类球红细菌发酵生产类胡萝卜素条件优化

本文对类球红细菌3757产类胡萝卜素进行了发酵条件优化,结果得到了较优的培养基组成:葡萄糖2%,苹果酸钠0.5%,酵母浸粉1.3%,硫酸铵0.9%,磷酸氢二钾0.09%,磷酸二氢钾0.06%,生长因子溶液1%,p H 8.0;其中,生长因子溶液配方:维生素B1 0.1%,烟酰胺(VPP)0.1%,生物素0.0016%。较优培养条件为:接种量5%,转速200 r/min,种龄24 h,发酵温度32℃,发酵时间40 h。优化后类胡萝卜素产率较优化前提高了76.2%。     

类球红细菌SOD发酵条件优化

本文对类球红细菌3757产SOD进行了发酵条件优化,结果得到了较优的培养基组成(g/L):苹果酸3,胰蛋白胨4,磷酸氢二钾0.9,磷酸二氢钾O.6,硫酸镁0.2,无水氯化钙0.075,硫酸亚铁0.012,EDATA 0.02,微量元素溶液10 mL,生长因子溶液10 mL,pH 7.5。其中,微量元素溶液配方(g/L):硼酸2.8,硫酸锰1.6,钼酸钠0.76,硫酸锌0.24,硫酸铜0.04;生长因子溶液配方(g/L):维生素B_1 1,烟酰胺(VPP)1,生物素0.016,对氨基苯甲酸1。较优培养条件为:接种量5%,转速150 r/min,种龄24 h,发酵温度32℃,发酵时间24 h。优化后酶活力较优化前提高了88.0%。     

类球红细菌的免疫活性评价

目的 :评价类球红细菌的免疫活性。方法 :巨噬细胞吞噬试验、淋巴细胞转化试验、IL- 2的诱生和检测试验。结果 :类球红细菌 1号株具有调节和增强巨噬细胞吞噬功能 ,表现在免疫抑制组小鼠用光合细胞灌胃数周后 ,腹腔巨噬细胞吞噬百分率提高 6 1% ,吞噬指数提高 5 9% (P<0 .0 1)。在体外实验中 ,光合细菌三种不同抗原 (Ag1 、Ag2 、Ag3 )在一定程度上都有刺激脾淋巴细胞转化功能 ,特别是 Ag3 作用更为明显 ;在正常组 ,刺激指数提高了 6 5 % ;免疫抑制组 ,提高了 38% (P<0 .0 5 )。不管在正常组或免疫抑制组 ,Ag1 、Ag2 、Ag3 都具有诱生脾淋巴细胞产生 IL- 2的活性 ,其中 Ag2 的活性较明显 .结论 :类球红细菌 1号株对机体有一定的免疫活性。     

类球红细菌类胡萝卜素抗氧化活性研究

研究了研磨法、超声波法、酸溶辅助超声波法和菌体浓度对类球红细菌类胡萝卜素抗氧化活性的影响。结果表明,不同提取方法和固液比条件下,类球红细菌类胡萝卜素均具有清除DPPH自由基能力、抗脂质过氧化能力和还原能力。酸溶辅助超声波法提取的类胡萝卜素产率最高、抗氧化活性最好。类球红细菌类胡萝卜素具有一定的抗氧化活性,其抗氧化活性随菌体浓度的增加而增加。     

提高类球红细菌5-氨基乙酰丙酸产率的措施

5-氨基乙酰丙酸是四吡咯化合物生物合成的必需前体物,它作为一种无公害的绿色除草剂、杀虫剂、植物生长促进剂以及治疗癌症的药物而受到广泛的关注。文章综述了类球红细菌5-氨基乙酰丙酸的发酵生产现状以及提高其发酵产率的策略与措施。     

