Microbial fuel cell-based biosensor for redox potential detection in fermentation process

Currently, fermentation research's primary objective is to develop economic and sustainable processes by increasing the product yield and reducing the operating cost. A tremendous effort had been made in the past few decades by discovering and developing various fermentative strains. The fermentation process measurement, control, and supervision are the next battlefield for further fermentation technology development. Fermentation manipulation is a complex process from both biological and engineering points of view. Different factors, including substrates type, substrates concentration, strain type, and operating modes, need to be taken into account. These aspects encourage the scientific community to find a robust, sophisticated, and versatile measure for controlling fermentation. Redox potential, also known as the oxidation-reduction potential (ORP), reflects the overall biochemical reactions, electron transfer, and redox balance within the fermentation broth. The biological significance of ORP includes indirectly explicating metabolic activities during fermentation and regulating the metabolic network, affecting the metabolic pathway and gene expression. The monitoring and controlling environmental ORP provides a thoughtful understanding to help control the intracellular metabolic activities and fermentation process. This approach has been proven and considered as a real-time approach to increase fermentation efficiency in scientific communities and industrial sectors. In particular, the ORP measurement can provide an online and consistent signal during fermentation. It can be used at any stage of fermentation, providing both high signal-integrity and measurement reliability. Although effective, the relatively high fabrication cost of these sensors has so far made it impractical for extensive applications in large-scale contaminated soil monitoring, in particular. Cost-effectiveness is an endless effort in engineering, an economically optimized ORP monitor tool is urgently needed. With the development of bio-electrochemical research, the microbial fuel cell (MFC) as an old technology has been adopted as a biosensor to produce power and electricity by bacteria catalyzation. In this work, an MFC-based biosensor device was designed and developed as a fermentation biosensor using an indigenous microorganism and modified Nernst equation to integrate among the MFC voltage output, fermentation ORP, and fermentation stages. This study investigated different factors on the performance of an MFC-based biosensor. These factors include strain types (Bacillus subtilis and Pseudomonas fluorescens) in the presence or absence of methylene blue mediator, cathodic treatments (sparging, aerated cathode, and potassium ferricyanide solution), and anodic aeration rates (0, 11.32, and 22.64 vvm). After optimal conditions were established, this study used turbidimetric measurement as the indicator for microbial growth. The correlational between microbial growth and ORP, voltage, potential parameter (X) were investigated. Results showed that B. subtilis exhibited superior performance under MFC condition. Sparging cathodic treatment provided a feasible and sustainable supply of electron acceptor. Keeping anodic aeration rate at 11.32 vvm constructed a suitable anodic environment not only to support B. subtilis growth but also to sustain the voltage generation from MFC device. After all conditions had been settled, the voltage signal was projected to a linear increase, and the ORP signal was likely to generate a bathtub-shaped curve. Two peaks occurred on the curve by integrating both signals into the potential parameter X and plotting the potential parameter X over time. Three distinct growth phases were revealed by comparing the potential parameter X with microbial growth information and ORP profile. Potential parameter X indicated the endpoint of lag phase, mid-point of exponential phase, and the starting point of stationary phase. Such a result proved that the potential parameters could provide fruitful and high-resolution information that enables precious and real-time fermentation monitoring and controlling. To conclude, this thesis demonstrated the development of a novel fermentation biosensor by utilizing an MFC device as a biosensor. By applying the unitless parameter (i.e., potential parameter) derived from the modified Nernst equation, an MFC device equipped with an ORP sensor could successfully unveil the hidden internal information during the course of fermentation and explicate microbial growth dynamics. Although successful, many questions were also raised during the course of this research. One main limiting factor the choice of the microorganism. In this research, Bacillus subtilis was selected as it could generate extracellular electrons which then pick up by the carbon electrode in anodic chamber, resulting in voltage flow. When different microbes were chosen, one needs to investigate whether such a microbial strain could export electron in MFC device. If not, one could attempt to supplement electron mediator to assist electron movement from microbial surface to carbon electron. The operating condition for this developed device needs to be optimized as different strains possess different growth requirements

Screening and Ranking Methodology Applied to Biochars Aimed at Acidic and Calcareous Sandy Soil Improvement

The application of biochar (the by-product of biomass pyrolysis), as a soil amendment has been accepted as a sustainable solution to improve soil quality. The current study aims to establish a decision support tool for characterizing, ranking, and selecting biochars of different origins for soil improvement, thereby contributing to the development of a systematic approach, which lacks in the existing literature.The development of a Multi-Criteria Decision Support Approach applying a banded and weighted rating and scoring system allowed the selection and ranking of various biochars suitable for improving sandy soils before application. First, 14 selected, different biochar products (produced from industrial by-products, herbaceous, wood-based and manure-based feedstocks) were characterized with several physicochemical, biological and ecotoxicological methods taking into account both the technological and the environmental efficiency aspects of biochar utilization. Then, a system for the assessment and ranking of biochars for acidic, and calcareous neutral sandy soil improvement was developed, which could be flexibly adapted to different soil problems as well. Based on their performance in the tests, scores from (−5) to (+5) were assigned to each biochar. As a result, the grain husks and paper fiber sludge biochar was ranked as the most suitable for both acidic and neutral calcareous sandy soil improvement, with 55 and 43 scores, respectively (from the maximum 100). The applicability of this innovative multicriteria scoring-ranking system, as a tool for potential biochar users, was verified in microcosms and field-scale experiments, demonstrating the positive influence of this biochar on the acidic sandy soil

