Abstract: A strain K-1 with carotenoid-producing potential was identified using morphological, physiological, biochemical tests and rDNA-ITS sequence analysis. A colorimetric method was used to determine mycelial growth and the stability of carotenoids produced by this strain. The fermentation conditions of strain K-1 were optimized by one-factor-at-a-time and orthogonal array design methods. The results indicated that K-1 was identified as Rhodotorula mucilaginosa. The optimum temperature for growth of the strain was 30 ℃, and it could be grown well in the initial pH range from 2 to 7. The characteristic absorption peak indicated that the acetone extract of cultured cells of K-1 contained torulene. The carotenoids produced by K-1 had good stability, but the stability was decreased under the conditions of high temperature (> 60 ℃), intense light and oxidant H2O2. The optimum fermentation conditions were determined as follows: glucose 20 g/L, (NH4)2SO4 20 g/L, anhydrous CaCl2 2 g/L, trisodium citrate 5 g/L, temperature 30 ℃, inoculum size 10%, shaking speed 150 r/min, medium volume 50 mL/250 mL, initial pH 5.5, and time 5 d. The yield of carotenoids on a dry mycelial mass basis was (180.14 ± 2.45) μg/g under the optimum culture conditions. Strain K-1 has the potential to produce a high yield of carotenoids, and the pigment produced by it has good stability. This strain represents a new microbial resource for carotenoids production.

Key words: carotenoids, Rhodotorula mucilaginosa, identification, pigment stability, fermentation process