Cellulosomal hemicellulases:Indispensable players for ensuring effective lignocellulose bioconversion

The bioconversion of lignocellulose has attracted global attention,due to the significant potential of agricultural and forestry wastes as renewable zero-carbon resources and the urgent need for substituting fossil carbon.The cellulosome system is a multi-enzyme complex produced by anaerobic bacteria,which comprises cellulases,hemicellulases,and associated enzymatic and non-enzymatic components that promote biomass conversion.To enhance their efficiency in degrading recalcitrant lignocellulosic matrices,cellulosomes have been employed to construct biocatalysts for lignocellulose bioconversion,such as consolidated bioprocessing and consolidated bio-saccharification.Hemicelluloses,the second most abundant polysaccharides in plant cell walls,hold valuable application potential but can also induce inhibitory effects on cellulose hydrolysis,thus highlighting the indispensable roles of hemicellulases within the cellulosome complex.This review evaluated current research on cellulosomal hemicellulases,comparing their types,abundance,and regulation,primarily focusing on eight known cellulosome-producing species of different origins.We also reviewed their growth conditions,their hemicellulose-degrading capabilities,and the inhibitory effects of hemicellulose on cellulosome-based lignocellulose saccharification.Finally,we proposed strategies for targeted enhancement of hemicellulase in cellulosomes to improve lignocellulose bioconversion in future studies.

Towards greener polymers:Trends in the German chemical industry

Global plastics production is expected to exceed 400 million tons and reach 600 million tons by 2060.Their synthesis currently accounts for approximately 3%of global greenhouse gas emissions.Approximately 60%of all polymers are produced for single-use.Examples include shopping bags,packaging materials,mulch films,and soluble polymers for cosmetics and other purposes.Currently,only a portion of single-use plastic is recycled or disposed of in incinerators or landfills.An estimated 20%is not disposed of properly and pollutes the global environment,especially the oceans.In response to these challenges,the United Nations,European Union,and many nation-states are developing regulatory frameworks that encourage the chemical industry to produce plastics with a smaller environmental footprint and often support this through research funding.Possible solutions include:(1)the use of green energy,green hydrogen,bio-based feedstocks,or CO_(2) in synthesis;(2)the reuse or recycling of plastics through conversion or pyrolysis;and(3)the production of biodegradable polymers.The German chemical industry contributes approximately one-third of polymer production in the EU.It is embedded in the EU regulatory and research landscape and anchored in the European Green Deal,which aims for carbon neutrality by 2050.In this paper,we describe how BASF and Evonik,two leading German chemical companies with strong but different polymer portfolios,respond to the call for greener polymers and how technologies are being developed to make polyurethanes,a particularly important and difficult-to-recycle family of elastomers and duromers,renewable and circular.Reducing the environmental footprint of plastics requires not only innovative materials but also proper governance,regulatory and collection systems,and public willingness to cooperate.In an international comparison of these competencies,expressed by the"polymer management index"(PMI),Germany achieved a top position.

Synergistic oxidation-reforming of biomass for high quality syngas production based on a bifunctional catalyst

Conventional O_(2)gasification for low-rank biomass/sludge conversion is prone to high CO_(2)concentrations in the syngas because of its high O content and low calorific value.This study establishes a synergistic oxidationreforming reaction route for the conversion of low-rank carbon-containing resources into high-quality syngas.The efficient oxidation-reforming reaction is based on the bifunctional catalyst NiO-Fe_(2)O_(3)/Al_(2)O_(3),which includes Fe_(2)O_(3) oxidation sites and NiO reforming sites.Hydrogen temperature-programmed reduction,together with X-ray diffraction and X-ray photoelectron spectroscopy experiments,demonstrated that the two functional active sites have strong interactions with the support,leading to efficient cooperation between the oxidation reaction and reforming reaction with regards to both the reaction sequence and C/H/O element balance.Syngas produced from biomass/sludge based on oxidation-reforming reactions has an extremely low CO_(2)concentration of approximately 3%,and the valid gas(CO,H_(2))concentration exceeds 95%.The valid gas yield of walnut shell reached 1452.9 mL/g,the total gas yield was 1507.2 mL/g,and the H_(2)/CO ratio was 1.02,which are all very close to the theoretical maximum values of 1553.1 mL/g and 1.01,respectively,demonstrating that the inherent CO_(2)/H_(2)O along with CH4/tar species were efficiently converted to H_(2)and CO through oxidation-reforming reactions.During a 60-cycle test,NiO-Fe_(2)O_(3)/Al_(2)O_(3) exhibited good redox stability.

