Metabolism of novel potential syntrophic acetate-oxidizing bacteria in thermophilic methanogenic chemostats.

Acetate is a major intermediate in the anaerobic digestion of organic waste to produce CH4. In methanogenic systems, acetate degradation is carried out by either acetoclastic methanogenesis or syntrophic degradation by acetate oxidizers and hydrogenotrophic methanogens. Due to challenges in the isolation of syntrophic acetate-oxidizing bacteria (SAOB), the diversity and metabolism of SAOB and the mechanisms of their interactions with methanogenic partners are not fully characterized. In this study, the in situ activity and metabolic characteristics of potential SAOB and their interactions with methanogens were elucidated through metagenomics and metatranscriptomics. In addition to the reported SAOB classified in the genera Tepidanaerobacter, Desulfotomaculum, and Thermodesulfovibrio, we identified a number of potential SAOB that are affiliated with Clostridia, Thermoanaerobacteraceae, Anaerolineae, and Gemmatimonadetes. The potential SAOB possessing the glycine-mediated acetate oxidation pathway dominates SAOB communities. Moreover, formate appeared to be the main product of the acetate degradation by the most active potential SAOB. We identified the methanogen partner of these potential SAOB in the acetate-fed chemostat as Methanosarcina thermophila. The dominated potential SAOB in each chemostat had similar metabolic characteristics, even though they were in different fatty-acid-fed chemostats. These novel syntrophic lineages are prevalent and may play critical roles in thermophilic methanogenic reactors. This study expands our understanding of the phylogenetic diversity and in situ biological functions of uncultured syntrophic acetate degraders and presents novel insights into how they interact with methanogens.IMPORTANCECombining reactor operation with omics provides insights into novel uncultured syntrophic acetate degraders and how they perform in thermophilic anaerobic digesters. This improves our understanding of syntrophic acetate degradation and contributes to the background knowledge necessary to better control and optimize anaerobic digestion processes.

Multi-omics association study of hexadecane degradation in haloarchaeal strain Halogranum rubrum RO2-11.

Haloarchaea with the capacity to degrade alkanes is promising to deal with petroleum pollution in hypersaline environments. However, only a limited number of haloarchaeal species are investigated, and their pathway and mechanism for alkane degradation remain unclear. In this study, Halogranum rubrum RO2-11, a haloarchaeal strain, verified the ability to degrade kerosene and hexadecane in 184 g/L NaCl, with 53% and 52% degradation rates after 9 and 4 days, respectively. Genome sequencing and gene annotation indicated that strain RO2-11 possesses a complete potential alkane-degrading pathway, of which alkane hydroxylases may include CYP450, AlmA, and LadA. Transcriptome and metabolome analyses revealed that the upregulation of related genes in TCA cycle, lysine biosynthesis, and acetylation may help improve hexadecane degradation. Additionally, an alternative degrading pathway of hexadecane based on dual-terminal ß-oxidation may occur in strain RO2-11. It is likely to be the first report of alkane degradation by the genus Halogranum, which may be helpful for applications of oil-pollution bioremediation under high-salt conditions.

Enrichment of microbial consortia for MEOR in crude oil phase of reservoir-produced liquid and their response to environmental disturbance.

Developing microbial consortiums is necessary for microbial enhanced oil recovery (MEOR) in heavy crude oil production. The aqueous phase of produced fluid has long been considered an ideal source of microorganisms for MEOR. However, it is recently found that rich microorganisms (including hydrocarbon-degrading bacteria) are present in the crude oil phase, which is completely different from the aqueous phase of produced fluid. So, in this study, the microbial consortia from the crude oil phase of produced fluids derived from four wells were enriched, respectively. The microbial community structure during passage was dynamically tracked, and the response of enriched consortia to successive disturbance of environmental factors was investigated. The results showed the crude oil phase had high microbial diversity, and the original microbial community structure from four wells was significantly different. After ten generations of consecutive enrichment, different genera were observed in the four enriched microbial consortia, namely, Geobacillus, Bacillus, Brevibacillus, Chelativorans, Ureibacillus, and Ornithinicoccus. In addition, two enriched consortia (eG1614 and eP30) exhibited robustness to temperature and oxygen perturbations. These results further suggested that the crude oil phase of produced fluids can serve as a potential microbial source for MEOR.

