高产虾青素红发夫酵母选育研究进展

虾青素是 60 0多种类胡萝卜素中的一种 ,具有抗氧化 ,抗肿癌和增强免疫力等许多重要的生理和生物学功能 ,在水产养殖、食品和医药等领域应用前景广阔。综述了虾青素的生物来源、生物转化途径以及高产虾青素红发夫酵母菌株的选育。     

Effect of the carbon source on the carotenoid profiles of Phaffia rhodozyma strains

Phaffia rhodozyma strains ATCC 24202, ATCC 24203, ATCC 24228, ATCC 24229, ATCC 24261, NRRL Y-10921, NRRL Y-10922 and NRRL Y-17268 were grown on culture media containing glucose, sucrose or xylose as carbon sources. Carotenoids were extracted from biomass and analyzed by HPLC with diode-array detection. The carotenoid profiles depended on both the strain considered and the carbon source employed. Astaxanthin, the main pigment found in P. rhodozyma, accounted for 42–91% of total carotenoids. Other carotenoids such as canthaxanthin, echinenone, 3-hydroxyechinenone, lycopene, 4-hydroxy-3′, 4′-didehydro-β-ψ-carotene and phoenicoxanthin were detected. The highest volumetric carotenoid concentration (3.60 mg L⁻¹) was obtained with strain NRRL Y-17268 growing on xylose. In this case, astaxanthin accounted for 82% of total carotenoids. Received 29 May 1997/ Accepted in revised form 08 August 1997     

实时定量PCR构建法夫酵母内参基因β-actin、 gpd、18S rRNA标准品质粒和标准曲线

为建立检测法夫酵母JMU-MVP14中虾青素合成相关基因在不同生长时期表达水平的实时定量PCR方法,构建法夫酵母JMU-MVP14的管家基因β-actin、gpd、18S rRNA的标准质粒,进行实时定量PCR,制作标准曲线及回归方程.β-actin基因标准曲线相关系数（R2）=0.9956,扩增效率（E） =96.93％;gpd基因标准曲线相关系数（R2） =0.9901,扩增效率（E） =93.78％;18S rRNA基因标准曲线相关系数（R2） =0.9981,扩增效率（E）=98.76％.3个基因片段的熔解曲线均呈单峰;扩增曲线呈典型的S型动力学曲线,指数期和平台期明显,为理想的熔解曲线和扩增曲线.用geNorm软件对三个管家基因的稳定性进行分析,三个基因的稳定性排序为β-actin＞ 18S rRNA＞ gpd,故β-actin和18S rRNA较适合作为研究法夫酵母JMU-MVP14定量实验的内参基因.     

Growth and carotenoid production of Phaffia Rhodozyma in fed-batch cultures with different feeding methods

The growth and carotenoid production of Phaffia rhodozyma in fed-batch cultures with different feeding methods and grown at specific growth rates similar to the batch culture was compared. With constant feeding, exponential feeding, DO-stat and pH-stat fed-batch cultures of Phaffia rhodozyma, the highest biomass (17.4 g/l) and lowest carotenoid content (307 g/g cell) of Phaffia rhodozyma was from the DO-stat fed-batch culture. The lowest biomass (14.7 g/l) and highest carotenoid content (412 g/g cell) was from the exponential, fed-batch culture.     

Use of n-hexadecane as an oxygen vector to improve Phaffia rhodozyma growth and carotenoid production in shake-flask cultures

AIMS: To identify beneficial oxygen vectors for Phaffia rhodozyma in liquid cultures, and to evaluate their use to improve the oxygen transfer and carotenoid production in the yeast cultures. METHODS AND RESULTS: Several liquid hydrocarbons were tested as oxygen vectors for improving the yeast growth and carotenoid production in shake-flask cultures of P. rhodozyma. While all nontoxic organic liquids (Log P: > or =5.6) showed a positive effect, n-hexadecane was proved to be the most beneficial for the yeast growth and carotenoid production. The addition of 9% (v/v) n-hexadecane to the liquid medium at the time of inoculation was found to be optimal, increasing the carotenoid yield by 58% (14.5 mg l(-1) vs 9.2 g l(-1) in the control) and the oxygen transfer rate (OTR) by 90%. CONCLUSIONS: The addition of n-hexadecane to shake-flask cultures of P. rhodozyma significantly improved the oxygen transfer in culture, thus increasing the carotenoid production. SIGNIFICANCE AND IMPACT OF THE STUDY: Use of organic oxygen vectors such as n-hexadecane may be a simple and useful means for enhancing oxygen transfer and carotenoid production in liquid fermentation of P. rhodozyma.     