Carbon nanotube-based photothermal membrane for efficient cold air heating and removal of particulate matter and airborne bacteria

Indoor heating results in high energy consumption and severe atmospheric pollution.Although the development of solar air heaters provides a sustainable route for indoor thermal comfort,such heaters still face challenges in terms of adequate heat exchange and filtering of atmospheric pollutants.Inspired by solar-driven interfacial evaporation,we propose a multifunctional carbon nanotube-based photothermal membrane for efficient cold air heating and purification via ventilation.Carbon nanotubes endow the membrane with high light absorption and thermal conversion capabilities,thereby sufficiently heating the approaching cold air.With the hierarchical structure formed by phase inversion,the thin upper skin of the composite membrane intercepts micropollutants via the size-sieving effect,whereas the finger-like pores and interpenetrating macrovoids inside the membrane ensure that the heated clear air passes through quickly.A proof-of-principle experiment indicated a cold airflow of 1 L/min across the membrane,yielding a temperature increase of ca.37℃ as well as a PM 2.5 rejection always higher than 93%.Further antibacterial experiments demonstrated that the membrane effectively removed airborne bacteria.This multifunctional carbon nanotube-based photothermal membrane with specific microstructures not only improves the indoor living quality but also provides a sustainable development scheme to coordinate the relationship among energy utilization,building heating,and air purification.

Monolithic metal-based/porous carbon nanocomposites made from dissolved cellulose for use in electrochemical capacitor

Porous metal-based carbon nanocomposites,with a monolithic shape,were prepared by a one-pot synthesis from dissolved cellulose and metallic salts using a simple,cheap,and environmentally friendly route.Their potential performances as electrochemical capacitors were tested with three metal precursors(M=Cu,Mn,and Fe)with two loadings and in an asymmetric cell for the Fe-based carbon material.Interestingly,here soluble metal precursors were not deposited on a hard cellulose template but mixed in a precooled concentrated NaOH solution where cellulose was previously dissolved,allowing for a good dispersion of the metallic species.After a freezing step where concomitant cellulose regeneration and pore ice-templating phenomena took place,followed by a carbonization step,the mixture led to a porous carbon monolith embedding well-dispersed metal-based nanoparticles having a diameter below 20 nm and present as metallic,oxide,or carbide phase(s)according to the element M.These materials were characterized by different physicochemical techniques and electrochemical tests.Their performances as supercapacitors are discussed in light of the specific behaviour of the metal-based phase and its influence on the carbon matrix properties such as mesopore formation and carbon graphitization.An asymmetric energy storage cell assembled with a Fe-based carbon electrode against a carbon xerogel electrode derived from a phenolic resin shows specific energy and power of 18.3 Wh kg^(−1)at 5 mA cm^(−2)and 1.6 kW kg^(−1)at 25 mA cm^(−2),respectively.

Generation and transformation ofα-oxy carbene intermediates enabled by copper-catalyzed carbonylation

Since the Fischer-Tropsch reaction was discovered by Otto Roelen in 1938,transition metal-catalyzed carbo-nylation reactions come in as one of the most important methods for preparing carbonyl-containing and carbon chain-increased compounds.As a result,the field of carbonylation research has received considerable attention over the past decades and continues to increase.With the continuous development of carbonylation and the in-depth study of the mechanism,more mechanistic details and variations have been revealed,which provide more possibilities for organic synthesis.Recently,copper catalysis has been introduced to the carbonylative functio-nalization of alkenes,thus enabling the rapid assembly of functionalized carbonyl compounds from simple starting materials.In this Account,we summarize the new findings in the Cu-catalyzed borocarbonylation of alkenes based on the generation and transformation ofα-oxy carbene intermediates.We believe that the results presented in this Account will further inspire the design of new carbonylation reactions.

