Towards the integration of dark- and photo-fermentative waste treatment. 2. Optimization of starch-dependent fermentative hydrogen production

Eight natural microbial consortia collected from different sites were tested for dark, hydrogen production during starch degradation. The most active consortium was from silo pit liquid under mesophilic (37 °C) conditions. The fermentation medium for this consortium was optimized (Fe, NH₄⁺, phosphates, peptone, and starch content) for both dark fermentation and for subsequent purple photosynthetic bacterial H₂ photoproduction [Laurinavichene TV, Tekucheva DN, Laurinavichius KS, Ghirardi ML, Seibert M, Tsygankov AA. Towards the integration of dark and photo fermentative waste treatment. 1. Hydrogen photoproduction by purple bacterium Rhodobacter capsulatus using potential products of starch fermentation. Int J Hydrogen Energy 2008;33(23):7020–26], in the presence of the spent dark, fermentation effluent. The addition of Zn (10 mg L⁻¹), as a methanogenesis inhibitor that does not inhibit purple bacteria at this concentration, also did not inhibit dark, fermentative H₂ production. The influence of various fermentation end products at different concentrations (up to 30 g L⁻¹) on dark, H₂ production was also examined. Added lactate stimulated, but added isobutyrate and butanol strongly inhibited gas production. Under optimal conditions the fermentation of starch (30 g L⁻¹) resulted in 5.7 L H₂ L⁻¹ of culture (1.6 mol H₂ per mole of hexose) with the co-production mainly of butyrate and acetate.     

Can Brazil replace 5% of the 2025 gasoline world demand with ethanol?

Increasing use of petroleum, coupled with concern for global warming, demands the development and institution of CO₂ reducing, non-fossil fuel-based alternative energy-generating strategies. Ethanol is a potential alternative, particularly when produced in a sustainable way as is envisioned for sugarcane in Brazil. We consider the expansion of sugarcane-derived ethanol to displace 5% of projected gasoline use worldwide in 2025. With existing technology, 21 million hectares of land will be required to produce the necessary ethanol. This is less than 7% of current Brazilian agricultural land and equivalent to current soybean land use. New production lands come from pasture made available through improving pasture management in the cattle industry. With the continued introduction of new cane varieties (annual yield increases of about 1.6%) and new ethanol production technologies, namely the hydrolysis of bagasse to sugars for ethanol production and sugarcane trash collection providing renewable process energy production, this could reduce these modest land requirements by 29–38%.     

A history of numerical modelling of the Wairakei geothermal field

The history of computer modelling of the Wairakei geothermal field is reviewed. It covers the development of lumped-parameter models during the 1970s and then discusses the evolution and first applications of geothermal reservoir simulation techniques. The development of reservoir models of Wairakei at the University of Auckland began in the early 1980s; current models produces good matches against field data. Many future scenarios have been run using the University's models and have been presented at various regulatory hearings. The general conclusion from these scenarios is that Wairakei can continue producing electricity at the current level for at least another 50 years, and if Wairakei is shut down after 100 years of operation it will recover to its pre-exploitation state after a further 300 years.     

Characterization and expression analysis of a gene cluster for nitrate assimilation from the yeast Arxula adeninivorans

In Arxula adeninivorans nitrate assimilation is mediated by the combined actions of a nitrate transporter, a nitrate reductase and a nitrite reductase. Single‐copy genes for these activities (AYNT1, AYNR1, AYNI1, respectively) form a 9103 bp gene cluster localized on chromosome 2. The 3210 bp AYNI1 ORF codes for a protein of 1070 amino acids, which exhibits a high degree of identity to nitrite reductases from the yeasts Pichia anomala (58%), Hansenula polymorpha (58%) and Dekkera bruxellensis (54%). The second ORF (AYNR1, 2535 bp) encodes a nitrate reductase of 845 residues that shows significant (51%) identity to nitrate reductases of P. anomala and H. polymorpha. The third ORF in the cluster (AYNT1, 1518 bp) specifies a nitrate transporter with 506 amino acids, which is 46% identical to that of H. polymorpha. The three genes are independently expressed upon induction with NaNO₃. We quantitatively analysed the promoter activities by qRT–PCR and after fusing individual promoter fragments to the phytase (phyK) gene from Klebsiella sp. ASR1. The AYNI1 promoter was found to exhibit the highest activity, followed by the AYNT1 and AYNR1 elements. Direct measurements of nitrate and nitrite reductase activities performed after induction with NaNO₃ are compatible with these results. Both enzymes show optimal activity at around 42°C and near‐neutral pH, and require FAD as a co‐factor and NADPH as electron donor. Copyright © 2009 John Wiley & Sons, Ltd.     

Atan1p—an extracellular tannase from the dimorphic yeast Arxula adeninivorans: molecular cloning of the ATAN1 gene and characterization of the recombinant enzyme

The tannase‐encoding Arxula adeninivorans gene ATAN1 was isolated from genomic DNA by PCR, using as primers oligonucleotide sequences derived from peptides obtained after tryptic digestion of the purified tannase protein. The gene harbours an ORF of 1764 bp, encoding a 587‐amino acid protein, preceded by an N‐terminal secretion sequence comprising 28 residues. The deduced amino acid sequence was similar to those of tannases from Aspergillus oryzae (50% identity), A. niger (48%) and putative tannases from A. fumigatus (52%) and A. nidulans (50%). The sequence contains the consensus pentapeptide motif (–Gly–X–Ser–X–Gly–) which forms part of the catalytic centre of serine hydrolases. Expression of ATAN1 is regulated by the carbon source. Supplementation with tannic acid or gallic acid leads to induction of ATAN1, and accumulation of the native tannase enzyme in the medium. The enzymes recovered from both wild‐type and recombinant strains were essentially indistinguishable. A molecular mass of ～320 kDa was determined, indicating that the native, glycosylated tannase consists of four identical subunits. The enzyme has a temperature optimum at 35–40 °C and a pH optimum at ～6.0. The enzyme is able to remove gallic acid from both condensed and hydrolysable tannins. The wild‐type strain LS3 secreted amounts of tannase equivalent to 100 U/l under inducing conditions, while the transformant strain, which overexpresses the ATAN1 gene from the strong, constitutively active A. adeninivorans TEF1 promoter, produced levels of up to 400 U/l when grown in glucose medium in shake flasks. Copyright © 2009 John Wiley & Sons, Ltd.     

