Enzyme precipitate coatings of glucose oxidase onto carbon paper for biofuel cell applications

Enzymatic biofuel cells (BFC) have a great potential as a small power source, but their practical applications are being hampered by short lifetime and low power density. This study describes the direct immobilization of glucose oxidase (GOx) onto the carbon paper in the form of highly stable and active enzyme precipitation coatings (EPCs), which can improve the lifetime and power density of BFCs. EPCs were fabricated directly onto the carbon paper via a three-step process: covalent attachment (CA), enzyme precipitation, and chemical crosslinking. GOx-immobilized carbon papers via the CA and EPC approaches were used as an enzyme anode and their electrochemical activities were tested under the BFC-operating mode. The BFCs with CA and EPC enzyme anodes produced the maximum power densities of 50 and 250 μW/cm(2) , respectively. The BFC with the EPC enzyme anode showed a stable current density output of >700 μA/cm(2) at 0.18 V under continuous operation for over 45 h. When a maple syrup was used as a fuel under ambient conditions, it also produced a stable current density of >10 μA/cm(2) at 0.18 V for over 25 h. It is anticipated that the direct immobilization of EPC on hierarchical-structured electrodes with a large surface area would further improve the power density of BFCs that can make their applications more feasible.     

Small-size biofuel cell on paper

In this work, we demonstrated a novel paper-based mediator-less and compartment-less biofuel cell (BFC) with small size (1.5 cm × 1.5 cm). Ionic liquid functionalized carbon nanotubes (CNTs-IL) nanocomposite was used as support for both stably confining the anodic biocatalyst (i.e., NAD(+)-dependent glucose dehydrogenase, GDH) for glucose electrooxidation and for facilitating direct electrochemistry of the cathodic biocatalyst (i.e., bilirubin oxidase, BOD) for O(2) electroreduction. Such BFC provided a simple approach to fabricate low-cost and portable power devices on small-size paper, which can harvest energy from a wide range of commercial beverages containing glucose (e.g., Nescafe instant coffee, Maidong vitamin water, Watermelon fresh juice, and Minute Maid grape juice). These made the low-cost paper-based biodevice potential for broad energy applications.     

'Non-destructive' biocomputing security system based on gas-controlled biofuel cell and potentially used for intelligent medical diagnostics

MOTIVATION: Biofuel cells (BFCs) based on enzymes and microbes are the promising future alternative sources of sustainable electrical energy under mild conditions (i.e. ambient temperature and neutral pH). By combining the adaptive behavior of BFCs self-regulating energy release with the versatility of biocomputing, we construct a novel gas-controlled biocomputing security system, which could be used as the potential implantable self-powered and 'smart' medical system with the logic diagnosis aim. RESULTS: We have demonstrated a biocomputing security system based on BFCs. Due to the unique 'RESET' reagent of N(2) applied in this work, the prepared biocomputing security system can be reset and cycled for a large number of times with no 'RESET' reagent-based 'waste'. This would be advantageous for the potential practical applications of such keypad lock as well as the development of biocomputing security devices. In order to validate the universality of the system and also to harvest energy directly from biofuels with enhanced power output, we replace the glucose with orange juice as the biofuel to operate BFCs-based biocomputing system, which also possesses the function of keypad lock. In addition, by introducing BFCs into the biocomputing security system, the adaptive behavior of the BFCs self-regulating the power release would be an immense advantage of such security keypad lock devices in potential self-powered implantable medical systems. The designed sequence gives the maximum power output and discriminate itself from the rest of the sequences. From this, we find that maximizing the dimensionless ratio of gap versus SD of the power output spectrum (a funnel in power outputs) gives the quantitative optimal design criterion. Therefore, our construction here may also provide a practical example and microscopic structural basis for mimicking the real biological network systems and bridge the gaps between the theoretical concepts and experiments important for biomolecular systems and synthetic biology.     

