Efficient Design Strategy for Whole-Cell and Cell-Free Biosensors based on Engineered Riboswitches

Abstract

We have applied dual genetic selection to design a bacterial riboswitch with improved sensitivity by employing a high-affinity heterologous thiamine pyrophosphate (TPP) aptamer and modified selection conditions in Escherichia coli. The cells transformed with the engineered TPP riboswitches were characterized as whole-cell biosensors. The riboswitches were further studied in cell-free translation systems where they exhibited characteristics similar to those in vivo and a shorter response time for analysis. The flexibility of the riboswitch-based biosensors to accommodate different reporter genes was also demonstrated. Tuning of biosensor characteristics in vivo enables efficient development of aptamer-based whole-cell and cell-free biosensors.     

华根霉全细胞脂肪酶催化合成生物柴油

比较了5种不同商品化脂肪酶和自制的华根霉CCTCCM201021全细胞脂肪酶(RCL)催化油脂合成生物柴油的转化效果,结果表明,RCL能有效应用于无溶剂体系催化合成生物柴油.在无溶剂体系中对该酶催化生物柴油的转酯化反应工艺进行优化,考察了甲醇用量、体系含水量、酶的添加量和反应温度对生物柴油收率的影响,使生物柴油最终收率大于86.0%.在有机溶剂体系中选择不同有机溶剂作为助溶剂进行转酯化反应,发现logP值在4.0～4.5的有机溶剂具有较好的转化效果.其中以正庚烷为助溶剂的转酯化反应具有最高的生物柴油收率86.7%.在无溶剂体系中RCL催化转化油酸和模拟高酸价油脂合成脂肪酸甲酯的研究表明,该酶具有很好的催化合成生物柴油的潜力.     

Hydrogen Production from Methanol Using Corona Discharges

Hydrogen production at room temperature from liquid methanol has been conducted using corona discharge.The content of water in methanol solution has a significant effect on this production.When water concentration increases from 1.0% to 16.7,the methanol conversion rate changes from 0.196 to 0.284 mol/h.An important finding in this investigation is the formation of ethylene glycol as a major by-product.The yield of ethylene glycol is ranged from 0.0045 to 0.0075 mol/h based on the water content.     

Biological Hydrogen Production Using Chloroform-treated Methanogenic Granules

In fermentative hydrogen production, the low-hydrogen-producing bacteria retention rate limits the suspended growth reactor productivity because of the long hydraulic retention time (HRT) required to maintain adequate bacteria population. Traditional bacteria immobilization methods such as calcium alginate entrapment have many application limitations in hydrogen fermentation, including limited duration time, bacteria leakage, cost, and so on. The use of chloroform-treated anaerobic granular sludge as immobilized hydrogen-producing bacteria in an immobilized hydrogen culture may be able to overcome the limitations of traditional immobilization methods. This paper reports the findings on the performance of fed-batch cultures and continuous cultures inoculated with chloroform-treated granules. The chloroform-treated granules were able to be reused over four fed-batch cultures, with pH adjustment. The upflow reactor packed with chloroform-treated granules was studied, and the HRT of the upflow reactor was found to be as low as 4 h without any decrease in hydrogen production yield. Initial pH and glucose concentration of the culture medium significantly influenced the performance of the reactor. The optimum initial pH of the culture medium was neutral, and the optimum glucose concentration of the culture medium was below 20 g chemical oxygen demand/L at HRT 4 h. This study also investigated the possibility of integrating immobilized hydrogen fermentation using chloroform-treated granules with immobilized methane production using untreated granular sludge. The results showed that the integrated batch cultures produced 1.01 mol hydrogen and 2 mol methane per mol glucose. Treating the methanogenic granules with chloroform and then using the treated granules as immobilized hydrogen-producing sludge demonstrated advantages over other immobilization methods because the treated granules provide hydrogen-producing bacteria with a protective niche, a long duration of an active culture, and excellent settling velocity. This integrated two-stage design for immobilized hydrogen fermentation and methane production offers a promising approach for modifying current anaerobic wastewater treatment processes to harvest hydrogen from the existing systems.     

甲烷氧化菌利用甲烷生产聚羟基脂肪酸的研究进展

化学合成塑料主要来自于不可再生的化石能源,化学合成塑料的大量使用既消耗了大量能源物质,也带来了严重的环境问题。而生物合成的高分子化合物聚羟基脂肪酸,具有与合成塑料相似的物理性质,生产原料具有可再生性,同时在环境能快速降解,结构多样可以满足不同用途等多种优点,成为合成塑料最佳的替代品。甲烷氧化菌能以甲烷为唯一碳源和能源物质生长,并在细胞内合成大分子聚羟基脂肪酸。利用甲烷氧化菌转化甲烷合成聚羟基脂肪酸不仅可以大幅降低生产成本,同时也减少了温室气体的排放。本文就甲烷氧化菌合成聚羟基脂肪酸的生物代谢途径,甲烷为原料生产聚羟基脂肪酸的方法及优缺点等方面进行了分析。     

