Study on the relationship between intracellular metabolites and astaxanthin accumulation during Phaffia rhodozyma fermentation

Background To study the relationship between intracellular anabolism and astaxanthin production, the influence of intracellular protein and fatty acids on astaxanthin production by four mutant Phaffia rhodozyma strains and their variations was investigated in this research. Results First, the content of astaxanthin in cells showed a reverse fluctuation in contrast to that of protein during the whole fermentation process. Moreover, compared with the three other strains, the astaxanthin-overproducing mutant strain of the yeast P. rhodozyma, called JMU-MVP14, had the highest specific productivity of astaxanthin as 6.8 mg/g, whereas its intracellular protein and fatty acid contents were the lowest. In addition, as a kind of sugar metabolic product, ethanol was only produced by P. rhodozyma JMU-VDL668 and JMU-7B12 during fermentation. Conclusions The results indicated that the accumulation of ethanol, intracellular protein, and fatty acids had competition effects on astaxanthin synthesis. This condition may explain why the P. rhodozyma strains JMU-VDL668 and JMU-7B12 achieved relatively lower astaxanthin production (1.7 and 1.2 mg/L) than the other two strains JMU-MVP14 and JMU-17W (20.4 and 3.9 mg/L).

Genomic organization of the structural genes controlling the astaxanthin biosynthesis pathway of Xanthophyllomyces dendrorhous

The cloning and nucleotide sequence of the genes (idi, crtE, crtYB, crtl and crtS) controlling the astaxanthin biosynthesis pathway of the wild-type ATCC 24230 strain of Xanthophyllomyces dendrorhous in their genomic and cDNA version were obtained. The idi, crtE, crtYB, crtl and crtS genes were cloned, as fragments of 10.9, 11.5, 15.8, 5.9 and 4 kb respectively. The nucleotide sequence data analysis indicates that the idi, crtE, crtYB, crtl and crtS genes have 4, 8,4, 11, and 17 introns and 5, 9, 5, 12 and 18 exons respectively. In addition, a highly efficient site-directed mutagenesis system was developed by transformation by integration, followed by mitotic recombination (the double recombinant method). Heterozygote idi (idi+ / idi-::hph), crtE (crtE+ / crtE -::hph), crtYB (crtYB + / crtYB -::hph), crtI (crtI+ / crtI-::hph) and crtS (crtS +/crtS -::hph) and homozygote mutants crtYB (crtYB -::hph/crtYB -::hph), crtI (crtI -::hph/crtI -::hph) and crtS (crtS -::hph / crtS -::hph) were constructed. All the heterozygote mutants have a pale phenotype and produce less carotenoids than the wild-type strain. The genetic analysis of the crtYB, crtl and crtS loci in the wild-type, heterozygote, and homozygote give evidence of the diploid constitution of ATCC 24230 strains. In addition, the cloning of a truncated form of the crtYB that lacks 153 amino acids of the N-terminal region derived from alternatively spliced mRNA was obtained. Their heterologous expression in Escherichia coli carrying the carotenogenic cluster of Erwinia uredovora result in trans-complementation and give evidence of its functionality in this bacterium, maintaining its phytoene synthase activity but not the lycopene cyclase activity.

Mutagenesis Screening of Astaxanthin-producing Phaffia rhodozyma and Fermentation Condition Optimization / 中国生物工程杂志

The original strain was treated with UV combining LiCl. The total carotenoid yield of the strain UL-61 was 7.62mg/L, the maximal yield of astaxanthin had reached 616.8?g/g under 25℃. 8 variables including fermentation temperature, initial pH were optimized by Plackett-Burman design and Response Surface Analysis of SAS software. The temperature, initial pH and corn steep liquor were the major factors. The optimal conditions were predictted to be 16.78℃, pH4.73 and 7.06 mg/L, respectively. Under these conditions, the theroretical maximal yield of carotenoid was 3.9407 mg/L and the practical maximal yield was about 3.9261mg/L. The carotenoid production was increased by 20.4% when Phaffia rhodozyma was cultivated under the optimal conditions as compared with the control.

Advances in Regulatory Mechanisms of Astaxanthin Accumulation in Phaffia rhodozyma / 微生物学通报

The astaxanthin synthesized by Phaffia rhodozyma is a commercially valuable carotenoid. Related advances in the biosynthetic pathway of astaxanthin and the regulatory mechanisms of biosynthesis in Phaffia rhodozyma in recent years were reviewed.The innovating research aspects in related fields in China were also proposed.

BREEDING OF PHAFFL4 RHODOZYMA FOR ASTAXANTHIN OVER-PRODUCTION / 微生物学通报

Phaffia rhodozyma is a good strain for astaxanthin production. An over-producing mutant YB-20-29 was obtained by means of Cs137-?ray and N-methy1-N'-nitro-N-nitrosoguanidin (NTG) treatment. The biomass for this strain by shake culture was 36.32 g/L, the pigment content was 1216.0 ?g/g, an increase of 308% compare to o-riginal strain. The astaxanthin content in broth was 30.9?g /mL. It was a potential strain for astaxanthin over-production.

STUDY ON THE ASTAXAN TH IN-PRODUCING YEAST PHAFFIA RHODOZYMA MUTATED BY NTG / 微生物学通报

astaxanthin is an effective antioxidant and natural pigment which has wide application. Phaffia rhodozyma is a good source of astaxantin, but wild strain has limited use in industry because of low production level of astaxanthin. Several mutants of Phaffia rhodozyma were obtained by exerting mutagen N-methyl-N-nitro-N -nitrosoguanidine. The growth curve suggested that pigments were mainly produced in the middle and latter periods of log phase. The pigments were extracted from Phaffia rhodozyma and analysed by esterification, thin layer chromatography and absorption spectrometry. It was proved that astaxanthin, astaxanthin diester and ?-carotene were the major components of the pigments produced by Phaffia rhodozyma. We also studied the pigments producing phase of Phaffia rhodozyma. and founded that astaxanthin was stable to light under butylated hydroxytoluene coexistance.