Dual-Proton Conductor for Fuel Cells with Flexible Operational Temperature.

The properties of proton conductors determine the operating temperature range of fuel cells. Typically, phosphoric acid (PA) proton conductors exhibit excellent proton conductivity owing to their high proton dissociation and self-diffusion abilities. However, at low temperatures or high current densities, water-induced PA loss causes rapid degradation of cell performance. Maintaining efficient and stable proton conductivity within a flexible temperature range can significantly reduce the start-up temperature of PA-doped proton exchange membrane fuel cells. In this study, a dual-proton conductor composed of an organic phosphonic acid (ethylenediamine tetramethylene phosphonic acid, EDTMPA) and an inorganic PA is developed for proton exchange membranes. The proposed dual-proton conductor can operate within a flexible temperature range of 80-160 °C, benefiting from the strong interaction between EDTMPA and PA, and the enhanced proton dissociation. Fuel cells with the EDTMPA-PA dual-proton conductor showed excellent cell stability at 80 °C. In particular, under the high current density of 1.5 A cm-2 at 160 °C, the voltage decay rate of the fuel cell with the dual-proton conductor is one-thousandth of that of the fuel cell with PA-only proton conductor, indicating excellent stability.

Phosphonate poly(vinylbenzyl chloride)-Modified Sulfonated poly(aryl ether nitrile) for Blend Proton Exchange Membranes: Enhanced Mechanical and Electrochemical Properties.

Blend proton exchange membranes (BPEMs) were prepared by blending sulfonated poly(aryl ether nitrile) (SPAEN) with phosphorylated poly(vinylbenzyl chloride) (PPVBC) and named as SPM-x%, where x refers to the proportion of PPVBC to the weight of SPAEN. The chemical complexation interaction between the phosphoric acid and sulfonic acid groups in the PPVBC-SPAEN system resulted in BPEMs with reduced water uptake and enhanced mechanical properties compared to SPAEN proton exchange membranes. Furthermore, the flame retardancy of the PPVBC improved the thermal stability of the BPEMs. Despite a decrease in ion exchange capacity, the proton conductivity of the BPEMs in the through-plane direction was significantly enhanced due to the introduction of phosphoric acid groups, especially in low relative humidity (RH) environments. The measured proton conductivity of SPM-8% was 147, 98, and 28 mS cm-1 under 95%, 70%, and 50% RH, respectively, which is higher than that of the unmodified SPAEN membrane and other SPM-x% membranes. Additionally, the morphology and anisotropy of the membrane proton conductivities were analyzed and discussed. Overall, the results indicated that PPVBC doping can effectively enhance the mechanical and electrochemical properties of SPAEN membranes.

Association of TNFAIP8 gene polymorphisms with cancer risk in Chinese population.

As TNFAIP8 plays an important role in the development of cancer, several studies have analyzed the relationship between potential functional polymorphic loci of the TNFAIP8 gene and cancer risk. However, some results were inconsistent. Therefore, the current study aims to systematically assess the relationship between these genetic polymorphisms and cancer risk using a meta-analysis approach. Relevant studies were obtained from CNKI, Embase, Web of Science, and PubMed databases. RevMan software was used to conduct data analysis. The combined analysis containing four studies with 2786 cancer patients and 2550 control individuals indicated that rs11064 polymorphism was not associated with cancer risk. The pooled analysis containing three studies with 950 cancer patients and 1036 control individuals showed that rs1045241 polymorphism was associated with cancer risk in the heterozygous model (CT vs. CC: OR = 1.34, 95%CI = 1.10-1.62, Pz=0.003) and dominant model [(TT + CT) vs. CC: OR = 1.38, 95% CI = 1.15-1.66, Pz=0.0006], but not in other models. The pooled analysis containing two studies 436 cancer patients and 479 control individuals showed that rs1045242 polymorphism was associated with cancer risk in the heterozygous model (AG vs. AA: OR = 1.52, 95%CI = 1.14-2.03, Pz=0.005), dominant model [(GG + AG) vs. AA: OR = 1.56, 95% CI = 1.18-2.07, Pz=0.002] and allelic model (G vs. A: OR = 1.48, 95%CI = 1.16-1.90, Pz=0.002).In conclusion, the current findings suggest that the rs1045241 and rs1045242 polymorphisms located on the TNFAIP8 gene were associated with cancer risk in Chinese population, and may serve as valuable genetic susceptibility markers.

