Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences
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Producing Designer Oils in Industrial Microalgae by Rational Modulation of Co-evolving Type-2 Diacylglycerol Acyltransferases
No full textMicroalgal oils, depending on their degree of unsaturation, can be utilized as either nutritional supplements or fuels; thus, a feedstock with genetically designed and tunable degree of unsaturation is desirable to maximize process efficiency and product versatility. Systematic profiling of ex vivo (in yeast), in vitro, and in vivo activities of type-2 diacylglycerol acyltransferases in Nannochloropsis oceanica (NoDGAT2s or NoDGTTs), via reverse genetics, revealed that NoDGAT2A prefers saturated fatty acids (SFAs), NoDGAT2D prefers monounsaturated fatty acids (MUFAs), and NoDGAT2C exhibits the strongest activity toward polyunsaturated fatty acids (PUFAs). As NoDGAT2A, 2C, and 2D originated from the green alga, red alga, and eukaryotic host ancestral participants of secondary endosymbiosis, respectively, a mechanistic model of oleaginousness was unveiled, in which the indigenous and adopted NoDGAT2s formulated functional complementarity and specific transcript abundance ratio that underlie a rigid SFA: MUFA:PUFA hierarchy in triacylglycerol (TAG). By rationally modulating the ratio of NoDGAT2A:2C:2D transcripts, a bank of N. oceanica strains optimized for nutritional supplement or fuel production with a wide range of degree of unsaturation were created, in which proportion of SFAs, MUFAs, and PUFAs in TAG varied by 1.3-, 3.7-, and 11.2-fold, respectively. This established a novel strategy to simultaneously improve productivity and quality of oils from industrial microalgae
Beneficiation of 6-0 mm fine-grain oil shale using vibrating air-dense medium fluidized bed separator
No full textHeterotrophy of filamentous oleaginous microalgae Tribonema minus for potential production of lipid and palmitoleic acid
No full textEnzyme-inorganic nanoflowers/alginatemicrobeads: an enzyme immobilization system and its potential application.
No full textIn this work, novel nanoflower/alginate microbeads were synthesized to immobilize α-acetolactate decarboxylase
(ALDC) with a facile approach. Typically, ALDC was first coprecipitated with Ca3(PO4)2 to form enzymeinorganic
hybrid nanoflowers (Ca3(PO4)2-ALDC), and then the nanoflowers containing micrometre-sized
particles and nanoscale flower-like petals were entrapped in alginate gel beads (Ca3(PO4)2-ALDC) @Alg).
Compared with free ALDC and Ca3(PO4)2-ALDC nanoflowers, the microbeads performed greatly improved
recyclability and stability, meanwhile, retained 98% of activity compared with free ALDC. Moreover, the
immobilized enzyme can be used in a 300 L beer fermentation tank to prevent the formation of diacetyl, solve
the problem of beer off-flavor and short the beer maturation time, thus exhibiting a great potential application in
beer brewing industry
Microbial production of mevalonate by recombinant Escherichia coli using acetic acid as a carbon source
No full textWe sought to produce mevalonate, an important organic acid, by recombinant Escherichia coli, using
acetic acid, a less costly alternative feedstock, as a carbon source. In this study, the mevalonate
biosynthesis pathway originating with acetate was constructed in recombinant E. coli, resulting in
the production of 1.06 g L¡1 mevalonate with a productivity of 0.03 g L¡1 h¡1 in a 5-L bioreactor.
The mevalonate concentration and productivity were significantly enhanced with increased cell
density during 2-stage aerobic fermentation, reaching 7.85 g L¡1 and 0.13 g L¡1 h¡1, respectively.