Recycled polymer:Green roads for polyester plastics

Plastics are integral to numerous significant social advancements.Nonetheless,their contribution to environmental pollution and climate crises cannot be disregarded,as their negative impact on the environment increases with incremental production capacity and demand.Concerted global action is urgently required to promote the green recycle of plastics to prevent their accumulation in the environment and mitigate carbon emissions.This review aims to reveal the paths of green development for polyester plastics,incorporating the trends of the green revolution in mature commercial polyester plastics,newly emerging biodegradable polyester plastics,and future polyester plastics.A critical discussion was conducted on the current and potential future research areas from multiple perspectives,including raw materials,processes,and recycling,to propel us into a future marked by sustainability.

Optimization of two-dimensional solid-state electrolyte-anode interface by integrating zinc into composite anode with dual-conductive phases

Solid-state electrolytes(SSEs)are a solution to safety issues related to flammable organic electrolytes for Li batteries.Insufficient contact between the anode and SSE results in high interface resistance,thus causing the batteries to exhibit high charging and discharging overpotentials.Recently,we reduced the overpotential of Li stripping and plating by introducing a high proportion of dual-conductive phases into a composite anode.The current study investigates the interface resistance and stability of a composite electrode modified with Zn and a lower proportion of dual-conductive phases.Zn-cation-adsorbed Prussian blue is synthesized as an intermediate component for a Zn-modified composite electrode(Li-FeZnNC).The Li-FeZnNC symmetric cell presents a lower interface resistance and overpotential compared with Li-FeNC(without Zn modification)and Li-symmetric cells.The Li-FeZnNC symmetric cell shows high electrochemical stability during Li stripping and plating at different current densities and high stability for 200 h.Full batteries with a Li-FeZnNC composite anode,garnet-type SSE,and LiFePO4 cathode show low charging and discharging overpotentials,a capacity of 152 mAh g^(−1),and high stability for 200 cycles.

Pilot-scale acetone-butanol-ethanol fermentation from corn stover

Biobutanol is an advanced biofuel that can be produced from excess lignocellulose via acetone-butanol-ethanol(ABE)fermentation.Although significant technological progress has been made in this field,attempts at largescale lignocellulosic ABE production remain scarce.In this study,1m^(3)scale ABE fermentation was investigated using high inhibitor tolerance Clostridium acetobutylicum ABE-P1201 and steam-exploded corn stover hydrolysate(SECSH).Before expanding the fermentation scale,the detoxification process for SECSH was simplified by process engineering.Results revealed that appropriate pH management during the fed-batch cultivation could largely decrease the inhibition of the toxic components in undetoxified SECSH to the solventogenesis phase of the ABE-P1201 strains,avoiding“acid crash”.Therefore,after naturalizing the pH by Ca(OH)_(2),the undetoxified SECSH,without removal of the solid components,reached 17.68±1.30 g/L of ABE production with 0.34±0.01 g/g of yield in 1 L scale bioreactor.Based on this strategy,the fermentation scale gradually expanded from laboratory-scale apparatus to pilot-scale bioreactors.Finally,17.05±1.20 g/L of ABE titer and 0.32±0.01 g/g of ABE yield were realized in 1m3 bioreactor,corresponding to approximately 145 kg of ABE production from 1 t of dry corn stover.The pilot-scale ABE fermentation demonstrated excellent stability during repeated operations.This study provided a simplified ABE fermentation strategy and verified the feasibility of the pilot process,providing tremendous significance and a solid foundation for the future industrialization of second-generation ABE plants.

Advances in electrocarboxylation reactions with CO_(2)

Recently,significant research has been conducted on the conversion of carbon dioxide(CO_(2))into value-added chemicals.With the decreasing cost of clean electricity,electrochemical methods have emerged as potential approaches for converting and fixing CO_(2).Organic electrochemical synthesis is a promising method for utilizing CO_(2)because it transforms CO_(2)into higher-value chemicals.This review introduces the research aspects of CO_(2)conversion and the mechanisms of CO_(2)organic electrocarboxylation reactions.Recent progress in electrocarboxylation with CO_(2)is discussed,considering organic substrates and cathode types under different reaction mechanisms.Finally,the challenges and prospects in this field are highlighted with the aim of further promoting the fundamental understanding of CO_(2)organic electrocarboxylation.

