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脂肪酶的包埋和交联固定化研究
No full text【目的】脂肪酶可以通过高效催化动植物油脂发生转酯反应得到生物柴油,而固定化技术可以极大地提高脂肪酶的使用效率并降低生产成本。【方法】以海藻酸钠为载体,采用海藻酸钠包埋和新型环氧交联剂乙二醇缩水甘油醚交联联合法固定脂肪酶,通过单因素试验和正交试验法共同确定脂肪酶的固定化方案。【结果】最佳固定条件为海藻酸钠浓度2.5%,给酶量400 U/mL海藻酸钠溶液,氯化钙5%,固定20 min,以0.35%的乙二醇缩水甘油醚为交联剂,25℃条件下交联1 h,由此制备得到酶活约为84.90 U/g的固定化酶。【结论】固定化酶的最适反应pH 8.5,比游离酶增大0.5 U,最适反应温度40℃,与游离酶相比保持不变。热稳定性和操作稳定性显著增强
污损性海鞘的生态特点及研究展望
No full text海鞘生长快,繁殖迅速,能产生大量在短时间内附着的幼虫,是海洋污损生物群落中的重要成员,对海上人工设施会产生严重危害。污损性海鞘主要由悉尼海鞘(Ascidia sydneiensis)、史氏菊海鞘(Botryllus schlosseri)、米氏小叶鞘(Diplosoma listerianum)、柄瘤海鞘(Styela clava)、红贺海鞘(Herdmania momus)等9科29属103种组成,其中在太平洋海域64种、印度洋23种、大西洋44种,而北冰洋海域仅3种;另外,其附着污损具有明显的地域性和季节特点,并与深度有关。今后应加强污损性海鞘的生态调查和分类研究,阐明深海及两极海域附着污损特点,揭示幼虫附着变态过程的分子调控机理,完善幼虫采集培养技术,以期更好地掌握海鞘生物学特性与生态特点,丰富和发展海洋生态学内容,并为海洋污损生物的防除奠定基础,促进海洋经济产业的发展
Epsilon-变形菌两个特有蛋白0275-0276调节趋化作用的分子机制研究
No full textEpsilon-变形菌纲(Epsilon-proteobacteria)是革兰氏阴性细菌中的一个重要的类群,分布广泛,包括人和动物的重要致病菌以及深海极端环境富集的菌株。宏基因分析发现Epsilon-变形菌编码了大量与趋化性(Chemotaxis)相关的膜传感蛋白,这些蛋白很可能在Epsilon-变形菌适应不同生存环境中起着重要作用,以感受不同的环境变化并有效传递信号,在极端环境适应中发挥着重要作用。目前对细菌趋向运动的信号转导途径研究较多,但是趋向运动基因的转录调控尤其是专一的调控因子还未见报道。我们课题组之前的研究工作筛选到了许多与Epsilon-变形菌鞭毛运动相关的基因,其中有两个基因组上相连的基因0275和0276的敲除突变菌株在软琼脂培养基上表现出明显的运动能力减弱;RNA-seq及荧光定量RT-q PCR实验发现0275与0276对趋化作用基因che VAW操纵子的表达有正调控作用。本课题拟对0275和0276的蛋白功能进行研究,鉴定这个潜在的双组份调控系统是如何感应上游信号并调控趋化基因表达的分子机理,并以此为例揭示这类细菌进化出的特有蛋白在环境适应性中的关键作用
红树林放线菌Stremptmeces costaricanus SCSIO ZS0073抗菌活性次级代谢产物的研究
No full text从红沙公园的红树林泥土中分离得到一株生产较强抑菌活性次级代谢产物的放线菌Strepomyces costaricanus SCSIO ZS0073,采用滤纸片法进行抑菌活性追踪,并利用硅胶、凝胶柱层析和HPLC等分离手段对其发酵产物进行分离纯化,得到3个化合物,通过NMR、MS等波谱数据分析并参阅文献将3个化合物分别鉴定为放线菌素D、放线菌素X_(Oβ)和制霉色基素(fungichromin)。其中放线菌素D在发酵条件未优化的情况下产量就达到300 mg/L以上
乡村型半城市化地区的土地利用特征和形成机制研究 ——以潮安区古巷镇为例
No full text 半城市化地区是城镇发展过程中形成的不同传统二元城乡结构、土地利用混杂交错且变化迅速的地域类型，已经初步具备某些城市功能和特点，但尚未被划为城市。根据其形成机制可分成城市型半城化地区（城市边缘区、城乡结合部、城乡交错带）和乡村型半城市化地区（经济快速发展的小镇、乡和非农产业发达的村）。该地区是城镇化发展最为敏感、变化最为迅速的地区，因其不稳定性、过渡性和复杂性而成为城镇发展问题、社会矛盾的集中、高发区。我国城市发展起步晚，发展快，现阶段年均城市化水平提高1%。快速的城镇化进程以及自上而下和自下而上相结合的城镇化方式催生了大量的半城市化地区。在乡镇企业较为发达的地区，这种情况尤为突出。研究该地区有助于深化城镇发展、城镇地域空间结构和城乡交互关系等议题的认识，推进小城镇健康发展。
为探析半城市化地域的土地利用特征和形成机制，本文以潮州市潮安区古巷镇为例，利用多个年份的土地利用数据，综合研究其土地利用演变规律、空间分布特征、土地利用效率和土地利用转移矩阵，分析其土地利用问题，并借鉴程序框图思维，研究探讨半城市化地区的形成机制，为其转型发展针对性地提出可行性对策。研究发现，古巷镇的建设用地存在总量大，范围广，增长快，效益低，结构不合理、工业用地不集中等问题。
（1）1996-2016年古巷镇的建设用地增加了1249.9公顷，年均增长速度9.2%。快速的用地增长导致村庄建设用地与镇区连成一体，形成用地组团，并不断向外延伸拓展。建设用地占镇域面积31.6%，存在用地比例过高的问题，威胁生态安全，城镇发展遭遇土地资源瓶颈。建设用地结构不合理，工业用地发展快，分布范围广，包围了村庄居民点。工业发展不集中，呈现“村村点火，处处冒烟”的景象。住宅用地经历了早期发展后增长速度开始减缓，与工业用地差距越来越大。人均建设用地和工矿用地高于国家法定水平，1996、2001、2006、2011和2016年人均建设用地113.7、137.3、197.5、188.8和207.3㎡，整体用地效益比较低。单位工矿用地产值较低，仅190.6万元/公顷，低于国家水平，不符合集约节约用地的要求。
（2）矩阵转移分析结果表明：以工矿用地为核心的建设用地增加主要是来自耕地、园地、坑塘水面和未利用地。在城镇发展早期，耕地是最容易受到侵占的用地类型。大量耕地转为工矿和住宅用地。近几年受耕地资源减少以及耕地严格保护政策影响，耕地转移速度减缓，园地和坑塘水面转移速度加快。大面积园地和坑塘水面被挖平或填平以建设工业厂房。
（3） 以卫生洁具产业为核心的工业发展是古巷镇建设用地变化的主要驱动力，为半城市化地域形成提供了基础条件。农民充分的自主发展权以及政府监管、规划引导缺位是半城市化地域形成的根本原因，如不介入管理和引导，环境恶化和本地人口外流进一步会促进半城市化地区的固化。如何破解半城市化地区空间固化的难题？古巷镇应该立足区域发展，加强与周边地区合作，重视规划对地区发展的引导和规范作用；发挥行业组织作用，促进陶瓷产业转型升级，加快产业集群发展；加强土地监管力度，由增量开发向存量利用转变，促进产业规模化发展；加快发展第三产业和服务业，提升人口吸引力，促进城镇化进程