Fed-batch fermentation was further optimized under anaerobic and microaerobic conditions, and
mevalonate concentrations reached 3.05 g L¡1 and 4.97 g L¡1, respectively, indicating that the
oxygen supply exerts a large impact on mevalonate production from acetate. This study describes a
method with high potential to produce mevalonate with the engineered E. coli strain XU143 using
the less costly alternative feedstock acetate as a carbon source
Three-Component Functional Additive in a LiPF6-Based Carbonate Electrolyte for a High-Voltage LiCoO2/Graphite Battery System
No full textThe effectiveness of multicomponent functional additives on the performances of lithium ion batteries has received increasing attention. Tris(2H-hexafluoroisopropyl) borate (THFPB) additive can totally suppress the appearance of a crystallized complex between LiPF6 and adiponitrile (ADN). Herein, ADN, THFPB, and cyclohexylbenzene are demonstrated to be an effective three-component functional additive in LiPF6-based carbonate electrolyte that improves the cyclability and rate capabilities of LiCoO2/graphite full cells charged to 4.4, 4.45, and 4.5 V, respectively. By systematic characterization, it is demonstrated rationally that, with the help of the three-component functional additive, the electrolyte is stabilized and new types of less resistant, thinner, more protective solid-electrolyte interfaces are constructed simultaneously on the surfaces of both electrodes
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No full text石油是重要的能源和化学工业品原料，主要成分包括烷烃、环烷烃以及芳香烃等烃类。随着石油化学工业的发展，石油烃污染对生态环境造成严重破坏。光能自养微生物蓝细菌能够降解石油烃的主要成分脂肪烃，但降解途径尚未得到鉴定。脂肪烃生物合成在蓝细菌中普遍存在，合成途径已经得到鉴定，主要包括两个关键酶：脂酰-酰基载体蛋白（acyl carrier protein，ACP）还原酶（acyl-ACP reductase， AAR）与脂肪醛去甲酰加氧酶（aldehyde deformylating oxygenase，ADO）。
体外酶学实验发现蓝细菌脂肪烃合成关键酶ADO能够催化从脂肪烃到脂肪醛的反应，而蓝细菌醛脱氢酶（Aldehyde Dehydrogenase，ADH）能够催化从脂肪醛到脂肪酸的反应。上述反应与需氧微生物中从脂肪烃到脂肪酸的降解反应是类似的。本论文围绕蓝细菌中ADO和ADH参与的脂肪烃降解途径开展体外酶学表征及生理功能研究，取得如下主要结果：
（1）ADO能够催化不同链长的脂肪醛底物生成少一个碳原子的脂肪烃、脂肪醇和脂肪醛，铁离子在ADO反应中扮演着关键的角色；（2）ADO-ADH酶系能够催化以Cn脂肪醛为底物，经Cn-1脂肪烃-脂肪醇-脂肪醛，生成Cn-1脂肪酸的反应；（3）高光培养条件下多株蓝细菌高产烃突变株生长明显变差，光合色素含量下降，出现漂白现象，且膜脂过氧化程度升高。在高光下能快速生长的聚球藻UTEX 2973细胞抽提物中检测到十四醛的存在。
从上述结果推测蓝细菌高产烃突变株出现上述表型可能的原因是高光强条件下，蓝细菌胞内活性氧自由基水平升高，过量表达的ADO行使烷烃单加氧酶功能将胞内的脂肪烃转化为脂肪醛，而相应的ADH活性不能完全匹配，导致脂肪醛积累对细胞造成毒害。本研究丰富了我们对光能自养微生物降解脂肪烃机制的理解，对蓝细菌脂肪烃的高效合成也具有借鉴作用。Petroleum hydrocarbon pollution can result in serious damage to the ecological environment. As photoautotrophic microorganisms, cyanobacteria can not only synthesize alkanes but also degrade them. So far, alkane biosynthesis pathways were identified in cyanobacteria but the degradation pathway is still unknown. A two-step alka(e)ne biosynthetic pathway consisting of acyl- acyl carrier protein (ACP) reductase (AAR), and aldehyde deformylating oxygenase (ADO) has been identified in cyanobacteria.
