Production Of Bulk Chemicals Research Articles

Biotechnological Approaches to Generate Biogenic Solvents and Energy Carriers from Renewable Resources

Abstract Background: Current threats connected to the ongoing depletion of fossil resources and elevated levels of greenhouse gases accelerating climate change and global warming provoke a renaissance of biotechnological production of various organic bulk chemicals, which, particularly during the second half of the 20th century, were almost exclusively produced from fossil resources via chemosynthetic processes. Scope: Besides the manufacture of bioethanol, a product obtained by microbial fermentation, biogenic production of solvents and energy carriers like acetone, isopropanol, 2,3-butanediol, or 1-butanol, hence, processes known since the beginning of the last century, experiences now a substantial revival. Summary of new synthesis and conclusions reached in the review: The review illustrates how to produce these products by resorting to fossil raw materials instead of petrochemical production processes, and how this can be accomplished by the cultivation of anaerobic organisms, namely facultatively anaerobic yeasts and bacteria (production of ethanol or 2,3-butanediol), and strictly anaerobic Clostridia (1-butanol, acetone, or isopropanol) on renewable resources. Moreover, novel methods for producing biodiesel-like methyl-esters of aerobically produced bacterial polyhydroxyalkanoate biopolyester building blocks combine the synthesis of microbial biopolyesters from wastewater with the progress of innovative renewable energy carriers. The biochemical background, the current state of research and development, and the status of industrialization of these processes are reviewed. Conclusion: Challenges to make these bioprocesses, based on inexpensive renewable resources, competitive with or even superior to petrochemical production routes in terms of sustainability, scalability, and economic feasibility still exist: however, they can be overcome by the concerted action of various scientific disciplines.

Value creation by converting pulp mill flue gas streams to green fuels

Climate change mitigation induces strong growth in renewable electricity production, partly driven by shifts in environmental policies and regulation. Intermittent renewable electricity requires supporting systems in the form of sustainable hydrocarbon chemicals such as transportation fuels. Bulk chemical production fits well into a pulp mill environment, given their large volumes, stable operation, and ample supply of biomass-based carbon feedstock in the form of flue gases. Until now, the utilization of the flue gases from conventional operation of a pulp mill has received little attention. Harnessing these flue gases into usable products could offer additional value to mill operators, while also diversifying their product portfolio. However, electricity-based fuels and products require extra energy in the conversion step and may not be commercially competitive with current fossil products under the current regulation. There might also be uncertainties about future commodity prices. Thus, the objective of this study is to estimate the economic competitiveness and the added value of selected side products that could be produced alongside conventional pulp and paper products. A typical modern pulp mill is modeled in different product configurations and operational environments, which allows testing of various development paths. This illustrates how the overall energy and mass balance of a pulp mill would react to changes in different final products and other parameters. The focus of the study is in synthetic methanol, which is produced from flue gases and excess resources from the mill, with minimal interference to the pulping process. The results aid in assessing the necessity and magnitude of a premium payment for subsidizing green alternatives to replace current fossil fuels and chemicals. Additionally, the results function as an indicator of the development state of the pulp and paper industry in the turmoil of climate change regulation. The results indicate that pow-er-to-X systems offer one more viable pathway alternative for broadening the product portfolio of the pulp and paper sector, as well as opening new flexibility measures and services to grid stabilization. Market conditions were found to have a significant impact on the perceived profitability.

Valorization of the pelagic Sargassum horneri for co-production of erythritol and alginate oligosaccharides

Pelagic Sargassum is invasive macroalgae with huge biomass. To produce bulk chemicals with profit from the biomass, innovative strategies need to be developed. In this study, maximum saccharification yield of Sargassum horneri biomass was obtained with the combined use of 3% alginate lyase and 3% cellulase, releasing 20.83 g/L glucose and 1.73 g/L mannitol at a 1:6 feed ratio. Subsequently, the crude S. horneri hydrolysate (pH 3.0) was proved most suitable for erythritol production of Yarrowia lipolytica strain. After 60 h fermentation in a 10-L fermenter, the erythritol concentration reached 18.42 g/L with a yield of 0.82 g/g; while the concentration of alginate oligosaccharides (AOS) was 37.56 g/L. Finally, AOS with a purity of 93.4% were obtained by ethanol precipitation, and erythritol was harvested via crystallization. This proposed strategy demonstrates the feasibility of transforming invasive Sargassum into two high-value chemicals for the first time.

