Effect of initial pH, different nitrogen sources, and cultivation time on the production of yellow or orange Monascus purpureus pigments and the mycotoxin citrinin.

Matej Patrovsky,Petra Patakova,Barbora Branska,Kristyna Sinovska

doi:10.1002/fsn3.1197

Abstract

Monascus purpureus was grown in submerged liquid culture using ammonium sulfate, sodium nitrate, and peptone as nitrogen sources while initial medium pH was adjusted to 2.5, 5.5, 6.5, or 8.0. The combined effect of culture pH and nitrogen source on the biosynthesis of yellow (ankaflavin and monascin) and orange (rubropunctatin and monascorubrin) pigments, plus the mycotoxin citrinin, was evaluated chromatographically. Optimum cultivation conditions, that is, initial pH 2.5 and 8.8 g/L peptone as a nitrogen source, resulted in high levels of production of yellow and orange pigments (sum of pigment concentration 1,138 mg/L) and negligible citrinin concentration (2 mg/L).

Highlights

The filamentous fungus Monascus purpureus is widely known, especially in Asian countries (China, Korea, Japan, Thailand, Indonesia, Taiwan, Philippines), for its use in the preparation of a traditional food called red fermented rice or red yeast rice (Patakova, 2013)
The main question regarding safety and usefulness of food colorings using Monascus pigments is their potential contamination with the mycotoxin citrinin, which can be produced together with the pigments
Attention was focused on the intracellular formation of yellow and orange pigments, for which it has been confirmed recently (Chen et al, 2017; Chen, Feng, Molnár, & Chen, 2019) that they are of biosynthetic origin while previously it was assumed that yellow pigments were formed chemically from orange ones

Summary

| INTRODUCTION

The filamentous fungus Monascus purpureus is widely known, especially in Asian countries (China, Korea, Japan, Thailand, Indonesia, Taiwan, Philippines), for its use in the preparation of a traditional food called red fermented rice or red yeast rice (Patakova, 2013). The color of Monascus pigment alcohol extracts is evaluated by spectrophotometric analysis, and usually, three values at the absorption maxima of yellow, orange and red pigments, that is, at 410, 470, and 510 nm, respectively, are compared. These values do not correspond with actual amounts of individual pigments in crude ethanol extracts. Red Monascus pigments are not formed biosynthetically but by a chemical reaction with compounds containing primary amino groups, such as amino acids, nucleotides, and others at an appropriate pH Such reactions can proceed during extraction (Shi et al, 2015) unless they are prevented by low pH of the solvent. Attention was focused on the intracellular formation of yellow and orange pigments, for which it has been confirmed recently (Chen et al, 2017; Chen, Feng, Molnár, & Chen, 2019) that they are of biosynthetic origin while previously it was assumed that yellow pigments were formed chemically from orange ones

| MATERIALS AND METHODS

| RESULTS AND DISCUSSION

| CONCLUSION