Construction of an enzyme-constrained metabolic network model for Myceliophthora thermophila using machine learning-based kcat data.

BACKGROUND: Genome-scale metabolic models (GEMs) serve as effective tools for understanding cellular phenotypes and predicting engineering targets in the development of industrial strain. Enzyme-constrained genome-scale metabolic models (ecGEMs) have emerged as a valuable advancement, providing more accurate predictions and unveiling new engineering targets compared to models lacking enzyme constraints. In 2022, a stoichiometric GEM, iDL1450, was reconstructed for the industrially significant fungus Myceliophthora thermophila. To enhance the GEM's performance, an ecGEM was developed for M. thermophila in this study. RESULTS: Initially, the model iDL1450 underwent refinement and updates, resulting in a new version named iYW1475. These updates included adjustments to biomass components, correction of gene-protein-reaction (GPR) rules, and a consensus on metabolites. Subsequently, the first ecGEM for M. thermophila was constructed using machine learning-based kcat data predicted by TurNuP within the ECMpy framework. During the construction, three versions of ecGEMs were developed based on three distinct kcat collection methods, namely AutoPACMEN, DLKcat and TurNuP. After comparison, the ecGEM constructed using TurNuP-predicted kcat values performed better in several aspects and was selected as the definitive version of ecGEM for M. thermophila (ecMTM). Comparing ecMTM to iYW1475, the solution space was reduced and the growth simulation results more closely resembled realistic cellular phenotypes. Metabolic adjustment simulated by ecMTM revealed a trade-off between biomass yield and enzyme usage efficiency at varying glucose uptake rates. Notably, hierarchical utilization of five carbon sources derived from plant biomass hydrolysis was accurately captured and explained by ecMTM. Furthermore, based on enzyme cost considerations, ecMTM successfully predicted reported targets for metabolic engineering modification and introduced some new potential targets for chemicals produced in M. thermophila. CONCLUSIONS: In this study, the incorporation of enzyme constraint to iYW1475 not only improved prediction accuracy but also broadened the model's applicability. This research demonstrates the effectiveness of integrating of machine learning-based kcat data in the construction of ecGEMs especially in situations where there is limited measured enzyme kinetic parameters for a specific organism.

Consolidated bioprocessing for bioethanol production by metabolically engineered cellulolytic fungus Myceliophthora thermophila.

Using cellulosic ethanol as fuel is one way to help achieve the world's decarbonization goals. However, the economics of the present technology are unfavorable, especially the cost of cellulose degradation. Here, we reprogram the thermophilic cellulosic fungus Myceliophthora thermophila to directly ferment cellulose into ethanol by mimicking the aerobic ethanol fermentation of yeast (the Crabtree effect), including optimizing the synthetic pathway, enhancing the glycolytic rate, inhibiting mitochondrial NADH shuttles, and knocking out ethanol consumption pathway. The final engineered strain produced 52.8 g/L ethanol directly from cellulose, and 39.8 g/L from corncob, without the need for any added cellulase, while the starting strain produced almost no ethanol. We also demonstrate that as the ethanol fermentation by engineered M. thermophila increases, the composition and expression of cellulases that facilitate the degradation of cellulose, especially cellobiohydrolases, changes. The simplified production process and significantly increased ethanol yield indicate that the fungal consolidated bioprocessing technology that we develop here (one-step, one-strain ethanol production) is promising for fueling sustainable carbon-neutral biomanufacturing in the future.

Development of the thermophilic fungus Myceliophthora thermophila into glucoamylase hyperproduction system via the metabolic engineering using improved AsCas12a variants.