Selective hydrogenolysis of lignin in the presence of Ni3Fe1 alloy supported on zirconium phosphate

Lignin is a promising renewable starting material for various value-added petrochemicals and high-quality fuels. However, current techniques for utilization of this natural aromatic biopolymer are challenging by the poor selectivity of desired products and the serious char formation. In this study, we provide a novel and efficient approach for selective hydrogenolysis of lignin using the cost-effective catalyst of Ni3Fe1 nanoparticles supported on zirconium phosphates. 77.0 % of lignin is converted, yielding 19.6 % monophenols, whereas, the formation of biochar is insignificant (1.7 %) at the conditions of 260 °C for 5 h in a 2.0 MPa hydrogen. Importantly, 42.1 % of these obtained monophenols are identified to be a versatile bulk chemical of para ethyl phenol (yield of 8.2 %), because of the selective cleavage of the p-coumaryl units of the lignin. The results of catalyst characterization further reveal that the formation of Ni3Fe1 nanoparticle facilitates the breakage of the specific structure of lignin and suppresses the phenolic oligomer's recondensation, which consequently enhance the lignin hydrogenolysis and char inhibition. These insights unveil that the production of bulk chemicals from sustainable resources is realizable through the rational design of catalytic processes, which substantially increase the economic feasibility of biomass biorefinery.

NaCl catalyzed transesterification and hydrolysis of ethylene carbonate

Sodium chloride (NaCl) was used as catalyst for the production of bulk chemicals of dimethyl carbonate and ethylene glycol by transesterification of ethylene carbonate with methanol first time in high activity with a TON of 770. Mechanism studies by kinetic isotope effect measurements and DFT calculations indicated that NaCl acted as Lewis base to catalyze transesterification via the SN2 mechanism. Moreover, NaCl was demonstrated to be an effective catalyst for the hydrolysis of ethylene carbonate.

Towards carbon neutral chemicals production: Opportunities for combining fermentation with electrochemical processes

A circular carbon economy offers a pathway towards sustainable industry, decoupling production from pervasive fossil fuel feedstocks. Global supply chains however have tremendous inertia, and so, in the short term, strategies are required to maximise decarbonisation with minimal intervention. Fortunately, there are only a handful of top-platform chemicals which are used to make all others through traditional chemicals manufacturing. Electrochemical processes offer significant opportunities to link renewable electricity with chemical productions. Currently, however, electrochemistry is at nearing commercialisation stages only for a handful of chemical products. More promise for product diversification may be obtained when it is used as an enabling technology to provide feedstocks for other technologies ( e.g. , biotechnology and thermochemistry). By utilising commercialised electrochemical products ( e.g. , hydrogen and carbon monoxide), these combinations can reach other platform chemicals at much higher overall energy efficiencies. This approach is being recognised in industry, with several companies at the forefront. • Power-to-X technologies offers a path towards sustainable production from CO 2 . • Limited overlap between existing bulk chemicals production and electrochemistry. • Biotechnology and thermochemistry can bridge this gap. • Energy efficiency is a useful metric to assess synergistic pathways. • Biotechnology offers the most complementary benefits.