Unveiling the relationship between structural evaluation and catalytic performance of InOOH during electroreduction of CO_(2)to formate

The electrochemical CO_(2)reduction reaction(ECO_(2)RR)to formate is perceived as a technoeconomic pathway for transforming renewable electricity into fuels.However,the indeterminate mechanism underlying structural self-reconstruction obstructs the strategic design of a high-performance In catalyst for the ECO_(2)RR.In this study,we chose InOOH as the model catalyst to illustrate the dynamic structure of In-based catalysts during reconstruction in the ECO_(2)RR.The findings of the current study indicate that the in situ electrochemical reconstruction of crystalline InOOH results in the creation of crystalline In clusters/InOOH,followed by In/InOOH heterostructures,and finally,metallic In over time.The efficiencies of the different phases conformed to the sequence:In clusters/InOOH>In/InOOH heterostructures>metallic In.This progression leads to a continuous drop in maximum current density and Faradaic efficiency from 29.6 mA/cm2 and 87%to 6.3 mA/cm^(2) and 75%,respectively with time extending to 7200 s,at-1.0 V relative to the reversible hydrogen electrode.Our in situ characterization and theoretical studies highlighted the crucial role of the In-cluster/InOOH interface in CO_(2)activation and conversion.

Zeolites for the environment

Zeolites are characterized by their microporous,crystalline structures with a four-connected framework with variable compositions,predominantly aluminosilicates.They are extensively utilized as adsorbents,catalysts,and ion exchangers across domestic and industrial sectors.With the ongoing energy transition from fossil fuels to renewable sources and the pursuit of environmentally sustainable development,zeolites are increasingly being explored beyond their traditional application fields.They are investigated for their adsorption and catalytic capabilities in the protection and restoration of air,water,and soil quality,as well as in the environmentally friendly“green”production of chemicals.This review article details these novel and potential applications of zeolites,emphasizing the unique properties that render them suitable for each specific use case and discussing how these properties can be fine-tuned through material selection or tailored synthesis methods.

Electronic interaction and oxygen vacancy engineering of g-C_(3)N_(4)/α-Bi_(2)O_(3) Zscheme heterojunction for enhanced photocatalytic aerobic oxidative homo-/hetero-coupling of amines to imines in aqueous phase

Photocatalytic oxidation coupling of amines represents a green and cost-effective method for the synthesis of highly value-added imines under visible light irradiation.However,the catalytic efficiency was severely limited by poor visible light response and easy recombination of photogenerated charge carriers.Herein,we report a g-CgN_(4)/α-Bi_(2)O_(3)Z-scheme heterojunction via electrostatic self-assembly of g-C_(3)N_(4)nanosheets and oxygen-va-cancy-rich aα-Bi_(2)O_(3)microsphere for visible-light driven oxidative coupling of amines to imines in H_(2)0 as green solvent at room temperature.Amines with diverse functional groups were efficiently converted into the corre-sponding imines in good to excellent yields.Impressively,this photocatalytic protocol is applicable for the challenging hetero-coupling of two structurally different amines to construct complicated asymmetric imines,which is the first report of photocatalytic hetero-coupling of amines to imines to our knowledge.Furthermore,the Z-scheme heterojunction also demonstrated high stability and could be readily separated and reused without obvious decay in activity and selectivity.Comprehensive characterizations and control experiments reveal the construction of Z-scheme heterojunction with intimate interface between g-CgN4 and a-Bi_(2)O_(3)greatly boosts the transfer and separation of photogenerated charge carries and enhances the redox capability.Meanwhile,the surface oxygen vacancies in a-Biz_(2)O_(3)also benefits the separation of photogenerated charge carriers and acti-vation of reactants.These jointly contributed to an enhanced photocatalytic performance for oxidative coupling of amines to imines.

