Auxiliary Substrate Research Articles

Biohydrogen Production from Co-Digestion of High Carbohydrate Containing Food Waste and Combined Primary and Secondary Sewage Sludge

In this paper, FW (Food Waste) and SS (Sewage Sludge) were co-digested for biohydrogen production. After characterization both FW and SS were found as better option forbiohydrogen production. FW was rich in carbohydrate containing specially rice, which was added as more than 50% and easily hydrolyzable waste. FW is considered as an auxiliary substrate for biohydrogen production and high availability of carbohydrate in FW makes it an important substrate for the production of biohydrogen. On the contrary, SS was rich in protein and has a high pH buffering capacity, which makes it appropriate for co-digestion. Adequate supplementation of inorganic salts, the addition of hydrogen producing inoculums, protein enrichment and pH buffering capacity of SS and carbohydrate content in FW increases the hydrogen production potential. Various experiments were performed by considering different mixing ratios like 90:10, 80:20, 70:30, 60:40 and 50:50 of FW and SS. The 50:50 and 90:10 mixing ratio of FW and SS were found as best among all other co-digested ratios. The maximum specific hydrogenyield 106.7 mL/gVS_(added) was obtained at a waste composition of 50:50 followed by 92.35 mL/gVS_(added) from 90:10 of FW to SS. The optimum pH and temperature for operating this process werein the range of 5.5-6.5 and 35°C. The production of clean energy and waste utilization in anaerobic co-digestion process makes biohydrogen generation a promising and novel approach to fulfilling the increasing energy needs as a substitute for fossil fuels.

Hindrance of 1,4-dioxane biodegradation in microcosms biostimulated with inducing or non-inducing auxiliary substrates

A microcosm study was conducted to assess two biostimulation strategies (relative to natural attenuation) to bioremediate 1,4-dioxane contamination at a site in west Texas. Dioxane concentrations were relatively low (<300 μg/L), which represents a potential challenge to sustain and induce specific degraders. Thus, biostimulation was attempted with an auxiliary substrate known to induce dioxane-degrading monooxygenases (i.e., tetrahydrohyran [THF]) or with a non-inducing growth substrate (1-butanol [1-BuOH]). Amendment of 1-BuOH (100 mg/L) to microcosms that were not oxygen-limited temporarily enhanced dioxane biodegradation by the indigenous microorganisms. However, this stimulatory effect was not sustained by repeated amendments, which might be attributed to i) the inability of 1-BuOH to induce dioxane-degrading enzymes, ii) curing of catabolic plasmids, iii) metabolic flux dilution and catabolite repression, and iv) increased competition by commensal bacteria that do not degrade dioxane. Experiments with the archetype dioxane degrader Pseudonocardia dioxanivorans CB1190 repeatedly amended with 1-BuOH (500 mg/L added weekly for 4 weeks) corroborated the partial curing of catabolic plasmids (9.5 ± 7.4% was the plasmid retention ratio) and proliferation of derivative segregants that lost their ability to degrade dioxane. Addition of THF (300 μg/L) also had limited benefit due to competitive inhibition; significant dioxane degradation occurred only when the THF concentration decreased below approximately 160 μg/L. Overall, these results illustrate the importance of considering the possibility of unintentional hindrance of catabolism associated with the addition of auxiliary carbon sources to bioremediate aquifers impacted with trace concentrations of dioxane.

