Color mutants of Monascus sp. KB9 and their comparative glucoamylases on rice solid culture

Monascus sp. KB9 strain was used to convert carbohydrate base agricultural commodities to value added pigments. Mutagenesis of this strain using UV light and successive isolation was found to improve the yield of pigment product. As a result, two hyper pigment productive strains, red and yellow mutants were obtained. In addition, one white mutant was also obtained. These color mutants together with their parental strain were used to compare glucoamylase production in rice solid culture. Initial moisture content of rice at 35–43% is found to affect glucoamylase of these four strains. It is noteworthy that the white mutant which lost its ability to produce pigment and revealed morphology indifference to its parental strain could produce the highest glucoamylase enzyme at 4.07×105 U/gdw (units per gram-dry weight). This is about 3, 7, and 16 times higher than the wild type strain, red, and yellow mutants, respectively. The crude enzyme showed its thermophilic property at optimal temperature, 65°C, and its optimal pH, 4.7.