含硒类球红细菌的研究

为了确定类球红细菌转硒培养的最佳条件 ,研究了无机硒的加入浓度、时间以及分批补料培养对菌体生长和转硒效率的影响。实验表明 ,无机硒的浓度低于 1× 10 -5mol/L时 ,对类球红细菌的生长基本没有影响 ,并能将6 3.9%的无机硒转化为有机硒。转硒的最佳时间是在接种后 12h左右 ,此时转硒效率最高。实验还表明 ,分批补料培养可以提高菌体浓度 ,可使转硒效率和绝对量增加。体内试验表明 ,用 5mL/kgbw和 10mL/kgbw剂量的含硒类球红细菌灌养小鼠 ,可以使其全血GSH Px酶活性提高 2 0 .9%和 2 5 .5 % ,使其血清丙二醛 (MDA)含量降低2 1.0 %和 2 3.2 %。     

强化类球红细菌辅因子NADPH再生以提高法尼醇的产量

法尼醇(Farnesol,FOH)是由焦磷酸异戊烯基(IPP)和焦磷酸二甲基烯丙基(DMAPP)合成的法尼酰基焦磷酸盐(FPP)去焦磷酸化作用生成的。在类球红细菌中IPP和DMAPP是由MEP途径生成,而完整的MEP途径需要消耗大量的辅因子NADPH,增加胞内NADPH的量有可能强化FOH的合成。文中从增加NADPH的生成和降低NADPH的消耗这两个策略出发,分别干扰了编码6-磷酸葡萄糖异构酶基因(pgi)和谷氨酸脱氢酶基因(gdhA)的表达,同时强化了磷酸戊糖途径中6-葡萄糖磷酸脱氢酶基因(zwf)和6-葡萄糖酸磷酸脱氢酶基因(gnd)的表达。实验结果表明,经改造的菌株NADPH含量显著增加,干扰菌株中菌株RSpgii的产量较高,为3.91 mg/g,在过表达的菌株中同时过表达zwf和gnd基因的重组菌株(RSzg)的FOH产量提高到了3.43 mg/g。为了获得FOH产量更高的菌株,以RSpgii为出发菌株,分别与zwf和gnd组合调控,获得的菌株RSzgpi的产量达到了最高量为4.48 mg/g,是出发菌株RS-GY2产率的2.24倍。     

类球红细菌XR12的分离、鉴定及其解毒效果研究

为丰富敌百虫污染治理的微生物资源,从养殖污泥中分离筛选了一株优良的敌百虫耐受菌XR12,综合生理生化特性与16S rRNA序列分析对其进行了鉴定,采用纸片扩散法分析了其耐药性,并进一步评价了其安全性与解毒效果。结果显示:菌株XR12对敌百虫的最大耐受浓度达到了7680 mg/L。通过生理生化特性以及16S rRNA序列分析,菌株XR12被鉴定为类球红细菌（Rhodobacter sphaeroides）,其16S rRNA序列与GenBank中类球红细菌菌株的16S rRNA序列有98%—100%的同源性,而且与类球红细菌菌株RSF1 （登录号:KF606891）的亲缘关系最近。此外,菌株XR12对卡那霉素、罗红霉素、吡哌酸、阿莫西林、氟苯尼考、多黏菌素B、新霉素、庆大霉素、氧氟沙星、恩诺沙星、诺氟沙星、链霉素、四环素、奈替米星等抗生素高度敏感,对多西环素中度敏感,对杆菌肽、萘啶酸、磺胺异噁唑等抗生素耐药,对斑马鱼的LC₅₀大于10～9 cfu/mL,能够将敌百虫对斑马鱼的LC₅₀从26.06 mg/L增加至59.51 mg/L,对敌百虫具有良好的解毒效果。研究证实了类球红细菌XR12的安全性及其对敌百虫良好的解毒效果,对养殖水体中敌百虫的解毒具有潜在的应用价值。     