BACKGROUND: Glucoamylase is an important enzyme for starch saccharification in the food and biofuel industries and mainly produced from mesophilic fungi such as Aspergillus and Rhizopus species. Enzymes produced from thermophilic fungi can save the fermentation energy and reduce costs as compared to the fermentation system using mesophiles. Thermophilic fungus Myceliophthora thermophila is industrially deployed fungus to produce enzymes and biobased chemicals from biomass during optimal growth at 45 °C. This study aimed to construct the M. thermophila platform for glucoamylase hyper-production by broadening genomic targeting range of the AsCas12a variants, identifying key candidate genes and strain engineering. RESULTS: In this study, to increase the genome targeting range, we upgraded the CRISPR-Cas12a-mediated technique by engineering two AsCas12a variants carrying the mutations S542R/K607R and S542R/K548V/N552R. Using the engineered AsCas12a variants, we deleted identified key factors involved in the glucoamylase expression and secretion in M. thermophila, including Mtstk-12, Mtap3m, Mtdsc-1 and Mtsah-2. Deletion of four targets led to more than 1.87- and 1.85-fold higher levels of secretion and glucoamylases activity compared to wild-type strain MtWT. Transcript level of the major amylolytic genes showed significantly increased in deletion mutants. The glucoamylase hyper-production strain MtGM12 was generated from our previously strain MtYM6 via genetically engineering these targets Mtstk-12, Mtap3m, Mtdsc-1 and Mtsah-2 and overexpressing Mtamy1 and Mtpga3. Total secreted protein and activities of amylolytic enzymes in the MtGM12 were about 35.6-fold and 51.9‒55.5-fold higher than in MtWT. Transcriptional profiling analyses revealed that the amylolytic gene expression levels were significantly up-regulated in the MtGM12 than in MtWT. More interestingly, the MtGM12 showed predominantly short and highly bulging hyphae with proliferation of rough ER and abundant mitochondria, secretion vesicles and vacuoles when culturing on starch. CONCLUSIONS: Our results showed that these AsCas12a variants worked well for gene deletions in M. thermophila. We successfully constructed the glucoamylase hyper-production strain of M. thermophila by the rational redesigning and engineering the transcriptional regulatory and secretion pathway. This targeted engineering strategy will be very helpful to improve industrial fungal strains and promote the morphology engineering for enhanced enzyme production.

MtTRC-1, a Novel Transcription Factor, Regulates Cellulase Production via Directly Modulating the Genes Expression of the Mthac-1 and Mtcbh-1 in Myceliophthora thermophila.

The thermophilic fungus Myceliophthora thermophila has been used to produce industrial enzymes and biobased chemicals. In saprotrophic fungi, the mechanisms regulating cellulase production have been studied, which revealed the involvement of multiple transcription factors. However, in M. thermophila, the transcription factors influencing cellulase gene expression and secretion remain largely unknown. In this study, we identified and characterized a novel cellulase regulator (MtTRC-1) in M. thermophila through a combination of functional genomics and genetic analyses. Deletion of Mttrc-1 resulted in significantly decreased cellulase production and activities. Transcriptome analysis revealed downregulation of not only the encoding genes of main cellulases but also the transcriptional regulator MtHAC-1 of UPR pathway after disruption of MtTRC-1 under cellulolytic induction conditions. Herein, we also characterized the ortholog of the yeast HAC1p in M. thermophila. We show that Mthac-1 mRNA undergoes an endoplasmic reticulum (ER) stress-induced splicing by removing a 23-nucleotide (nt) intron. Notably, the protein secretion on cellulose was dramatically impaired by the deletion of MtHAC-1. Moreover, the colonial growth on various carbon sources was defective in the absence of MtHAC-1. Electrophoretic mobility shift assays and chromatin immunoprecipitation assays verified MtTRC-1 regulates the transcription of Mthac-1 and the major cellulase gene Mtcbh-1 by binding directly to the promoters in vitro and in vivo. Furthermore, DNase I footprinting assays identified the putative consensus binding site (5'-GNG/C-3'). These results revealed the importance of MtTRC-1 for positively regulating cellulase production. This finding has clarified the complex regulatory pathways involved in cellulolytic enzyme production. IMPORTANCE In the present study, we characterized a novel regulator MtTRC-1 in M. thermophila, which regulated cellulase production through direct transcriptional regulation of the Mthac-1 and Mtcbh-1 genes. Our data demonstrated that MtHAC-1 is a key factor for the cellulase secretion capacity of M. thermophila. Our data indicate that this thermophilic fungus regulates cellulase production through a multilevels network, in which the protein secretory pathway is modulated by MtHAC-1-dependent UPR pathway and the cellulase gene expression is directly regulated in parallel by transcription factors. The conservation of Mttrc1 in filamentous fungi suggests this mechanism may be exploited to engineer filamentous fungal cell factories capable of producing proteins on an industrial scale.