Affinity-induced covalent protein-protein ligation via the SpyCatcherSpyTag interaction

Production of economically viable bioethanol is potentially an environmentally and financially worthwhile endeavor.One major source for fermentable sugars is lignocellulose.However,lignocellulosic biomass is difficult to degrade,owing to its inherent structural recalcitrance.Cellulosomes are complexes of cellulases and associated polysaccharide-degrading enzymes bound to a protein scaffold that can efficiently degrade lignocellulose.Integration of the enzyme subunits into the complex depends on intermodular cohesin-dockerin interactions,which are robust but nonetheless non-covalent.The modular architecture of these complexes can be used to assemble artificial designer cellulosomes for advanced nanotechnological applications.Pretreatments that promote lignocellulose degradation involve high temperatures and acidic or alkaline conditions that could dismember designer cellulosomes,thus requiring separation of reaction steps,thereby increasing overall process cost.To overcome these challenges,we developed a means of covalently locking cohesin-dockerin interactions by integrating the chemistry of SpyCatcher-SpyTag approach to target and secure the interaction.The resultant cohesin-conjugated dockerin complex was resistant to high temperatures,SDS,and urea while high affinity and specificity of the interacting modular components were maintained.Using this approach,a covalently locked,bivalent designer cellulosome complex was produced and demonstrated to be enzymatically active on cellulosic substrates.The combination of affinity systems with SpyCatcher-SpyTag chemistry may prove of general use for improving other types of protein ligation systems and creating unconventional,biologically active,covalently locked,affinity-based molecular architectures.

Turning light into electricity,biologically

1.Introduction There is an urgent need to develop new technologies to convert solar energy into fuels or electricity for a sustainable circular economy,eventually contributing to carbon neutrality.In terms of electricity generation,a biological technology referring to as biophotovoltaics(BPV)or microbial solar cells represents the greenest route.The BPV technology uses oxygenic photosynthetic microorganisms,e.g.cyanobacteria and eukaryotic algae,to convert light into electricity directly[1].The green characteristics of BPV technology lie in taking advantage of the only known biological oxidation reaction with water as electron donor,i.e.oxygenic photosynthesis.The water-derived electrons are transferred to the anode,flowing towards the cathode in a bioelectrochemical system and generating electrical current.In addition to the clean electron source,the carbon-negative growth of photosynthetic microorganisms used in BPV systems is another feature why BPV technology received increasing attentions.

Investigating formate tolerance mechanisms in Saccharomyces cerevisiae and its application

Current global energy and environmental crisis have spurred efforts towards developing sustainable biotechnological solutions,such as utilizing CO_(2) and its derivatives as raw materials.Formate is an attractive onecarbon source due to its high solubility and low reduction potential.However,the regulatory mechanism of formate metabolism in yeast remains largely unexplored.This study employed adaptive laboratory evolution(ALE)to improve formate tolerance in Saccharomyces cerevisiae and characterized the underlying molecular mechanisms.The evolved strain was applied to produce free fatty acids(FFAs)under high concentration of formate with glucose addition.The results showed that the evolved strain achieved a FFAs titer of 250 mg/L.Overall,this study sheds light on the regulatory mechanism of formate tolerance and provides a platform for future studies under high concentrations of formate.

Opportunities of CO_(2)-based biorefineries for production of fuels and chemicals

Biorefinery production of fuels and chemicals represents an attractive route for solving current energy crisis,as well as reducing green-house gas(GHG)emissions from ships,planes,and long-haul trucks.The current biorefinery industry is under transition from the use of food(1G,1st generation),to the use of biomass(2G,2nd generation).Moreover,the use of atmospheric CO_(2)(3G,3rd generation)has caught increased attention as the possible next-generation biorefinery.Here we discuss how microorganisms can be engineered for CO_(2)-based biorefineries to produce fuels and chemicals.We start through reviewing different metabolic pathways that can be recruited for CO_(2)fixation,followed by different opportunities for CO_(2)fixation,either through co-consumption with sugars or used as the sole carbon source.Key challenges and future research directions for advancing 3rd-generation biorefineries are also be discussed.