快速提取类球红细菌中辅酶Q10的方法研究

目的：建立一种从类球红细菌中快速分离纯化辅酶Q10的方法。方法：对影响超声提取辅酶Q10的各因素,包括提取试剂、超声频率、循环次数及工作时间的最佳条件进行正交试验,比较超声破碎法与碱醇皂化法提取辅酶Q10的差异。结果：在超声提取中,提取试剂和循环次数对辅酶Q10提取效果具有显著性影响;在超声频率0.5s、丙酮提取3min、循环3次的条件下提取的辅酶Q10的含量比碱醇皂化法提高了近6倍。结论：超声破碎法是一种简单、迅速、高效的提取辅酶Q10方法。     

酸溶辅助超声波法提取类球红细菌类胡萝卜素条件优化

通过单因素和正交试验,对类球红细菌3757产类胡萝卜素的提取条件进行了研究。先采用超声波法、酸溶法、研磨法、冻融法、酸溶辅助超声波法和冻融辅助超声波法优化了从类球红细菌3757菌株中提取类胡萝卜素的方法,然后开展了酸溶辅助超声波法的单因素和正交实验,最后进行了重复性实验。结果表明,酸溶辅助超声波法是较优的提取方法,丙酮是较好的提取溶剂。最佳提取条件为料液比110、超声波处理总时间20 min、酸浓度3 mol/L、酸溶时间25 min、超声波振幅40%、超声工作/间隔时间2 min/1 min、酸溶温度27℃,实验重现较好。优化后类胡萝卜素的提取率较优化前提高了74.8%,为其产业化创造了条件。     

Bioremediation of cadmium by growing Rhodobacter sphaeroides: kinetic characteristic and mechanism studies

The removal kinetic characteristic and mechanism of cadmium by growing Rhodobacter sphaeroides were investigated. The removal data were fitted to the second-order equation, with a correlation coefficient, R2=0.9790-0.9916. Furthermore, it was found that the removal mechanism of cadmium was predominantly governed by bioprecipitation as cadmium sulfide with biosorption contributing to a minor extent. Also, the results revealed that the activities of cysteine desulfhydrase in strains grown in the presence of 10 and 20 mg/l of cadmium were higher than in the control, while the activities in the presence of 30 and 40 mg/l of cadmium were lower than in the control. Content analysis of subcellular fractionation showed that cadmium was mostly removed and transformed by precipitation on the cell wall.     

Acquisition of photosynthetic capacity by a reaction centre that lacks the QA ubiquinone; possible insights into the evolution of reaction centres?

A photosynthetically impaired strain of Rhodobacter sphaeroides containing reaction centres with an alanine to tryptophan mutation at residue 260 of the M-polypeptide (AM260W) was incubated under photosynthetic growth conditions. This incubation produced photosynthetically competent strains containing suppressor mutations that changed residue M260 to glycine or cysteine. Spectroscopic analysis demonstrated that the loss of the Q_A ubiquinone seen in the original AM260W mutant was reversed in the suppressor mutants. In the mutant where Trp M260 was replaced by Cys, the rate of reduction of the Q_A ubiquinone by the adjacent (H_A) bacteriopheophytin was reduced by three-fold. The findings of the experiment are discussed in light of the X-ray crystal structures of the wild-type and AM260W reaction centres, and the possible implications for the evolution of reaction centres as bioenergetic complexes are considered.     

Genetic analysis of the bchC and bchA genes of Rhodobacter sphaeroides

Summary This study has identified by sequence analysis a single gene in the bchC locus of Rhodobacter sphaeroides and three genes, designated bchX, Y and Z, in the bchA locus, which was previously thought to contain only a single gene. All four genes may reside within the same operon and are transcribed in the order bchC-X-Y-Z. Complementation analysis of eight transposon insertion mutants within these genes suggests that bchX, Y and Z are essential for the reduction of 2-devinyl-2hydroxyethyl chlorophyllide a and that bchC encodes the 2-desacetyl-2-hydroxyethyl bacteriochlorophyllide a dehydrogenase. Similarity between the putative BchX protein and dinitrogenase reductase proteins suggests that BchX may also be a reductase, supplying electrons for reduction of 2-devinyl-2-hydroxyethyl chlorophyllide a.     

