Climate Change and Energy Technologies in Undergraduate Introductory Science Textbooks

<p>Global climate change and the implementation of energy technologies are among the most pressing issues facing society and the environment today. Related educational content spans the science disciplines. Through an analysis of introductory-level university textbooks from four major US publishers in Biology, Chemistry, and Physics, this study presents trends in terminology and content. As the defining terms, “global warming” and “climate change” are used nearly equally. However, the first location of a working definition for climate change appears earlier. Energy technologies, climate change, and related environmental issues are found, on average, on ≤4% of textbook pages, and variation is large among individual textbooks. Discipline-based trends exist, especially for the energy technologies presented. Addressed separately as a non-renewable, non-fossil fuel, nuclear energy is found on ≤1% of textbook pages and unfavorably represented. The discussion within these science disciplines has implications on introductory-level education, public perception of science, and informed citizenship.</p

Predicting Dissolved Inorganic Carbon in Photoautotrophic Microalgae Culture via the Nitrogen Source

Dissolved inorganic carbon (DIC) and pH are key factors that control the growth rate of microalgae growing photoautotrophically. Being able to quantify how DIC and pH independently affect growth kinetics requires a means to control each parameter independently. In this study, we used the Proton Condition (PC) to develop means to control pH and DIC independently. Using the PC, we found that different N sources systematically affect the alkalinity and the DIC in distinct ways. With pH controlled at a fixed level by CO₂ addition, using nitrate as the N source increased the alkalinity and DIC concentration in proportion to the increase in biomass concentration. In contrast, using ammonium caused the alkalinity and DIC to decline, while using ammonium nitrate left the DIC nearly unchanged. Experiments with a model photoautotroph cyanobacterium, <i>Synechocystis</i> sp. PCC 6803, in batch experiments with modified BG-11 media and a pH-stat confirmed all of the DIC predictions of the PC-based model. Thus, this study provides a mechanistic basis for managing the DIC for photoautotrophic cultures through the N source. In particular, using ammonium nitrate makes it possible to control DIC and pH independently in a pH-stat

Changes in Glucose Fermentation Pathways as a Response to the Free Ammonia Concentration in Microbial Electrolysis Cells

When a mixed-culture microbial electrolysis cell (MEC) is fed with a fermentable substrate, such as glucose, a significant fraction of the substrate’s electrons ends up as methane (CH₄) through hydrogenotrophic methanogenesis, an outcome that is undesired. Here, we show that free ammonia-nitrogen (FAN, which is NH₃) altered the glucose fermentation pathways in batch MECs, minimizing the production of H₂, the “fuel” for hydrogenotrophic methanogens. Consequently, the Coulombic efficiency (CE) increased: 57% for 0.02 g of FAN/L of fed-MEC, compared to 76% for 0.18 g of FAN/L of fed-MECs and 62% for 0.37 g of FAN/L of fed-MECs. Increasing the FAN concentration was associated with the accumulation of higher organic acids (e.g., lactate, iso-butyrate, and propionate), which was accompanied by increasing relative abundances of phylotypes that are most closely related to anode respiration (<i>Geobacteraceae</i>), lactic-acid production (<i>Lactobacillales</i>), and syntrophic acetate oxidation (<i>Clostridiaceae</i>). Thus, the microbial community established syntrophic relationships among glucose fermenters, acetogens, and anode-respiring bacteria (ARB). The archaeal population of the MEC fed 0.02 g FAN/L was dominated by <i>Methanobacterium</i>, but 0.18 and 0.37 g FAN/L led to <i>Methanobrevibacter</i> becoming the most abundant species. Our results provide insight into a way to decrease CH₄ production and increase CE using FAN to control the fermentation step, instead of inhibiting methanogens using expensive or toxic chemical inhibitors, such as 2-bromoethanesulfonic acid

The Role of Syntrophic Associations in Sustaining Anaerobic Mineralization of Chlorinated Organic Compounds-1

<p><b>Copyright information:</b></p><p>Taken from "The Role of Syntrophic Associations in Sustaining Anaerobic Mineralization of Chlorinated Organic Compounds"</p><p>Environmental Health Perspectives 2004;113(3):310-316.</p><p>Published online 8 Dec 2004</p><p>PMCID:PMC1253757.</p><p>This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original DOI.</p

The Role of Syntrophic Associations in Sustaining Anaerobic Mineralization of Chlorinated Organic Compounds-6

<p><b>Copyright information:</b></p><p>Taken from "The Role of Syntrophic Associations in Sustaining Anaerobic Mineralization of Chlorinated Organic Compounds"</p><p>Environmental Health Perspectives 2004;113(3):310-316.</p><p>Published online 8 Dec 2004</p><p>PMCID:PMC1253757.</p><p>This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original DOI.</p

Bioreduction of Antimonate by Anaerobic Methane Oxidation in a Membrane Biofilm Batch Reactor

