Chien-Yen Chen

Glycerol degradation in single-chamber microbial fuel cells.

Glycerol degradation with electricity production by a pure culture of Bacillus subtilis in a single-chamber air cathode of microbial fuel cell (MFC) has been demonstrated. Steady state polarization curves indicated a maximum power density of 0.06 mW/cm(2) with an optimal external resistance of 390Ω. Analysis of the effect of pH on MFC performance demonstrated that electricity generation was sustained over a long period of time under neutral to alkaline conditions. Cyclic voltammetry exhibited the increasing electrochemical activity with the increase of pH of 7, 8 and 9. Voltammetric studies also demonstrated that a two-electron transfer mechanism was occurring in the reactor. The low Coulombic efficiency of 23.08% could be attributed to the loss of electrons for various activities other than electricity generation. This study describes an application of glycerol that could contribute to transformation of the biodiesel industry to a more environmentally friendly microbial fuel cell-based technology.

Comparative bioelectricity production from various wastewaters in microbial fuel cells using mixed cultures and a pure strain of Shewanella oneidensis

Current and power density from four wastewaters, agriculture (AWW), domestic (DWW), paper (PWW), and food/dairy (FDWW), were comparatively evaluated in combination with three inocula: wastewater endogenous microbes (MFC1), Shewanella oneidensis MR-1 (MFC2), and wastewater endogenous microbes with MR-1 (MFC3) in single chamber microbial fuel cells (MFC). Using AWW (0.011 mA/cm(2); 0.0013 mW/cm(2)) and DWW (0.017 mA/cm(2); 0.0036 mW/cm(2)), MFC2 was the best candidate providing the maximum current, whereas AWW-MFC1 and DWW-MFC1 were unable to construct a well-established MFC. FDWW produced a maximum current from MFC3 (0.037 mA/cm(2); 0.015 mW/cm(2)), and confirmed the unsuitability of MFC2 at an alkaline pH. FDWW-MFC3 also performed best with the highest substrate degradation and coulombic efficiency. Mixed culture in MFC3 resulted in higher current generation under the influence of MR-1 (except in PWW), indicating the endogenous microbes were not solely responsible for the current but the outperformance was significantly attributed to the association of MR-1.

Screening of plant growth-promoting traits in arsenic-resistant bacteria isolated from agricultural soil and their potential implication for arsenic bioremediation

Twelve arsenic (As)-resistant bacteria (minimum inhibitory concentration ranging from 10 to 30mM and 150 to 320mM for As(III) and As(V), respectively) were isolated from the agricultural soil of the Chianan Plain in southwestern Taiwan using enrichment techniques. Eight isolates capable of oxidizing As(III) (rate of oxidation from 0.029 to 0.059μMh(-1) 10(-9) cell) and exhibiting As(III)-oxidase enzyme activity belong to Pseudomonas, Acinetobacter, Klebsiella and Comamonas genera, whereas four isolates that did not show As(III)-oxidizing activity belong to Geobacillus, Bacillus, Paenibacillus, and Enterobacter genera. Assessment of the parameters of plant growth promotion revealed that Pseudomonas sp. ASR1, ASR2 and ASR3, Geobacillus sp. ASR4, Bacillus sp. ASR5, Paenibacillus sp. ASR6, Enterobacter sp. ASR10 and Comamonas sp. ASR11, and ASR12 possessed some or all of the studied plant growth-promoting traits, including phosphate-solubilization, siderophore, IAA-like molecules and ACC deaminase production. In addition, the ability of As-resistant isolates to grow over wide ranges of pH and temperatures signify their potential application for sustainable bioremediation of As in the environment.