Decolorization of azo dyes by Rhodobacter sphaeroides

Rhodobacter sphaeroides AS1.1737 decolorized more than 90% of several azo dyes (200 mg dyes l^–1) in 24 h. The optimal culture conditions were: anaerobic illumination (1990 lx), peptone as carbon source, temperature 35–40 °C and pH 7–8. Intracellular crude enzyme from this strain had azoreductase activity, optimized temperature as 45–50 °C, and decolorization kinetics which were consistent with a ping-pong mechanism.     

Rhodethrin: a novel indole terpenoid ether produced by Rhodobacter sphaeroides has cytotoxic and phytohormonal activities

A novel metabolite was isolated from the culture supernatants of Rhodobacter sphaeroides OU5 when grown on l-tryptophan as sole source of nitrogen under photoheterotrophic conditions. It was identified by IR, NMR (¹H, ¹³C) and MS as an indole terpenoid ether [3-hydroxy-6-(1H-indol-3-yloxy)-4-methylhexanoic acid] and is named as rhodethrin. Rhodethrin at 0.5 μM gave positive test in auxin bioassay and initiated early rooting in tissue-cultured plants than IAA at 5 μM. Rhodethrin has cytotoxic activity against Sup-T₁ lymphoma and Colo-125 cancer cell lines at 10 nM.     

Biological Synthesis of Semiconductor Zinc Sulfide Nanoparticles by Immobilized Rhodobacter sphaeroides

A novel, clean biological transformation reaction by immobilized Rhodobacter sphaeroides has been developed for the synthesis of zinc sulfide (ZnS) nanoparticles with an average diameter of 8 nm. The nanoparticles were examined by X-ray diffraction, transmission electron microscopy, energy dispersive analyses of X-rays, UV–vis optical absorption and photoluminescence spectra. The average diameter of ZnS nanoparticles varied according to the culture time.     

Equilibration kinetics in isolated and membrane-bound photosynthetic reaction centers upon illumination: a method to determine the photoexcitation rate

Kinetics of electron transfer, following variation of actinic light intensity, for photosynthetic reaction centers (RCs) of purple bacteria (isolated and membrane-bound) were analyzed by measuring absorbance changes in the primary photoelectron donor absorption band at 865 nm. The bleaching of the primary photoelectron donor absorption band in RCs, following a sudden increase of illumination from the dark to an actinic light intensity of I _exp, obeys a simple exponential law with the rate constant , in which α is a parameter relating the light intensity, measured in mW/cm², to a corresponding theoretical rate in units of reciprocal seconds, and k _rec is the effective rate constant of the charge recombination in the photosynthetic RCs. In this work, a method for determining the α parameter value is developed and experimentally verified for isolated and membrane-bound RCs, allowing for rigorous modeling of RC macromolecule dynamics under varied photoexcitation conditions. Such modeling is necessary for RCs due to alterations of the forward photoexcitation rates and relaxation rates caused by illumination history and intramolecular structural dynamics effects. It is demonstrated that the classical Bouguer–Lambert–Beer formalism can be applied for the samples with relatively low scattering, which is not necessarily the case with strongly scattering media or high light intensity excitation. An erratum to this article can be found at     

Site-directed mutagenesis of substrate binding sites of azoreductase from Rhodobacter sphaeroides

Comparison of three-dimensional structures of flavin-dependent azoreductases revealed two conserved loops around the flavin mononucleotide (FMN) cofactor. Tyr74, His75 and Lys109 in the two loops of azoreductase AZR from Rhodobacter sphaeroides were replaced with Trp, Asn and Ala/His by site-directed mutagenesis, respectively. The optimal pH values of K109H and H75N were pH 6, and those of K109A and Y74W were pH 9. The optimal temperature (30°C) was not affected by mutation. Positively charged residues at position 109 is critical for the binding of methyl red. K109 might only be involved in the binding of the 2′-phosphate group of NADPH and have no effect on the binding of NADH. Y74W and H75N mutations decreased the binding of methyl red/nitrofurazone and had no affect on the binding of NADPH.