Abstract
Monascus pigments (MPs) with different color characteristics, produced by submerged fermentation of Monascus purpureus M9, have potential application in food industry. In the present study, the effects and regulatory mechanisms of ammonium nitrate (AN) on the color characteristics of MPs were investigated. The concentration of intracellular pigments was significantly decreased when subjected to AN. The hue and lightness value indicated AN altered the total pigments appearance from original red to orange. The HPLC analysis for six major components of MPs showed that the production of rubropunctatin or monascorubrin, was significantly reduced to the undetectable level, whereas the yields of monascin, ankaflavin, rubropunctamine and monascorubramine, were apparently increased with AN supplement. To be noted, via real-time quantitative PCR strategy, the expression level of mppG, closely relative to orange pigments biosynthesis, was significantly down-regulated. However, the expression of mppE, involved in yellow pigments pathway, was up-regulated. Moreover, the broth pH value was dropped to 2.5–3.5 in the fermentation process resulted from AN treatment, along with the increased extracellular polysaccharide biosynthesis. Taken together, the change of MPs categories and amounts by AN might be the driving force for the color characteristics variation in M. purpureus M9. The present study provided useful data for producing MPs with different compositions and modified color characteristics.
Highlights
Color pigments are widely used in food industry to restore color lost in processing or to improve the appearance of a product
The pH decreased remarkably when exposed to ammonium nitrate (AN), the phenomenon might be caused by the fact that AN is strong acidweak base, tending to react with OH− to form NH3 · H2O, which resulted in increasing the concentration of dissociative H+ in liquid medium (Peters and Smuła-Ostaszewska 2012)
Many reports demonstrated that nitrogen, the pivotal nutrient factors, significantly influences Monascus pigments (MPs) biosynthesis (Carels and Shepherd 1977; Chen and Johns 1993; Shi et al 2015)
Summary
Color pigments are widely used in food industry to restore color lost in processing or to improve the appearance of a product. MPs are a complex mixture of compounds with a common azaphilone skeleton. They are mainly composed of yellow, orange and red pigments. More than 90 MP members have been identified, which include 44 yellow, 8 orange and 42 red pigments based on recent reports (Chen et al 2017; Patakova 2013). Among those the top six well-known pigments were 2 yellow (monascin and ankaflavin), 2 orange (rubropunctatin and monascorubrin), and 2 red (rubropunctamine and monascorubramine) (Jůzlová et al 1996). To find simple approaches to produce MPs with diversiform color characteristics will be greatly beneficial to the amelioration of their economic value
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