Effects of combined growth of biogenic and xenobiotic substrates on degradation of xenobiotic by activated sludge

The purpose of this study was to research about supplementation of different concentrations of the substrate on the degradation rate of xenobiotic and to determine the optimal concentrations of the auxiliary substrates that are most beneficial of xenobiotic degradation rate. 2,4-dichlorophenol acid (2,4-D) was used representative xenobiotic organic compounds, while peptone and sugar used for auxiliary substrates. The activated sludge was completely break down 100 mg/l of 2,4-D for three consecutive times. The different concentrations between biogenic substracts of sucrose and peptone were fed separately or combined into the medium containing 200 mg/l of 2,4-D and 140 mg SS/l of activated sludge. The results showed that sugar and peptone could affect 2,4-D degradation rate to several different degree at different concentrations. In separate supplementation, 2,4-D degradation completed within 25 hours, 40 mg/l sugar and 150 mg/l peptone concentrations were found to be the optimal concentrations. In combined case, 2,4-D was consumed totally within 20 hours and the optimal concentration of the combined sugar and peptone concentrations were 40 and 150 mg/l, respectively.

A high efficiency all-PMOS charge pump for 3D NAND flash memory

For 3D vertical NAND flash memory, the charge pump output load is much larger than that of the planar NAND, resulting in the performance degradation of the conventional Dickson charge pump. Therefore, a novel all PMOS charge pump with high voltage boosting efficiency, large driving capability and high power efficiency for 3D V-NAND has been proposed. In this circuit, the Pelliconi structure is used to enhance the driving capability, two auxiliary substrate bias PMOS transistors are added to mitigate the body effect, and the degradation of the output voltage and boost efficiency caused by the threshold voltage drop is eliminated by dynamic gate control structure. Simulated results show that the proposed charge pump circuit can achieve the maximum boost efficiency of 86% and power efficiency of 50%. The output voltage of the proposed 9 stages charge pump can exceed 2 V under 2 MHz clock frequency in 2X nm 3D V-NAND technology. Our results provide guidance for the peripheral circuit design of high density 3D V-NAND integration.

Improving methionine and ATP availability by MET6 and SAM2 co-expression combined with sodium citrate feeding enhanced SAM accumulation in Saccharomyces cerevisiae.

S-adenosyl-L-methionine (SAM), biosynthesized from methionine and ATP, exhibited diverse pharmaceutical applications. To enhance SAM accumulation in S. cerevisiae CGMCC 2842 (wild type), improvement of methionine and ATP availability through MET6 and SAM2 co-expression combined with sodium citrate feeding was investigated here. Feeding 6g/L methionine at 12h into medium was found to increase SAM accumulation by 38% in wild type strain. Based on this result, MET6, encoding methionine synthase, was overexpressed, which caused a 59% increase of SAM. To redirect intracellular methionine into SAM, MET6 and SAM2 (encoding methionine adenosyltransferase) were co-expressed to obtain the recombinant strain YGSPM in which the SAM accumulation was 2.34-fold of wild type strain. The data obtained showed that co-expression of MET6 and SAM2 improved intracellular methionine availability and redirected the methionine to SAM biosynthesis. To elevate intracellular ATP levels, 6g/L sodium citrate, used as an auxiliary energy substrate, was fed into the batch fermentation medium, and an additional 19% increase of SAM was observed after sodium citrate addition. Meanwhile, it was found that addition of sodium citrate improved the isocitrate dehydrogenase activity which was associated with the intracellular ATP levels. The results demonstrated that addition of sodium citrate improved intracellular ATP levels whichpromoted conversion of methionine into SAM. This study presented a feasible approach with considerable potential for developing highly SAM-productive strains based on improving methionine and ATP availability.

Response Surface Optimization for Decaffeination and Theophylline Production by Fusarium solani.

