Selection of Glucose Depression Mutants for the Improvement of Ang-Kak Production and Regulation of Pigmentation

Abstract

For the improvement of fungal strain used in Chinese red rice (ang-kak) fermentation, glucose derepression mutants, R8 and R53 was selected after UV exposure of the wild type Monascus sp. NP1. The mutants produced higher pigment with a faster rate compared to the parent strain. Although 37.2% served as optimal initial moisture for both the wild type and its mutants, success of ang-kak production could be made at higher initial moisture contents. Red pigment with λ_max at 500 nm which was corresponded to their parent strain was produced at 2.54 by R8 and 2.47 times by R53 higher than that by the wild type. Mutant R8 and R53 gave yellow pigment with λ_max  410 and 396 respectively compared to 384 of that obtained from Monascus sp. NP1. Ratios of yellow to red compounds produced, using strain R8 and R53 were 1.278 and 1.612 respectively, whereas that of the wild type was 1.693. By studying time course of glucoamylase production and effects of added glucose on fermentation, it implied that the mutants pigmentation efficiency in solid state fermentation resulted from two mechanisms. Firstly: toleration to glucose repression and secondly through their ability to regulate glucose concentration liberated to a level under which the mold could tolerate by a sharp drop in glucoamylase production after the maximal activity was achieved in day 5.