Ultrahigh-Throughput Screening of High-ß-Xylosidase-Producing Penicillium piceum and Investigation of the Novel ß-Xylosidase Characteristics.

A droplet-based microfluidic ultrahigh-throughput screening technology has been developed for the selection of high-ß-xylosidase-producing Penicillium piceum W6 from the atmospheric and room-temperature plasma-mutated library of P. piceum. ß-xylosidase hyperproducers filamentous fungi, P. piceum W6, exhibited an increase in ß-xylosidase activity by 7.1-fold. A novel ß-D-xylosidase was purified from the extracellular proteins of P. piceum W6 and designated as PpBXL. The optimal pH and temperature of PpBXL were 4.0 and 70 °C, respectively. PpBXL had high stability an acidic pH range of 3.0-5.0 and exhibited good thermostability with a thermal denaturation half-life of 10 days at 70 °C. Moreover, PpBXL showed the bifunctional activities of α-L-arabinofuranosidase and ß-xylosidase. Supplementation with low-dose PpBXL (100 µg/g substrate) improved the yields of glucose and xylose generated from delignified biomass by 36-45%. The synergism between PpBXL and lignocellulolytic enzymes enhanced delignified biomass saccharification, increased the Xyl/Ara ratio, and decreased the strength of hydrogen bonds.

A GFP-fusion coupling FACS platform for advancing the metabolic engineering of filamentous fungi.

BACKGROUND: The filamentous fungus Trichoderma reesei, the most widely used cellulase producer, also has promising applications in lignocellulose-based biorefinery: consolidated bioprocessing for the production of high value-added products. However, such applications are thwarted by the time-consuming metabolic engineering processes (design-build-test-learn cycle) for T. reesei, resulted from (i) the spore separation-mediated purification as the multinucleate hyphae, (ii) transformant screening for high expression levels since unavailable of episomal expression system, and (iii) cases of inexpressible heterologous proteins. RESULTS: In this study, a GFP-fusion coupled fluorescence-activated cell sorting (FACS) platform was established to speed up the build and test process of the DBTL cycle, by enabling rapid selection for expressible heterologous genes and bypassing both laborious spore separation and transformant screening. Here, the feasibility of flow cytometry in analyzing and sorting T. reesei cells harboring GFP-fused expressible protein was proven, as well as the application of the platform for constitutive promoter strength evaluation. As a proof-of-concept, the platform was employed to construct the first T. reesei strain producing fatty alcohol, resulting in up to 2 mg hexadecanol being produced per gram biomass. Pathway construction was enabled through rapid selection of functional fatty acyl-CoA reductase encoding gene Tafar1 from three candidate genes and strains with high expression level from spore pools. As a result of using this method, the total costed time for the build and test cycle using T. reesei, subsequently, reduced by approx. 75% from 2 months to 2 weeks. CONCLUSION: This study established the GFP-fusion coupling FACS platform and the first filamentous fungal fatty alcohol-producing cell factory, and demonstrated versatile applications of the platform in the metabolic engineering of filamentous fungi, which can be harnessed to potentially advance the application of filamentous fungi in lignocellulose-based biorefinery.

Trpac1, a pH response transcription regulator, is involved in cellulase gene expression in Trichoderma reesei.

Fungi grow over a relatively wide pH range and adapt to extracellular pH through a genetic regulatory system mediated by a key component PacC, which is a pH transcription regulator. The cellulase production of the filamentous fungi Trichoderma reesei is sensitive to ambient pH. To investigate the connection between cellulase expression regulation and ambient pH, an ortholog of Aspergillus nidulans pacC, Trpac1, was identified and functionally characterized using a target gene deletion strategy. Deleting Trpac1 dramatically increased the cellulase production and the transcription levels of the major cellulase genes at neutral pH, which suggested Trpac1 is involved in the regulation of cellulase production. It was further observed that the expression levels of transcription factors xyr1 and ace2 also increased in the ΔTrpac1 mutant at neutral pH. In addition, the ΔTrpac1 mutant exhibited conidiation defects under neutral and alkaline pH. These results implied that Trpac1 in involved in growth and development process and cellulase gene expression in T. reesei.