Glucose/O2 biofuel cell based on enzymes, redox mediators, and multiple-walled carbon nanotubes deposited by AC-electrophoresis then stabilized by electropolymerized polypyrrole

In this study, we developed an automated strategy to manufacture an enzyme BFC powered by glucose/O(2). The bioanode consists of GOx enzyme and PQQ redox mediator adsorbed over night on MWCNTs then deposited by means of AC-electrophoresis at 30 Hz and 160 V(p-p) and, finally stabilized by electropolymerized polypyrrole. The biocathode is constructed from LAc enzyme and ABTS redox mediator adsorbed over night on MWCNTs, then electrophoretically deposited under AC-electric field at 30 Hz and 160 V(p-p) and, finally stabilized by electrodeposited polypyrrole. The BFC was studied under air in phosphate buffer solution pH 7.4 containing 10 mM glucose and in human serum with 5 mM glucose addition at the physiological temperature of 37°C. Under these conditions, the maximum power density reaches 1.1 μW · mm(-2) at a cell voltage of 0.167 V in buffer solution and 0.69 μW · mm(-2) at cell voltage of 0.151 V in human serum. Such automated BFCs have a great potential to be optimized, miniaturized to micro and nanoscale devices suitable for in vivo studies.     

Application of an enzyme-based biofuel cell containing a bioelectrode modified with deoxyribonucleic acid-wrapped single-walled carbon nanotubes to serum

Enzyme-based biofuel cells (EFCs) are a form of biofuel cells (BFCs) that can utilize redox enzymes as biocatalysts. Applications of an EFC to an implantable system are evaluated under mild conditions, such as ambient temperature or neutral pH. In the present study, an EFC containing a bioelectrode modified with deoxyribonucleic acid (DNA)-wrapped single-walled carbon nanotubes (SWNTs) was applied to a serum system. The protection of immobilized glucose oxidase (GOD) using DNA-wrapped SWNTs was investigated in a trypsin environment, which can exist in a serum. GOD is immobilized by masking the active site onto the anode electrode. The anode/cathode system in the cell was composed of GOD/laccase as the biocatalysts and glucose/oxygen as the substrates in serum. The electrical properties of the anode in serum according to cyclic voltammetry (CV cycle) were improved using the DNA-wrapped SWNTs. Overall, an EFC that employed DNA-wrapped SWNTs and GOD immobilization in conjunction with protection of the active site increased the stability of GOD in serum, which enabled a high level of power production (ca. 190 μW/cm(2)) for up to 1 week.     

Inactivation of Escherichia coli and Shigella in acidic fruit and vegetable juices by peroxidase systems

AIMS: To study the bactericidal properties of the lactoperoxidase (LPER)-thiocyanate and soybean peroxidase (SBP)-thiocyanate systems at low pH, their efficiency for inactivation of Escherichia coli and Shigella in acidic fruit and vegetable juices, their effect on colour stability of the juices and interaction with ascorbic acid. METHODS AND RESULTS: Three-strain cocktails of E. coli and Shigella spp. in selected juices were supplemented with the LPER or SBP system. Within 24 h at 20 degrees C, the LPER system inactivated both cocktails by > or = 5 log10 units in apple, 2-5 log10 units in orange and < or = 1 log10 unit in tomato juices. In the presence of SBP, browning was significant in apple juice and white grape juice, slight in pink grape juice and absent in orange or tomato juice. Ascorbic acid protected E. coli and Shigella against inactivation by the LPER system, and peroxidase systems significantly reduced the ascorbic acid content of juices. CONCLUSIONS: Our results suggest a different specificity of LPER and SBP for SCN-, phenolic substrates of browning and ascorbic acid in acidic juices. The LPER system appeared a more appropriate candidate than the SBP system for biopreservation of juices. SIGNIFICANCE AND IMPACT OF THE STUDY: This work may open perspectives towards the development of LPER or other peroxidases as biopreservatives in acidic foods.     

