• Journal of Electrochemical Science and Technology
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• v.12 no.3
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• pp.297-301
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• 2021

Microbial fuel cells (MFCs) convert chemical energy to electrical energy via electrochemically active microorganisms. The interactions between microbes and the surface of a carbon electrode play a vital role in capturing the respiratory electrons from bacteria. Therefore, improvements in the electrochemical and physicochemical properties of carbon materials are essential for increasing performance. In this study, a microwave and sulfuric acid treatment was used to modify the surface structure of graphite granules. The prepared expandable graphite granules (EGG) exhibited a 1.5 times higher power density than the unmodified graphite granules (1400 vs. 900 mW/m³). Scanning electron microscopy and Fourier transform infrared spectroscopy revealed improved physical and chemical characteristics of the EGG surface. These results suggest that physical and chemical surface modification using sulfuric acid and microwave heating improves the performance of electrode-based bioprocesses, such as MFCs.

• Environmental Engineering Research
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• v.25 no.1
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• pp.80-87
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• 2020

Landfill waste decomposition generates a dark effluent named, leachate which is characterized by high organic matter content. To minimize these polluting effects, it becomes necessary to develop an effective landfill leachate treatment process. The objective of this study was to evaluate the performance of an innovative approach based on air stripping, anaerobic digestion (AD) and aerobic activated sludge treatment. A reduction of 80% of ammonia and an increase of carbon to nitrogen ratio to 25 were obtained, which is a suitable ratio for AD. This latter AD was performed in fixed bed reactor with progressive loading rate that reached 2 and 3.2 g COD/L/d for the raw and diluted leachate (1:2), respectively. The anaerobic treatment led to significant removal of chemical oxygen demand (COD) and biogas production, especially for the diluted leachate. The COD removal was of 78% for the raw leachate and a biogas production of 4 L/d with 70% methane content. The use of the diluted leachate led to 81% of COD removal and 7 L/d biogas with 75% methane content. It allowed a removal of 77% COD and more than 97% of the organic compounds present in the initial leachate sample.

• KSBB Journal
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• v.29 no.4
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• pp.225-231
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• 2014

A microbial fuel cell (MFC) and bioelectrochemical systems are novel bioprocesses which employ exoelectrogenic biofilm on electrode as a biocatalyst for electricity generation and various useful chemical production. Previous reports show that electrogenic biofilms of MFCs are time varying systems and dynamically interactive with the electrically conductive media (carbon paper as terminal electron acceptor). It has been reported that maximum power point tracking (MPPT) method can automatically control load by algorithm so that increase power generation and columbic efficiency. In this study, we developed logic based control strategy for external load resistance by using $LabVIEW^{TM}$ which increases the power production with using flat-plate MFCs and MPPT circuit board. The flat-plate MFCs inoculated with anaerobic digester sludge were stabilized with fixed external resistance from $1000{\Omega}$ to $100{\Omega}$. Automatic load control with MPPT started load from $52{\Omega}$ during 120 hours of operation. MPPT control strategy increased approximately 2.7 times of power production and power density (1.95 mW and $13.02mW/m^3$) compared to the initial values before application of MPPT (0.72 mW and $4.79mW/m^3$).

• Environmental Engineering Research
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• v.24 no.1
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• pp.144-149
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• 2019

Landfill leachate constitutes one of the most polluting wastewaters. Their treatment was considered difficult due to the presence of high concentration of organic matter, ammonia, toxic organic compounds and heavy metals. Biological processes were found to be effective in several cases, but they are limited by the presence of inhibitory compounds in leachate. In this study we develop a biological process for the leachate biodetoxification using Trametes trogii (T. trogii; CLBE55). Results show that laccase activity, mycelia growth and chemical oxygen demand (COD) removal efficiencies varied depending on the leachate and ammonium concentration. Indeed T. trogii was able to grow in the presence of low concentration of landfill leachate of 10 and 30%. In fact, the biomass produced was 4.7 and 3.7 g/L, respectively leading to a COD removal of 66 and 53%, respectively. However, when the concentration of the introduced leachate exceeds 30%, the treatment efficiency and particularly the COD removal decreases to reach 15% at 100% leachate. The effect of the ammonia was also studied and results showed that the addition of 5 g/L of ammonia inhibited totally the production of laccase and the COD removal.

• Journal of Microbiology and Biotechnology
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• v.21 no.2
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• pp.204-211
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• 2011

To yield high concentrations of protein expressed by genetically modified Escherichia coli, it is important that the bacterial strains are cultivated to high cell density in industrial bioprocesses. Since the expressed target protein is mostly accumulated inside the E. coli cells, the cellular product formation can be directly correlated to the bacterial biomass concentration. The typical way to determine this concentration is to sample offline. Such manual sampling, however, wastes time and is not efficient for acquiring direct feedback to control a fedbatch fermentation. An E. coli K12-derived strain was cultivated to high cell density in a pressurized stirred bioreactor on a pilot scale, by detecting biomass concentration online using a capacitance probe. This E. coli strain was grown in pure minimal medium using two carbon sources (glucose and glycerol). By applying exponential feeding profiles corresponding to a constant specific growth rate, the E. coli culture grew under carbon-limited conditions to minimize overflow metabolites. A high linearity was found between capacitance and biomass concentration, whereby up to 85 g/L dry cell weight was measured. To validate the viability of the culture, the oxygen transfer rate (OTR) was determined online, yielding maximum values of 0.69 mol/l/h and 0.98mol/l/h by using glucose and glycerol as carbon sources, respectively. Consequently, online monitoring of biomass using a capacitance probe provides direct and fast information about the viable E. coli biomass generated under aerobic fermentation conditions at elevated headspace pressures.