Construction of a constitutively expressed homo-fermentative pathway in Lactobacillus brevis.

Lactobacillus brevis is a promising lactic acid producing strain that simultaneously utilizes glucose and xylose from lignocellulosic hydrolysate without carbon catabolic repression and inhibition. The production of by-products acetic acid and ethanol has been the major drawback of this strain. Two genes, pfkA (fructose-6-phosphate kinase [PFK]) and fbaA (fructose-1,6-biphosphate aldolase [FBA]), that encode the key enzymes of the EMP/glycolytic pathway from Lactobacillus rhamnosus, were fused to the downstream of the strong promoter P32 and expressed in L. brevis s3f4 as a strategy to minimize the formation of by-products. By expressing the two enzymes, a homo-fermentative pathway for lactic acid production was constructed. The lactic acid yields achieved from glucose in the transformants were 1.12 and 1.16 mol/mol, which is higher than that of the native strain (0.74 mol/mol). However, the lactic acid yield from xylose in the transformants stayed the same as that of the native strain. Enzyme assay indicated that the activity of the foreign protein FBA in the transformants was much higher than that of the native strains, but was ten times lower than that in L. rhamnosus. This result was consistent with the metabolic flux analysis, which indicated that the conversion efficiency of the expressed PFK and FBA was somewhat low. Less than 20 % of the carbons accumulated in the form of fructose-6-phosphate were converted into glyceraldehyde-3-phosphate (GAP) by the expressed PFK and FBA. Metabolic flux analysis also indicated that the enzyme phosphoketolase (XPK) played an important role in splitting the carbon flow from the pentose phosphate pathway to the phosphoketolase pathway. This study suggested that the lactic acid yield of L. brevis could be improved by constructing a homo-fermentative pathway.

Kinetic studies on batch cultivation of Trichoderma reesei and application to enhance cellulase production by fed-batch fermentation.

Reducing the production cost of cellulase as the key enzyme for cellulose hydrolysis to fermentable sugars remains a major challenge for biofuel production. Because of the complexity of cellulase production, kinetic modeling and mass balance calculation can be used as effective tools for process design and optimization. In this study, kinetic models for cell growth, substrate consumption and cellulase production in batch fermentation were developed, and then applied in fed-batch fermentation to enhance cellulase production. Inhibition effect of substrate was considered and a modified Luedeking-Piret model was developed for cellulase production and substrate consumption according to the growth characteristics of Trichoderma reesei. The model predictions fit well with the experimental data. Simulation results showed that higher initial substrate concentration led to decrease of cellulase production rate. Mass balance and kinetic simulation results were applied to determine the feeding strategy. Cellulase production and its corresponding productivity increased by 82.13% after employing the proper feeding strategy in fed-batch fermentation. This method combining mathematics and chemometrics by kinetic modeling and mass balance can not only improve cellulase fermentation process, but also help to better understand the cellulase fermentation process. The model development can also provide insight to other similar fermentation processes.

Performances of Lactobacillus brevis for producing lactic acid from hydrolysate of lignocellulosics.

Utilizing all forms of sugars derived from lignocellulosic biomass via various pretreatment and hydrolysis process is a primary criterion for selecting a microorganism to produce biofuels and biochemicals. A broad carbon spectra and potential inhibitors such as furan, phenol compounds and weak acids are two major obstacles that limited the application of dilute-acid hydrolysate of lignocellulosics in lactic acid fermentation. Two strains of bacteria isolated from sour cabbage, S3F4 (Lactobacillus brevis) and XS1T3-4 (Lactobacillus plantrum), exhibited the ability to utilize various sugars present in dilute-acid hydrolysate of biomass. The S3F4 strain also showed strong resistance to potential fermentation inhibitors such as ferulic acid and furfural. Fermentation in flasks by this strain resulted in 39.1 g/l of lactic acid from dilute acid hydrolysates of corncobs that had initial total sugar concentration of 56.9 g/l (xylose, 46.4 g/l; glucose, 4.0 g/l; arabinose, 6.5 g/l). The hydrolysate of corncobs was readily utilized by S3F4 without detoxification, and the lactic acid concentration obtained in this study was higher compared to other reports.