Improvement on Red Pigment Production and Citrinin Degradation of Monascus purpureus

• Main Authors: Chen Ya-Hui, 陳雅惠
• Other Authors: Hsieh Pao-Chuan
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/94454738303357765637

博士 === 國立屏東科技大學 === 食品科學系所 === 98 === Red rice yeast is one of the important sources for natural food pigment. In Asia, this kind of fungus, which can produce pigment for rice wine, fermented preparation, soybean cheese and red meats, is cultivated on the solid base substance, such as rice husk or bread. Many studies have reported its various physiological activities, thus it has been regarded highly. The second metabolite consists of monacolin K, which can reduce cholesterol, γ-aminobutyric acid (GABA), can lower blood pressure, and citrinin. Citrinin is a typical mycotoxin that was first found in Penicillium citrinum, and has toxic effect on liver and the kidney, thus lowering human acceptance to the product of red rice yeast. Therefore, this study selected M. purpureus NPUST M 6-5 which can produce dark red pigment, and explored the effects of different stirred speeds, inoculum sizes, carbon sources, nitrogen sources, inorganic salts, pH values, and temperatures on the generateon of red pigment and citrinin, in order to find out the optimal cultivation conditions for cultivating M. purpureus. The results showed that the best cultivation condition is 100ml of culture fluid in 500ml Hinton’s triangle bottle, and the culture medium consisting of 1.5% potato starch, 0.15% urea, 0.05 % KH2PO4、0.1 % KCl、0.2 %K2HPO4、0.1 %MgSO4•7H2O and 0.05 %NaH2PO4•2H2O and initial pH 6.0, the inoculum size 10% (V/V), at 30℃, with 150 rpm stirred speeds. Under this condition, the optimal red pigment of about 17 (O.D. 500nm) can be obtained on the 9th day. However, citrinin is accompanied by the red pigment, thus, this study selected one kind of microbe from the soil, which can degrade citrinin. This strain is identified Klebsiella pneumoniae NPUST B11. The K. pneumoniae NPUST B11 was incubated in the mineral broth containing 10 ppm of citrinin, 1.2% glucose, 0.3% peptone and 100 ppm vitamin C under optimal conditions, including pH 7, 200 rpm and 37°C. Citrinin was rapidly degraded and completely depleted at 10 h. For industrial application, the study was conducted by co-culture both M. purpureus NPUST M 6-5 and K. pneumoniae NPUST B11. According to test result, when M. purpureus was cultivated at 37°C on the fifth day, by adding 5 % K. pneumoniae NPUST B11, 0.5 ppm citrinin can be degraded 90% within 24 h and the K. pneumoniae NPUST B11 can increase from 2 × 10 7 CFU/mL to 5 × 10 9 CFU/mL. It indicates that K. pneumoniae NPUST B11 can grow in the culture medium which contains M. purpureus NPUST M 6-5. In safe tests, the results showed that the co-culture of M. purpureus and K. pneumoniae NPUST B11 (5mg/plate) are no toxic, and do not cause the mutagenicity to Salmonella typhimurium TA 97 and TA 100. The cytotoxicity test showed that the BNL CL.2 and Hep G2 were treated in different concentrations culture (10-200 ug/ml) of M. purpureus NPUST M 6-5 and K. pneumoniae NPUST B11 for 72 hours. After 72 hours, the results showed that the growth of BNL CL.2 has been affected but lower survival rate to Hep G2. Therefore, this method was proven to be feasible for industrial application, it can be further developed to reduce the content of citrinin and enhance the applicability of red rice product.