Reconstruction and analysis of genome-scale metabolic model for thermophilic fungus Myceliophthora thermophila.

Myceliophthora thermophila, a thermophilic fungus that can degrade and utilize all major polysaccharides in plant biomass, has great potential in biotechnological industries. Here, the first manually curated genome-scale metabolic model iDL1450 for M. thermophila was reconstructed using an autogenerating pipeline with thorough manual curation. The model contains 1450 genes, 2592 reactions, and 1784 unique metabolites. High accuracy was shown in predictions related to carbon and nitrogen source utilization based on data obtained from Biolog experiments. Besides, metabolism profiles were analyzed using iDL1450 integrated with transcriptomics data of M. thermophila at various growth temperatures. The refined model provides new insights into thermophilic fungi metabolism and sheds light on model-driven strain design to improve biotechnological applications of this thermophilic lignocellulosic fungus.

Two Facile Aniline-Based Hypercrosslinked Polymer Adsorbents for Highly Efficient Iodine Capture and Removal.

Effective capture and safe disposal of radioactive iodine (129I or 131I) during nuclear power generation processes have always been a worldwide environmental concern. Low-cost and high-efficiency iodine removal materials are urgently needed. In this study, we synthesized two aniline-based hypercrosslinked polymers (AHCPs), AHCP-1 and AHCP-2, for iodine capture in both aqueous and gaseous phases. They are obtained by aniline polymerization through Friedel-Crafts alkylation and Scholl coupling reaction, respectively, with high chemical and thermal stability. Notably, AHCP-1 exhibits record-high static iodine adsorption (250 wt%) in aqueous solution. In the iodine vapor adsorption, AHCP-2 presents an excellent total iodine capture (596 wt%), surpassing the most reported amorphous polymer adsorbents. The rich primary amine groups of AHCPs promote the rapid physical capture of iodine from iodine water and iodine vapor. Intrinsic features such as low-cost preparation, good recyclability, as well as excellent performance in iodine capture indicate that the AHCPs can be used as potential candidates for the removal of iodine from radioactive wastewater and gas mixtures.

Molecular simulation and experimental studies of a mesoporous ZSM-5 type molecular sieve.

The mesoporous zeolite is a novel porous material possessing mesopores as well as the inherent micropores of zeolites. This material can exhibit the dual merits of two different pore structures and enable zeolites to have maximum structural functions. During the past few decades, various synthetic strategies have been well developed. However, up to now, there has only been a few attempts to model mesoporous zeolites. In this paper, the structural properties of a mesoporous ZSM-5 type molecular sieve, which has mesopore walls that are made up of ZSM-5 zeolite-like frameworks, were studied using an atomistic model. The full-atom model of the mesoporous ZSM-5 type molecular sieve was constructed using a molecular modeling technique. The structure model was characterized by estimating the nitrogen accessible solvent surface area, small-angle and wide-angle X-ray diffraction patterns, toluene and benzene adsorption. It was found that these simulated results match well with the experimental data. Furthermore, the present approach can be extended to construct other micro-mesoporous molecular sieve structure models in the future.

Construction and application of high-quality genome-scale metabolic model of Zymomonas mobilis to guide rational design of microbial cell factories.