Coffee processing industries generate caffeine-containing waste that needs to be treated and decaffeinated before being disposed. Five fungal isolates obtained on caffeine-containing mineral media were tested for their ability to utilize caffeine at high concentrations. An isolate identified as Fusarium solani could utilize caffeine as a sole source of carbon and nitrogen up to 5 g/l and could degrade it to an extent of 30-53 % in 120 h. Sucrose that was added as an auxiliary substrate (5 g/l) enhanced the biodecaffeination of caffeine to 88 % in 96 h. The addition of co- substrate (sucrose) not only resulted in higher biodecaffeination efficiency, but also reduced the incubation period from the initial 120 to 96 h. Theophylline and 3-methyl xanthine were obtained as the major metabolites of decaffeination at 96 and 120 h, respectively. Response surface methodology used to optimize the process parameters for maximum biodecaffeination as well as theophylline production showed that a pH of 5.8, temperature of 24 °C and inoculum size of 4.8 × 10(5) spores/ml have resulted in a complete biodecaffeination of caffeine as well as the production of theophylline with a yield of 33 % (w/w). Results thus show that a viable and sustainable process can be developed for the detoxification of caffeine along with the recovery of theophylline, a commercially important chemical.

Highly selective anti-Prelog synthesis of optically active aryl alcohols by recombinant Escherichia coli expressing stereospecific alcohol dehydrogenase

ABSTRACTBiocatalytic asymmetric synthesis has been widely used for preparation of optically active chiral alcohols as the important intermediates and precursors of active pharmaceutical ingredients. However, the available whole-cell system involving anti-Prelog specific alcohol dehydrogenase is yet limited. A recombinant Escherichia coli system expressing anti-Prelog stereospecific alcohol dehydrogenase from Candida parapsilosis was established as a whole-cell system for catalyzing asymmetric reduction of aryl ketones to anti-Prelog configured alcohols. Using 2-hydroxyacetophenone as the substrate, reaction factors including pH, cell status, and substrate concentration had obvious impacts on the outcome of whole-cell biocatalysis, and xylose was found to be an available auxiliary substrate for intracellular cofactor regeneration, by which (S)-1-phenyl-1,2-ethanediol was achieved with an optical purity of 97%e.e. and yield of 89% under the substrate concentration of 5 g/L. Additionally, the feasibility of the recombinant cells toward different aryl ketones was investigated, and most of the corresponding chiral alcohol products were obtained with an optical purity over 95%e.e. Therefore, the whole-cell system involving recombinant stereospecific alcohol dehydrogenase was constructed as an efficient biocatalyst for highly enantioselective anti-Prelog synthesis of optically active aryl alcohols and would be promising in the pharmaceutical industry.

음식물쓰레기 이용 혐기 산발효에 의한 수소 및 유기산 생산: 축산폐수 첨가 효과

Organic wastes such as food waste (FW), livestock wastewater (LW), and sewage sludge (SWS) can produce hydrogen (<TEX>$H_2$</TEX>) by anaerobic acid fermentation. Expecially, FW which has high carbohydrate content produces <TEX>$H_2$</TEX> and short chain fatty acids by indigenous <TEX>$H_2$</TEX> producing microorganisms without adding inoculum, however <TEX>$H_2$</TEX> production rate (HPR) and yield have to be improved to use a commercially available technology. In this study, LW was mixed to FW in different ratios (on chemical oxygen demand (COD) basis) as an auxiliary substrate. The mixture of FW and LW was pretreated at pH 2 using 6 N HCl for 12 h and then fermented at <TEX>$37^{\circ}C$</TEX> for 28 h. HPR of FW, 254 mL <TEX>$H_2/L/h$</TEX>, was increased with the addition of LW, however, mixing ratio of LW to FW was reversely related to HPR, exhibiting HPR of 737, 733, 599, and 389 mL <TEX>$H_2/L/h$</TEX> at the ratio of FW:LW=10:1, 10:2, 10:3, and 10:4 on COD basis, respectively. Maximum HPR and <TEX>$H_2$</TEX> production yield of 737 <TEX>$H_2/L/h$</TEX> and 1.74 mol <TEX>$H_2/mol$</TEX> hexoseadded were obtained respectively at the ratio of FW:LW=10:1. Butyrate was the main organic acid produced and propionate was not detected throughout the experiment.

Metabolic engineering of Corynebacterium glutamicum for methanol metabolism.