Microbial cell factories

<p indent="0mm">Microbial cell factories are among the key subjects in synthetic biology research. Microbial cell factories produce bulk chemicals and natural products through renewable biomass resources. These green and clean biological manufacturing routes can supplement nonrenewable petrochemical resources and rare plant resources; thus, these routes can partially replace petrochemical manufacturing and plant extraction routes, which consume high amounts of energy and generate high pollution levels. The green routes provide an important method for society to address resource, energy and environmental problems. To successfully commercialize microbial cell factories, the regulatory mechanisms that microorganisms use to efficiently produce chemicals were investigated from two perspectives, including carbon metabolism and energy metabolism. Regarding carbon metabolism, a synthetic biology platform for enzyme mining was established, and the synthetic pathways of several triterpenoids were characterized using this platform. Furthermore, some cell factories that produce triterpenoids, such as hawthorn acid, corosolic acid and trichoparic acid, were created by <italic>Saccharomyces cerevisiae</italic>. In addition, precision pathway regulation technologies, including simultaneous modulation of multiple genes in chromosomes and glycosylase base editor (GBE), were developed and could improve the rate of xylose utilization by 3-fold compared with that of the control. The rate-limiting steps of the synthetic pathways for a series of chemicals were identified, and the rate-limiting enzymes were activated to increase the rate of chemical production by 2.5- to 600-fold; thus, the adaptation problems between enzyme parts and synthetic pathways were solved. When considering energy metabolism, four new modules of generating energy through glucose metabolism were designed according to the requirements of synthetic products; thus, the imbalance problems between the supply and the necessity of reducing equivalents in the synthetic pathway were solved. Based on the knowledge of the regulatory mechanisms for synthetic metabolism, efficient microbial cell factories were constructed by our research team to produce a series of chemicals. Technologies to microbially produce 14 chemicals have been licensed. Among these chemicals, four have been successfully commercialized, and the annual production of each chemical can reach over <sc>10000 t.</sc> In addition, one company realized IPO. All these factors have promoted the industrial application of microbial cell factories. The future directions of research on microbial cell factories are discussed at the end of this paper. Most of the synthetic pathways of these cell factories are based on existing biosynthetic pathways in nature. However, for the vast majority of chemicals, the biosynthetic pathways are often unknown or do not occur in nature. How to microbially synthesize these chemicals is among the difficulties encountered when constructing a microbial cell factory. The principle of designing new pathways and new enzymes, the regulation of energy metabolism based on nonnatural coenzymes and the mechanism of chemical stress on cells can be studied in substance metabolism, energy metabolism, and physiological metabolism, respectively.

Microalgae biorefinery: An integrated route for the sustainable production of high-value-added products

Microalgae are pervasive organisms regarded as conservative alternatives for the sustainable synthesis of various high-value-added bio-products to replace depleting fossil fuels and reduce CO2 emissions. However, microalgae biorefinery is still very far from being commercially viable due to high costs, intensive energy requirements, and low availability of biomass and biomolecules. In this review, the current status of microalgae biorefinery is discussed by establishing the efficiency of green biotechnology in producing microalgae from wastewater and the diverse bio-products derived from the biotechnology of microalgae biorefinery. In addition, various aspects involved in the sustainable production of bulk chemicals and value-added bio-products from microalgae biorefinery, including their roles in environmental protection and the promotion of an integrated green circular bio-economy are elucidated. Lastly, the challenges facing microalgae biorefinery and recommendations to guide future research toward cost-effective, more efficient, and sustainable microalgae biorefinery are presented.

Developing methylotrophic microbial platforms for a methanol-based bioindustry.

Methanol, a relatively cheap and renewable single-carbon feedstock, has gained considerable attention as a substrate for the bio-production of commodity chemicals. Conventionally produced from syngas, along with emerging possibilities of generation from methane and CO2, this C1 substrate can serve as a pool for sequestering greenhouse gases while supporting a sustainable bio-economy. Methylotrophic organisms, with the inherent ability to use methanol as the sole carbon and energy source, are competent candidates as platform organisms. Accordingly, methanol bioconversion pathways have been an attractive target for biotechnological and bioengineering interventions in developing microbial cell factories. This review summarizes the recent advances in methanol-based production of various bulk and value-added chemicals exploiting the native and synthetic methylotrophic organisms. Finally, the current challenges and prospects of streamlining these methylotrophic platforms are discussed.

Conversion of CO2 into organic acids by engineered autotrophic yeast.

