Isolation and identification of carotenoid-producing Rhodotorula sp. from soils collected in the coastal environment of Kien Giang and Tra Vinh provinces

Abstract

Rhodotorula is a genus of marine yeasts that is considered the most suitable for carotenoid production. In this study, collected soils at Kien Giang and Tra Vinh provinces were cultured on yeast extract peptone dextrose (YEPD) agar for 72 hours at room temperature. Twenty-three isolates exhibiting yellow, orange, and pink pigments were tested for physiological and biochemical characteristics such as carbohydrate fermentation and assimilation, nitrate assimilation, urease production, and growth temperature. Their oval dimensions were 4.24x3.64 μm for isolate 5S1-T and 3.88x3.17 μm for isolate 5S4-T. The two isolates could assimilate carbohydrate and nitrate sources and produce urease. The ITS rDNA sequence of isolates 5S1-T and 5S4-T both had 100% matches to Rhodotorula sphaerocarpaCBS:5940 and Rhodotorula sphaerocarpa CBS:5939, respectively. The maximum absorbance wavelengths of the solution extractions from the 5S1-T and 5S4-T were 496 and 487 nm, respectively. The total carotenoid content of strain 5S1-T was found to be the highest (1.81 mg/l) followed by strain 5S4-T (1.16 mg/ml). The antioxidant abilities of the 5S1-T and 5S4-T were demonstrated by scavenging the free radical DPPH and ferric reducing capacity. The free radical scavenging activity of the extract from isolate 5S1-T (96.15%) was higher than that of isolate 5S4-T (88.61%) at 0.14 mg/ml. The absorbance at 700 nm of the extracts of both 5S1-T and 5S4-T significantly increased from 0.05 to 0.3 mg/ml. The two strains 5S1-T and 5S4-T of Rhodotorulasphaerocarpa discovered in this study could contribute to carotenoid and antioxidant-producing yeasts for industries in the future.