Methanol is already an important carbon feedstock in the chemical industry, but it has found only limited application in biotechnological production processes. This can be mostly attributed to the inability of most microbial platform organisms to utilize methanol as a carbon and energy source. With the aim to turn methanol into a suitable feedstock for microbial production processes, we engineered the industrially important but nonmethylotrophic bacterium Corynebacterium glutamicum toward the utilization of methanol as an auxiliary carbon source in a sugar-based medium. Initial oxidation of methanol to formaldehyde was achieved by heterologous expression of a methanol dehydrogenase from Bacillus methanolicus, whereas assimilation of formaldehyde was realized by implementing the two key enzymes of the ribulose monophosphate pathway of Bacillus subtilis: 3-hexulose-6-phosphate synthase and 6-phospho-3-hexuloisomerase. The recombinant C. glutamicum strain showed an average methanol consumption rate of 1.7 ± 0.3 mM/h (mean ± standard deviation) in a glucose-methanol medium, and the culture grew to a higher cell density than in medium without methanol. In addition, [(13)C]methanol-labeling experiments revealed labeling fractions of 3 to 10% in the m + 1 mass isotopomers of various intracellular metabolites. In the background of a C. glutamicum Δald ΔadhE mutant being strongly impaired in its ability to oxidize formaldehyde to CO2, the m + 1 labeling of these intermediates was increased (8 to 25%), pointing toward higher formaldehyde assimilation capabilities of this strain. The engineered C. glutamicum strains represent a promising starting point for the development of sugar-based biotechnological production processes using methanol as an auxiliary substrate.

Auxiliary Factors and RNA Substrates Regulate Dead-Box Protein Activity by Modulation of the Dead-Box Protein Conformational Cycle

DEAD-box proteins unwind RNA duplexes at the expense of ATP hydrolysis in virtually all processes involving RNA. During unwinding, they alternate between open and closed conformations, and the transition to the closed conformation has previously been linked to duplex destabilization. The eukaryotic translation initiation factor 4A (eIF4A) is a DEAD-box helicase that is thought to resolve secondary structure elements from the 5′-UTR of mRNAs to enable ribosome scanning. Its RNA-stimulated ATPase and ATP-dependent helicase activities are enhanced by other translation initiation factors, but the underlying mechanisms are unclear. eIF4A can adopt three different conformations, an open state in the absence of ligands, a half-open state stabilized by eIF4G, and a closed state populated in the presence of eIF4G and eIF4B. In single molecule FRET experiments on donor/acceptor-labeled eIF4A, we have dissected the effect of eIF4B and eIF4G on RNA-dependent ATPase- and RNA helicase activities, and on the eIF4A conformational cycle in the context of different unwinding substrates. We show that eIF4B and eIF4G, as well as different structures in the 5′-UTR, modulate the energy landscape underlying the eIF4A conformational cycle by changing the energetic differences and the energy barriers between functionally relevant conformational states, leading to changes in rate constants for inter-conversion and in equilibrium distributions. Our results reveal on a molecular level how translation initiation factors synergistically stimulate the eIF4A helicase activity in the mRNA scanning process, and show that the eIF4A conformational cycle is central for the multi-layered regulation of eIF4A activity, and for its role as a regulatory hub in translation initiation.

Unconventional Cyclometalation Reactions

Cyclometalation reactions are usually defined as the reactions of metal compounds with conventional substrates, such as benzylamines and 2-phenylpyridines. In contrast, unconventional cyclometalation reactions are the reactions of metal compounds with unconventional base substrates, such as 2-amino-3-picoline, anilines and 2- aminopyridines, and with auxiliary substrates, such as aldehydes and alkynes. Other unconventional cyclometalation reactions also exist, examples include the cyclocarbonylations of metal carbonyl compounds with unsaturated hydrocarbons, such as alkynes, alkenes and aryl compounds; reactions with 2-vinylpyridines; and rollover cyclometalation reactions. Keywords: 2-vinylpyridine, aminopicoline, aniline, cyclocarbonylation, cyclometalation, rollover, unconventional cyclometalation.