High-quality genome-scale metabolic models (GEMs) could play critical roles on rational design of microbial cell factories in the classical Design-Build-Test-Learn cycle of synthetic biology studies. Despite of the constant establishment and update of GEMs for model microorganisms such as Escherichia coli and Saccharomyces cerevisiae, high-quality GEMs for non-model industrial microorganisms are still scarce. Zymomonas mobilis subsp. mobilis ZM4 is a non-model ethanologenic microorganism with many excellent industrial characteristics that has been developing as microbial cell factories for biochemical production. Although five GEMs of Z. mobilis have been constructed, these models are either generating ATP incorrectly, or lacking information of plasmid genes, or not providing standard format file. In this study, a high-quality GEM iZM516 of Z. mobilis ZM4 was constructed. The information from the improved genome annotation, literature, datasets of Biolog Phenotype Microarray studies, and recently updated Gene-Protein-Reaction information was combined for the curation of iZM516. Finally, 516 genes, 1389 reactions, 1437 metabolites, and 3 cell compartments are included in iZM516, which also had the highest MEMOTE score of 91% among all published GEMs of Z. mobilis. Cell growth was then predicted by iZM516, which had 79.4% agreement with the experimental results of the substrate utilization. In addition, the potential endogenous succinate synthesis pathway of Z. mobilis ZM4 was proposed through simulation and analysis using iZM516. Furthermore, metabolic engineering strategies to produce succinate and 1,4-butanediol (1,4-BDO) were designed and then simulated under anaerobic condition using iZM516. The results indicated that 1.68 mol/mol succinate and 1.07 mol/mol 1,4-BDO can be achieved through combinational metabolic engineering strategies, which was comparable to that of the model species E. coli. Our study thus not only established a high-quality GEM iZM516 to help understand and design microbial cell factories for economic biochemical production using Z. mobilis as the chassis, but also provided guidance on building accurate GEMs for other non-model industrial microorganisms.

The Weimberg pathway: an alternative for Myceliophthora thermophila to utilize D-xylose.

BACKGROUND: With D-xylose being the second most abundant sugar in nature, its conversion into products could significantly improve biomass-based process economy. There are two well-studied phosphorylative pathways for D-xylose metabolism. One is isomerase pathway mainly found in bacteria, and the other one is oxo-reductive pathway that always exists in fungi. Except for these two pathways, there are also non-phosphorylative pathways named xylose oxidative pathways and they have several advantages over traditional phosphorylative pathways. In Myceliophthora thermophila, D-xylose can be metabolized through oxo-reductive pathway after plant biomass degradation. The survey of non-phosphorylative pathways in this filamentous fungus will offer a potential way for carbon-efficient production of fuels and chemicals using D-xylose. RESULTS: In this study, an alternative for utilization of D-xylose, the non-phosphorylative Weimberg pathway was established in M. thermophila. Growth on D-xylose of strains whose D-xylose reductase gene was disrupted, was restored after overexpression of the entire Weimberg pathway. During the construction, a native D-xylose dehydrogenase with highest activity in M. thermophila was discovered. Here, M. thermophila was also engineered to produce 1,2,4-butanetriol using D-xylose through non-phosphorylative pathway. Afterwards, transcriptome analysis revealed that the D-xylose dehydrogenase gene was obviously upregulated after deletion of D-xylose reductase gene when cultured in a D-xylose medium. Besides, genes involved in growth were enriched in strains containing the Weimberg pathway. CONCLUSIONS: The Weimberg pathway was established in M. thermophila to support its growth with D-xylose being the sole carbon source. Besides, M. thermophila was engineered to produce 1,2,4-butanetriol using D-xylose through non-phosphorylative pathway. To our knowledge, this is the first report of non-phosphorylative pathway recombinant in filamentous fungi, which shows great potential to convert D-xylose to valuable chemicals.

Understanding the microfluidic generation of double emulsion droplets with alginate shell.