• KSBB Journal
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• v.29 no.3
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• pp.155-164
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• 2014

Succinic acid, a representative biomass-derived platform chemical, is a major fermentation product of Actinobacillus succinogenes. It is well known that carbon dioxide is consumed during the succinate fermentation, but the biochemical mechanism behind this phenomenon is not yet understood well. In this study, it was found that the addition of carbonic anhydrase (CA)s into media significantly enhances the succinic acid production by A. succinogenes during the fermentation supplied with carbon dioxide. It is likely that the (bi) carbonate produced by the CA activity from gaseous carbon dioxide is favoured by A. succinogenes for consumption and utilization. Therefore, the $MgCO_3$ requirement could be significantly reduced without compromising the succinate productivity. Furthermore, because of too high price of the commercial carbonic anhydrase, it was undertaken to economically overproduce a cyanobacterial carbonic anhydrase by the use of a recombinant Pichia pastoris. An expression vector system was constructed with the carbonic anhydrase gene PCR-cloned from Cyanobacterium Synechocystis sp., and introduced into P. pastoris for fermentation studies. About 95.9 g/L of succinic acid was produced in the production medium with 30 ppm of carbonic anhydrase, approximately 2 fold higher productivity compared to the parallel process with no supplementation of the enzyme. It is expected that this method can provide a valuable way of overcoming inefficiencies inherent in gas supply during $CO_2$-based bioprocesses like succinic acid fermentation.

• KSBB Journal
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• v.14 no.3
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• pp.291-296
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• 1999

Chiral epoxides are key intermediates for the production of chiral pharmaceuticals, agrochemicals, and functional food additives. Chiral epoxides can be produced by either chemical or biological method. In biocatalytic production routes, chiral epoxides can be produced via epoxidations of prochiral alkenes by monooxygenase or peroxidase. Kinetic resolution of racemic epoxides using whole cells of bacteria or fungi might be commercially useful, since it is possible to obtain chiral epoxides with high optical purities from relatively cheap and readily avaiable racemic epoxides. Some bioprocesses already are commercially developed: the biocatalytic production of chiral epichlorohydrin via microbial stereospecific dehalogenation, and lipase-catalyzed enantioselective hydrolysis in a hollow fiber membrane bioreactor for the production of chiral methyl trans-3-(4-methoxyphenyl)glycidate. the intermediate for calcium antagonist diltiazem. The importance of biocatalytic production of chiral epoxides with several examples from literature are presented.

• KSBB Journal
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• v.18 no.5
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• pp.377-384
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• 2003

On-line monitoring techniques for fumaric acid and succinic acid were developed by flow injection analysis (FIA). For the determination of fumaric acid, two enzymes, fumarase and malic dehydrogenase were immobilized on VA-epoxy Biosynth E3-carrier and integrated into a FIA-system with a fluorescence detector. For the analysis of succinic acid, isocitrate lyase and isocitrate dehydrogenase were also immobilized on VA-epoxy polymer support and used in a FIA system. The immobilized enzymes in two FIA systems were characterized systematically, e.g. optimum pH and temperature, inhibitory effects etc. Two FIA systems were also used to on-line monitor the concentrations of fumaric acid and succinic acid in biotechnological processes. Good agreement between on-line monitored data and off-line data measured by HPLC showed extensive application of the FIA systems in bioprocesses.

• KSBB Journal
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• v.20 no.3
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• pp.183-191
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• 2005

Ionic liquids, composed of organic cations and either organic or inorganic anions remain liquid over a wide range of temperature. ionic liquids are a new group of solvents or extractants of great interest as a potential 'green solvent'. Ionic liquids are gaining wide recognition as novel solvents in many research fields, such as chemistry, chemical engineering, electrochemitry, etc. However, not much researches have been done related to biotechnology using ionic liquids, while a lot of researches have been performed in chemistry. The merits of ionic liquids in bioseparation technology are originated from some unique properties of ionic liquids, such as negligible vapor pressure, good thermal stability, controllable viscosity and miscibility with water and organic solvents. An appropriate selection of ionic liquid for bioprocesses requires basic knowledge on physicochemical properties of ionic liquids. This review gives a brief overview on the application of ionic liquids in biotechnology, including bioconversion and bioseparation.

• Current Optics and Photonics
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• v.1 no.4
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• pp.412-420
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• 2017

Multinucleated bone resorptive osteoclasts differentiate from bone marrow-derived monocyte/macrophage precursor cells. During osteoclast differentiation, mononuclear pre-osteoclasts change their morphology and biochemical characteristics. In this study, Raman spectroscopy with multivariate techniques such as Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) were used to extract biochemical information related to various cellular events during osteoclastogenesis. This technique allowed for label-free and noninvasive monitoring of differentiating cells, and clearly discriminated four different time points during osteoclast differentiation. The Raman band intensity showed significant time-dependent changes that increased up to day 4. The results of Raman spectroscopy agreed with results from atomic force microscopy (AFM) and tartrate-resistant acid phosphatase (TRAP) staining, a conventional biological assay. Under AFM, normal spindle-like mononuclear pre-osteoclasts became round and smaller at day 2 after treatment with a receptor activator of nuclear $factor-{\kappa}B$ ligand and they formed multinucleated giant cells at day 4. Thus, Raman spectroscopy, in combination with PCA-LDA, may be useful for noninvasive label-free quality assessment of cell status during osteoclast differentiation, enabling more efficient optimization of the bioprocesses.