Interestingly, it has recently been shown that ADO, the key enzyme in biosynthesis, is capable of catalyzing incorporation of an oxygen atom into the alkane to yield alcohol and aldehyde. Aldehyde dehydrogenase (ADH) in cyanobacteria can mediate the oxidation of aldehyde into the corresponding fatty acids. In aerobic alkane degradation pathways, alkane is converted to alcohol, and subsequently oxidized to the corresponding aldehyde and fatty acid. In vitro activity of ADO/ADH enzyme and the roles of ADO and ADH in alkane degradation were investigated in this study. The main results are as follows:
(1) ADO can convert Cn fatty aldehyde with different carbon chain length to Cn-1 alkane, alcohol and aldehyde, and ferrous ion plays an important role in ADO reactions. (2) ADO-ADH enzyme system can catalyze Cn aldehyde to Cn-1 alcohol, aldehyde, and then to the Cn-1 fatty acid. (3) Under high light condition, growth of Synechocystis sp. PCC 6803 wild type strain is much better than high-alkane content mutants. Photobleaching of photosynthetic pigments was also observed in high-alkane content mutant LX56 under high light condition. Enhanced level of membrane lipid peroxidation in LX56 mutant indicated oxidative damage to lipids under high light.
It is speculated that the high content of alkanes can be converted to aldehyde by overexpressed ADO. Aldehyde can be accumulated due to deficiency of ADH enzyme activity relative to monooxygenase activity of ADO in high-alkane content mutants under high light. These studies help to understand alkane biodegradation pathways in photoautotrophic microorganisms. Approaches and strategies will also be provided for improving alkane production in cyanobacteria
掺杂钙钛矿薄膜的气体修复技术及电池器件研究
No full text有机无机杂化钙钛矿材料凭借其合适的带隙宽度、较大的载流子扩散长度、大的吸收系数、低廉的成本、可溶液法制备等优势，吸引了科研工作者的广泛关注。有机无机杂化钙钛矿太阳能电池自2009年诞生以来，电池效率从开始的3.8%，上升为目前的22.1%，展现出巨大的发展潜力和商业前景。钙钛矿太阳能电池效率的飞速提升，与钙钛矿的成膜工艺不断改善密切相关。抗溶剂法和两步法等是制备小面积钙钛矿膜的常用方法，但制备高质量大面积的钙钛矿太阳能电池仍面临一定的困难。另一方面有机无机杂化材料本身由于其离子活化能较低，造成其对水，热，光等的稳定性较差，限制着其进一步发展。因此，钙钛矿薄膜的大面积制备技术及其器件稳定性是目前钙钛矿太阳能电池发展所面临的两大核心问题。我们课题组前期开发的甲胺气体后修复技术与商业化涂布技术兼容度较高，基本满足了大面积制备钙钛矿薄膜的要求，本文将重点研究该技术在掺杂钙钛矿太阳能电池方面的应用。 本文首先研究了卤素掺杂钙钛矿薄膜的制备技术及其稳定性问题。通过甲胺气体修复技术得到了高度均匀的甲胺类钙钛矿(MAPbI3，MAPbBr3，MAPb(I1-xBrx)3 ) 薄膜并系统研究了Br掺杂钙钛矿太阳能电池分别作为硅叠层器件顶部电池和单节电池的应用。在单节太阳能电池研究中发现适量的卤素掺杂可以稍微提高电池器件的开路电压，但由于掺杂带来吸收范围变窄，总体效果不佳。更为严重的是我们发现卤素Br的引入，不仅没有限制卤素离子的扩散，还加速了Ag电极的腐蚀速率，造成器件性能的衰减。原因可能是其Br的离子半径更小，更容易在钙钛矿层、空穴传输层中扩散，对器件持续光照稳定性方面尤为不利。 我们继而选择无机阳离子掺杂方案，选用较甲胺离子电负性更强的铯（Cs+）离子，因为其与I-更强的作用力，从而提高了材料中碘离子的活化能。我们发现铯掺杂的钙钛矿材料同样适用于甲胺气体修复工艺，原因是CsI和MA气体同样可以生成可流动的CsI•xCH3NH2中间相。这种方法制备的Cs掺杂钙钛矿太阳能电池的光电效率达到17%，更为明显的是其稳定性比纯相MAPbI3钙钛矿电池得到较大改善。这是由于Cs离子更高电负性和非极化结构，其掺杂后钙钛矿材料中PbI6八面体的对称性得到了显著提高，10%的Cs掺杂后材料的降解速率降低了2倍。从而获得了更加稳定的钙钛矿材料及电池器件。 本文的研究针对于钙钛矿太阳能电池商业化发展的瓶颈问题，相关实验结果和基础理论的分析对进一步优化钙钛矿薄膜的制备工艺、材料体系以及器件结构等具有一定借鉴意义。In the past few years, organo-lead halide perovskites (such as CH3NH3PbI3, MAPbI3 and NH2CH=NH2PbI3, FAPbI3) have drawn the attention of many scientists due to their attractive optical and electrical properties, together with their moderate cost and low temperature solution-process ability. These merits make them one of the most promising candidates for the industrial development of next-generation optoelectronic devices. The first reported solar cell of CH3NH3PbI3 achieved an efficiency of 3.81% in 2009, and now, the certified record for power conversion efficiency (PCE) of PSCs has been 22.1%. The increase of efficiency of PSC can be contributed to the improvement of perovskite film fabrication technology. The fabrication technologies, such as two-step solution method, antisolvent method and so on, show the advantage in the small-area perovskite film fabrication. But there are also some hard challenges for the large-area perovskite solar cells fabrication. Besides, perovskite solar cell is not stable to water, heat, light and so on. In this case, A technology suitable for large scale fabrication of perovskite films and the stability of devices are the two core problems of perovskite solar cells. The technology of methylamine gas