Fosfomycin enhances the expression of penicillin-binding protein 2 in methicillin-sensitive and methicillin-resistant Staphylococcus aureus strains

The effects of fosfomycin on penicillin-binding proteins (PBPs) were studied on the methicillin-resistant Staphylococcus aureus strain CIP (Collection de l'Institut Pasteur, Paris, France) 65-25 and on a methicillin-susceptible S. aureus strain CIP 65-6. The combinations of fosfomycin and oxacillin were synergistic, additive or antagonistic, depending on antibiotic concentrations. Fosfomycin induced modifications of the PBP profile of the two strains studied. In particular, it increased the expression of PBP2. This suggested that this protein is inducible; the only PBP not affected by fosfomycin was PBP3.     

物化因子结合诱变选育耐温型法夫酵母

以法夫酵母为出发菌株,采用紫外线及甲基磺酸乙酯对其进行诱变育种,筛选出1株最适生长温度比诱变前提高10℃且虾青素产量可达到5．08mg／L的突变菌株,该菌株经多次传代生产性能稳定。     

协同诱变法选育虾青素高产优良酵母菌株

以红法夫酵母(Phaffia rhodozyma)野生型菌株GH1为研究对象,选育虾青素高产优良酵母菌株,并初步研究其生长特性。对野生型菌株GH1用紫外线(UV)和亚硝基胍(NTG)协同诱变,用抗霉素A筛选,选育出虾青素高产突变菌株GH1-7.1。突变菌株GH1-7.1的虾青素最高产量达1200μg/gDCW,比野生菌株GH1的虾青素最高产量271μg/gDCW高出4倍,并且生长加快,达到最高生物量和最高虾青素产量的时间比野生菌株缩短了24h;野生菌株GH1的最适生长温度为20℃,高于28℃则不生长,而突变菌株GH1-7.1的最适生长温度为28～30℃,比野生菌株GH1提高8～10℃。首次采用协同诱变的方法成功选育了虾青素高产酵母菌株,并且生长周期短,最适的生长温度提高,是适宜南方高温环境发酵工程应用的优良菌株。     

生物技术生产虾青素研究的最新进展

虾青素是一种具有极强的生物抗氧化性的酮式类胡萝卜素在医药,食品,化妆品等方面有着极广阔的应用前景。对目前生物技术生产虾青素的两种主要方法：即雨生红球藻(haematococcus pluvialis)培养法和红发夫酵母(xanthopltyllomyces dendrorhous,formedy Phaffia raodazyma)发酵法的最新研究进展,包括采用的微生物的生理代谢特性、虾青素合成途径、生产技术特点、工程菌种的构建等方面进行了系统的总结。针对天然虾青素生产技术研究中存在的问题和不足,提出了建议和解决的方法。     

Genetics and electrophoretic karyotyping of wild-type and astaxanthin mutant strains of Phaffia rhodozyma

In this work we establish the chromosomal composition of a wild-type, one astaxanthin and two -carotene overproducer strains of the red yeast Phaffia rhodozyma. The method used has been pulsed field gel electrophoresis, which has determined 9 DNA chromosomal bands in the yeast genome. The two largest bands are triplets and two other bands, VI and VIII, seem to be doublets. The size of the chromosomal bands varies between 0.35 and 2.5 Mb, suggesting a genome size of 25 Mb. The technique used, complemented with hybridization assays using specific DNA probes, provides direct information about the genomic organization of P. rhodozyma. We have also cloned and located in chromosomal bands different DNA sequences that code for the translation elongation factor 1 alpha (ef-1), a 7.6 kb BamHI fragment of repetitive DNA (possibly rDNA) and a randomly chosen fragment (named locus R2). Additionally, we have detected a chromosomal length polymorphism between wild-type strains and mutant strains affecting carotenogenesis obtained in our laboratory.