Microbial fuel cells: methodology and technology

Microbial fuel cell (MFC) research is a rapidly evolving field that lacks established terminology and methods for the analysis of system performance. This makes it difficult for researchers to compare devices on an equivalent basis. The construction and analysis of MFCs requires knowledge of different scientific and engineering fields, ranging from microbiology and electrochemistry to materials and environmental engineering. Describing MFC systems therefore involves an understanding of these different scientific and engineering principles. In this paper, we provide a review of the different materials and methods used to construct MFCs, techniques used to analyze system performance, and recommendations on what information to include in MFC studies and the most useful ways to present results.     

Microbial fuel cells for sulfide removal

Thus far, microbial fuel cells (MFCs) have been used to convert carbon-based substrates to electricity. However, sulfur compounds are ubiquitously present in organic waste and wastewater. In this study, a MFC with a hexacyanoferrate cathodic electrolyte was used to convert dissolved sulfide to elemental sulfur. Two types of MFCs were used, a square type closed to the air and a tubular type in which the cathode compartment was open to the air. The square-type MFCs demonstrated a potential-dependent conversion of sulfide to sulfur. In the tubular system, up to 514 mg sulfide L(-1) net anodic compartment (NAC) day(-1) (241 mg L(-1) day(-1) total anodic compartment, TAC) was removed. The sulfide oxidation in the anodic compartment resulted in electricity generation with power outputs up to 101 mW L(-1) NAC (47 W m(-3) TAC). Microbial fuel cells were coupled to an anaerobic upflow anaerobic sludge blanket reactor, providing total removals of up to 98% and 46% of the sulfide and acetate, respectively. The MFCs were capable of simultaneously removing sulfate via sulfide. This demonstrates that digester effluents can be polished by a MFC for both residual carbon and sulfur compounds. The recovery of electrons from sulfides implies a recovery of energy otherwise lost in the methane digester.     

微生物胆固醇氧化酶的研究进展

微生物来源的胆固醇氧化酶在医疗诊断、食品加工、生化制药、抗虫基因工程等方面具有良好的应用价值,引起了国内外学者的广泛关注,并开展了大量的研究工作。本文就胆固醇氧化酶的种类、酶学性质、结构、功能、应用及近年来基因工程等方面的研究进展作一综述。     

内酯类化合物代谢中的微生物酶及其应用

内酯类化合物在活生物体内经酶的作用产生代谢变化,可生成有利于生物体利用的物质.文中概述了近年来报道的几种有关内酯类化合物代谢中的微生物酶及其在生物技术中的应用情况和研究进展.     

Microbial fuel cells generating electricity from rhizodeposits of rice plants

Living plants transport substantial amounts of organic material into the soil. This process, called rhizodeposition, provides the substrate for the rhizospheric microbial community. In this study, a laboratory-scale sediment microbial fuel cell, of which the anode is positioned in the rhizosphere of the rice plants, is used to microbially oxidize the plant-derived organics. An electrical current was generated through the in situ oxidation of rhizodeposits from living rice plants. The electrical power output of a sediment microbial fuel cell was found to be a factor 7 higher in the presence of actively growing plants. This process offers the potential of light-driven power generation from living plants in a nondestructive way. Sustainable power productions up to 330 W ha(-1) could be attributed to the oxidation of the plant-derived compounds.     

玉米燃料乙醇技术发展趋势与产业化应用

概述了国际玉米燃料乙醇生产技术的研发进展,结合国内及美国燃料乙醇装置,重点介绍了不同生产工艺的特点,分析出之间存在的差异,对我国燃料乙醇产业技术提升方向给出了建议。     

Microbial fuel cell operation with continuous biological ferrous iron oxidation of the catholyte

The oxygen reduction rate at the cathode is a limiting factor in microbial fuel cell (MFC) performance. In our previous study, we showed the performance of an MFC with ferric iron (Fe3+) reduction at the cathode. Instead of oxygen, ferric iron was reduced to ferrous iron (Fe2+) at the cathode with a bipolar membrane between the anode and cathode compartment. This resulted in a higher cathode potential than is usually obtained with oxygen on metal-based chemical catalysts in MFCs. In this study, we investigated the operation of the same MFC with ferric iron reduction at the cathode and simultaneous biological ferrous iron oxidation of the catholyte. We show that the immobilized microorganism Acidithiobacillus ferrooxidans is capable of oxidizing ferrous iron to ferric iron at a rate high enough to ensure an MFC power output of 1.2 W/m2 and a current of 4.4 A/m2. This power output was 38% higher than in our previous study at a similar current density without ferrous iron oxidation. The bipolar membrane is shown to split water into 65-76% of the needed protons and hydroxides. The other part of the protons was supplied as H2SO4 to the cathode compartment. The remaining charge was transported by K+ and HSO4-/SO4(2-) from the one compartment to the other. This resulted in increased salt concentrations in the cathode. The increased salt concentrations reduced the ohmic losses and enabled the improved MFC power output. Iron could be reversibly removed from the bipolar membrane by exchange with protons.     