Trophic consequences of non-native pumpkinseed Lepomis gibbosus for native pond fishes
No full textIntroduced non-native fishes can cause considerable adverse impacts on freshwater ecosystems. The pumpkinseed Lepomis gibbosus, a North American centrarchid, is one of the most widely distributed non-native fishes in Europe, having established self-sustaining populations in at least 28 countries, including the U.K. where it is predicted to become invasive under warmer climate conditions. To predict the consequences of increased invasiveness, a field experiment was completed over a summer period using a Control comprising of an assemblage of native fishes of known starting abundance and a Treatment using the same assemblage but with elevated L. gibbosus densities. The trophic consequences of L. gibbosus invasion were assessed with stable isotope analysis and associated metrics including the isotopic niche, measured as standard ellipse area. The isotopic niches of native gudgeon Gobio gobio and roach Rutilus rutilus overlapped substantially with that of non-native L. gibbosus, and were also substantially reduced in size compared to ponds where L. gibbosus were absent. This suggests these native fishes shifted to a more specialized diet in L. gibbosus presence. Both of these native fishes also demonstrated a concomitant and significant reduction in their trophic position in L. gibbosus presence, with a significant decrease also evident in the somatic growth rate and body condition of G. gobio. Thus, there were marked changes detected in the isotopic ecology and growth rates of the native fish in the presence of non-native L. gibbosus. The implications of these results for present and future invaded pond communities are discussed
Ring-contraction from benzo[b][1,4]thiazines to benzo[d]thiazolines induced by oxygen
No full textAn unexpected ring-contraction from benzo[b]pyrazino[1,2-d][1,4]thiazine-1,4-diones (6) to benzo[4,5] thiazolo[3,2-a]pyrazine-1,4-diones (7) has been developed. The preliminary mechanistic studies showed the transformation contained two independent steps: the first step is the formation of a Michael adduct upon the addition of the protic solvent, in the presence of base, to the C-2-C-3 double bond of compound 6, and the second step is a ring-contraction induced by oxygen via the migration of sulfur atom from C-2 to C-3 position. And its scope is also studied. (C) 2016 Elsevier Ltd. All rights reserved
A New Isoflavan from Abrus precatorius
No full textA new isoflavan, (3S)-1',4'-dihydroxy-6,7,8,2',3'-pentamethoxyisoflavan (1), together with six known compounds, abruquinone G (2), abruquinone B (3), isoliquiritigenin (4), gallic acid (5), ethyl gallate (6), and 1-O-galloyl-beta-D-glucose (7) were isolated from Abrus precatorius. Their structures were elucidated on the basis of physical and spectral analysis, respectively. Compounds 1, 4, and 7 were isolated from this plant for the first time
Efficient purification protocol for bioengineering allophycocyanin trimer with N-terminus Histag