The monodisperse double emulsions obtained by microfluidic method can serve as ideal templates for preparing core-shell alginate microcapsules, which have attracted much attention in biological applications, such as drug delivery systems and cell encapsulation, tissue engineering. However, the formation behavior and dynamic analysis of double emulsion with an alginate shell is still unclear due to the complex rheological behavior of alginate solutions. Herein, we employ a dual-coaxial microfluidic device to generate the high-quality double emulsion droplets with alginate shell, focusing on the effects of the fluid properties of alginate solution in the middle phase (viscosity, µm) and the fluid flow rate on the droplet formation mechanism. As the viscosity of the middle fluid (µm) increased, the size of compound droplets (D2) increased and the size of inner droplets (D1) decreased, and the break-up regimes occurred a dripping-to-jetting transition when µm = 160 mPa s. The number of encapsulated inner droplets can be predicted and precisely controlled by regulating the generation frequency of inner (f1) and outer droplets (f2). The breakup dynamics of the alginate thread are also analyzed by using the volume-of-fluid/continuum-surface-force (VOF/CSF) method. The results show that the pressure and velocity in the neck of pinch-off is lower in the jetting than that in the dripping regime. This study will provide useful guidance for the rational design and controllable preparation of core-shell alginate microcapsules.

The arabinose transporter MtLat-1 is involved in hemicellulase repression as a pentose transceptor in Myceliophthora thermophila.

BACKGROUND: Filamentous fungi possess an array of secreted enzymes to depolymerize the structural polysaccharide components of plant biomass. Sugar transporters play an essential role in nutrient uptake and sensing of extracellular signal molecules to inhibit or trigger the induction of lignocellulolytic enzymes. However, the identities and functions of transceptors associated with the induction of hemicellulase genes remain elusive. RESULTS: In this study, we reveal that the L-arabinose transporter MtLat-1 is associated with repression of hemicellulase gene expression in the filamentous fungus Myceliophthora thermophila. The absence of Mtlat-1 caused a decrease in L-arabinose uptake and consumption rates. However, mycelium growth, protein production, and hemicellulolytic activities were markedly increased in a ΔMtlat-1 mutant compared with the wild-type (WT) when grown on arabinan. Comparative transcriptomic analysis showed a different expression profile in the ΔMtlat-1 strain from that in the WT in response to arabinan, and demonstrated that MtLat-1 was involved in the repression of the main hemicellulase-encoding genes. A point mutation that abolished the L-arabinose transport activity of MtLat-1 did not impact the repression of hemicellulase gene expression when the mutant protein was expressed in the ΔMtlat-1 strain. Thus, the involvement of MtLat-1 in the expression of hemicellulase genes is independent of its transport activity. The data suggested that MtLat-1 is a transceptor that senses and transduces the molecular signal, resulting in downstream repression of hemicellulolytic gene expression. MtAra-1 protein directly regulated the expression of Mtlat-1 by binding to its promoter region. Transcriptomic profiling indicated that the transcription factor MtAra-1 also plays an important role in expression of arabinanolytic enzyme genes and L-arabinose catabolism. CONCLUSIONS: M. thermophila MtLat-1 functions as a transceptor that is involved in L-arabinose transport and signal transduction associated with suppression of the expression of hemicellulolytic enzyme-encoding genes. The data presented in this study add to the models of the regulation of hemicellulases in filamentous fungi.

The putative methyltransferase LaeA regulates mycelium growth and cellulase production in Myceliophthora thermophila.