The responses of mesophilic and thermophilic anaerobic digestion of municipal sludge to periodic fluctuation disturbance of organic loading rate.

Fluctuation disturbance of organic loading rate (OLR) is common in actual anaerobic digestion (AD), but its effects on AD of municipal sludge gets little attention. This study investigated the responses of reactor performance and active microbial community in mesophilic and thermophilic AD of municipal sludge before, during and after OLR periodic fluctuation disturbance. The performance of both reactors were similar before and after disturbance although some parameter values changed during the disturbance, which indicated their enough buffer capacity to OLR periodic fluctuation. Different microbial community at RNA level was observed in the two reactors. When the OLR disturbance commenced, the microbial community changed greatly in thermophilic AD. Error and attack tolerance of the microbial network was analyzed in order to learn the response mechanisms to OLR disturbance. The results assisted that the thermophilic microbial community was more vulnerable, but the reactor performance of which could be maintained using the functional redundancy strategy under OLR fluctuation disturbance.

Response of Microbial Communities on Cathode with Different Potentials in a Single-Chamber Reactor.

Microbes use both organic and inorganic compounds as electron donors, with different electronic potentials, to produce energy required for growth in environments. Conventional studies on the effects of different electron donors on microbial community has been extensively studied with a set cathode potential. However, it remains under-researched how a microbial community response to the different redox potentials in different environments. Here, we incubated a lake sediment in a single-chamber reactor equipped with three working electrodes, i.e., with potentials of - 0.29 V, - 0.05 V versus standard hydrogen electrode and open-circuit, respectively. Results reveal that the structure of bacterial communities was highly similar for all closed-circuit electrodes (- 0.29 V, - 0.05 V), while differing significantly from those on open-circuit electrodes. We also show that specific bacteria were preferentially enriched by different electrode potentials, i.e., Pseudomonas and Rhodobacter preferentially grew on - 0.05 V and - 0.29 V cathode potentials, Azospirillum and Bosea preferentially grew on - 0.05 V; while Ferrovibrio, Hydrogenophaga, Delftia, and Sphingobium preferentially grew on - 0.29 V. In addition, microorganisms selectively enriched on open-circuit electrodes possess higher connectivity and closer relationship than microorganisms selectively enriched on closed-circuit electrode.

High-throughput Sequencing Analysis of the Effects of Vanadium on Bacterial Community Structure in Purple Soil.

Vanadium (V) contamination in soil has received extensive attention due to its high toxicity. The change of mobility and bioavailability of soil V and the effects of V on the soil microbial community were studied under conditions of different V(V) spiking concentrations (0, 100, 250, and 500 mg kg-1) and aging time (1, 7, 14, 30, 45, and 60 d). The results showed that soil V mainly presented as V(IV) of all treatments throughout the aging process. At high levels of V(V) loading (250 and 500 mg kg-1), soil V(V) showed a downward trend, while bioavailable V did not change significantly within 60 d's aging. The analysis of soil bacterial community showed that Proteobacteria was the most abundant phylum in all soils, and the dominant genera Sphingomonas and Lysobacter can well adapt to high concentration V. These microorganisms exhibited great potential for bioremediation of V-contaminated soils.

Optimizing Photochirogenic Performance by Solvent-Driven Conformational Fixation in Enantiodifferentiating Photoisomerization of (Z)-Cyclooctene Mediated by Sensitizing ß-Cyclodextrin Hosts.

