Investigation of pigment production by fungal Monascus purpureus in nutrient media obtained from different food wastes

In this thesis study, the production of yellow and red pigments secreted extracellularly by the Monascus purpureus fungus in batch stirred vessel was investigated in natural liquid nutrient media prepared from molasses and those containing sugars extracted with hot water from orange and grape waste, as well as in a synthetic nutrient medium containing glucose used as a reference for comparison. In the studies, first of all, the effects of initial pH and initial glucose concentration on the production rate and efficiency of yellow and red pigments in artificial nutrient medium containing glucose were investigated. For both pigments, the highest production rate and efficiency values were obtained at an initial pH of 4. At pH 4, it was observed that increasing the initial glucose concentration up to 40 g/L resulted in yellow pigment production reaching 8,68 g/L, while increasing the initial glucose concentration up to 60 g/L led to red pigment production reaching 14,04 g/L. In the following step of the studies, at pH 4, the effect of initial sucrose concentration on the production rate and yield of yellow and red pigment production from M. purpureus in the nutrient medium prepared from molasses was investigated, within an initial sucrose concentration range of 10-40 g/L, at 30 g/L sucrose concentration, the highest yellow pigment production was observed 0,96 g/L, at 40 g/L sucrose concentration, the highest red pigment production was observed 3,35 g/L. In the next stage of the studies, the effects of initial substrate concentration on the production of Monascus pigments were investigated in nutrient media at pH 4, obtained from pulpy orange peel waste different waste/liquid (A/S) ratios, containing total reducing sugar (TİŞ) concentration ranging from 10-60 g/L and at 60 g/L TİŞ concentration highest yellow pigment production was found to be 0,82 g/L, and at 40 g/L TİŞ concentration, the highest red pigment production was found to be 2,13 g/L. In the final stage of the studies, the effects of the initial substrate concentration on the production of Monascus pigments were investigated in nutrient media obtained from waste grape pulp at pH 4 in two different waste/liquid (A/S) ratios, containing 10 and 20 g/L total reducing sugar (TİŞ) concentrations and at 20 g/L TİŞ concentration, the highest yellow pigment production was found to be 0,57 g/L and the highest red pigment production was found to be 1,72 g/L. Experimental results showed that Monascus purpureus reached the highest rate and efficiency values in the production of both pigments in glucose nutrient medium, the red pigment production was higher than yellow pigment production in all nutrient media studied, pigment production in a glucose nutrient medium generally occurred in the exponential growth phase, while in other nutrient media it occured in the stationary phase depending on the substrate concentration. In this thesis, the production of yellow and red pigments with high added value, suitable for multi-purpose uses, with a low-cost and environmentally friendly method, using the Monascus purpureus mold fungus, in liquid nutrient media obtained from molasses, a by-product of the sugar industry, as well as pulpy orange peel and grape pomace from food industry wastes.