Comparative study of photoluminescence of single-walled carbon nanotubes wrapped with sodium dodecyl sulfate, surfactin and polyvinylpyrrolidone

Single-walled carbon nanotubes (SWCNTs) have been dispersed with three types of amphiphilic materials in aqueous solutions: (i) an anionic aliphatic surfactant, sodium dodecyl sulfate (SDS), (ii) a cyclic lipopeptide biosurfactant, surfactin, and (iii) a water-soluble polymer, polyvinylpyrrolidone (PVP). Solution photoluminescence (PL) studies suggest that SDS wrapping is very sensitive to the temperature whereas the other two give relatively robust wrapping around the SWCNTs. Low temperature PL spectra from both surfactin and PVP dispersed SWCNTs show that peak shifts are strongly dependent on their chiralities, which can be explained by the bandgap modulations with the environmental strain. The uniaxial and torsional strains deduced from their bandgap shifts were similar, indicating the strains are mainly due to the different rates of thermal expansion in SWCNTs and ice.

Cloning and characterization of β-agarase AgaYT from Flammeovirga yaeyamensis strain YT.

A bacterium with potent agar-degrading capability was isolated from the surface of a red algae, Gracilaria tenuistipitata. Based on phenotypic characteristics, 16S rDNA gene sequence and a phylogenetic analysis, this bacterium was identified and named as Flammeovirga yaeyamensis strain YT. PCR using homology-based degenerate primers was employed to clone any agarase gene belonging to GH16 family encoded in F. yaeyamensis strain YT. The resolved 1512 nucleotides revealed that the cloned gene, namely AgaYT, encodes a protein of 503 amino acids comprising a signal peptide, a glycosyl hydrolase catalytic module and a C-terminal domain with an unknown function. The recombinant protein r-AgaYT is an endo-type β-agarase hydrolyzing agarose to yield neoagarobiose and neoagarotetraose as the main hydrolytic products. The specific activity of r-AgaYT was determined about 178.6 U mg(-1) at 40°C and pH 8.0.

Naturally occurring arsenic in terrestrial geothermal systems of western Anatolia, Turkey: Potential role in contamination of freshwater resources

Arsenic (As) contamination in terrestrial geothermal systems has been identified in many countries worldwide. Concentrations higher than 0.01 mg/L are detrimental to human health. We examined potential consequences for As contamination of freshwater resources based on hydrogeochemical investigations of geothermal waters in deep wells and hot springs collected from western Anatolia, Turkey. We analyzed samples for major ions and trace element concentrations. Temperature of geothermal waters in deep wells showed extreme ranges (40 and 230 °C), while, temperature of hot spring fluids was up to 90 °C. The Piper plot illustrated two dominant water types: Na-HCO3(-) type for geothermal waters in deep wells and Ca-HCO3(-) type for hot spring fluids. Arsenic concentration ranged from 0.03 to 1.5mg/L. Dominance of reduced As species, i.e., As(III), was observed in our samples. The Eh value ranged between -250 and 119 mV, which suggests diverse geochemical conditions. Some of the measured trace elements were found above the World Health Organization guidelines and Turkish national safe drinking water limits. The variation in pH (range: 6.4-9.3) and As in geothermal waters suggest mixing with groundwater. Mixing of geothermal waters is primarily responsible for contamination of freshwater resources and making them unsuitable for drinking or irrigation.

Removal of Mercury by Foam Fractionation Using Surfactin, a Biosurfactant

The separation of mercury ions from artificially contaminated water by the foam fractionation process using a biosurfactant (surfactin) and chemical surfactants (SDS and Tween-80) was investigated in this study. Parameters such as surfactant and mercury concentration, pH, foam volume, and digestion time were varied and their effects on the efficiency of mercury removal were investigated. The recovery efficiency of mercury ions was highly sensitive to the concentration of the surfactant. The highest mercury ion recovery by surfactin was obtained using a surfactin concentration of 10 × CMC, while recovery using SDS required < 10 × CMC and Tween-80 >10 × CMC. However, the enrichment of mercury ions in the foam was superior with surfactin, the mercury enrichment value corresponding to the highest metal recovery (10.4%) by surfactin being 1.53. Dilute solutions (2-mg L−1 Hg2+) resulted in better separation (36.4%), while concentrated solutions (100 mg L−1) enabled only a 2.3% recovery using surfactin. An increase in the digestion time of the metal solution with surfactin yielded better separation as compared with a freshly-prepared solution, and an increase in the airflow rate increased bubble production, resulting in higher metal recovery but low enrichment. Basic solutions yielded higher mercury separation as compared with acidic solutions due to the precipitation of surfactin under acidic conditions.