Recirculating sand filter design and operating criteria for removal of nitrogen from domestic septic tank effluent

A physical model of a recirculating sand filter (RSF) system was constructed to determine the ability of the system to remove nitrogen from domestic septic tank effluent and to learn the effects on the removal ability of the specific operating parameters depth of sand, recirculation ratio, loading rate. The RSF system model consisted of a sand filter reactor, denitrification chamber reactor, and a polishing sand filter reactor. A research investigation was conducted with the help of twelve model units in which domestic septic tank effluent was treated on a continuous basis. Then, optimum and appropriate combinations of operating parameters were found and the systems were evaluated on the ability to remove mineral nitrogen, TOC, coliform and streptococcus bacteria. To measure RSF system performance, water quality samples were collected weekly from the effluent of the three reactors and analyzed for concentration of several quality parameters. The samples collected were analyzed for concentrations of NH3-N, NOx--N, TOC, and bacteria in the form of total coliform, fecal coliform, and streptococcus populations. The research model units were successful in achieving biological treatment of domestic septic tank effluent. Prediction equations developed from model system data indicated that maximum mineral nitrogen removal for circulation factors (R) of 4 and 6, should be 73.69% at a sand bed depth of 16.50 cm and a wastewater loading rate of 40. 74 cm/day. Results revealed that an increase in circulation factor (R) from 4 to 6 produced no significant impact on the overall system mineral nitrogen removal efficiency. In the recirculating sand filter reactor system, TOC removal responded significantly to variations in R value. For an R factor of 6, a maximum TOC removal efficiency of 80.70% at a sand depth of 17.00 cm and loading rate of 22.92 cm/day can be expected. The reduction of bacterial count in the RSF system model was in the order of 99%. The investigation showed that redox potential and NO3--N concentration have a definite relationship. An estimate of the obtainable maximum NO3--N concentration can be predicted by measuring the redox potential in the DNC water. Measurements of redox potential below -150 mV gave indication of excellent denitrification potential with very high removal efficiency

Program and the Book of Abstracts / Fifteenth Young Researchers' Conference Materials Sciences and Engineering, December 7-9, 2016, Belgrade

Young Researchers' meetings are held annually late in December since 2002 and they are organized by the Materials Research Society of Serbia. Originally conceived as seminars, since 2007 these meetings were transformed into conferences. The previous eleven meetings featured presentations based on the research of various young scientists from Serbia, Bosnia and Herzegovina, Montenegro, Slovenia, Brazil, Germany, United States of America, China, Poland, Belgium, Spain, Romania, United Kingdom, Austria, Italy, Hungary, Russia, Canada, etc. At the Conference, young researchers, students of doctoral, master and undergraduate studies, are given the opportunity to make an overview of their research into materials science and engineering through oral and poster presentations. As for the scientific content of the conference, we have given full priority to research topics that are currently considered as being on the frontier of the field. Nanotechnology and Advanced Materials, Synthesis and Engineering of Biomaterials, Application of Biomaterials, Theoretical Modeling of Materials and Advanced Methods for Synthesis and Processing present only some of those exciting topics that will be given the central stage and most attention during this meeting. The 15th Young Researchers' Conference Materials Science and Engineering was held in Belgrade, Serbia on December 7-9, 2016, Belgrade, Serbia. It was organized by the Materials Research Society of Serbia and Institute of Technical Sciences of the Serbian Academy of Sciences and Arts

