Wild strains of Rhodotorula glutinis and R. rubra were investigated concerning their carotenoid production, proportion of beta-carotene and cell mass yield. R. glutinis NCIM 3353 produced 2.2 mg carotenoid/l in 72 h; and the amount of beta-carotene was 14% (w/w) of the total carotenoid content (17 microg/g cell dry weight). It was subjected to mutagenesis using UV radiation for strain improvement. Out of 2,051 isolates screened, the yellow coloured mutant 32 produced 120-fold more beta-carotene (2,048 microg/g cell dry weight) than the parent culture in 36 h, which was 82% (w/w) of the total carotenoid content. Mutant 32 was grown on different carbon and nitrogen sources. The best yield of beta-carotene (33+/-3 mg/l) was obtained when glucose and yeast extract were supplied as carbon and nitrogen sources, respectively. Divalent cation salts further increased the total carotenoid content (66+/-2 mg/l) with beta-carotene as the major component (55+/-2%, w/w).
Several wild strains and mutants of Rhodotorula spp. were screened for growth, carotenoid production and the proportion of -carotene produced in sugarcane molasses. A better producer, Rhodotorula glutinis mutant 32, was optimized for carotenoid production with respect to total reducing sugar (TRS) concentration and pH. In shake flasks, when molasses was used as the sole nutrient medium with 40 g l(-1) TRS, at pH 6, the carotenoid yield was 14 mg l(-1) and -carotene accounted for 70% of the total carotenoids. In a 14-l stirred tank fermenter, a 20% increase in torulene content was observed in plain molasses medium. However, by addition of yeast extract, this effect was reversed and a 31% increase in -carotene content was observed. Dissolved oxygen (DO) stat fed-batch cultivation of mutant 32 in plain molasses medium yielded 71 and 185 mg l(-1) total carotenoids in double- and triple-strength medium, respectively. When supplemented with yeast extract, the yields were 97 and 183 mg l(-1) total carotenoid with a 30% increase in -carotene and a simultaneous 40% decrease in torulene proportion. Higher cell mass was also achieved by double- and triple-strength fed-batch fermentation.
Eighteen bacterial strains were isolated from soil samples and screened for alkaline, thermophilic lipase production. Pseudomonas fluorescens NS2W was selected and its production of lipase was optimized in shake flasks using a statistical experimental design. Cell growth and lipase production were studied in shake flasks and in a 1-l fermenter in the optimized medium. Maximum lipase yields were 69.7 and 68.7 U ml(-1), respectively. The optimized medium resulted in about a five-fold increase in the enzyme production, compared to that obtained in the basal medium. The lipase had an optimal activity at pH 9.0 and was stable over a wide pH range of 3-11 with more than 70% activity retention. The lipase had an optimal activity at 55 degrees C and was stable up to 60 degrees C with more than 70% activity retention for at least 2 h.
Aims: Enhancement in the production of b-carotene by the hyper producer mutant 32 of Rhodotorula glutinis by manipulation of temperature and illumination. Methods and Results: Growth and b-carotene production was investigated in a 1 litre fermenter at different temperature and illumination conditions. The optimum temperature for growth and b-carotene production was 30 and 20°C, respectively. At 30°C, b-carotene production was 125 ± 2 mg l )1 and accounted for 66% of the total carotenoids in 72 h; at 20°C, it was 250 ± 7 mg l )1 and accounted for 92% of total carotenoid content. Continuous illumination of the fermenter by 1000 lx white light hampered growth as well as carotenoid synthesis. At 30°C, illuminating the fermenter in late logarithmic phase resulted in a 58% increase in b-carotene production with a concurrent decrease in torulene; at 20°C, however, it showed no appreciable increase. Significance and Impact of the Study: Proper manipulation of culture conditions enhanced b-carotene production by R. glutinis which makes it a significant source of b-carotene.
Aims: Optimization of carotenoid production by a mutant of Rhodotorula glutinis.
Methods: The growth and carotenoid production was optimized in shake flasks using a two‐level, three‐variable factorial design.
Results: The volumetric carotenoid production could be increased to 129 ± 2 mg 1−1 in a medium containing (g l−1) yeast extract 11·74, glucose 46 and threonine 18 along with other micronutrients, wherein, β‐carotene yield was 102 ± 2 mg l−1, accounting for 80% of the total carotenoids.
Significance and Impact of the Study: The medium optimization resulted in a fourfold increase in volumetric production and a twofold increase in the cellular accumulation of carotenoids. In view of such high yields, the mutant of Rhodotorula glutinis can be a potential source of β‐carotene.
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