The increase of CO2 emissions due to human activity is one of the preeminent reasons for the present climate crisis. In addition, considering the increasing demand for renewable resources, the upcycling of CO2 as a feedstock gains an extensive importance to establish CO2-neutral or CO2-negative industrial processes independent of agricultural resources. Here we assess whether synthetic autotrophic Komagataella phaffii (Pichia pastoris) can be used as a platform for value-added chemicals using CO2 as a feedstock by integrating the heterologous genes for lactic and itaconic acid synthesis. 13C labeling experiments proved that the resulting strains are able to produce organic acids via the assimilation of CO2 as a sole carbon source. Further engineering attempts to prevent the lactic acid consumption increased the titers to 600 mg L-1, while balancing the expression of key genes and modifying screening conditions led to 2 g L-1 itaconic acid. Bioreactor cultivations suggest that a fine-tuning on CO2 uptake and oxygen demand of the cells is essential to reach a higher productivity. We believe that through further metabolic and process engineering, the resulting engineered strain can become a promising host for the production of value-added bulk chemicals by microbial assimilation of CO2, to support sustainability of industrial bioprocesses.

Modeling Formic Acid Combustion

Nowadays, the knowledge of the gas-phase chemistry of formic acid is paramount for several industrial sectors, including energy supply and the production of bulk chemicals. In this work, a simplified kinetic mechanism and a detailed kinetic mechanism deriving from a rate-based selection algorithm were developed and tested against experimental data available in the literature. The former contains 141 species and 453 reactions, whereas the latter comprises 90 species and 1047 reactions. A focus on a low initial temperature (i.e., up to 500 K) was provided by comparing the numerical estimations with laminar burning velocity and jet-stirred measurements at several conditions. A good agreement among numerical predictions and experimental data was observed, especially for the simplified kinetic mechanism. The accuracy of the generated mechanism allowed for further analysis of the chemistry of the system, enlightening some determining aspects of the chemistry of formic acid. The produced mechanism can be also intended as per seed mechanism for the generation of kinetic models focused on the chemistry of biofuels. Indeed, the characterization of chemical aspects of formic acid occurring in an oxidative environment is crucial due to its relevance as an energy vector as well as an intermediate compound in the decomposition of larger hydrocarbons and bio-oils.

Recent Advances In Microbe-Photocatalyst Hybrid Systems for Production of Bulk Chemicals: A Review.

Solar-driven biocatalysis technologies can combine inorganic photocatalytic materials with biological catalysts to convert CO2, light, and water into chemicals, offering the promise of high energy efficiency and a broader product scope than that of natural photosynthesis. Solar energy is the most abundant renewable energy source on earth, but it cannot be directly utilized by current industrial microorganisms. Therefore, the establishment of a solar-driven bio-catalysis platform, a bridge between solar energy and heterotrophic microorganisms, can dramatically increase carbon flux in biomanufacturing systems and consequently may revolutionize the biorefinery. This review first discusses the main applications of microbe-photocatalyst hybrid (MPH) systems in biorefinery processes. Then, various strategies to improve the electron transfer by microorganisms at the inorganic photocatalytic material interface are discussed, especially biohybrid systems based on autotrophic or heterotrophic bacteria and photocatalytic materials. Finally, we discuss the current challenges and offer potential solutions for the development of MPH systems.

Engineering the xylose metabolism in Schizochytrium sp. to improve the utilization of lignocellulose