犬蝠对不同浓度香蕉汁的选择

为了解犬蝠的嗅觉灵敏度,我们以6 只成年犬蝠对不同浓度的成熟香蕉汁和纯水对照的选择倾向和取食时间各进行了连续5 个夜晚的室内观察。香蕉汁的浓度分别为100% (120 g),50% (60 g 香蕉汁和60 g 纯水),25% (30 g 香蕉汁和90 g 纯水),12. 5% (15 g 香蕉汁和105 g 纯水);另取纯水(W)与熟烂的香蕉汁(OR)各120 g 作为对照。将以上食物和对照随机注入不同的容器内,观察犬蝠对不同浓度的香蕉汁、熟烂香蕉汁和纯水的选择。结果表明,犬蝠对纯成熟香蕉汁的选择性最强,取食次数和取食量均最高,而停留时间也最长;说明犬蝠具有分辨不同浓度的气味差异。我们推测犬蝠在野外觅食时可能优先取食成熟水果。     

Trophic relationships between Saccharomyces cerevisiae and Lactobacillus plantarum and their metabolism of glucose and citrate

Glucose and citrate are two major carbon sources in fruits or fruit juices such as orange juice. Their metabolism and the microorganisms involved in their degradation were studied by inoculating with an aliquot of fermented orange juice a synthetic model medium containing glucose and citrate. At pH 3.6, their degradation led, first, to the formation of ethanol due to the activity of yeasts fermenting glucose and, eventually, to the formation of acetate resulting from the activity of lactobacilli. The yeast population always outcompeted the lactobacilli even when the fermented orange juice used as inoculum was mixed with fermented beet leaves containing a wider variety of lactic acid bacteria. The evolution of the medium remained similar between pH 3.3 and 5.0. At pH 3.0 or below, the fermentation of citrate was totally inhibited. Saccharomyces cerevisiae and Lactobacillus plantarum were identified as the only dominant microorganisms. The evolution of the model medium with the complex microbial community was successfully reconstituted with a defined coculture of S. cerevisiae and L. plantarum. The study of the fermentation of the defined model medium with a reconstituted microbial community allows us to better understand the behavior not only of fermented orange juice but also of many other fruit fermentations utilized for the production of alcoholic beverages.     

Trophic relationships between Saccharomyces cerevisiae and Lactobacillus plantarum and their metabolism of glucose and citrate.

Glucose and citrate are two major carbon sources in fruits or fruit juices such as orange juice. Their metabolism and the microorganisms involved in their degradation were studied by inoculating with an aliquot of fermented orange juice a synthetic model medium containing glucose and citrate. At pH 3.6, their degradation led, first, to the formation of ethanol due to the activity of yeasts fermenting glucose and, eventually, to the formation of acetate resulting from the activity of lactobacilli. The yeast population always outcompeted the lactobacilli even when the fermented orange juice used as inoculum was mixed with fermented beet leaves containing a wider variety of lactic acid bacteria. The evolution of the medium remained similar between pH 3.3 and 5.0. At pH 3.0 or below, the fermentation of citrate was totally inhibited. Saccharomyces cerevisiae and Lactobacillus plantarum were identified as the only dominant microorganisms. The evolution of the model medium with the complex microbial community was successfully reconstituted with a defined coculture of S. cerevisiae and L. plantarum. The study of the fermentation of the defined model medium with a reconstituted microbial community allows us to better understand the behavior not only of fermented orange juice but also of many other fruit fermentations utilized for the production of alcoholic beverages.     