No full textAllophycocyanin plays a key role for the photon energy transfer from the phycobilisome to reaction center chlorophylls with high efficiency in cyanobacteria. Previously, the high soluble self-assembled bioengineering allophycocyanin trimer with N-terminus polyhistidine from Synechocystis sp. PCC 6803 had been successfully recombined and expressed in Escherichia coli strain. The standard protocol with immobilized metal-ion affinity chromatography with chelating transition metal ion (Ni2+) was used to purify the recombinant protein. Extensive optimization works were performed to obtain the desired protocol for high efficiency, low disassociation, simplicity and fitting for large-scale purification. In this study, a 3(3) full factorial response surface methodology was employed to optimize the varied factors such as pH of potassium phosphate (X-1), NaCl concentration (X-2), and imidazole concentration (X-3). A maximum trimerization ratio (Y-1) of approximate A(650 nm)/A(620 nm) at 1.024 was obtained at these optimum parameters. Further examinations, with absorbance spectra, fluorescence spectra and SDS-PAGE, confirmed the presence of bioengineering allophycocyanin trimer with highly trimeric form. All these results demonstrate that optimized protocol is efficient in purification of bioengineering allophycocyanin trimer with Histag. (C) 2017 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University
Enhanced catalytic degradation of ciprofloxacin with FeS2/SiO2 microspheres as heterogeneous Fenton catalyst: Kinetics, reaction pathways and mechanism
No full textIn this study, the application of FeS2/SiO2 microspheres as a catalyst to activate H2O2 for the degradation of ciprofloxacin (CIP) was systematically investigated. Results demonstrated that the presence of SiO2 microspheres on the surface of FeS2 could effectively make the reaction of aqueous Fe2+ and H2O2 smoothly continuous by controlling the release of aqueous Fe2+ from FeS2. Nearly 100% of CIP was degraded after 60 min under the optimum conditions. A superior performance on the CIP degradation and high reusability of the catalyst was obtained in FeS2/SiO2 microspheres activated H2O2 system. A low concentration of ethylene diamine tetraacetie acid (EDTA) did positively affect the degradation rate of CIP. A synergetic effect between adsorption and oxidation processes contributed to the significant enhancement of CIP degradation. Seven oxidation intermediates were identified during the CIP degradation process, and the direct HO oxidation proved to be a main CIP degradation pathway. For degradation pathway of CIP, oxidation of piperazine ring would be its first step, followed by cleavage of the heterocyclic ring. Subsequently, the substitution, hydroxylation and decarboxylation processes occurred. This is the first report on the feasibility of FeS2/SiO2 microspheres activated H2O2 system for the enhanced degradation of CIP. (C) 2016 Elsevier B.V. All rights reserved