Alternative Carbon Sources Research Articles

Generation of a Vibrio-based platform for efficient conversion of raffinose through Adaptive Laboratory Evolution on a solid medium.

Raffinose, a trisaccharide abundantly found in soybeans, is a potential alternative carbon source for biorefineries. Nevertheless, residual intermediate di- or monosaccharides and low catabolic efficiency limit raffinose use through conventional microbial hosts. This study presents a Vibrio-based platform to convert raffinose efficiently. Vibrio sp. dhg was selected as the starting strain for the Adaptive Laboratory Evolution (ALE) strategy to leverage its significantly higher metabolic efficiency. We conducted ALE on a solid minimal medium supplemented with raffinose to prevent the enrichment of undesired phenotypes due to the shared effect of extracellular raffinose hydrolysis among multiple strains. As a result, we generated the VRA10 strain that efficiently utilizes raffinose without leaving behind degraded di- or monosaccharides, achieving a notable growth rate (0.40 h-1) and raffinose consumption rate (1.2g/gdcw/h). Whole genome sequencing and reverse engineering identified that a missense mutation in the melB gene (encoding a melibiose/raffinose:sodium symporter) and the deletion of the two galR genes (encoding transcriptional repressors for galactose catabolism) facilitated rapid raffinose utilization. The further engineered strain produced 6.2g/L of citramalate from 20g/L of raffinose. This study will pave the way for the efficient utilization of diverse raffinose-rich byproducts and the expansion of alternative carbon streams in biorefinery applications.

Sustainable production of the drug precursor tyramine by engineered Corynebacterium glutamicum.

Tyramine has attracted considerable interest due to recent findings that it is an excellent starting material for the production of high-performance thermoplastics and hydrogels. Furthermore, tyramine is a precursor of a diversity of pharmaceutically relevant compounds, contributing to its growing importance. Given the limitations of chemical synthesis, including lack of selectivity and laborious processes with harsh conditions, the biosynthesis of tyramine by decarboxylation of L-tyrosine represents a promising sustainable alternative. In this study, the de novo production of tyramine from simple nitrogen and sustainable carbon sources was successfully established by metabolic engineering of theL-tyrosine overproducing Corynebacterium glutamicum strain AROM3. A phylogenetic analysis of aromatic-L-amino acid decarboxylases (AADCs) revealed potential candidate enzymes for the decarboxylation of tyramine. The heterologous overexpression of the respective AADC genes resulted in successful tyramine production, with the highest tyramine titer of 1.9gL-1 obtained for AROM3 overexpressing the tyrosine decarboxylase gene of Levilactobacillus brevis. Further metabolic engineering of this tyramine-producing strain enabled tyramine production from the alternative carbon sources ribose and xylose. Additionally, up-scaling of tyramine production from xylose to a 1.5L bioreactor batch fermentation was demonstrated to be stable, highlighting the potential for sustainable tyramine production. KEY POINTS: • Phylogenetic analysis revealed candidate l-tyrosine decarboxylases • C. glutamicum was engineered for de novo production of tyramine • Tyramine production from alternative carbon substrates was enabled.

Unveiling the roles of CaSDH8 in Candida albicans: Implications for virulence and azole resistance

ABSTRACT Candida albicans is the most common pathogen in systemic fungal diseases, exhibits a complex pathogenic mechanism, and is increasingly becoming drug tolerant. Therefore, it is particularly important to study the genes associated with virulence and resistance of C. albicans. Here, we identified a gene (orf19.1588) that encodes a conserved mitochondrial protein known as CaSDH8, upon deletion of CaSdh8, the deleted strain (Casdh8Δ/Δ) experienced impaired growth, hyphal development, and virulence. Casdh8Δ/Δ displayed a reduced capacity to utilize alternative carbon sources, along with detrimental alterations in reactive oxygen species (ROS), mitochondrial membrane potential (MMP) depolarization, and adenosine triphosphate (ATP) levels. Interestingly, Casdh8Δ/Δ demonstrated resistance to azole drugs, and under the influence of fluconazole, the cell membrane permeability and mitochondrial function of Casdh8Δ/Δ were less compromised than those of the wild type, indicating a reduction in the detrimental effects of fluconazole on Casdh8Δ/Δ. These findings highlight the significance of CaSDH8 as a crucial gene for the maintenance of cellular homoeostasis. Our study is the first to document the effects of the CaSDH8 gene on the virulence and azole resistance of C. albicans at both the molecular and animal levels, providing new clues and directions for the antifungal infection and the discovery of antifungal drug targets.