BackgroundSchizochytrium sp. is a heterotrophic, oil-producing microorganism that can efficiently produce lipids. However, the industrial production of bulk chemicals using Schizochytrium sp. is still not economically viable due to high-cost culture medium. Replacing glucose with cheap and renewable lignocellulose is a highly promising approach to reduce production costs, but Schizochytrium sp. cannot efficiently metabolize xylose, a major pentose in lignocellulosic biomass.ResultsIn order to improve the utilization of lignocellulose by Schizochytrium sp., we cloned and functionally characterized the genes encoding enzymes involved in the xylose metabolism. The results showed that the endogenous xylose reductase and xylulose kinase genes possess corresponding functional activities. Additionally, attempts were made to construct a strain of Schizochytrium sp. that can effectively use xylose by using genetic engineering techniques to introduce exogenous xylitol dehydrogenase/xylose isomerase; however, the introduction of heterologous xylitol dehydrogenase did not produce a xylose-utilizing engineered strain, whereas the introduction of xylose isomerase did. The results showed that the engineered strain 308-XI with an exogenous xylose isomerase could consume 8.2 g/L xylose over 60 h of cultivation. Xylose consumption was further elevated to 11.1 g/L when heterologous xylose isomerase and xylulose kinase were overexpressed simultaneously. Furthermore, cultivation of 308-XI-XK(S) using lignocellulosic hydrolysates, which contained glucose and xylose, yielded a 22.4 g/L of dry cell weight and 5.3 g/L of total lipid titer, respectively, representing 42.7 and 30.4% increases compared to the wild type.ConclusionThis study shows that engineering of Schizochytrium sp. to efficiently utilize xylose is conducive to improve its utilization of lignocellulose, which can reduce the costs of industrial lipid production.

Cu-Bx (X: N, CN, P) Composites for CO2 Electroreduction: Materials Vs. Gas Diffusion Electrode Characteristics

The conversion of CO2 is an attractive strategy towards the mitigation of environmental pollution, and the production of bulk chemicals and fuels by renewables. In the field of CO2 electroreduction, copper constitutes the most versatile catalyst, being able to generate CO, C2H4, CH4, as well as alcohols and acids from CO2. Lately, research on Cu-based CO2 electroreduction has focused on two main topics: firstly, the operation under elevated current densities through the development of stable and selective gas diffusion electrodes (GDEs), and electrolyzers; secondly, the tuning of the selectivity of Cu-catalysts towards a specific product. Regarding the latter, common methods, include doping with other metals and heteroatoms, alloying, as well as creating electrode architectures consisting often of Cu/Ag and Cu/Zn structures.Contrary to Cu, only a few heterogeneous electrocatalysts have shown the ability to generate more complex molecules beyond CO and HCOOH, such as hydrocarbons and alcohols. Among these catalysts, the chemically robust and synthetically scalable, boron phosphide (BP) has shown the ability to favor the production of CH3OH from CO2 under low current densities of ca. 2 mA cm-2.Aiming to achieve a synergistic effect between Cu and BP, we herein investigate the role of electrode characteristics versus material properties in gas diffusion electrodes under industrially relevant current densities > 100 mA cm-2. Starting from GDE-properties, we report on the influence of the layer arrangement of Cu and BP on the surface of the GDL, their mixing ratio as well as the deposition method and cell type on the CO2 electroreduction. Furthermore, in order to elucidate the role of material properties towards deciding the product spectrum, we compared the activity of B-compounds with different structural characteristics, possessing cubic as well as hexagonal structures. Concretely, cubic boron nitride (c-BN), and phosphide (BP) as well as hexagonal boron carbon nitride (h-BCN), and hexagonal BN (h-BN) are evaluated in a series of Cu-based GDEs. Depending on the selected layer arrangement, material combination and mixing ratio we are able to steer the main CO2RR product to either CO, C2H4 or CH4 at 200 mA cm-2. Beyond Cu-BX GDEs, our results demonstrate that in the case of synergistic effects, material/electrocatalyst development and electrode/electrolyzer architecture must go hand-in-hand, providing important strategies towards the optimization of composite electrocatalysts. Figure 1