Catalytic enantiodifferentiating photoisomerization of cyclooctene (1Z) included and sensitized by regioisomeric 6-O-(o-, m-, and p-methoxybenzoyl)-ß-cyclodextrins (CDs) was performed under a variety of solvent conditions for higher enantioselectivities. The enantiomeric excess (ee) of chiral (E)-isomer (1E) produced was a critical function of all the internal and external factors examined, in particular, the sensitizer structure and the solvent conditions, to afford (R)-1E in record-high ee's of up to 67% upon sensitization with the meta-substituted ß-CD host in water and salt solutions but neither in 50% aqueous ethanol nor with the ortho- and para-substituted hosts. The mechanistic origin of the sudden ee enhancement achieved under the specific conditions is discussed on the basis of the circular dichroism spectral behaviors upon substrate inclusion and the compensatory enthalpy-entropy relationship of the activation parameters for the enantiodifferentiating photoisomerization.

Microbial communities in crude oil phase and filter-graded aqueous phase from a Daqing oilfield after polymer flooding.

AIMS: The aim was to characterize indigenous micro-organisms in oil reservoirs after polymer flooding (RAPF). METHODS: The microbial communities in the crude oil phase (Oil) and in the filter-graded aqueous phases Aqu0.22 (>0.22 µm) and Aqu0.1 (0.1-0.22 µm) were investigated by 16S rRNA gene high-throughput sequencing. RESULTS: Indigenous micro-organisms related to hydrocarbon degradation prevailed in the three phases of each well. However, obvious differences in bacterial compositions were observed amongst the three phases of the same well and amongst the same phase of different wells. The crude oil and Aqu0.22 shared many dominant bacteria. Aqu0.1 contained a unique bacterial community in each well. Most bacteria in Aqu0.1 were affiliated to culturable genera, suggesting that they may adapt to the oil reservoir environment by reduction of cell size. Contrary to the bacterial genera, archaeal genera were similar in the three phases but varied in relative abundances. The observed microbial differences may be driven by specific environmental factors in each oil well. CONCLUSIONS: The results suggest an application potential of microbial enhanced oil recovery (MEOR) technology in RAPF. The crude oil and Aqu0.1 contain many different functional micro-organisms related to hydrocarbon degradation. Both should not be overlooked when investing and exploring the indigenous micro-organisms for MEOR. SIGNIFICANCE AND IMPACT OF THE STUDY: This work facilitates the understanding of microbial community structures in RAPF and provides information for microbial control in oil fields.

Improving xylitol yield by deletion of endogenous xylitol-assimilating genes: a study of industrial Saccharomyces cerevisiae in fermentation of glucose and xylose.

Engineered Saccharomyces cerevisiae can reduce xylose to xylitol. However, in S.cerevisiae, there are several endogenous enzymes including xylitol dehydrogenase encoded by XYL2, sorbitol dehydrogenases encoded by SOR1/SOR2 and xylulokinase encoded by XKS1 may lead to the assimilation of xylitol. In this study, to increase xylitol accumulation, these genes were separately deleted through CRISPR/Cas9 system. Their effects on xylitol yield of an industrial S. cerevisiae CK17 overexpressing Candida tropicalis XYL1 (encoding xylose reductase) were investigated. Deletion of SOR1/SOR2 or XKS1 increased the xylitol yield in both batch and fed-batch fermentation with different concentrations of glucose and xylose. The analysis of the transcription level of key genes in the mutants during fed-batch fermentation suggests that SOR1/SOR2 are more crucially responsible for xylitol oxidation than XYL2 under the genetic background of S.cerevisiae CK17. The deletion of XKS1 gene could also weaken SOR1/SOR2 expression, thereby increasing the xylitol accumulation. The XKS1-deleted strain CK17ΔXKS1 produced 46.17 g/L of xylitol and reached a xylitol yield of 0.92 g/g during simultaneous saccharification and fermentation (SSF) of pretreated corn stover slurry. Therefore, the deletion of XKS1 gene provides a promising strategy to meet the industrial demands for xylitol production from lignocellulosic biomass.