The effect of a scattering layer on the edge output of a luminescent solar concentrator

The effect of adding white scattering layers to the bottom side of luminescent solar concentrator waveguides is evaluated. It is determined that adding a rear scatterer separated from the waveguide by an air gap results in a large increase of energy output from the waveguides, and this enhancement persists over long (>30 cm) distances, although the magnitude of the enhancement decreases with distance. An attached scatterer resulted in the greatest improvement of light output for short (∼6 cm) distances, but actually reduced edge emissions over longer distances. We provide estimates for the relative contribution of dye-emitted light and scattered light to the total waveguide emission, as well as distinguishing between the contributions of direct and indirect scattering of light to the total output as a function of dye content of the waveguides.     

Bio-methanol: How energy choices in the western United States can help mitigate global climate change

Converting available biomass from municipal, agricultural and forest wastes to bio-methanol can result in significant environmental and economic benefits. Keeping these benefits in mind, one plausible scenario discussed here is the potential to produce energy using bio-methanol in five states of the western United States. In this scenario, the bio-methanol produced is from different biomass sources and used as a substitute for fossil fuels in energy production. In the U.S. West, forest materials are the dominant biomass waste source in Idaho, Montana, Oregon and Washington, while in California, the greatest amount of available biomass is from municipal wastes. Using a 100% rate of substitution, bio-methanol produced from these sources can replace an amount equivalent to most or all of the gasoline consumed by motor vehicles in each state. In contrast, when bio-methanol powered fuel cells are used to produce electricity, it is possible to generate 12–25% of the total electricity consumed annually in these five states.As a gasoline substitute, bio-methanol can optimally reduce vehicle C emissions by 2–29 Tg of C (23–81% of the total emitted by each state). Alternatively, if bio-methanol supported fuel cells are used to generate electricity, from 2 to 32 Tg of C emissions can be avoided. The emissions avoided, in this case, could equate to 25–32% of the total emissions produced by these particular western states when fossil fuels are used to generate electricity. The actual C emissions avoided will be lower than the estimates here because C emissions from the methanol production processes are not included; however, such emissions are expected to be relatively low. In general, there is less carbon emitted when bio-methanol is used to generate electricity with fuel cells than when it is used as a motor vehicle fuel.In the state of Washington, thinning “high-fire-risk” small stems, namely 5.1–22.9 cm diameter trees, from wildfire-prone forests and using them to produce methanol for electricity generation with fuel cells would avoid C emissions of 3.7–7.3 Mg C/ha. Alternatively, when wood-methanol produced from the high-fire-risk wood is used as a gasoline substitute, 3.3–6.6 Mg C/ha of carbon emissions are avoided. If these same “high-fire-risk” woody stems were burned during a wildfire 7.9 Mg C/ha would be emitted in the state of Washington alone. Although detailed economic analyses of producing methanol from biomass are in its infancy, we believe that converting biomass into methanol and substituting it for fossil-fuel-based energy production is a viable option in locations that have high biomass availability.     

A CFD model of autothermal reforming

A numerical model based on computational fluid dynamics (CFD) was developed and validated to simulate the performance of a catalytic monolith reformer for the production of hydrogen that could be used in fuel cell systems. The whole reactor was modeled as porous media for the process of autothermal reforming with n-hexadecane feed. CFD results provided an adequate match to experimental data from literature with respect to temperature and the mole fractions of H₂, CO₂ and CO products. The percentage difference between each experimental measurement of the mole fraction of hydrogen and the corresponding CFD prediction was less than 16.8%. It was found that the thermal conductivity of the solid catalyst substrate affected the temperature profile in the reactor, but its effect on product hydrogen concentration was negligible. The calculated reforming efficiency based on hydrogen decreased by 11.8% as power input was increased from 1.7 to 8.4 kW.     

Coal dust alters β-naphthoflavone-induced aryl hydrocarbon receptor nuclear translocation in alveolar type II cells

Background  

Many polycyclic aromatic hydrocarbons (PAHs) can cause DNA adducts and initiate carcinogenesis. Mixed exposures to coal dust (CD) and PAHs are common in occupational settings. In the CD and PAH-exposed lung, CD increases apoptosis and causes alveolar type II (AT-II) cell hyperplasia but reduces CYP1A1 induction. Inflammation, but not apoptosis, appears etiologically associated with reduced CYP1A1 induction in this mixed exposure model. Many AT-II cells in the CD-exposed lungs have no detectable CYP1A1 induction after PAH exposure. Although AT-II cells are a small subfraction of lung cells, they are believed to be a potential progenitor cell for some lung cancers. Because CYP1A1 is induced via ligand-mediated nuclear translocation of the aryl hydrocarbon receptor (AhR), we investigated the effect of CD on PAH-induced nuclear translocation of AhR in AT-II cells isolated from in vivo-exposed rats. Rats received CD or vehicle (saline) by intratracheal (IT) instillation. Three days before sacrifice, half of the rats in each group started daily intraperitoneal injections of the PAH, β-naphthoflavone (BNF).