Modelling the Electrochemical Reduction of CO2 Under Gas-Liquid Channel Flow

Electrochemical reduction of CO2 using renewable energy sources is a promising avenue for sustainable production of bulk chemicals. The feasibility of electrochemical CO2 conversion has been demonstrated at lab scale, leading researchers to propose several reactor designs. However, CO2 electrolysis in aqueous systems is severely limited by mass transfer leading to performance parameters insufficient for industrial application. A strategy to enhance mass transfer is to actively introduce CO2 as a gas flow, while keeping diffusion paths between reactants and catalyst short, by separating the gas flow from the liquid electrolyte through a gas diffusion electrode. However, flooding, salt formation, or drying out of the gas diffusion electrode are common problems and present a major obstacle towards commercialisation. A promising reactor concept that enhances mass transfer without the complexity of a gas diffusion electrode is a structured reactor operated under gas-liquid Taylor flow: gas–liquid flow consisting of elongated bubbles in micro- or milli-channels. While this is a proven concept to enhance mass transfer for heterogeneous catalysis in flow cells, literature on this approach for electrochemical processes is scarce and the effect of process conditions on the reactor performance are poorly understood.In this work, we propose a tubular cell design, inspired from the field of fuel cells, for CO2 electrolysis with a zero-gap membrane electrode assembly. We further, develop a simple analytical model revealing how reactor performance in terms of faradaic efficiency and current density is governed by the key features of Taylor flow. These features film thickness, bubble velocity, and volume fraction of CO2 bubbles over aqueous electrolyte, for a given cathode potential.We find that the film thickness and the volume ratio of CO2/electrolyte fed to the reactor significantly affect the limiting current density and the faradaic efficiency. Additionally, we find industrially relevant performance with faradaic efficiencies (> 90 %) at current densities of up to 500 mA cm-2, when operating the reactor at elevated pressure beyond 5 bar. This demonstrates the general potential of this reactor concept to overcome mass transfer limitations in the field of electrolysis. We compare our predictions with numerical simulations, showing good agreement for a large window of operation conditions, illustrating when the simple predictive expressions for the current density and faradaic efficiency can be applied. We will discuss the importance of including interdependencies on the reactor scale to assess the economic viability of a reactor design and presents a tool to evaluate reactor design choices. We expect that the simple predictive expressions are instrumental in guiding experimental studies and reactor design choices, taking into account both technical and economic considerations.

Unusual pathway of epoxide hydration over a novel CoIII(salen)-based pseudohomogeneous catalyst with excellent performance

Due to high H2O/epoxide molar ratio for non-catalytic hydration, industrial production of bulk chemicals 1,2-diols is much energy-intensive. As a very promising route to produce 1,2-diols with low energy consumption, catalytic hydration of epoxides has aroused much interest from both academy and industry. The key is to develop a catalyst with high activity and stability at a low H2O/epoxide molar ratio. It has been demonstrated that encapsulating a homogeneous catalytic species into the cavity of porous material is a very efficient way to obtain a high-performance heterogeneous catalyst. Herein, a novel pseudohomogeneous catalyst with the distinctive Co(salen)-PF6 encapsulated in nanocages of a typical mesoporous material FDU-12 has been successfully developed, which exhibits both unexpectedly tremendously enhanced activity at the low H2O/epoxide molar ratio close to stoichiometric ratio and unique surprising recyclability without regeneration between runs in propylene oxide hydration. Especially, based on the systematic experimental design/implementation, particular structural characterizations and in-depth calculations, the pathway the newly developed catalyst going through has been investigated and determined to be an unusual bisubstrate-directly-activated cooperative mechanism (i.e. a bimolecular cooperative activation mechanism not involving Co(salen)–OH). The cooperative activation effect gives rise to the unexpectedly tremendously enhanced activity of our new catalyst, while no involving of Co(salen)–OH during the catalytic process leads to its best and unique catalytic stability in epoxide hydration among all the reported CoIII(salen)-based heterogeneous catalyst. It is believed that this study and the developed catalyst are of great significance for developing the catalytic hydration technology with low energy consumption and for developing high-performance heterogeneous catalysts.

BioBulkFoundary: a customized webserver for exploring biosynthetic potentials of bulk chemicals.

Advances in metabolic engineering have boosted the production of bulk chemicals, resulting in tons of production volumes of some bulk chemicals with very low prices. A decrease in the production cost and overproduction of bulk chemicals makes it necessary and desirable to explore the potential to synthesize higher-value products from them. It is also useful and important for society to explore the use of design methods involving synthetic biology to increase the economic value of these bulk chemicals. Therefore, we developed 'BioBulkFoundary', which provides an elaborate analysis of the biosynthetic potential of bulk chemicals based on the state-of-art exploration of pathways to synthesize value-added chemicals, along with associated comprehensive technology and economic database into a user-friendly framework. Freely available on the web at http://design.rxnfinder.org/biobulkfoundary/. Supplementary data are available at Bioinformatics online.