BACKGROUND: Filamentous fungi with the ability to use complex carbon sources has been developed as platforms for biochemicals production. Myceliophthora thermophila has been developed as the cell factory to produce lignocellulolytic enzymes and plant biomass-based biofuels and biochemicals in biorefinery. However, low fungal growth rate and cellulose utilization efficiency are significant barriers to the satisfactory yield and productivity of target products, which needs our further exploration and improvement. RESULTS: In this study, we comprehensively explored the roles of the putative methyltransferase LaeA in regulating mycelium growth, sugar consumption, and cellulases expression. Deletion of laeA in thermophile fungus Myceliophthora thermophila enhanced mycelium growth and glucose consumption significantly. Further exploration of LaeA regulatory network indicated that multiple growth regulatory factors (GRF) Cre-1, Grf-1, Grf-2, and Grf-3, which act as negative repressors of carbon metabolism, were regulated by LaeA in this fungus. We also determined that phosphoenolpyruvate carboxykinase (PCK) is the core node of the metabolic network related to fungal vegetative growth, of which enhancement partially contributed to the elevated sugar consumption and fungal growth of mutant ΔlaeA. Noteworthily, LaeA participated in regulating the expression of cellulase genes and their transcription regulator. ΔlaeA exhibited 30.6% and 5.5% increases in the peak values of extracellular protein and endo-glucanase activity, respectively, as compared to the WT strain. Furthermore, the global histone methylation assays indicated that LaeA is associated with modulating H3K9 methylation levels. The normal function of LaeA on regulating fungal physiology is dependent on methyltransferase activity. CONCLUSIONS: The research presented in this study clarified the function and elucidated the regulatory network of LaeA in the regulation of fungal growth and cellulase production, which will significantly deepen our understanding about the regulation mechanism of LaeA in filamentous fungi and provides the new strategy for improvement the fermentation properties of industrial fungal strain by metabolic engineering.

PFK2/FBPase-2 is a potential target for metabolic engineering in the filamentous fungus Myceliophthora thermophila.

The key enzyme 6-phosphofructo-2-kinase (PFK2)/fructose-2,6-bisphosphatase (FBPase-2) is responsible for regulating the rates of glycolysis and gluconeogenesis in eukaryotes. However, its functions and mechanisms in filamentous fungi remain largely enigmatic. In this study, we systematically investigated the function of this enzyme in Myceliophthora thermophila, a thermophilic filamentous fungus with great capacity to produce industrial enzymes and organic acids. Our results showed that the M. thermophila genome encodes three isomers, all with the PFK2/FBPase-2 structure: pfk2-a, pfk2-b, and pfk2-c. Overexpression of each gene revealed that endogenous expression of pfk2-c (PFK2 activity) promoted glucose metabolism, while overexpression of pfk2-a (FBPase-2 activity) inhibited strain growth. Using knockouts, we found that each gene was individually non-essential, but the triple knockout led to significantly slower growth compared with the wild-type strain. Only the pfk2-a single knockout exhibited 22.15% faster sugar metabolism, exerted through activation of 6-phosphofructo-1-kinase (PFK1), thereby significantly promoting glycolysis and the tricarboxylic acid cycle. The FBPase-2 deletion mutant strain also exhibited overflow metabolism, and knocking out pfk2-a was proved to be able to improve the production and synthesis rate of various metabolites, such as glycerol and malate. This is the first study to systematically investigate the function of PFK2/FBPase-2 in a thermophilic fungus, providing an effective target for metabolic engineering in filamentous fungi.

[Plant biomass degradation by filamentous fungi and production of renewable chemicals: a review].

Plant biomass represents a vast resource of carbon. In China, it is estimated that 1 billion tons of biomass is available each year. The conversion of these biomass resources into bioethanol or other bio-based chemicals, if fully commercialized, may reduce at least 200 million tons of crude oil import. Therefore, bioethanol and bulk chemicals are the core components of the biomanufacturing using plant biomass as carbon sources. Since the foundation of Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences (TIB, CAS), we have proposed a strategy of "two replacements and one upgrade". Utilizing renewable carbon resources instead of non-renewable petrochemical resources to produce bulk chemicals is included in our strategy. It is a long-term effort for TIB to develop plant biomass biomanufacturing to produce renewable chemicals. Continuous and systematic research was carried out in these two fields, and significant progress has been made in the past 10 years since the foundation of TIB. Here we review the progress of TIB in this field, mainly focusing on fungal system, including the mechanism of cellulose degradation by filamentous fungi and the strategy of consolidated bioprocessing of biomass. Based on this, malic acid, fuel ethanol and other bulk chemicals were produced through one-step conversion of biomass. Besides, the commercial processes for production of bulk chemicals such as succinic and lactic acid from renewable carbon resources, which were developed by TIB, were also be discussed. These examples clearly demonstrated that bulk chemicals can be obtained from biomass instead of from petroleum. Research on plant biomass biotransformation and renewable chemicals production in TIB has provided an alternative route for the development of low-carbon bioeconomy in China, and will contribute to the goal of carbon neutralization of China.