Chloroethene degradation and expression of Dehalococcoides dehalogenase genes in cultures originating from Yangtze sediments.

The anaerobic Dehalococcoides spp. is the only microorganism known to completely dechlorinate the hazardous compounds tetrachloroethene (PCE) or trichloroethene (TCE) via dichloroethene (DCE) and vinyl chloride (VC) to the terminal product, ethene. In this study, growth of Dehalococcoides spp. (DHC) and the expression of DHC dehalogenase genes were demonstrated for Yangtze enrichment cultures. Reductive dechlorination of chloroethenes occurred in Yangtze sediment without the addition of any external auxiliary substrates. All Yangtze enrichment cultures completely dechlorinated PCE and cis-DCE to ethene. To investigate expression of the dehalogenase genes pceA, tceA, vcrA, and bvcA, a protocol for messenger RNA (mRNA) extraction followed by reverse transcription and quantitative PCR analysis was established. During dechlorination, an increase in gene copy numbers of pceA, tceA, and vcrA was observed. However, temporary formation of mRNA was only measured in the case of the dehalogenase genes tceA and vcrA. Comparison of DHC dehalogenase patterns indicated that the Yangtze DHC community does not match any of the previously published enrichment cultures that were obtained from contaminated areas in the USA or Europe.

ULTRA-LOW-VOLTAGE GAIN-ENHANCED FOUR-PHASE CHARGE PUMP WITHOUT BODY EFFECT

In this paper, an ultra-low-voltage gain-enhanced four-phase charge pump is proposed. The proposed charge pump is designed in 0.18 μm 1.8 V standard CMOS process with high voltage boosting efficiency when the supply voltage is between 0.5 V and 1.8 V. Moreover, it eliminates the body effect by means of adding two auxiliary substrate switching PMOS transistor. The simulation results show that the proposed charge pump has higher efficiency than the other two low voltage charge pumps when the resistive load is 100 M ohm and the supply voltage is between 0.5 and 1.8 V. A test chip has been realized in a 0.18 μm 1.8 V standard CMOS process. The test results show perfect performance when the supply voltage is between 0.7 and 1.8 V. The proposed charge pump is quite suitable for low power applications.

Aerobic biodegradation of trichloroethene without auxiliary substrates

Trichloroethene (TCE) represents a priority pollutant and is among the most frequently detected contaminants in groundwater. The current bioremediation measures have certain drawbacks like e.g. the need for auxiliary substrates. Here, the aerobic biodegradation of TCE as the sole growth substrate is demonstrated. This new process of metabolic TCE degradation was first detected in groundwater samples. TCE degradation was stable in an enriched mixed bacterial culture in mineral salts medium for over five years and repeated transfers of the culture resulting in a 1010 times dilution of the original groundwater. Aerobic TCE degradation resulted in stoichiometric chloride formation. Stable carbon isotope fractionation was observed providing a reliable analytical tool to assess this new biodegradation process at field sites. The results suggest that aerobic biodegradation of TCE without auxiliary substrate could be considered as an option for natural attenuation or engineered bioremediation of contaminated sites.

Widespread Distribution of Soluble Di-Iron Monooxygenase (SDIMO) Genes in Arctic Groundwater Impacted by 1,4-Dioxane

