OPTIMIZATION OF FOOD COLOURANT PRODUCTION IN CAPABLE FUNGI ISOLATED FROM THE SOIL IN NSUKKA
Colouring of food substances has been an age long practice by man in order to improve appearance, preserve or add nutrient to foods. Health risk and damages caused by the use of currently more available synthetic colourants in foods had necessitated the search for biological alternative. In this study, four fungi isolated from the soil in Nsukka were evaluated for their ability to produce colourants. Two of the isolates identified as Acremonium cellulolyticus and Trichoderma viride elaborating red and yellow pigments (colourants) respectively, were selected for optimization in a liquid mineral salt medium. Spectral patterns of the pigments extracted with acetone, methanol, cold acetone-methanol, hexane or benzene revealed that they contained carotenoids. In A. cellulolyticus, the initial pH values of 4.0 and 5.0, nitrogen sources of urea and NaNO3, inoculum volumes of 0.1 and 0.3 ml, incubation periods of 7 and 11 days, and CN ratios of 40:1.75 and 16:1.05 were the best for mycelia growth and pigment production respectively. For T. viride, the initial pH values of 7.5 and 6.0, nitrogen sources of NaNO3 and yeast extract, inoculum volumes of 0.3 and 0.2 ml, incubation periods of 7 and 9 days, and CN ratios of 32:3.50 and 24:1.05 were the best for mycelia growth and pigment production respectively. Studies on effect of some Agro-residues like cassava bagasse as sole carbon source revealed that they can support growth and pigmentation in both isolates. Glucose medium with combinatorial of all the observed optimum factors gave extracellular pigments that was 1.425 folds higher in Acremonium cellulolyticus (161.40 U.ml/g DMW) and 1.930 folds higher in Trichoderma viride (140.15 U.ml/g DMW) than in normal/non-oprtimized glucose medium. Hence, this investigation has demonstrated the possibilities of commercializing the production of food colourants from our isolates by optimizing their culture conditions.
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