healing which is reported by our research group previously is highly compatible with the commercial coating technology. It can basically meet the requirements for a large scale fabrication of perovskite thin film. In the article. based on the technology of MA gas healing，the doped perovskite solar cells has been researched systematically. In this article, The fabrication process and the stability of Br doped perovskite film are studied firstly. A highly uniform methylamine perovskite (MAPbI3, MAPbBr3 and MAPb(I1-xBrx)3) thin film have been gained by methylamine gas healing process and the applications of Br doped perovskite in tandom and single solar cells are researched systematically. In the research of Br doped single solar cell, it is found that the open circuit voltage can be improved a little, and the absorption range of material is narrowed due to Br doping, as a result of very little improvement of PCE for the Br doped perovskite solar cells. What is more important is that the corrosion of Ag electrode is accelerated after the introduction of Br, due to the more smaller Br ion radius smaller, which is more easily to migrate in the perovskite layer and the hole transport layer. In order to solve this problem, a Cs doped perovskite solar cell is studied. In theory, There is a stronger electronegativity for Cs+ compared to MA+ ,which can provide a stronger force with iodin ion, as a result of an increased activation energy in the material. We found that the MA gas healing process is also suitable for the Cs doping perovskite material due to a fatasy reaction between CsI and MA gas with a liquid CsI.xCH3NH2 as mesophase. The Cs doped perovskite solar cell prepared by this method has a PCE of 17%, and its stability is greatly improved，compared to that of pure MAPbI3 perovskite cell. Besides, through structure calculation, it is found that due to the introduction of smaller Cs ion, the symmetry of PbI6 has been significantly improved, which result in more stable perovskite materials. This study is focused on bottleneck problems of perovskite solar cell business development. we believe the relevant experimental results and theoretical analysis in this article will have an important effect on the further optimization of perovskite solar cells
材料工程
No full textIt is highly required to develop high specific energy density battery systems for the development of electrical vehicles. The Li-O2 battery is a potential candidate to meet the demand due to its high theoretical energy density. However, Li-O2 batteries still suffer from poor round-trip efficiency and poor cycle life. To reduce the charge over-potential of Li-O2 batteries, redox mediators (RMs) were introduced to the electrolyte of Li-O2 batteries to promote the decomposition of discharge product Li2O2. Among the reported RMs, LiI is the most intensely studied one with lots of controversial reports. Here, we studied the Li-O2 battery employing LiI as RM. Firstly, we studied the discharge product LiOH and its decomposition mechanism during charge process of Li-O2 cell employing LiI as RM with trace of H2O impurity. Then we studied the oxidative mechanism of traditional discharge product Li2O2 by the oxidized I- (I3-, I2) in the anyhydrous Li-O2 cell employing LiI as RM. Moreover, we presented a design method of a more efficient I- redox mediator for Li-O2 cell. The main research contents are summarized as follows:
(1) We found that the corresponding discharge product was LiOH and LiOH•H2O when the H2O content was 200 ppm and 2000 ppm in Li-O2 cell employing LiI as RM. We studied the discharge mechanism of discharge product LiOH in Li-O2 cell contained trace H2O. We also studied the decomposition mechanism of LiOH during charge process by XRD and gas spectrometer (MS). The MS datas demonstrated that the discharge product LiOH was not reversibly oxidized to O2 during charge process. Instead, the reaction of LiOH and I2 generated side-product LiIO3, which accumulated and destroyed the electrochemical performance of the Li-O2 cell.
