World Journal of Microbiology and Biotechno/ogy, 9, 383-384 Short Communication L-malic acid production by an albino strain of Monascus araneosus S. Lumyong* and F. Tomita An albino mutant was isolated after treating Monascus araneosus AI-W9087 with IV-methyl-IV’-nitro-AJ- nitrosoguanidine. All other physiological and biochemical characteristics were retained. The mutant did not produce any pigment but produced L-malic acid at 28 g/l, compared with 20 g/l by the parent strain, in media containing 10% (w/v) glucose after incubation under aerobic conditions for 5 days at 37’C. I&y words: L-malic acid, Monuscus, mutagenesis. L-malic acid is commonly used directly, or as an alternative to citric acid, as a food and beverage acidulant and, to a lesser exent, in the treatment of hyperamonemia and liver disease. Fermentation of L-malic acid is carried out by various microorganisms, but mainly Aspergihts +W (Peleg ef al. 1988; Battat ef al. 1991). Lumyong et al. (1991) first showed that Monascus araneosus AHU9087 (syn. M. prpureous) produces large amounts of L-malic acid from glucose by aerobic fermentation. In this paper, we describe mutation induction in A4, araneosus AHU9087 to produce albino malic acid-producing strains and increase the productivity of L-malic acid while eliminating the production of red pigments. Materials and Methods A4onuscus ararzeosm AHUgO was from Faculty of Agriculture, Hokkaido University, Japan. A suspension of conidia (lo7 spores/mI) was treated with N-methyl-u-nitro-nitrosoguanidine (NTG) at 30 or 50 pg/ml for 10 min at .2S°C, giving percentage survivals of 20.9% and 3.4%, respectively. After treatment, 0.1 mI of the suspension was spread on YM agar medium and incubated at 27’C for 4 to 7 days. Albino colonies were selected. Malic acid productivity among the albino strains was tested in a solid fermentation medium (Z medium) described by Lumyong et ul. (1991) with 0.5% (w/v) CaCOA, 0.05% (v/v) Triton-X 100 and 2% (w/v) agar, and incubated at 27’C for 7 days. Colonies S. Lumyong is with the Department of Biology, Faculty of Science, Chiang Mai University, Chiang Mai 50002, Thailand. F. Tomita is with the Labor- atory of Applied Microbiology, Faculty of Agriculture, Hokkaido University, Sapporo 060, Japan. Fax: 66 53 216409. ‘Corresponding author. @ 1993 Rapid Communications of Oxford Ltd which showed a clear zone were streaked on to YM agar medium to get single colonies. Each colony was tested for organic acid production in 50 ml liquid Z medium, pH 6, containing 100 g glucose/l and 3% (w/v) CaCOJ, and incubated at 37’C with shaking for 7 days. Amdyses Organic acids produced after incubation were determined by high performance liquid chromatography (HPLC) using an Aminex HPK-87 H column (7.8 x 300 mm) with de-gassed 4mM HzS04 as solvent at a flow rate of 0.6 ml/min and room temperature. Glucose was measured by the glucose oxidase method. Biomass was determined after drying 2M HCI-washed mycelium to constant weight at 80°C. Results and Discussion Eighteen non-pigmented strains were isolated from the conidia treated with 50 pg NTG/ml; only one such mutant was obtained using 30 pg/NTG/ml. The 18 mutants possessed unstable albino characters and were further streaked out to pick up 22 stable single colonies (WI-W22). All the albino mutants were morphologically similar to the parent strain except they had no red pigment. As shown in Table 1, submerged cultivation of each mutant using Z medium showed that the albino strain W$ST91) gave the highest acid production. A maximum amount of about 27.9 g/l of L-malic acid was obtained after s days incubation (during which the pH dropped from 6.8 to 5.25) and 76% glucose was consumed; in comparison, the parent strain maximally produced 19.8 g/l. The growth rate of the albino strain was also higher than that of the parent strain. Glucose was almost completely consumed