight of C100, ΔMareA and OE-MareA in media with different nitrogen sources
3.3.2 Total color value of solid fermented red yeast rice
Color value is one of the main quality indicators of natural pigments,
which can reflect the pigment production. In the fermentation medium of
rice without an additional nitrogen source, the total color value of
ΔMareA decreased compared to that of C100, while the color value
of OE-MareA increased. Under the fermentation culture conditions
with the addition of Gln, there was little difference in the total color
values among the three strains and they were largely unaffected by theAreA gene. In rice fermentation medium with
(NH4)2SO4 added, all
three strains had very low total color values. When
NaNO3 was added to the medium, ΔMareA strain had
a lower color value than C100 while OE-MareA strain had a higher
color value than that of the original strain. This effect was most
pronounced. In fermentation medium with Urea added, similar but less
significant results were observed compared to NaNO3addition. In summary, MareA gene affects monascus’ color value
mainly through reducing MPs’ color value when MareA gene is
deleted and accelerating pigment accumulation when MareA gene is
overexpressed, under different nitrogen sources culture conditions
adding different sources of nitrogen, overexpression of MareA gene increases MPs’ color value . Among them, the most significant
effect occurred in culture medium with NaNO3. As shown
in Figure 3-10.