Selection of Monascus mutants for the improvement of ang-kak production

Improvement of fungal strain for Chinese red rice (ang-kak) fermentation was carried out by exposing the wild type Monascus sp. NPl to ultraviolet. Three mutants namely mutant R8, R32 and R53 were selected based on ability to form red colonies on medium containing high glucose concentration. All mutants possessed the following characteristics: 1) Producing red pigment with lambda max at 500 nm which corresponded to that of their parent strain. Amount of pigment obtained using mutant R8, R32 and R53 was 2.54, 1.18 and 2.47 times respectively higher than that produced by the wild type. 2) Mutant R8, R32, and R53 gave yellow pigment with lambda max 410,372-412 and 396 respectively compared to 384 of that obtained from Monascas sp. NPl. 3) Ratios of the absorbancy of the yellow pigment to that of the red produced by R8, R32 and R53 were 1.278, 1.297 and 1.612 respectively, whereas that of the wild type was 1.693. 4) All mutants resisted to repression by glucose at a higher concentration that fermentation could be accomplished when 8, 7 and 7 percent of sugar was added respectively, using strain R8, R32 and R53 while 7 percent glucose completely repressed pigmentation by the wild type. 5) Patterns of time course of glucoamylase production were different from that of parent strain that there was a rapidly drop in activities at late fermentation (day 4-5) of the former. Thus beside resistance to high sugar concentrations, dropping of enzyme activities resulted in limitation of glucose liberated to a level under which the molds could tolerate. 6) Fermentation could be carried on by mutant R8 and R53 at higher moisture contents with the optimum at 37.2 percent. At which pigmentation proceeded at a faster rate, whereas strain R32 produced the pigment at lower moisture levels with the optimum at 33.7 percent . 7) Pigmentation by all cultures was found to be growth associated at late fermentation. Mutant R8 and R53 were genetically stable in term of pigmentation capability after 7 passages transfering, whereas strain R32 could be maintained for 6 passages. Identification of the parent strain, Monascus NPl revealed that it was closely related to Monascus purpureus.