Microbial fuel cell using anaerobic respiration as an anodic reaction and biomineralized manganese as a cathodic reactant

We have operated a microbial fuel cell in which glucose was oxidized by Klebsiella pneumoniae in the anodic compartment, and biomineralized manganese oxides, deposited by Leptothrix discophora, were electrochemically reduced in the cathodic compartment. In the anodic compartment, to facilitate the electron transfer from glucose to the graphite electrode, we added a redox mediator, 2-hydroxy-1,4-naphthoquinone. We did not add any redox mediator to the cathodic compartment because the biomineralized manganese oxides were deposited on the surface of a graphite electrode and were reduced directly by electrons from the electrode. We have demonstrated that biomineralized manganese oxides are superiorto oxygen when used as cathodic reactants in microbial fuel cells. The current density delivered by using biomineralized manganese oxides as the cathodic reactant was almost 2 orders of magnitude higher than that delivered using oxygen. Several fuel cells were operated for 500 h, reaching anodic potentials of -441.5 +/- 31 mVscE and cathodic potentials of +384.5 +/- 64 mVscE. When the electrodes were connected by a 50 Ohms resistor, the fuel cell delivered the peak power density of 126.7 +/- 31.5 mW/m2.     

微生物产生的类胡萝卜素及其工业化

在自然界中已发现有６００多种类胡萝卜素，被多数国家批准使用于食品、饲料、药物及化妆品的类胡萝卜素约有１０多种，许多微生物能产生复杂多样的类胡萝卜素，本文评述在利用微生物产生除β－胡萝卜素以外的其它５种有用的类胡萝卜素方面的研究发展近况及产业化价值。     

微生物菌剂对烟草根结线虫及根际微生物群落多样性的影响

为寻找对烟草根结线虫病有良好控制效果的药剂,探究药剂施用对烟草根际土壤微生物群落的代谢情况,改善土壤微生态环境,以烟草品种红花大金元为试验材料,通过田间试验研究施用枯草芽孢杆菌、淡紫拟青霉、荧光假单胞杆菌、哈茨木霉和阿维菌素、阿维·丁硫对烟草根结线虫病病害控制、根际土壤微生物群落多样性变化及烟草生长的影响。结果表明,淡紫拟青霉、荧光假单胞杆菌能够分别达到89%、76%的防治效果。AWCD值、McIntosh指数、Simpson指数均显示土壤中增施微生物菌剂能够提高根际土壤微生物群落代谢能力,促进土壤微生物群落对碳源的整体利用,增强代谢活性。Pearson相关分析表明,根际土壤中微生物群落对31种碳源的代谢利用与病情指数呈负相关。土壤中添加微生物菌剂淡紫拟青霉、枯草芽孢杆菌、荧光假单胞杆菌均能够控制烟草根结线虫病,增强土壤微生物群落多样性,促进烟株生长,淡紫拟青霉效果最好。淡紫拟青霉处理后通过提高根际土壤微生物对碳水化合物类（D-半乳糖酸-γ-内酯）碳源的代谢利用,达到对病情指数的有效调控。淡紫拟青霉处理除最大叶长外,株高、茎围、有效叶片数、最大叶宽均为最大增幅分别为44.91%、20.11%、11.78%、39.05%。     

微生物溶菌酶的研究及应用

微生物溶菌酶是区别于卵清溶菌酶,而是由微生物分泌产生的一种能溶解细菌细胞壁的酶,介绍了微生物溶菌酶的研究历史、分类以及其作用机制。对近年来其在食品、医学、酶工程和饲料工业上的应用进行了综述;分析了溶菌酶应用中存在的主要问题,并对其应用前景进行了展望。     

发酵香肠与微生物发酵剂(二)

概括介绍了目前国内外关于发酵香肠的研究现状和今后的发展趋势。国外有关发酵香肠的研究主要集中在改进生产工艺和筛选及构建优良发酵剂菌种两方面；国内对发酵香肠的研究和开发处于起步阶段。发酵香肠类产品其本身所具有的特点决定了必将在我国受到消费者的欢迎。     