[Advances in metabolic engineering of filamentous fungi].

Filamentous fungi are important industrial microorganisms that play important roles in the production of bio-based products such as organic acids, proteins and secondary metabolites. The development of metabolic engineering and its enabling techniques have greatly promoted the design, construction and application of filamentous fungal cell factories. This article systematically reviews the development of filamentous fungal cell factories constructed through metabolic engineering, and discusses the challenges and future perspectives for systems metabolic engineering of filamentous fungi.

Coordination of consolidated bioprocessing technology and carbon dioxide fixation to produce malic acid directly from plant biomass in Myceliophthora thermophila.

BACKGROUND: Consolidated bioprocessing (CBP) technique is a promising strategy for biorefinery construction, producing bulk chemicals directly from plant biomass without extra hydrolysis steps. Fixing and channeling CO2 into carbon metabolism for increased carbon efficiency in producing value-added compounds is another strategy for cost-effective bio-manufacturing. It has not been reported whether these two strategies can be combined in one microbial platform. RESULTS: In this study, using the cellulolytic thermophilic fungus Myceliophthora thermophila, we designed and constructed a novel biorefinery system DMCC (Direct microbial conversion of biomass with CO2 fixation) through incorporating two CO2 fixation modules, PYC module and Calvin-Benson-Bassham (CBB) pathway. Harboring the both modules, the average rate of fixing and channeling 13CO2 into malic acid in strain CP51 achieved 44.4, 90.7, and 80.7 mg/L/h, on xylose, glucose, and cellulose, respectively. The corresponding titers of malic acid were up to 42.1, 70.4, and 70.1 g/L, respectively, representing the increases of 40%, 10%, and 7%, respectively, compared to the parental strain possessing only PYC module. The DMCC system was further improved by enhancing the pentose uptake ability. Using raw plant biomass as the feedstock, yield of malic acid produced by the DMCC system was up to 0.53 g/g, with 13C content of 0.44 mol/mol malic acid, suggesting DMCC system can produce 1 t of malic acid from 1.89 t of biomass and fix 0.14 t CO2 accordingly. CONCLUSIONS: This study designed and constructed a novel biorefinery system named DMCC, which can convert raw plant biomass and CO2 into organic acid efficiently, presenting a promising strategy for cost-effective production of value-added compounds in biorefinery. The DMCC system is one of great options for realization of carbon neutral economy.

Formate-Selective CO2 Electrochemical Reduction with a Hydrogen-Reduction-Suppressing Bronze Alloy Hollow-Fiber Electrode.

Electroreduction carbon dioxide into formate has been regarded as a hopeful measure to relieve global warming. Copper-based hollow fibers demonstrated good performances on converting carbon dioxide in previous researches. Herein Cu-Sn alloy hollow fibers were synthesized in an innovative way, combining the structure advantages of hollow fiber and high selectivity towards formate on η' bronze. Tests under different gas injection conditions were conducted to analyze the contribution of the hollow fiber structure on suppression of hydrogen evolution and promotion on kinetics. Strikingly, Cu-Sn45 % hollow fiber, the optimal catalyst in this work, achieved a highest faradaic efficiency towards formate of 90.96 % at a lower potential of -0.75 V vs. RHE than most non-noble catalysts, and the FE of H2 was below 4 %.