Soluble di-iron monooxygenases (SDIMOs), especially group-5 SDIMOs (i.e., tetrahydrofuran and propane monooxygenases), are of significant interest due to their potential role in the initiation of 1,4-dioxane (dioxane) degradation. Functional gene array (i.e., GeoChip) analysis of Arctic groundwater exposed to dioxane since 1980s revealed that various dioxane-degrading SDIMO genes were widespread, and PCR-DGGE analysis showed that group-5 SDIMOs were present in every tested sample, including background groundwater with no known dioxane exposure history. A group-5 thmA-like gene was enriched (2.4-fold over background, p < 0.05) in source-zone samples with higher dioxane concentrations, suggesting selective pressure by dioxane. Microcosm assays with (14)C-labeled dioxane showed that the highest mineralization capacity (6.4 ± 0.1% (14)CO2 recovery during 15 days, representing over 60% of the amount degraded) corresponded to the source area, which was presumably more acclimated and contained a higher abundance of SDIMO genes. Dioxane mineralization ceased after 7 days and was resumed by adding acetate (0.24 mM) as an auxiliary substrate to replenish NADH, a key coenzyme for the functioning of monoxygenases. Acetylene inactivation tests further corroborated the vital role of monooxygenases in dioxane degradation. This is the first report of the prevalence of oxygenase genes that are likely involved in dioxane degradation and suggests their usefulness as biomarkers of dioxane natural attenuation.

Sustained apnea induced by GABAA receptor blockade at ventrolateral pons/A5 region is reversed by subsequent blockade of glutamatergic receptors

The A5 region in ventrolateral pons (vl‐pons/A5) is thought to be an auxiliary substrate for the putative pneumotaxic center in the dorsolateral pons that modulates inspiratory‐expiratory phase switching (inspiratory off‐switch), post‐inspiratory activity (post‐I) and expiratory duration (TE). In urethane‐anesthetized, vagotomized and ventilated adult SD rats, we observed that blockade of GABAA receptors at vl‐pons/A5 by unilateral microinjection of bicuculline (BIC) caused prolongation of vagal post‐I motor activity and TE, an effect that was similar to that evoked by electrical or chemical stimulations in this region. Bilateral microinjections of BIC caused further protracted prolongation of TE or even sustained apnea with complete cessation of phrenic activity and prolongation of post‐I activity. Remarkably, the apnea so induced was reversed and rhythmic phrenic discharges gradually resumed upon subsequent blockade of excitatory glutamatergic receptors by bilateral microinjections of CNQX and AP‐5 at the same vl‐pons/A5 sites, or by the application of hypoxic or hypercapnic stimuli. These findings indicated that the vl‐pons/A5 plays an important role in promoting post‐I activity and inspiratory off‐switch subject to a delicate balance between GABAA receptor‐mediated inhibitory and glutamatergic receptor‐mediated excitatory modulations. (Supported by HL093225)

Improved co-production of S-adenosylmethionine and glutathione using citrate as an auxiliary energy substrate

The effects of sodium citrate on the fermentative co-production of S-adenosylmethionine (SAM) and glutathione (GSH) using Candida utilis CCTCC M 209298 were investigated. Sodium citrate was beneficial for the biosynthesis of SAM and GSH and in turn improved intracellular SAM and GSH contents. Adding 2g/L of sodium citrate at 15h was the most efficient approach for achieving elevated co-production of SAM and GSH. Using this sodium citrate addition mode, co-production of SAM and GSH reached 663.9mg/L, which was increased by 27.5% compared to the control. Based on analysis of the kinetic parameters, evaluation of the energy metabolism and assay of key enzymes, sodium citrate was verified to act as an auxiliary energy substrate for the overproduction of SAM and GSH.

Auxiliary drying to prevent pattern collapse in high aspect ratio nanostructures

Many defects are generated in densely packed high aspect ratio structures duringnanofabrication. Pattern collapse is one of the serious problems that may arise, mainly dueto the capillary force during drying after the rinsing process. In this paper, a method ofauxiliary drying is presented to prevent pattern collapse in high aspect ratio nanostructuresby adding an auxiliary substrate as a reinforcing rib to restrict deformation and to balancethe capillary force. The principle of the method is presented based on the analysis ofpattern collapse. A finite element method is then applied to analyze the deformation of theresist beams caused by the surface tension using the ANSYS software, and the effect of thenanostructure’s length to width ratio simulated and analyzed. Finally, the possible range ofapplications based on the proposed method is discussed. Our results show that theaspect ratio may be increased 2.6 times without pattern collapse; furthermore, thismethod can be widely used in the removal of solvents in micro- and nanofabrication.