植物果实、颜色和形状对橘小实蝇产卵选择的影响

橘小实蝇Bactrocera dorsalis(Hendel)是近几年入侵江苏南部地区,严重危害当地水果、蔬菜的重要害虫。为深入了解其在该地区果树、蔬菜上的产卵特性,进行植物果实、颜色和形状对其产卵选择影响的研究。实验室中"纸杯法"的产卵选择试验结果表明,橘小实蝇对不同水果的产卵偏好性由高到低依次为:柑橘、香蕉、芒果、枣、石榴、苹果、桃子、梨、李、葡萄、柿;对不同蔬菜的产卵偏好性由高到低依次为:丝瓜、豇豆、苦瓜、黄瓜、茄子、南瓜、青椒、番茄。对不同寄主颜色和形状的产卵选择特点为,雌虫常选择桔黄色、绿色,以及圆球形的寄主产卵,而较少选择黑色、方形的寄主产卵。从试验结果可以看出,寄主果实散发出的气味,及其颜色和形状对橘小实蝇的产卵选择有影响。     

High-performance bioanode based on the composite of CNTs-immobilized mediator and silk film-immobilized glucose oxidase for glucose/O2 biofuel cells

A high-performance bioanode based on the composite of carbon nanotubes (CNTs)-immobilized mediator and silk film (SF)-immobilized glucose oxidase (GOD) was developed for glucose/O(2) biofuel cell (BFC). Ferrocenecarboxaldehyde (Fc) was used as the mediator and covalently immobilized on the ethylenediamine (EDA)-functionalized CNTs (CNTs-EDA). GOD was cross-linked on the SF with glutaraldehyde (GA) as the cross-linking agent. The resulting electrode (CNTs-Fc/SF-GOD/glassy carbon (GC) electrode) exhibited good catalytic activity towards glucose oxidation and excellent stability. For the assembled glucose/O(2) BFC with the CNTs-Fc/SF-GOD/GC electrode as the bioanode and a commercial E-TEK Pt/C modified GC electrode as the cathode, the open circuit potential is 0.48 V and the maximum power density of 50.70 μW cm(-2) can be achieved at 0.15 V.     

Evaluation of baits for trapping of Neotropical flower chafer beetles (Coleoptera: Scarabaeoidea: Cetoniinae)

The lack of a standardized protocol to efficiently capture flower chafer beetles (Coleoptera: Scarabaeoidea: Cetoniinae) in the wild limits studies regarding the ecology of the group, as well as systematic collections seeking species surveys for taxonomic studies, especially in the Neotropical region. We investigate the efficiency of different baits to capture flower chafer beetles in the Brazilian Cerrado: (i) banana; (ii) banana + sugarcane juice; (iii) pineapple; (iv) pineapple + sugarcane juice; (v) sugarcane juice; or (vi) water (control). From January to December 2014, we sampled these beetles using a typical aerial fruit‐baited trap, every 15 days in ten sites of Brazilian Cerrado, in Aquidauana, Mato Grosso do Sul, Brazil. Traps baited with banana + sugarcane juice, pineapple + sugarcane juice and sugarcane juice alone sampled the greatest species richness and abundance of flower chafer beetles when compared to the other baits used. Our results indicated the importance of sugarcane juice, either used in isolation or as a coadjutant in the fermentation process of the tested fruits for efficient sampling of flower chafer beetle biodiversity. Finally, studies that investigate the addition of other substances in the fermentation process of the fruits, as well as the attractiveness of other native or exotic fruits that are widely distributed in the Neotropical region, can advance our knowledge of sampling of these beetles.     

Photoautotrophic cathodic oxygen reduction catalyzed by a green alga,Chlamydomonas reinhardtii

Biofuel cells (BFCs) use enzymes and microbial cells to produce energy from bioavailable substrates and treat various wastewaters, and cathodic oxygen reduction is a key factor governing the efficiency of BFCs. In this study, we demonstrated that a green alga, Chlamydomonas reinhardtii, could directly mediate oxygen reduction. Cyclic voltammogram analysis revealed that the C. reinhardtii biofilm formed on a solid electrode was responsible for oxygen reduction without dosing of electron mediator. Furthermore, 4‐electron oxygen reduction pathway was found in this self‐sustained, light‐responded BFC. The results of this study could expand our understanding and viewpoints of biocathode catalysis, which is essential for novel catalyst design and development for BFCs. Biotechnol. Bioeng. 2013; 110: 173–179. © 2012 Wiley Periodicals, Inc.     