MnO2-decorated N-doped carbon nanotube with boosted activity for low-temperature oxidation of formaldehyde.

Low-temperature oxidative degradation of formaldehyde (HCHO) using non-noble metal catalysts is challenging. Herein, novel manganese dioxide (MnO2)/N-doped carbon nanotubes (NCNT) composites were prepared with varying MnO2 content. The surface properties and morphologies were analyzed using X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and transmission electron microscope (TEM). Comparing with MnO2/carbon nanotubes (CNTs) catalyst, the 40% MnO2/NCNT exhibited much better activity and selectivity for HCHO oxidation, mineralizing 95% of HCHO (at 100 ppm) into CO2 at 30 °C at a gas hourly space velocity (GHSV) of 30,000 mL h-1  g-1. Density functional theory (DFT) calculation was used to analyze the difference in the catalytic activity of MnO2 with CNTs and NCNT carrier. It was confirmed that the oxygen on NCNT was more active than CNTs, which facilitated the regeneration of MnO2. This resulted in remarkably boosted activity for HCHO oxidation. The present work thus exploited an inexpensive approach to enhance the catalytic activity of transition metal oxides via depositing them on a suitable support.

Deciphering Microbiome Related to Rusty Roots of Panax ginseng and Evaluation of Antagonists Against Pathogenic Ilyonectria.

Plant roots host diverse microbes that are closely associated with root fitness. Currently, the relationship between microbes and rusty roots of Panax ginseng remains unclear. Here, we described the root-associated microbiome in rusty and healthy ginseng by metagenomic sequencing of 16S rRNA and ITS regions. Being enriched in Diseased-roots (Dr) of ginseng and their rhizosphere soil, the fungus of Ilyonectria, was identified as the most probable cause of the disease after ITS analysis. Meanwhile, an increase of Mortierella was observed in Healthy-roots (Hr). Surprisingly, an enriched Fusarium was found in both Hr and their rhizosphere soil. Besides, in comparison with Hr, decreased relative abundance of Actinomycetales and increased relative abundance of Pseudomonadales was observed in Dr after 16S rRNA analysis. What's more, we isolated several microorganisms as antagonists that showed strong inhibiting effects on Ilyonectria in plate assays. In field trials, inoculation of Bacillus sp. S-11 displayed apparent suppression effect against Ilyonectria and shifted microbial communities in rhizosphere soil. Our research identified key microbiota involved in rusty roots of P. ginseng and offered potential biocontrol solutions to rusty disease.

Dual-Function Conductive Copper Hollow Fibers for Microfiltration and Anti-biofouling in Electrochemical Membrane Bioreactors.

Membrane bioreactors (MBRs) with polymeric/ceramic microfiltration (MF) membranes have been commonly used for wastewater treatment today. However, membrane biofouling often results in a dramatically-reduced service life of MF membranes, which limits the application of this technology. In this study, Cu hollow fiber membranes (Cu-HFMs) with low resistivity (104.8-309.8 nΩ·m) and anti-biofouling properties were successfully synthesized. Further analysis demonstrated that Cu-HFMs reduced at 625°C achieved the bimodal pore size distribution of ~1 µm and a porosity of 46%, which enable high N2 permeance (1.56 × 10-5 mol/m2 s pa) and pure water flux (5812 LMH/bar). The Cu-HFMs were further applied as the conductive cathodes, as well as MF membranes, in the electrochemical membrane bioreactor (EMBR) system that was enriched with domestic wastewater at an applied voltage of 0.9 V. Excellent permeate quality (Total suspended solids (TSS) = 11 mg/L) was achieved at a flux of 9.47 LMH after Cu-HFM filtration, with relatively stable transmembrane pressure (TMP) and low Cu2+ dissolvability (<25 µg/L). The anti-biofouling over time was demonstrated by SEM characterization of the rare biofilm formation on the Cu-HFM cathode surface. By using Cu-HFMs in EMBR systems, an effective strategy to control the membrane biofouling is developed in this study.