Type 2 IDI performs better than type 1 for improving lycopene production in metabolically engineered E. coli strains

In this study a comparison was made between type 1 and type 2 isopentenyl diphosphate isomerases (IDI) in improving lycopene production in Escherichia coli. The corresponding genes of Bacillus licheniformis and the host (i(Bl) and i(Ec), respectively) were expressed in lycopene producing E. coli strains by pTlyci(Bl) and pTlyci(Ec) plasmids, under the control of tac promoter. The results showed that the overexpression of i(Ec) improved the lycopene production from 33 ± 1 in E. coli Tlyc to 68 ± 3 mg/gDCW in E. coli Tlyci(Ec). In contrast, the expression of i(Bl) increased the lycopene production more efficiently up to 80 ± 9 mg/gDCW in E. coli Tlyci(Bl). The introduction of a heterologous mevalonate pathway to elevate the IPP abundance resulted in a lycopene production up to 132 ± 5 mg/gDCW with i(Ec) in E. coli Tlyci(Ec)-mev and 181 ± 9 mg/gDCW with i(Bl) in E. coli Tlyci(Bl)-mev, that is, 4 and 5.6 times respectively. When fructose, mannose, arabinose, and acetate were each used as an auxiliary substrate with glycerol, lycopene production was inhibited by different extents. Among auxiliary substrates tested, only citrate was an improving one for lycopene production in all strains with a maximum of 198 ± 3 mg/gDCW in E. coli Tlyci(Bl)-mev. It may be concluded that the type 2 IDI performs better than the type 1 in metabolic engineering attempts for isoprenoid production in E. coli. In addition, the metabolic engineering of citrate pathway seems a promising approach to have more isoprenoid accumulation in E. coli.

1,4-Dioxane biodegradation at low temperatures in Arctic groundwater samples

1,4-Dioxane biodegradation was investigated in microcosms prepared with groundwater and soil from an impacted site in Alaska. In addition to natural attenuation conditions (i.e., no amendments), the following treatments were tested: (a) biostimulation by addition of 1-butanol (a readily available auxiliary substrate) and inorganic nutrients; and (b) bioaugmentation with Pseudonocardia dioxanivorans CB1190, a well-characterized dioxane-degrading bacterium, or with Pseudonocardia antarctica DVS 5a1, a bacterium isolated from Antarctica. Biostimulation enhanced the degradation of 50 mg L −1 dioxane by indigenous microorganisms (about 0.01 mg dioxane d −1 mg protein −1) at both 4 and 14 °C, with a simultaneous increase in biomass. A more pronounced enhancement was observed through bioaugmentation. Microcosms with 50 mg L −1 initial dioxane (representing source-zone contamination) and augmented with CB1190 degraded dioxane fastest (0.16 ± 0.04 mg dioxane d −1 mg protein −1) at 14 °C, and the degradation rate decreased dramatically at 4 °C (0.021 ± 0.007 mg dioxane d −1 mg protein −1). In contrast, microcosms with DVS 5a1 degraded dioxane at similar rates at 4 °C and 14 °C (0.018 ± 0.004 and 0.015 ± 0.006 mg dioxane d −1 mg protein −1, respectively). DVS 5a1 outperformed CB1190 when the initial dioxane concentration was low (500 μg L −1, which is representative of the leading edge of plumes). This indicates differences in competitive advantages of these two strains. Natural attenuation microcosms also showed significant degradation over 6 months when the initial dioxane concentration was 500 μg L −1. This is the first study to report the potential for dioxane bioremediation and natural attenuation of contaminated groundwater in sensitive cold-weather ecosystems such as the Arctic.