Radio frequency pasteurization and disinfestation techniques applied on low-moisture foods.

The shelf life of foods is usually limited due to the frequent contamination by pests and microorganisms. Although low risk of pathogen contamination and no growth potential compared to those in high water activity animal- or vegetal-derived products, the low-moisture food has still significantly contributed to the total number of foodborne infections and outbreaks. Radio frequency (RF) treatments can be classified as a dielectric heating, which is a promising technology for achieving effective food pasteurization and disinfestations because of the associated rapid and volumetric heating with large penetration depth. The RF technique could be applied at low-moisture food as both the dipole dispersion and ionic conductivity may play effective roles. It can selectively heat and kill the microorganisms/pests without damaging the agricultural product because of the large difference of dielectric loss factors between target microorganisms/pests and host foods. In this article, the low-moisture foods sterilized and disinfested by RF energy are reviewed through basic theories, dielectric properties, heating effect, and uniformity. The potential research directions for further RF heating applications are finally recommended in low-moisture foods.

Different transcriptional responses of haploid and diploid S. cerevisiae strains to changes in cofactor preference of XR.

BACKGROUND: Xylitol accumulation is a major barrier for efficient ethanol production through heterologous xylose reductase-xylitol dehydrogenase (XR-XDH) pathway in recombinant Saccharomyces cerevisiae. Mutated NADH-preferring XR is usually employed to alleviate xylitol accumulation. However, it remains unclear how mutated XR affects the metabolic network for xylose metabolism. In this study, haploid and diploid strains were employed to investigate the transcriptional responses to changes in cofactor preference of XR through RNA-seq analysis during xylose fermentation. RESULTS: For the haploid strains, genes involved in xylose-assimilation (XYL1, XYL2, XKS1), glycolysis, and alcohol fermentation had higher transcript levels in response to mutated XR, which was consistent with the improved xylose consumption rate and ethanol yield. For the diploid strains, genes related to protein biosynthesis were upregulated while genes involved in glyoxylate shunt were downregulated in response to mutated XR, which might contribute to the improved yields of biomass and ethanol. When comparing the diploids with the haploids, genes involved in glycolysis and MAPK signaling pathway were significantly downregulated, while oxidative stress related transcription factors (TFs) were significantly upregulated, irrespective of the cofactor preference of XR. CONCLUSIONS: Our results not only revealed the differences in transcriptional responses of the diploid and haploid strains to mutated XR, but also provided underlying basis for better understanding the differences in xylose metabolism between the diploid and haploid strains.

Identification of Novel Butyrate- and Acetate-Oxidizing Bacteria in Butyrate-Fed Mesophilic Anaerobic Chemostats by DNA-Based Stable Isotope Probing.

Butyrate is one of the most important intermediates during anaerobic digestion of protein wastewater, and its oxidization is considered as a rate-limiting step during methane production. However, information on syntrophic butyrate-oxidizing bacteria (SBOB) is limited due to the difficulty in isolation of pure cultures. In this study, two anaerobic chemostats fed with butyrate as the sole carbon source were operated at different dilution rates (0.01/day and 0.05/day). Butyrate- and acetate-oxidizing bacteria in both chemostats were investigated, combining DNA-Stable Isotope Probing (DNA-SIP) and 16S rRNA gene high-throughput sequencing. The results showed that, in addition to known SBOB, Syntrophomonas, other species of unclassified Syntrophomonadaceae were putative butyrate-oxidizing bacteria. Species of Mesotoga, Aminivibrio, Acetivibrio, Desulfovibrio, Petrimonas, Sedimentibacter, unclassified Anaerolineae, unclassified Synergistaceae, unclassified Spirochaetaceae, and unclassified bacteria may contribute to acetate oxidation from butyrate metabolism. Among them, the ability of butyrate oxidation was unclear for species of Sedimentibacter, unclassified Synergistaceae, unclassified Spirochaetaceae, and unclassified bacteria. These results suggested that more unknown species participated in the degradation of butyrate. However, the corresponding function and pathway for butyrate or acetate oxidization of these labeled species need to be further investigated.