Mirror,mirror on the wall,which is the greenest of them all?A critical comparison of chemo-and biocatalytic oxyfunctionalisation reactions

This review article critically compares two widely used types of catalysis,chemo-and biocatalysis,and provides insights on their greenness according to specified parameters.A comparative analysis of the environmental impact of chemo-and biocatalytic oxyfunctionalisation reactions based on published experimental data reveals that both methods produce comparable amounts of waste,with the majority stemming from the solvent used.However,it is emphasised that the synthesis of the catalysts themselves,including biocatalysts,should also be considered when assessing their environmental impact.The review underscores the complexity of assessing the environmental impact of catalytic oxyfunctionalisation reactions.The article also discusses the relationship between solvent properties and the energy demands for chemical transformations and downstream processing,underlining that the choice of solvent can significantly influence the environmental impact of a catalytic process.Additionally,the review highlights the importance of considering the recyclability of reagents and the secondary CO_(2)emissions caused by the energy requirements of the reaction when evaluating the environmental impact of a catalytic process.Each chemo-and biocatalysis produce a certain environmental impact,the greenness of either method is dependent on several factors,including the type of waste generated,the recyclability of reagents,and secondary CO_(2)emissions.This review therefore recommends using consistent metrics and a comprehensive life cycle assessment approach to evaluate this environmental impact,and highlights the importance of considering the synthesis of the catalysts themselves.

Advances in reactive co-precipitation technology for preparing high-performance cathodes

Reactive crystallization plays an essential role in the synthesis of high-quality precursors with a narrow particle size distribution,dense packing,and high sphericity.These features are beneficial in the fabrication of high-specific-capacity and long-cycle-life cathodes for lithium-ion and sodium-ion batteries.However,in industrial production,designing and scaling-up crystallizers involves the use of semi-empirical approaches,making it challenging to satisfactorily meet techno-economic requirements.Furthermore,there is still a lack of in-depth knowledge on the theoretical models and technical calculations of the current co-precipitation process.This review elaborates on critical advances in the theoretical guidelines and process regulation strategies using a reactive crystallizer for the preparation of precursors by co-precipitation.The research progress on the kinetic models of co-precipitation reactive crystallization is presented.In addition,the regulation strategies for the reactive crystallization process of lithium-ion ternary cathodes are described in detail.These include the influence of different reactive crystallizer structures on the precursor's morphology and performance,the intelligent online measurement of efficient reactive crystallizers to ensure favorable conditions of co-precipitation,and preparing the precursor with a high tap density by increasing its solid holdup.A controllable reactive crystallization process is described in terms of the structural design with concentration gradient materials and bulk gradient doping of advantageous elements(such as magnesium ion)in lithium-ion cathodes and the fabrication of sodium-ion cathodes with three typical materials-Prussian blue analogues,transition metal oxides,and polyanionic phosphate compounds being involved.

Multiple routes toward engineering efficient cyanobacterial photosynthetic biomanufacturing technologies

Developing efficient CO_(2)utilization technologies can alleviate the urgent pressure on energy and the environment.Moreover,these technologies are crucial for achieving the goal of net zero emissions.Microalgae are photoautotrophic microorganisms that are the main sources of primary productivity in the biosphere.Cyanobacteria,the only prokaryotic microalgae,have also been considered as promising chassis for photosynthetic biosynthesis,directly converting solar energy and CO_(2)into various bio-based products.This technological route is called photosynthetic biomanufacturing,and is advantageous to simultaneous carbon fixation and clean production.This review focuses on development mode,application and suggests trends related to the further development of photosynthetic biomanufacturing.With regard to the link between photosynthetic CO_(2)fixation and the production of desired metabolites,we summarized and compared three widely adopted strategies.“Screening to find”,screening a large number of high-quality cyanobacterial resources and analyzing their intracellular metabolites are of significance for screening novel cyanobacterial species with high-value chemicals and properties of industrial relevance.“Engineering to modify”,the emergence and application of synthetic biological tools and metabolic engineering strategies have enhanced the ability to modify different cyanobacterial species to reshape more carbon to flow toward synthetic tailored chemicals.“Stressing to activate”,through special culture conditions and strategies,combined with omics analysis techniques,silent metabolic pathways and functional modules are activated to induce the accumulation of high-value chemicals.This review provides valid and updated information to facilitate the development of photosynthetic biosynthesis route with carbon fixation and clean production,providing specific feasible solutions for net zero emissions.