Direct Synthesis of Hydrogen Peroxide from Hydrogen and Oxygen Using Tailored Pd Nanocatalysts: A Review of Recent Findings

Direct synthesis of hydrogen peroxide from hydrogen and oxygen is being actively studied as an alternative to the current manufacturing process. The direct synthesis route has not reached the point of commercialization because of low yields, but significant effort is being spent on enhancing the productivity. With advances in computational capacity, simulation studies based on DFT calculations now offer directions for catalyst improvement, but such modifications can only be realized through the application of nanoparticle synthesis techniques that allow for nanocrystal morphology and size control and unique immobilization. To date, there have only been a small number of studies on such nanoparticles with size and crystallographic homogeneity for the direct hydrogen peroxide synthesis. According to our knowledge no other group has systematically investigated application of nanoparticles in direct synthesis of hydrogen peroxide, and thus included in this review are primarily previous studies conducted by our group. In this review, we discuss the utilization of nanotechnology for the synthesis of Pd catalysts and its effect on the direct synthesis of hydrogen peroxide, and we suggest a direction for future studies.     

Production of Modified Starch Using System Hydrogen Peroxide-Thiourea Dioxide

A new method for producing oxidized starches using hydrogen peroxide and thiourea dioxide is proposed. It is shown that this method makes it possible to broadly control the number of functional groups arising in modified starch as well as the viscosity of the paste made from modified starch. This is achieved by changing the molar ratio of thiourea dioxide and hydrogen peroxide. The oxidative modification of starch is carried out under mild conditions and proceeds at high speed.

     

电解醇制氢

发展了利用甲醇直接电解制氢这种经济的制氢方法, 实验结果表明电解甲醇制氢能够极大地降低电能消耗. 此方法的新颖之处在于方法简单和成本低. 将直接甲醇燃料电池膜电极作为电解装置, 可以达到任何规模的要求. 如果将这种电解装置与太阳能电池联用, 可非常经济地制氢及氢气储存, 或直接向燃料电池或其它化学工程装置供氢.     

MoS2 as a Co-Catalyst for Photocatalytic Hydrogen Production: A Mini Review

Molybdenum disulfide (MoS₂), with a two-dimensional (2D) structure, has attracted huge research interest due to its unique electrical, optical, and physicochemical properties. MoS₂ has been used as a co-catalyst for the synthesis of novel heterojunction composites with enhanced photocatalytic hydrogen production under solar light irradiation. In this review, we briefly highlight the atomic-scale structure of MoS₂ nanosheets. The top-down and bottom-up synthetic methods of MoS₂ nanosheets are described. Additionally, we discuss the formation of MoS₂ heterostructures with titanium dioxide (TiO₂), graphitic carbon nitride (g-C₃N₄), and other semiconductors and co-catalysts for enhanced photocatalytic hydrogen generation. This review addresses the challenges and future perspectives for enhancing solar hydrogen production performance in heterojunction materials using MoS₂ as a co-catalyst.     

Improvement of the Production Efficiency of l-(+)-Tartaric Acid by Heterogeneous Whole-Cell Bioconversion

An Escherichia coli-engineered bacterium with cis-epoxysuccinate hydrolase (ESH) activity was used to catalyze the stereospecific hydrolysis of cis-epoxysuccinic acid to l-(+)-tartaric acid. The effect of the substrate composition on the production efficiency of l-(+)-tartaric acid was investigated. Based on the sodium-type homogeneous substrate system, a heterogeneous substrate system, composed of 1.2 M sodium-type substrate and 1.8 M calcium-type substrate, was designed to improve ESH catalytic efficiency. After process optimization, a catalytic efficiency of 9.37?×?10^?3 g U^?1 h^?1 was obtained with fed-batch mode in the heterogeneous substrate system, about a twofold increase compared to the traditional bioconversion process with Nocardia tartaricans cells. The scale-up tests were carried out in a 15-m³ stirred tank reactor, which indicated that the heterogeneous substrate system had great application prospect for the l-(+)-tartaric acid industrial production.     

TiO2光催化分解水制氢研究进展

综述了近几年改善TiO2光催化分解水制氢的方法措施.向水中添加供电子物质可减少光生电子与空穴的复合,添加碳酸盐或碘化物有利于光生电子与空穴分离;TiO2表面沉积适量的金属颗粒也有利于实现电子和空穴分离,但沉积太多的金属颗粒不但降低TiO2对光的吸收而且还可能成为光生电荷复合的中心;掺杂合适的金属离子通过形成杂质能级可把TiO2的吸光范围至拓宽可见光,掺杂非金属元素使TiO2的带隙(Eg)变窄,从而使TiO2的吸光红移更明显,但掺杂离子有可能成为光生电荷复合的中心;染料敏化或半导体复合有利于实现电荷分离,提高光电转换效率.将多种修饰方法有机结合起来制取氢足目前的一个研究方向,最后分析了未来的研究重点.     