Novel Syntrophic Isovalerate-Degrading Bacteria and Their Energetic Cooperation with Methanogens in Methanogenic Chemostats.

Isovalerate is an important intermediate in anaerobic degradation of proteins/amino acids. Little is known about how this compound is degraded due to challenges in cultivation and characterization of isovalerate-degrading bacteria, which are thought to symbiotically depend on methanogenic archaea. In this study, we successfully enriched novel syntrophic isovalerate degraders (uncultivated Clostridiales and Syntrophaceae members) through operation of mesophilic and thermophilic isovalerate-fed anaerobic reactors. Metagenomics- and metatranscriptomics-based metabolic reconstruction of novel putative syntrophic isovalerate metabolizers uncovered the catabolic pathway and byproducts (i.e., acetate, H2, and formate) of isovalerate degradation, mechanisms for electron transduction from isovalerate degradation to H2 and formate generation (via electron transfer flavoprotein; ETF), and biosynthetic metabolism. The identified organisms tended to prefer formate-based interspecies electron transfer with methanogenic partners. The byproduct acetate was further converted to CH4 and CO2 by either Methanothrix (mesophilic) and Methanosarcina (thermophilic), which employed different approaches for acetate degradation. This study presents insights into novel mesophilic and thermophilic isovalerate degraders and their interactions with methanogens.

Identification of novel potential acetate-oxidizing bacteria in thermophilic methanogenic chemostats by DNA stable isotope probing.

Syntrophic oxidization of acetate and propionate are both critical steps of methanogenesis during thermophilic anaerobic digestion. However, knowledge on syntrophic acetate-oxidizing bacteria (SAOB) and syntrophic propionate-oxidizing bacteria (SPOB) is limited because of the difficulty in pure culture isolation due to symbiotic relationship. In this study, two thermophilic acetate-fed anaerobic chemostats, ATL (dilution rate of 0.025 day-1) and ATH (0.05 day-1) and one thermophilic propionate-fed anaerobic chemostat PTL (0.025 day-1) were constructed, AOB and POB in these chemostats were studied via microbial community analysis and DNA stable-isotope probing (SIP). The results showed that, in addition to Tepidanaerobacter, a known SAOB, species of Thauera, Thermodesulfovibrio, Anaerobaculum, Ruminiclostridium, Comamonas, and uncultured bacteria belonging to Lentimicrobiaceae, o_MBA03, Thermoanaerobacteraceae, Anaerolineaceae, Clostridiales, and Ruminococcaceae were determined to be potential AOB in chemostats. Pelotomaculum was the key SPOB detected in the propionate-fed chemostat. Based on the intense fluorescence of coenzyme F420, majority of Methanosarcina cells in acetate-fed chemostats were involved in hydrogenotrophic methanogenesis, suggesting the existence of highly active SAOB among the detected AOB. In the propionate-fed chemostat, most of the species detected as AOB were similar to those detected in the acetate-fed chemostats, suggesting the contribution of the syntrophic acetate oxidization pathway for methane generation. These results revealed the existence of previously unknown AOB with high diversity in thermophilic chemostats and suggested that methanogenesis from acetate via the syntrophic oxidization pathway is relevant for thermophilic anaerobic digestion.

Fracture of Zirconia Abutments in Implant Treatments: A Systematic Review.