Specialization and trade-offs in plant-feeding insects

The immense diversity of life on Earth has been attributed to the partitioning of available resources into ecological niches, but it is not obvious what determines the niche size of each species. For example, most plant-feeding insects consume only one or a few closely-related host-plant species despite the advantages of having a broader diet. Many researchers have therefore suggested that the evolution of broad diets in plant-feeding insects must be constrained by genetic trade-offs between adaptations to alternative host-plants. Despite its intuitive feel, however, little empirical evidence in support of the trade-off hypothesis has emerged from decades of experimental studies comparing individual performance on alternative hosts within insect populations. Here I use a broader approach to evaluate the role of trade-offs in driving ecological specialization in plant-feeding insects. By collecting host-use data for thousands of insect species and fitting those data into long-term evolutionary models, I investigate whether trade-off constraints have left observable signatures in the present ecological niches of existing species. Chapter 1 focuses on a single family of insects, the armored scales (Hempitera: Diaspididae), revealing that positive correlations between evolutionary changes in host performance best fit the observed patterns of diaspidid presence and absence on nearly all focal host taxa, suggesting that adaptations to particular hosts enhance rather than reduce performance on other hosts. In chapter 2, I uncovered a complex network of evolutionary interactions between caterpillar adaptations to eleven host-plant orders, indicating that different host-use trade-offs act over long- and short-term evolutionary timescales. In contrast, host-use patterns of true bugs revealed a total lack of trade-offs for the same host-plant orders over both timescales. Chapter 3 turns to armored scale insects again, this time those that we collected in systematic surveys across a large diversity of trees in two tropical rainforest habitats. Using each insect species’ abundance on each tree as a proxy for host-plant performance, we found no evidence for performance trade-offs on alternative hosts despite apparent host-use specialization. Overall, these results suggest that the extreme specialization of plant-feeding insects arises from long-term, potentially nonadaptive evolutionary processes rather than simple genetic trade-offs

Conference on Planetary Volatiles

Initial and present volatile inventories and distributions in the Earth, other planets, meteorites, and comets; observational evidence on the time history of volatile transfer among reservoirs; and volatiles in planetary bodies, their mechanisms of transport, and their relation to thermal, chemical, geological and biological evolution are addressed

Digest of Russian Space Life Sciences, issue 33

This is the thirty-third issue of NASA's USSR Space Life Sciences Digest. It contains abstracts of 55 papers published in Russian journals. The abstracts in this issue have been identified as relevant to the following areas of space biology and medicine: biological rhythms, body fluids, botany, cardiovascular and respiratory systems, developmental biology, endocrinology, equipment and instrumentation, gastrointestinal system, genetics, hematology, human performance, metabolism, microbiology, musculoskeletal system, neurophysiology, nutrition, operational medicine, psychology, radiobiology, and reproductive system

Preassembled GPCR signaling complexes mediate distinct cellular responses to ultralow ligand concentrations

G protein–coupled receptors (GPCRs) are the largest class of cell surface signaling proteins, participate in nearly all physiological processes, and are the targets of 30% of marketed drugs. Typically, nanomolar to micromolar concentrations of ligand are used to activate GPCRs in experimental systems. We detected GPCR responses to a wide range of ligand concentrations, from attomolar to millimolar, by measuring GPCR-stimulated production of cyclic adenosine monophosphate (cAMP) with high spatial and temporal resolution. Mathematical modeling showed that femtomolar concentrations of ligand activated, on average, 40% of the cells in a population provided that a cell was activated by one to two binding events. Furthermore, activation of the endogenous β2-adrenergic receptor (β2AR) and muscarinic acetylcholine M3 receptor (M3R) by femtomolar concentrations of ligand in cell lines and human cardiac fibroblasts caused sustained increases in nuclear translocation of extracellular signal–regulated kinase (ERK) and cytosolic protein kinase C (PKC) activity, respectively. These responses were spatially and temporally distinct from those that occurred in response to higher concentrations of ligand and resulted in a distinct cellular proteomic profile. This highly sensitive signaling depended on the GPCRs forming preassembled, higher-order signaling complexes at the plasma membrane. Recognizing that GPCRs respond to ultralow concentrations of neurotransmitters and hormones challenges established paradigms of drug action and provides a previously unappreciated aspect of GPCR activation that is quite distinct from that typically observed with higher ligand concentrations

Reliability analysis for subsea pipeline cathodic protection systems /

Subsea pipelines, as the main transportation means for oil and gas produced offshore, are a key element of the production system. Cathodic protection systems (CPS) are used in combination with surface coatings to protect the pipeline from external corrosion. Although cases of pipeline failure due to external corrosion remain rare, such failures can have catastrophic effects in terms of human lives, environment degradation and financial losses. The offshore industry was led to the use of risk analysis techniques subsequent to major disasters, such as Piper Alpha and Alexander Kjelland. These accidents made the development and use of risk analysis techniques of highly significant interest, and reliability analysis is presently becoming a more important management tool in that field for determining reliability of components such as pipelines, subsea valves and offshore structures. This research is based on an analysis of subsea pipeline cathodic protection systems and on a model of the electrochemical potentials at the pipeline surface. This potential model uses finite element modelling techniques, and integrates probabilistic modules for taking into account uncertainties on input parameters. Uncertainties are used to calculate standard deviations on the potential values. Based on the potentials and potential variances obtained, several parameters characteristic of the cathodic protection system reliability, such as probability of failure and time to failure, are calculated. The model developed proved suitable for simulating any pipeline, under any environmental and operational conditions. It was used as a reliability prediction tool, and to assess the effects of some parameters on the cathodic protection system reliability