光电催化海水分解制氢

自20世纪70年代以来,利用阳光将水分解,从而将太阳能转换为清洁可再生的氢气燃料成为人们关注的焦点。太阳能是取之不尽用之不竭的能源,而海水是地球上最丰富且易获取的自然资源,利用光电催化海水分解制氢成为目前解决实际能源问题和缓解淡水资源短缺的理想途径之一。本文总结了目前为止探索过光电催化分解海水制取氢气的研究工作,对研究内容和机理进行了梳理分析,并对光电催化海水制氢这一领域进行了展望。     

微生物电解电池制氢

在微生物燃料电池（MFC）的基础上发展而来的微生物电解电池（MEC）为生物制氢提供了一种全新的方法。本文综述了自2005年MEC发明以来取得的研究进展。简要介绍了MEC制氢的基本原理和系统的评价参数;比较了不同MEC系统结构和电极材料对体系产氢效能的影响;讨论了MEC制氢实际应用中存在问题和限制因素;提出了MEC制氢今后的研究思路和发展趋势;展望了MEC在利用生物质制氢和有机废水资源化利用中的应用前景。     

Production of Hydrogen Peroxide by Photocatalytic Processes

Hydrogen peroxide (H₂O₂) has received increasing attention because it is not only a mild and environmentally friendly oxidant for organic synthesis and environmental remediation but also a promising new liquid fuel. The production of H₂O₂ by photocatalysis is a sustainable process, since it uses water and oxygen as the source materials and solar light as the energy. Encouraging processes have been developed in the last decade for the photocatalytic production of H₂O₂. In this Review we summarize research progress in the development of processes for the photocatalytic production of H₂O₂. After a brief introduction emphasizing the superiorities of the photocatalytic generation of H₂O₂, the basic principles of establishing an efficient photocatalytic system for generating H₂O₂ are discussed, highlighting the advanced photocatalysts used. This Review is concluded by a brief summary and outlook for future advances in this emerging research field.     

Generation of Hydrogen from Photolysis of Organic Acids by Photosynthetic Bacteria

Photodccomposition of ten kinds of organic acids by Rhodopseudomonas palustris for producing hydrogen has been investigated,By using acctate as hydrogen donor,dynamics of hydrogen production and cell growth has been determined;the influences of acetate concentration,temperature,light intensity and the effects of the ineraction among metal ions (Fe^3 ,Ni^ ),acctate and glutamatc in aqueous solution on hydrogen production have been examined for optimizing the conditions of H2 generation .The results show that H2 production is partially correlated with cell growth ;Ni^2 inhibits hydrogen production,but enhances cell growth; Fe^3 promotes hydrogen production evidcntly,The highest rate of H2 production is 22.1 mL L^-1h^-1 under the conditions of 35-37℃,6000-8000lx,30 mmolL^-1 of acetate, 9mmolL^-1 of glutamate, and 50μmolL^-1 of Fe^3 .     

AuPd和AgPd枝晶纳米催化剂催化甲酸分解制氢

由枝晶构成的AuPd和AgPd三维多孔泡沫薄膜在室温下分解甲酸制氢具有高催化活性。该高催化活性是由于纳米枝晶中存在大量的活性位点,如台阶、角、扭结、边缘以及合金间的电子效应。多孔泡沫膜除了具有较高的活性外,还具有其他优良的性能：在不需要有机添加剂的情况下,利用氢气泡模板法在Ti基板上可在5 min内快速沉积多孔泡沫催化剂,无需后处理便可用于催化甲酸分解制氢;通过将电沉积泡沫膜浸入或者拉出HCOOH+HCOONa溶液,可控制氢气的产生或停止;该泡沫催化剂通过去离子水清洗或者在H₂SO₄溶液中进行循环伏安扫描、干燥后就可活化重新使用。     

Hydrogen Production by Steam Reforming of Ethanol: A Two Step Process

A two-layer fixed-bed catalytic reactor for hydrogen production by steam reforming of ethanol is proposed. In this reactor ethanol is first converted to acetaldehyde over a Cu-based catalyst and then acetaldehyde is converted to a hydrogen-rich mixture over a Ni-based catalyst. It is shown that the use of such type of reactor prevents coke formation and provides hydrogen yields closed to equilibrium.     

利用钴-氨基硫脲类配合物作为氧化还原催化剂光分解水制备氢气

通过将磷配体与氨基硫脲结合进一步增加螯合配体的配位能力,并引入磺酸根增强其水溶性,合成了一个钴配合物Co-NSP(配体HNSP:4-[2-(2-二苯基膦-苯烯基)-氨基硫脲腙]苯甲酸),利用其氧化还原特性开展均相体系的光驱动从水中制备氢气的研究。新的NSP三齿配体能够稳定低价的金属中心,有助于提升催化剂的催化性能。利用其与荧光素所构筑的光催化体系,在电子牺牲剂三乙胺存在下显示出良好的性能,光照6h其TON(turnover number)可达2000molH₂每摩尔催化剂。为了研究和比较其性能特点,对这一光催化体系的荧光滴定和氧化还原性能也进行了较细致的研究。