PURPOSE: The purpose of this systematic review was to identify and summarize clinical studies related to the fracture of zirconia abutments in implant treatments. MATERIAL AND METHODS: Medline, Embase, and Cochrane library searches were performed and complemented by manual searches from database inception to February 11, 2018, for title and abstract analysis. RESULTS: Initially, 645 articles were obtained through database searches. Fifty-three articles were selected for full-text analysis, and 15 studies met the inclusion criteria. The selected studies were analyzed regarding fracture rate, abutment-implant connection, time point of fracture, location of critical crack, causes, managements, and preventive measures with respect to zirconia abutment fracture. CONCLUSIONS: Lower fracture rates were reported for internal connection with metal component (2-piece) zirconia abutments compared with external and internal full-zirconia connection (one-piece) zirconia abutments. Overpreparation and overload should be avoided in case of zirconia abutments.

Antagonist enamel wear of tooth-supported monolithic zirconia posterior crowns in vivo: A systematic review.

STATEMENT OF PROBLEM: An assessment of the evidence for the antagonist enamel wear of tooth-supported monolithic zirconia posterior crowns is lacking. PURPOSE: The purpose of this systematic review was to identify and summarize clinical studies related to the antagonist enamel wear of tooth-supported monolithic zirconia posterior crowns. MATERIAL AND METHODS: PubMed, Embase, and Cochrane library searches were performed and complemented by manual searches from database inception to December 25, 2017, for title and abstract analysis. RESULTS: Initially, 198 articles were obtained through database searches. Twenty-one articles were selected for full-text analysis, and 5 studies met the inclusion criteria. Because of the heterogeneity in design, surface treatment, measurement methods, and wear parameters, a meta-analysis was not possible. The selected studies were analyzed regarding the antagonist natural enamel wear of zirconia, measurement methods, and surface treatment. The results of the antagonist enamel wear varied widely, which made comparing them scientifically with absolute values difficult. CONCLUSIONS: This review indicated that the antagonist enamel wear of zirconia was similar to or more than that of natural teeth but less than that of metal-ceramics. Additional properly designed, longer follow-up clinical trials with larger sample sizes are needed to evaluate the antagonist enamel wear of monolithic zirconia crowns in vivo.

The compositional, physicochemical and functional properties of germinated mung bean flour and its addition on quality of wheat flour noodle.

Despite sprouted grains have high nutritional and functional properties, their exploration in mung bean and application in traditional foods are limited. The effects of germination of mung bean for 12, 24, 36, 48, 60 and 72 h on compositional, physicochemical and functional properties of its flour were investigated. The effects of incorporation of germinated mung bean flour at different levels (0, 10, 20 and 30%) on noodles making properties of wheat flour were evaluated 0. The protein content increased while the amylose increased initially and then decreased with increase in germination time. Water absorption index, oil binding capacity and water retention capacity increased, while water soluble index initially increased and then decreased. The germinated mung bean flour became darker with increase in germination time. The protein bound to starch in noodlesed to increase in hardness, cohesiveness, gumminess, chewiness, resilience and cooking time of noodles. Additionally, the water absorption, cooking loss, adhesiveness and springiness of raw noodles and springiness, cohesiveness and chewiness of cooked noodles decreased with the addition of germinated flour.

Transcriptome changes in adaptive evolution of xylose-fermenting industrial Saccharomyces cerevisiae strains with δ-integration of different xylA genes.

It is of utmost importance to construct industrial xylose-fermenting Saccharomyces cerevisiae strains for lignocellulosic bioethanol production. In this study, two xylose isomerase-based industrial S. cerevisiae strains, O7 and P5, were constructed by δ-integration of the xylose isomerase (XI) gene xylA from the fungus Orpinomyces sp. and from the bacterium Prevotella ruminicola, respectively. The xylose consumption of the strains O7 and P5 at 48-h fermentation was 17.71 and 26.10 g/L, respectively, in synthetic medium with xylose as the sole sugar source. Adaptive evolution further improved the xylose fermentation capacity of the two strains to 51.0 and 28.9% in average, respectively. The transcriptomes of these two strains before and after evolution were analyzed using RNA-Seq. The expression levels of the genes involved in cell integrity, non-optimal sugar utilization, and stress response to environment were significantly up-regulated after evolution and did not depend on the origin of xylA; the expression levels of the genes involved in transmembrane transport, rRNA processing, cytoplasmic translation, and other processes were down-regulated. The expression of genes involved in central carbon metabolism was fine-tuned after the evolution. The analysis of transcription factors (TFs) indicated that most of the genes with significant differential expression were regulated by the TFs related to cell division, DNA damage response, or non-optimal carbon source utilization. The results of this study could provide valuable references for the construction of efficient xylose-fermenting XI strains.