Employing a special anaerobic membrane biofilm batch reactor (MBBR), we demonstrated antimonate (Sb­(V)) reduction using methane (CH₄) as the sole electron donor. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman and photoluminescence (PL) spectra identified that Sb₂O₃ microcrystals were the main reduced products. The Sb­(V) reduction rate increased continually over the 111-day experiment, which supports the enrichment of the microorganisms responsible for Sb­(V) reduction to Sb­(III). Copy numbers of the <i>mcrA</i> gene and archaeal and bacterial 16 S rRNA genes increased in parallel. Clone library and Illumina sequencing of 16S rRNA gene demonstrated that Methanosarcina became the dominant archaea in the biofilm, suggesting that Methanosarcina might play an important role in Sb­(V) reduction in the CH₄-based MBBR

Treatment of Alcohol Distillery Wastewater Using a Bacteroidetes-Dominant Thermophilic Microbial Fuel Cell

Simultaneous electricity generation and distillery wastewater (DWW) treatment were accomplished using a thermophilic microbial fuel cell (MFC). The results suggest that thermophilic MFCs, which require less energy for cooling the DWW, can achieve high efficiency for electricity generation and also reduce sulfate along with oxidizing complex organic substrates. The generated current density (2.3 A/m²) and power density (up to 1.0 W/m²) were higher than previous wastewater-treating MFCs. The significance of the high Coulombic efficiency (CE; up to 89%) indicated that electrical current was the most significant electron sink in thermophilic MFCs. Bacterial diversity based on pyrosequencing of the 16S rRNA gene revealed that known Deferribacteres and Firmicutes members were not dominant in the thermophilic MFC fed with DWW; instead, uncharacterized Bacteroidetes thermophiles were up to 52% of the total reads in the anode biofilm. Despite the complexity of the DWW, one single bacterial sequence (OTU D1) close to an uncultured <i>Bacteriodetes</i> bacterium became predominant, up to almost 40% of total reads. The proliferation of the D1 species was concurrent with high electricity generation and high Coulombic efficiency

Biogenic Melanin-Modified Graphene as a Cathode Catalyst Yields Greater Bioelectrochemical Performances by Stimulating Oxygen–Reduction and Microbial Electron Transfer

Bioelectrochemical systems (BES) can recover energy from organic-bearing waste streams, but their use has been stymied by poor electron transfer from the cathode. Redox-active electron shuttles could stimulate electron transfer provided that they are compatible with the exoelectrogenic bacteria. This work evaluated melanin-modified carboxylated graphene (M/CG) as a novel cathode catalyst in a microbial fuel cell. Biogenic melanin catalysts (i.e., bio-M/CG) significantly increased bioelectricity production due to its abundant pyrrole N, which lowered charge-transfer resistance and, thus, promoted the cathodic oxygen–reduction reaction (ORR). The high content of pyrrole N in the bio-M/CG catalyst also enriched exoelectrogens, such as Azospirillum, Chryseobacterium, and Azoarcus, which accounted for over 50% of the total abundance of bacteria in biofilms on the anode. Moreover, the functional genes of key enzymes involved in microbial electron transfer (MET) were increased by the bio-M/CG catalyst. These data confirm that the bio-M/CG catalyst improved the bioelectrochemical performance via synergetic promotion of cathodic ORR and microbial electron transfer, thus providing a new alternative for advancing BES technology. This work highlights the potential application of melanin in enhancing cathodic oxygen–reduction reaction kinetics and improving microbial electron transfer in BES. This study emphasizes the promising application of melanin in enhancing the ORR kinetics and improving MET in BES, offering exciting prospects for future sustainable and environmentally friendly applications

UV Photolysis for Accelerating Pyridine Biodegradation

Pyridine, a nitrogen-containing heterocyclic compound, is slowly biodegradable, and coupling biodegradation with UV photolysis is a potential means to accelerate its biotransformation and mineralization. The initial steps of pyridine biodegradation involve mono-oxygenation reactions that have molecular oxygen and an intracellular electron carrier as cosubstrates. We employed an internal circulation baffled biofilm reactor for pyridine biodegradation following three protocols: direct biodegradation (B), biodegradation after photolysis (P+B), and biodegradation with succinic acid added (B+S). Succinic acid was the main UV-photolysis product from pyridine, and its catabolic oxidation generates internal electron carriers that may accelerate the initial steps of pyridine biodegradation. Compared with direct biodegradation of pyridine (B), the removal rate for the same concentration of photolyzed pyridine (P+B) was higher by 15 to 43%, depending on the initial pyridine concentrations (increasing through the range of 130 to 310 mg/L). Adding succinic acid alone (B+S) gave results similar to P+B, which supports that succinic acid was the main agent for accelerating the pyridine biodegradation rate. In addition, protocols P+B and B+S were similar in terms of increasing pyridine mineralization over 10 h: 84% and 87%, respectively, which were higher than with protocol B (72%). The positive impact of succinic acidwhether added directly or produced via UV photolysisconfirms that its catabolism, which produced intracellular electron carriers, accelerated the initial steps of pyridine biotransformation