微生物絮凝剂研究进展

主要介绍了微生物絮凝剂的种类、产生菌、发酵、分离与纯化及其在环境工程、食品工业、发酵行业和重金属富集等方面的应用,对其存在问题和发展趋势进行了探讨。     

Biolumix微生物实时荧光光电检测系统：创新性的食源性微生物检测技术

近年来,国际、国内食品安全事件不断发生,人们越来越重视饮食安全。而由微生物引起的食源性疾病作为食品安全的主要问题也受到广泛关注。对食源性病原微生物的检测成为预防和控制食源性疾病的重要方面。针对目标微生物的有效检测,需要快速、敏感和特异的方法。传统培养方法虽具有较高的敏感性和特异性,但通常需要数天甚至一周以上的时间才能报告检测结果。因而对货架寿命较短的食品在产品卫生状况方面的评估作用不大,难以满足食品生产厂家、监管部门等方面的需求。     

单一菌种和混合菌种发酵对发酵火腿品质的影响

通过单一乳酸菌、乳酸菌和微球菌组成的混合发酵剂来发酵火腿,并探讨单一菌种和混合菌种对产品的pH、感官品质、色泽"a"和脂肪酸的影响。结果表明:单一菌种发酵火腿与混合菌种发酵火腿相比,它的pH变化快,感官品质不佳,颜色差,但脂肪酸变化基本相同。微球菌对发酵火腿的pH、感官品质、色泽影响较大,对脂肪影响较小。     

传统风吹肉加工过程中的微生物演替及优势菌群分析

研究传统风吹肉在整个生产过程的不同阶段中微生物的种类、优势菌群及其数量变化情况。选用7 种培养基对不同加工阶段风吹肉样品中的不同微生物进行分离纯化,并对其进行16S或18S rDNA分子生物学鉴定,鉴定得到加工过程存在于样品肉中的优势微生物9 种,其中细菌7 种和真菌2 种。结果表明：在传统风吹肉生产过程中,料泡引起微生物大量死亡后,风吹肉样品中的各类微生物总数在风吹前10 d持续上升,在中后期达到稳定。以乳酸乳球菌（Lactococcus lactis）为主的乳酸菌是川味风吹肉风吹过程中的主要优势菌群,其次是以巴氏葡萄球菌（Staphylococcus pasteuri）为主的葡萄球菌,汉逊德巴利酵母（Debaryomyces hansenii）和解脂耶氏酵母（Yarrowialipolytica）次之。此外,芽孢杆菌（Bacillus spp.）和水生拉恩菌（Rahnella aquatilis）为川味风吹肉制作过程中的主要腐败菌,但随着风吹过程显著减少。     

不同菌肥对土壤养分、酶活性和微生物功能多样性的影响

为了解不同菌肥对土壤养分和微生物功能的影响,通过田间试验,研究了配施不同菌肥后土壤养分、酶活性以及微生物功能多样性的变化。结果表明,配施菌肥显著增加了土壤有机碳、速效磷和速效钾的含量,其中以配施土著菌扩繁剂增加幅度最大,分别较对照提高了7.82%,39.19%和48.95%,但土壤碱解氮有小幅下降;土壤脲酶活性以配施土著菌扩繁剂最高,为1.03 mg/（g·24 h）,土壤蔗糖酶活性以配施生物有机肥最高,为70.96 mg/（g·24 h）。此外,配施菌肥均不同程度的提高了土壤微生物功能多样性以及呼吸速率。因此,配施菌肥不仅能显著提高土壤有机碳和速效养分含量,而且能够增加土壤微生物功能多样性以及酶活性,从而提高土壤的肥力。综合菌剂对养分、酶活性和微生物多样性来看,配施土著菌扩繁剂的效果最好。     

Microbial modeling in foods

Predictive food microbiology is a field of study that combines elements of microbiology, mathematics, and statistics to develop models that describe and predict the growth or decline of microbes under specified environmental conditions. Models can be thought of as having three levels: primary level models describe changes in microbial numbers with time, secondary level models show how the parameters of the primary model vary with environmental conditions, and the tertiary level combines the first two types of models with user‐friendly application software or expert systems that calculate microbial behavior under the specified conditions. Primary models include time‐to‐growth, Gompertz function, exponential growth rate, and inactivation/survival models. Commonly used secondary models are response surface equations and the square root and Arrhenius relationships. Microbial models are valuable tools in planning Hazard Analysis, Critical Control Point (HACCP) programs and making decisions, as they provide the first estimates of expected changes in microbial populations when exposed to a specific set of conditions. This review describes the models currently being developed for food‐borne microorganisms, particularly pathogens, and discusses their uses.