Synergistic and additive interactions among components of food-based baits underlie female fruit fly attraction

Attraction of tephritid fruit flies to some food sources can be enhanced by the presence of ammonia derivatives, compounds that are perceived as volatile cues for protein-rich food sources. Using a comparative approach, we (1) evaluated the behavioral responses of females of three invasive fruit fly species, Bactrocera (Zeugodacus) cucurbitae (Coquillett), Bactrocera dorsalis (Hendel), and Ceratitis capitata (Wiedemann) (all Diptera: Tephritidae) to trub (a protein-rich waste brewer’s yeast product generated during the production of beer), Concord grape juice (a protein-deficient material), and ammonium acetate, and (2) identified synergistic and additive interactions between low- and high-attractiveness materials and ammonium acetate. We established the attractiveness of fresh trub, grape juice, and ammonium acetate when tested singly to females of all three fly species. Although ammonium acetate did not enhance significantly the response of females of any species to fresh trub, the most attractive material, ammonium acetate, did significantly enhance females’ level of response to aged trub (a comparatively less attractive material) and to grape juice. Our research found a synergistic interaction between diluted grape juice and ammonium acetate for B. cucurbitae, as well as between aged trub and ammonium acetate for B. dorsalis. For C. capitata, additive effects among food attractants and ammonium acetate were identified. Our findings increase our understanding of fruit fly female olfactory-driven behavior in response to food-based materials and the extent to which ammonium acetate modulates female response to protein-rich and protein-deficient materials.     

Methods for the detection and enumeration of Alicyclobacillus acidoterrestris and investigation of growth and production of taint in fruit juice and fruit juice-containing drinks

Methods for the detection of Alicyclobacillus acidoterrestris at a level of 1 cell per 100 ml and enumeration with a sensitivity of 5 cells ml⁻¹ were developed. Spores of A. acidoterrestris survived pasteurization and outgrew and multiplied at a similar rate to vegetative cells in both orange juice and apple juice. Alicyclobacillus acidoterrestris grew readily in orange juice, apple juice and a non-carbonated fruit juice-containing drink at temperatures of 25–44°C producing a taint and elevated levels (1–100 ppb) of guaiacol. Isolates of A. acidoterrestris can be identified using the DuPont RiboPrinter. It was isolated from apple drinks, apple juice concentrate and freshly squeezed orange juice.     

Detection of citrus yellow mosaic virus by PCR and nucleic acid spot hybridisation using non-radioactive probes in commercial citrus species

Citrus yellow mosaic virus (CYMV) was detected by polymerase chain reaction (PCR) in leaf samples of sweet orange, Rangpurlime, Pumello pink and acid lime and also in twig bark, fruit rind, fruit juice except fruit rag of sweet orange cv. Sathgudi, where all the positive samples showed bright amplification of the 726 bp band except in fruit rind. The CYMV could be detected by the biotin labelled probe of CYMV up to 1:100 dilutions by TE and TNE extraction methods in sweet orange cv. Sathgudi as well as Rangpurlime.     

Electrically Contacted Bienzyme‐Functionalized Mesoporous Carbon Nanoparticle Electrodes: Applications for the Development of Dual Amperometric Biosensors and Multifuel‐Driven Biofuel Cells

The capping of electron relay units in mesoporous carbon nanoparticles (MPC NPs) by crosslinking of different enzymes on MPC NPs matrices leads to integrated electrically contacted bienzyme electrodes acting as dual biosensors or as functional bienzyme anodes and cathodes for biofuel cells. The capping of ferrocene methanol and methylene blue in MPC NPs by the crosslinking of glucose oxidase (GOx) and horseradish peroxidase (HRP) yields a functional sensing electrode for both glucose and H₂O₂, which also acts as a bienzyme cascaded system for the indirect detection of glucose. A MPC NP matrix, loaded with ferrocene methanol and capped by GOx/lactate oxidase (LOx), is implemented for the oxidation and detection of both glucose and lactate. Similarly, MPC NPs, loaded with 2,2′‐azino‐bis(3‐ethylbenzo­thiazoline‐6‐sulphonic acid), are capped with bilirubin oxidase (BOD) and catalase (Cat), to yield a bienzyme O₂ reduction cathode. A biofuel cell that uses the bienzyme GOx/LOx anode and the BOD/Cat cathode, glucose and/or lactate as fuels, and O₂ and/or H₂O₂ as oxidizers is assembled, revealing a power efficiency of ≈90 μW cm^?2 in the presence of the two fuels. The study demonstrates that multienzyme MPC NP electrodes may improve the performance of biofuel cells by oxidizing mixtures of fuels in biomass.     

