Profiling the Monascus pilosus Proteome during Nitrogen Limitation

Abstract

Monascus species have the unique ability to economically produce many secondary metabolites. However, the influence of nitrogen limitation on Monascus secondary metabolite production and metabolic performance remains unclear. Varying the carbon/nitrogen (C/N) ratios in the range from 20 to 60 in cultivation of Monascus pilosus by glucose nitrate medium, our resulting data showed that red pigment production was significantly suppressed and more sensitive to nitrogen limitation than cellular biomass growth at a C/N ratio of 60. Using a comparative proteomic approach, combining two-dimensional gel electrophoresis, matrix-assisted laser desorption ionization time-of-flight/time-of-flight liquid chromatography-mass spectrometry, and tandem mass spectrometry, proteins with modified expression in the nitrogen-limited (C/N ratio 60) Monascus filamentous cells were identified. The results revealed that the deregulated proteins identified were involved in amino acid biosynthesis, protein translation, antioxidant-related enzymes, glycolysis, and transcriptional regulation. The results suggested that, under nitrogen limitation-induced suppression of protein translation and of expression of the related energy-generating enzymes, nitrogen limitation induced a switch of metabolic flux from glycolysis to the tricarboxylic acid (TCA) cycle for maintaining cellular energy homeostasis, resulting in repression of the metabolic shift of the polyketide biosynthesis pathway for red pigment production.

Biocatalytic activity of Monascus mycelia depending on physiology and high sensitivity to product concentration

“…Thus, nitrogen sources in the defined media (Kang et al 2013, 2014) as well as complex media (Xiong et al 2014) also influences the profile of Monascus pigments and citrinin accumulation. The influence of nitrogen concentration on profiling of Monascus proteome is also reported (Lin et al 2008). …”

Effect of the cultivation mode on red pigments production from Monascus ruber

“…In contrast, the specific red pigment production was maximal at a C/N around 10 and then decreased steadily above this ratio to almost nil at C/N > 90. This result was in accordance with previous results made with Monascus pilosus for the production of red pigments (Lin et al ., ). The fact that both citrinin production and red pigment production were extremely low at high C/N ratio (in the range of 45–90) could be merely due to high concentrations of glucose (50 g L −l ) used for the fermentation, which results in the induction of a respiro‐fermentative metabolism (also called Crabtree effect ) (Yong et al ., ) accompanied by high production of ethanol (9 g L −1 ).…”

Ammonium nitrate regulated the color characteristic changes of pigments in Monascus purpureus M9

“…It has been consistently shown that selective nitrogen sources largely influence the composition of MPs. Some studies showed that the red MPs production is significantly suppressed under nitrogen limitation (Lin et al 2007). To be noted, red or orange pigments can be formed when yeast extract/nitrate or ammonium salt is supplemented, respectively (Carels and Shepherd 1977).…”