Synthesis of Brushite Particles in Reverse Microemulsions of the Biosurfactant Surfactin

In this study the “green chemistry” use of the biosurfactant surfactin for the synthesis of calcium phosphate using the reverse microemulsion technique was demonstrated. Calcium phosphates are bioactive materials that are a major constituent of human teeth and bone tissue. A reverse microemulsion technique with surfactin was used to produce nanocrystalline brushite particles. Structural diversity (analyzed by SEM and TEM) resulted from different water to surfactin ratios (W/S; 250, 500, 1000 and 40,000). The particle sizes were found to be in the 16–200 nm range. Morphological variety was observed in the as-synthesized microemulsions, which consisted of nanospheres (~16 nm in diameter) and needle-like (8–14 nm in diameter and 80–100 nm in length) noncalcinated particles. However, the calcinated products included nanospheres (50–200 nm in diameter), oval (~300 nm in diameter) and nanorod (200–400 nm in length) particles. FTIR and XRD analysis confirmed the formation of brushite nanoparticles in the as-synthesized products, while calcium pyrophosphate was produced after calcination. These results indicate that the reverse microemulsion technique using surfactin is a green process suitable for the synthesis of nanoparticles.

A single-chamber microbial fuel cell without an air cathode.

Microbial fuel cells (MFCs) represent a novel technology for wastewater treatment with electricity production. Electricity generation with simultaneous nitrate reduction in a single-chamber MFC without air cathode was studied, using glucose (1 mM) as the carbon source and nitrate (1 mM) as the final electron acceptor employed by Bacillus subtilis under anaerobic conditions. Increasing current as a function of decreased nitrate concentration and an increase in biomass were observed with a maximum current of 0.4 mA obtained at an external resistance (Rext) of 1 KΩ without a platinum catalyst of air cathode. A decreased current with complete nitrate reduction, with further recovery of the current immediately after nitrate addition, indicated the dependence of B. subtilis on nitrate as an electron acceptor to efficiently produce electricity. A power density of 0.0019 mW/cm2 was achieved at an Rext of 220 Ω. Cyclic voltammograms (CV) showed direct electron transfer with the involvement of mediators in the MFC. The low coulombic efficiency (CE) of 11% was mainly attributed to glucose fermentation. These results demonstrated that electricity generation is possible from wastewater containing nitrate, and this represents an alternative technology for the cost-effective and environmentally benign treatment of wastewater.

Role of organic matter and humic substances in the binding and mobility of arsenic in a Gangetic aquifer

Arsenic (As) enrichment in groundwater has led to extensive research, particularly on the factors responsible for its release into groundwater. In the Gangetic plain, organic matter driven microbial reduction of Fe-oxyhydroxides is considered as the most plausible mechanism of As release into groundwater. However, the role of organic matter in the aqueous environment is not well known and particularly that of organometallic complex. In this study, we have characterized bulk sediment and groundwater samples, collected from Barasat, West Bengal, India, to understand the effect of organic matter in the binding and mobility of As in the subsurface environment. The results showed a moderate correlation (R(2) = 0.49, p < 0.05) between dissolved organic carbon (DOC) and As in groundwater, suggesting that DOC has a role in releasing As into groundwater. The relative fluorescent intensity (RFI) of the dissolved humic substances in groundwater showed a maximum value of 65 QSU (mean: 47 ± 8 QSU). FT-IR spectra of the extracted humic acid fractions of the sediment showed COO-, C = O, OH, and C = C (aromatic ring) functional groups, which may act as a chelating agents with the metal(loid)s. FT-IR spectra of the HA-As complex exhibited specific peaks at 1242 and 832 cm(-1) in the fingerprint region. This is similar to the extracted humic acid fractions of the Gangetic sediment, suggesting binding of As with humic substances.