Understanding the Level of Integration in Existing Chemical Clusters: Case Study in the Port of Rotterdam

AbstractThe petrochemical industry is composed of several interconnected processes that use fossil-based feedstock for producing chemicals. These processes are typically geographically clustered and often belong to different parties. Reducing the environmental impacts of the petrochemical industry is not straightforward due to, on the one hand, their reliance on fossil fuels for energy and as a feedstock and, on the other hand, the significant level of interconnected energy and material flows among processes. Current methods for analyzing changes to existing processes cannot capture the multitude and level of interactions. The goal of this paper is to create a model of a petrochemical cluster and analyze its physical characteristics and performance. This paper addresses this goal by developing an assessment method that combines process simulations, multiplex graph analysis, and key performance indicators. The method is applied to a case study based on the petrochemical cluster in the Port of Rotterdam, resulting in a uniquely highly detailed model of a petrochemical cluster. The network analysis results show that only some of the processes are very interconnected. From the performance analysis, it can be observed that the olefins process is the most carbon-intense and has high CO2 emissions. Additionally, the results showed the importance of considering existing interconnections when assessing the current performance of existing petrochemical clusters or the performance due to future changes to chemical processes. For instance, some changes would occur to an industrial cluster by introducing alternative carbon sources, such as biomass or CO2.

Mechanism of enhanced salt tolerance in Saccharomyces cerevisiae by CRZ1 overexpression

Achieving high-gravity fermentation in the industrial production of fuel ethanol, and enhancing the fermentation efficiency of high-salt raw materials, such as waste molasses, can significantly reduce wastewater output and process costs. Therefore, the development of hyperosmotic-tolerant industrial Saccharomyces cerevisiae strains, capable of resisting high-salt stress, offers both environmental and economic benefits. Our previous study highlighted the potential of CRZ1 overexpression as a strategy to improve the yeast strain’s resistance to high-salt stress, however, the underlying molecular mechanisms remain unexplored. The fermentation capabilities of the CRZ1-overexpressing strain, KCR3, and its parental strain, KF7, were evaluated under condition of 1.25 M NaCl at 35 °C. Compared to KF7, KCR3 showed an 81% increase in glucose consumption (129.25 ± 0.83 g/L) and a 105% increase in ethanol production (47.59 ± 0.93 g/L), with a yield of 0.37 g/g. Comparative transcriptomic analysis showed that under high-salt stress, KCR3 exhibited significantly upregulated expression of genes associated with ion transport, stress response, gluconeogenesis, and the utilization of alternative carbon sources, while genes related to glycolysis and the biosynthesis of ribosomes, amino acids, and fatty acids were notably downregulated compared to KF7. Crz1 likely expands its influence by regulating the expression of numerous transcription factors, thereby impacting genes involved in multiple aspects of cellular function. The study revealed the regulatory mechanism of Crz1 under high-salt stress, thereby providing guidance for the construction of salt-tolerant strains.

Cyanobacterial hydrothermal carbonization carbon as photocatalyst for selective aerobic oxidation of cyclohexane

The exploration of catalyst preparation techniques that incorporate environmental-friendly methodologies has consistently been the focus of scientific inquiry within the field of green synthesis of oxygen-containing organic chemicals. Herein, a metal-free hydrothermal carbonation carbon (HTCC) has been prepared utilizing cyanobacterial biomass produced during a water bloom in a freshwater lake. The HTCC produced is capable of performing photocatalytic selective oxidation of cyclohexane to cyclohexanol and cyclohexanone (KA oil) under ambient conditions. The use of cyanobacterial biomass allows for the efficient preparation of HTCC, which exhibits a conversion rate of cyclohexane that is 4.1 times of HTCC prepared with alternative carbon sources (glucose). The selectivity to KA oil over the samples are almost 100%. Characterizations and analysis reveal that cyanobacteria can lead to self-doping of nitrogen and hydrophobicity of the resulting HTCC, while sulfuric acid etching endow it with more photoactive sp2 hybridized structure units that contribute to a higher photogenerated carrier separation efficiency. The suitable band structure enables the cyanobacterial HTCC to produce superoxide radicals to oxidize cyclohexane. These findings are of great significance for the development of eco-friendly photocatalysts and the utilization of biomass resources.

Inhibition of ACSS2 triggers glycolysis inhibition and nuclear translocation to activate SIRT1/ATG5/ATG2B deacetylation axis, promoting autophagy and reducing malignancy and chemoresistance in ovarian cancer

