PRODUCTION OF RED PIGMENTS BY MONASCUS RUBER IN SYNTHETIC MEDIA WITH A STRICTLY CONTROLLED NITROGEN-SOURCE

A complete factorial design was used to determine the composition of a synthetic culture medium with glucose as carbon source and monosodium glutamate as sole nitrogen source for Monascus ruber to maximize simu ltaneously strict exocellular pigment production and their red-to-yell ow proportion. When culture conditions improved pigment production, th e red/yellow ratio decreased. The compromise conditions for both objec tives were obtained when the concentrations of glucose, monosodium glu tamate, KH2PO4 and K2HPO4 in the culture medium were respectively 26, 5, 5 and 5 g/litre. In Erlenmeyer flask cultures, high ethanol product ion and CO2 as coproducts were found associated with large pellet size , while for smaller pellet size a decrease in ethanol production and a n increase in pigment synthesis were detected. Fermenter analysis of k inetic data showed a growth limitation that could be overcome by aerat ion with CO2-air mixtures. In all cases the maximum specific rate of p igment production occurred unexpectedly before the maximum specific gr owth rate was reached. Mycelial morphological changes are the precurso r to decreasing specific rates of pigment production. Neither a comple te sexual cycle nor pigment accumulation structures into mycelium were detected.