Fig.3-8 Mycelium and spore morphology of C100, ΔMareA and OE-MareA in media with different nitrogen sources
3.3 Solid-state fermentation of C100, ΔMareA and
OE-MareA
3.3.1 Yield of red yeast rice by solid state fermentation
Monascus consumes nutrients in rice to meet its own growth and
development needs during solid-state fermentation. Different strains of
bacteria utilize rice to varying degrees, so the dry weight of red yeast
rice can reflect the growth and metabolism of different Monascus strains in the solid-state fermentation process. In the rice
fermentation medium without adding any nitrogen source, the knockout
strain ΔMareA weighed the heaviest at 10.48g, indicating slower
growth in the rice medium, while the overexpression strain
OE-MareA weighed the lightest at 9.67g, suggesting better
utilization of nutrients in rice. When comparing the dry weights of red
yeast rice with different nitrogen sources added, it was observed that
OE-MareA had the lightest weight after fermentation, followed by
C100, and ΔMareA had the heaviest weight. The addition of Gln
resulted in a consistent lighter weight for red yeast rice around 9.10
g, indicating that Gln addition was most favorable for Monascus ’
fermentation of rice and was not affected by AreA gene. The
weight of Monascus was the heaviest compared to other nitrogen
sources, reaching more than 15g, as it could not effectively utilize
(NH4)2SO4. However, when
NaNO3 was added, ΔMareA showed poor utilization
resulting in heavier red yeast rice. On the other hand, OE-MareA red yeast rice was lighter in weight. When Urea was added to the
fermentation medium, both ΔMareA and OE-MareA fermented
red yeast rice weighed less compared to NaNO3. In
conclusion, the addition of Gln had no effect on red yeast fermentation
regardless of deletion or overexpression of the AreA gene,
whereas NaNO3 best demonstrated the impact of this gene
on red yeast fermentation. As shown in Figure 3-9.