Comparative transcriptomes reveal novel evolutionary strategies adopted by Saccharomyces cerevisiae with improved xylose utilization capability.

Production of ethanol from xylose by recombinant Saccharomyces cerevisiae is suboptimal with slow fermentation rate, compared with that from glucose. In this study, a strain-expressing Scheffersomyces stipitis xylose reductase-xylitol dehydrogenase (XR-XDH) pathway was subjected to adaptive evolution on xylose; this approach generated populations with the significantly improved cell growth and ethanol production rate. Mutants were isolated, and the best one was used for sporulation to generate eight stable mutant strains with improved xylose fermentation ability. They were used in a microarray assay to study the molecular basis of the enhanced phenotype. The enriched transcriptional differences among the eight mutant strains and the native strain revealed novel responses to xylose, which likely contributes to the improved xylose utilization. The upregulated vitamin B1 and B6 biosynthesis indicated that thiamine served as an important cofactor in xylose metabolism and may alleviate the redox stress. The increased expression of genes involved in sulfur amino acid biosynthesis and the decreased expression of genes related to Fe(II) transport may alleviate redox stress as well. Meanwhile, it was remarkable that several glucose-repressible genes, including genes of the galactose metabolism, gluconeogenesis, and ethanol catabolism, had a lower expression level after adaptive evolution. Concomitantly, the expression levels of two regulators of the glucose signaling pathway, Rgs2 and Sip4, decreased, indicating a reshaped signaling pathway to xylose after adaptive evolution. Our findings provide new targets for construction of a superior bioethanol producing strain through inverse metabolic engineering.

Xylose fermentation efficiency and inhibitor tolerance of the recombinant industrial Saccharomyces cerevisiae strain NAPX37.

Industrial yeast strains with good xylose fermentation ability and inhibitor tolerance are important for economical lignocellulosic bioethanol production. The flocculating industrial Saccharomyces cerevisiae strain NAPX37, harboring the xylose reductase-xylitol dehydrogenase (XR-XDH)-based xylose metabolic pathway, displayed efficient xylose fermentation during batch and continuous fermentation. During batch fermentation, the xylose consumption rates at the first 36 h were similar (1.37 g/L/h) when the initial xylose concentrations were 50 and 75 g/L, indicating that xylose fermentation was not inhibited even when the xylose concentration was as high as 75 g/L. The presence of glucose, at concentrations of up to 25 g/L, did not affect xylose consumption rate at the first 36 h. Strain NAPX37 showed stable xylose fermentation capacity during continuous ethanol fermentation using xylose as the sole sugar, for almost 1 year. Fermentation remained stable at a dilution rate of 0.05/h, even though the xylose concentration in the feed was as high as 100 g/L. Aeration rate, xylose concentration, and MgSO4 concentration were found to affect xylose consumption and ethanol yield. When the xylose concentration in the feed was 75 g/L, a high xylose consumption rate of 6.62 g/L/h and an ethanol yield of 0.394 were achieved under an aeration rate of 0.1 vvm, dilution rate of 0.1/h, and 5 mM MgSO4. In addition, strain NAPX37 exhibited good tolerance to inhibitors such as weak acids, furans, and phenolics during xylose fermentation. These findings indicate that strain NAPX37 is a promising candidate for application in the industrial production of lignocellulosic bioethanol.