Electrochemical Reduction of CO2 in Tubular Flow Cells under Gas-Liquid Taylor Flow.

Electrochemical reduction of CO2 using renewable energy is a promising avenue for sustainable production of bulk chemicals. However, CO2 electrolysis in aqueous systems is severely limited by mass transfer, leading to low reactor performance insufficient for industrial application. This paper shows that structured reactors operated under gas–liquid Taylor flow can overcome these limitations and significantly improve the reactor performance. This is achieved by reducing the boundary layer for mass transfer to the thin liquid film between the CO2 bubbles and the electrode. This work aims to understand the relationship between process conditions, mass transfer, and reactor performance by developing an easy-to-use analytical model. We find that the film thickness and the volume ratio of CO2/electrolyte fed to the reactor significantly affect the current density and the faradaic efficiency. Additionally, we find industrially relevant performance when operating the reactor at an elevated pressure beyond 5 bar. We compare our predictions with numerical simulations based on the unit cell approach, showing good agreement for a large window of operating parameters, illustrating when the easy-to-use predictive expressions for the current density and faradaic efficiency can be applied.

Valorization of sugarcane bagasse through biofuel and value-added soluble metabolites production: Optimization of alkaline hydrothermal pretreatment

Sugarcane bagasse (SCB) is increasingly considered as a potential source for bioenergy or bulk chemicals production. However, efficient pretreatment techniques need to be developed to make full use of its potential. A central composite design was employed to evaluate the effect of temperature (146.4–213.6 °C), NaOH concentration (0.7–2.3 M) and treatment time (3.2–36.8 min) on the hydrothermal pretreatment of SCB. Glucose was the abundant fermentable sugar released in the hydrolysate (4.0 g/L) and its concentration was significantly (p-value < 0.05) affected by temperature and NaOH concentration. Sugars released in the hydrolysate and the remaining cellulose, hemicellulose, and lignin in the pretreated fiber were anaerobically co-digested in batch thermophilic assays (55 °C). Propionate, one of the most promising platform chemicals, was the main metabolite produced (0.5 g/L) and its concentration was significantly affected by temperature and NaOH concentration. Both NaOH concentration and pretreatment duration significantly affected methane composition in the biogas (p-value <0.05 and 0,10 respectively). Defluviitoga, and Methanothermobacter genera were favored in response to alkaline hydrothermal pretreatment at the central point conditions (180 °C, 1.5 M NaOH, 20 min).

Fungi-on-a-Chip: microfluidic platforms for single-cell studies on fungi.

This review highlights new advances in the emerging field of 'Fungi-on-a-Chip' microfluidics for single-cell studies on fungi and discusses several future frontiers, where we envisage microfluidic technology development to be instrumental in aiding our understanding of fungal biology. Fungi, with their enormous diversity, bear essential roles both in nature and our everyday lives. They inhabit a range of ecosystems, such as soil, where they are involved in organic matter degradation and bioremediation processes. More recently, fungi have been recognized as key components of the microbiome in other eukaryotes, such as humans, where they play a fundamental role not only in human pathogenesis, but also likely as commensals. In the food sector, fungi are used either directly or as fermenting agents and are often key players in the biotechnological industry, where they are responsible for the production of both bulk chemicals and antibiotics. Although the macroscopic fruiting bodies are immediately recognizable by most observers, the structure, function, and interactions of fungi with other microbes at the microscopic scale still remain largely hidden. Herein, we shed light on new advances in the emerging field of Fungi-on-a-Chip microfluidic technologies for single-cell studies on fungi. We discuss the development and application of microfluidic tools in the fields of medicine and biotechnology, as well as in-depth biological studies having significance for ecology and general natural processes. Finally, a future perspective is provided, highlighting new frontiers in which microfluidic technology can benefit this field.