(2) In the ideal anyhydrous Li-O2 cell employed LiI as RM, the MS datas confirmed that the traditional discharge product Li2O2 can be oxidized by I2 rather than I3-. Meanwhile, we found that the free I- or the generated I- from Li2O2 oxidation can be complexed with effective I2 to give ineffective I3- species, reducing the oxidation efficiency of Li2O2 on charge. Inspired by this, we found a compound LiI(HPN)2, which has lower I- dissociation in ether electrolyte. So it can exhibit as an I- trap to reduce the concentration of I- in the electrolyte solution thus improve the generation of I2 species during charge and higher Li2O2 oxidation efficiency. Our work demonstrated that compound LiI(HPN)2 was a more efficient I- RM than LiI, which can largely enhance the Li2O2 oxidation efficiency during charge process and the cycling performance of Li-O2 cell.中
生物化学与分子生物学
No full textBafilomycins, belongs to class B Plecomacrolides, are a group of 16-membered macrolide biosynthetized by type I polyketide synthase. From now on, nearly thirty bafilomycin derivatives have been isolated and identified. Despite bafilomycins have attracted significant attention from pharmaceutists due to their diverse bioactivities, the toxicity prevents them from clinical application. As the core structure of all bafilomycins, bafilomycin A1 is a potent and specific vacuolar H+-ATPase (V-ATPase) which might be applied in the therapy of osteoporosis in the future.
Streptomyces lohii ATCC BAA-1276, isolated from the Crown Island, Papua New Guinea can produce bafilomycin A1, C1, B1. Although the bafilomycin biosynthetic gene cluster have been elucidated in our previous study, but the post- polyketide synthase (PKS) tailoring steps for structural diversification and bioactivity improvement remain largely unknown. In this study, the tailoring steps of bafilomycin biosynthetic pathway has been elucidated for the first time through in vivo gene inactivation and in vitro reconstitution of enzyme activities: Orf3 is characterized as a novel fumarate adenylyltransferase activing the fumarate by forming the fumaryl-AMP; Orf2 with high substrate specificity is responsible for transferring the fumarate moiety from fumaryl-AMP to bafilomycin A1, giving rise to bafilomycin C1; acyl-CoA ligase BafX and 5-aminolevulinic acid (5-ALA) synthase BafZ cooperatively synthesize the C5N unit, and ATP-dependent amino synthetase BafY catalyzes the amide bond formation between bafilomycin C1 and C5N.
Due to the complex structure of bafilomycins, to generate the bafilomycin A1 high-yielding strains through genetic engineering is more eco-friendly and low-cost compared with total synthesis. In this study, BafG and Orf1 have been identified as AfsR family and LuxR family activator involved in bafilomycins biosynthesis through in vivo gene inactivation, complementation and overexpression, respectively. Finally, the Orf1 was overexpressed in the Streptomyces lohii Δorf2&orf3 to give a maximum bafilomycin A1 production titer of 535.1 ± 25.0 mg/L to meet the industry application.
Fumarate, as an important intermediate in the tricarboxylic acid cycle, exist in several structures of natural products. But the incorporation mechanism of fumarate into the natural product have not been elucidated so far. The biotransformation of
bafilomycin A1 to bafilomycin C1 by Orf2 and Orf3 will give a paradigm. The bafilomycin biosynthetic pathway show us an interesting crosstalk between primary metabolites and secondary metabolites, providing a new horizon for the rational design of efficient and low-toxicity bafilomycin derivatives or new drugs.中