Comparative bioelectrochemical analysis of Pseudomonas aeruginosa and Escherichia coli with anaerobic consortia as anodic biocatalyst for biofuel cell application

Aims: To study the bioelectrochemical behaviour of Pseudomonas aeruginosa (MTCC 17702) and Escherichia coli (MTCC 10436) and to assess their potential to act as anodic biocatalyst with the function of anaerobic consortia for microbial (bio) fuel cell (BFC) application. Methods and Results: Three BFCs (single chamber; open‐air cathode; noncatalysed electrodes) were operated simultaneously in acidophilic microenvironments. Pseudomonas aeruginosa (BFC_P) showed higher current density (264 mA m^?2) followed by mixed culture (BFC_M; 166 mA m^?2) and E. coli (BFC_E; 147 mA m^?2). However, total operating period and substrate degradation were relatively found to be effective with mixed culture (58%; 72 h) followed by BFC_P (39%; 60 h) and BFC_E (31%; 48 h). Higher electron discharge (ED) was observed with Ps. aeruginosa while mixed culture showed the involvement of redox mediators in the ED process. Conclusions: Mixed culture showed to sustain biopotential for longer periods along with a stable ED. The presence of redox signals and high substrate degradation was also evidencing its performance compared to the pure strains studied. This supports the practical utility of mixed culture over the pure cultures for real‐field BFC applications especially while operating with wastewater. Significance and Impact of the Study: This study revealed the efficiency and viability of mixed consortia in comparison with pure strains for microbial (bio) fuel cell applications.     

Amounts and variation in grapefruit juice of the main components causing grapefruit–drug interaction

A method for the determination of three furocoumarins containing two new chemicals (GF-I-1 and GF-I-4) in commercially available grapefruit juice and grapefruit itself was developed using high-performance liquid chromatography (HPLC). These components isolated from grapefruit juice have 5-geranyloxyfurocoumarin dimer structures showing extremely high affinities for a form of cytochrome P450 (CYP3A4). Considerable differences were observed on the contents among commercial brands and also batches. The contents were determined to be 321.4±95.2 ng/ml GF-I-1, 5641.2±1538.1 ng/ml GF-I-2 and 296.3±84.9 ng/ml GF-I-4 in twenty-eight white grapefruit juices. These chemicals were not detected in beverages from orange, apple, grape and tangerine, except that trace amount of GF-I-2 and GF-I-4 were found in lemon juice. The average levels of these furocoumarins were lower in the juice from red grapefruit than a white one. The highest level of these components were found in the fruit meat.     

Maximizing power production in a stack of microbial fuel cells using multiunit optimization method

This study demonstrates real‐time maximization of power production in a stack of two continuous flow microbial fuel cells (MFCs). To maximize power output, external resistances of two air–cathode membraneless MFCs were controlled by a multiunit optimization algorithm. Multiunit optimization is a recently proposed method that uses multiple similar units to optimize process performance. The experiment demonstrated fast convergence toward optimal external resistance and algorithm stability during external perturbations (e.g., temperature variations). Rate of the algorithm convergence was much faster than in traditional maximum power point tracking algorithms (MPPT), which are based on temporal perturbations. A power output of 81–84 mW/L_A (A = anode volume) was achieved in each MFC. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009