99D-22 |
|
J. JANG, N. Sun, S. Lee, and K. B. Song. Dept. of Food Science & Technology, Chungnam National Univ., College of Agriculture & Life Sciences, 220 Gung-dong, Yuseong-gu, Daejon, 305-764, South Korea Astaxanthin is not only an important pigment but also a strong antioxidant that plays a role in preventing degenerative diseases. Phaffia rhodozyma is the only yeast that produces astaxanthin, and there have been considerable interest in the commercial use and many studies on strain improvement. The objectives of this study were to use a low-dose gamma irradiation as a mutagenesis method to produce a carotenoid-hyperproducing strain and to characterize the mutant. Phaffia rhodozyma was irradiated at room temperature using a 60Co gamma ray irradiator under air with dosages of 1, 2, 3, 3.5, 4, 4.5, 5, 5.5, 6, and 7 kGy. Through the repeated rounds of gamma irradiation below 10 kGy and visual screening, a mutant 2GM was isolated and its characterization such as growth pattern and carotenoid production were studied. The mutant 2GM produced 3.3 mg/g yeast, 50% higher carotenoid content than that of the unirradiated strain. Glucose and peptone were the most suitable carbon and nitrogen sources for the production of astaxanthin, based on the growth experiment of the mutant under various carbon and nitrogen sources. Astaxanthin content of the yeast was determined using high performance liquid chromatography. After 10 days of growth, 2GM produced 2.5 mg/g yeast, 78 % higher astaxanthin content than 1.4 mg/g yeast of the parent strain. The carotenoid hyperproducing mutant, 2GM, exhibited higher catalase activity than the wild strain. Transmission electron microscope study of the yeast showed that 2GM has smaller size of mitochondria than the wild type. These results clearly suggest that low-dose gamma irradiation could be used as a means of mutagenesis for the production of a carotenoid-hyperproducing strain of Phaffia rhodozyma by providing a selection process due to oxygen radicals generated by gamma irradiation.
Session 99D, Food Microbiology: General
|