BackgroundMetabolic reprogramming is a hallmark of cancer, characterized by a high dependence on glycolysis and an enhanced utilization of acetate as an alternative carbon source. ACSS2 is a critical regulator of acetate metabolism, playing a significant role in the development and progression of various malignancies. ACSS2 facilitates the conversion of acetate to acetyl-CoA, which participates in multiple metabolic pathways and functions as an epigenetic regulator of protein acetylation, thereby modulating key cellular processes such as autophagy. However, the roles and intrinsic connections of ACSS2, glycolysis, protein acetylation, and autophagy in ovarian cancer (OC) remain to be elucidated. Basic proceduresUtilizing clinical specimens and online databases, we analysed the expression of ACSS2 in OC and its relationship with clinical prognosis. By knocking down ACSS2, we evaluated its effects on the malignant phenotype, acetate metabolism, glycolysis, and autophagy. The metabolic alterations in OC cells were comprehensively analysed using Seahorse assays, transmission electron microscopy, membrane potential measurements, and stable-isotope labeling techniques. CUT&TAG and co-immunoprecipitation techniques were employed to explore the deacetylation of autophagy-related proteins mediated by ACSS2 via SIRT1. Additionally, through molecular docking, transcriptome sequencing, and metabolomics analyses, we validated the pharmacological effects of paeonol on ACSS2 and the glycolytic process in OC cells. Finally, both in vitro and in vivo experiments were performed to investigate the impact of paeonol on autophagy and its anti-OC effects mediated through the ACSS2/SIRT1 deacetylation axis. Main findingsACSS2 is significantly upregulated in OC and is associated with poor prognosis. Knockdown of ACSS2 inhibits OC cells proliferation, migration, invasion, angiogenesis, and platinum resistance, while reducing tumour burden in vivo. Mechanistically, inhibiting ACSS2 reduces acetate metabolism and suppresses glycolysis by targeting HXK2. This glycolytic reduction promotes the translocation of ACSS2 from the cytoplasm to the nucleus, leading to increased expression of the deacetylase SIRT1. SIRT1 mediates the deacetylation of autophagy-related proteins, such as ATG5 and ATG2B, thereby significantly activating autophagy in OC cells and exerting antitumor effects. Paeonol inhibits acetate metabolism and glycolysis in OC cells by targeting ACSS2. Paeonol activates autophagy through the ACSS2/SIRT1/ATG5/ATG2B deacetylation axis, demonstrating inhibition of OC in vitro and in vivo. Principal conclusionsPae can serve as an effective, low-toxicity, multi-targeted drug targeting ACSS2 and glycolysis. It activates autophagy through the ACSS2/SIRT1/ATG5/ATG2B deacetylation signalling cascade, thereby exerting anti-OC effects. Our study provides new insights into the malignant mechanisms of OC and offers a novel strategy for its treatment.

Microbial oil from R. opacus: Sustainable biodiesel production

Generating additional and efficient biodiesel routes will rely heavily on advancements in clean energy technologies along with the creation of novel fermentation tactics and analyses. To create biofuels of the second generation from alternative carbon sources other than food, oleaginous microbes with the capacity to accumulate methyl esters of fatty acids (FAMEs), such as Rhodococcus species, can be utilised. These "micro biorefineries" offer a technique to convert waste streams from industry and agriculture into fungible fuels or compounds that can be used as building blocks for other substances and chemicals. Due to their similar content to typical raw materials like plant-based oils, oils from bacteria have become a feasible substitute to create biodiesel from raw material. The fact that they do not compete for arable land or with food for people or animals is another benefit of them. Using hydrolysate as the only source of carbon, a carbon and energy balance for the model species R. opacus was assessed in this study. A favourable energy balance was shown by the method. The viability of bacterial oil as a biofuel substrate was also assessed by measuring the lipid fatty acid profile and cetane number. Also, an analysis of the oil yields from bacterial, microalgae and plant-based oils is shown in terms of how much land each uses. The findings revealed that R. opacus oil production is significantly more than plant-based oils (650 times) and microalgae (30 times).

Carbon and Nitrogen Sources Influence Parasitic Responsiveness in Trichoderma atroviride NI-1.

Parasitic species of Trichoderma use hydrolytic enzymes to destroy the host cell wall. Preferent carbon and nitrogen sources suppress the expression of genes related to parasitism. Here, different nutrients were evaluated in the parasitic isolated NI-1, which was identified as Trichoderma atroviride. The genes cbh1 and chb2 (cellobiohydrolases), bgl3.1 (endoglucanase), and pra1 and prb1 (proteinases) were poorly expressed during the interaction between NI-1 and Phytophthora capsici on PDA. However, gene expression improved on minimal medium with preferent and alternative carbon sources. Dextrin and glucose stimulated higher transcript levels than cellulose, sucrose, and glycerol. Also, ammonium stimulated a stronger parasitic responsiveness than the alternative nitrogen sources. During interaction against different phytopathogens, NI-1 detects their host differentially from a distance due to the cbh1 and cbh2 genes being only induced by P. capsici. The pra1 and ech42 genes were induced before contact with Botrytis cinerea and Rhizoctonia solani, while when confronted with P. capsici they were stimulated until contact and overgrowth. The prb1 and bgl3.1 genes were induced before contact against the three-host assayed. Overall, T. atroviride prefers to parasitize and has the capacity to distinguish between an oomycete and a fungus, but nutrient quality regulates its parasitic responsiveness.

Optimizing bioencapsulation of yeast cells by Aspergillus tubingensis TSIP9 and applications in bioethanol production through repeated-batch fermentation

This study aimed to immobilize yeast cells using filamentous fungi owing to a number of advantages including less chemical usage, spontaneous encapsulation, strong adhesion and biocompatibility. Filamentous fungus, Aspergillus tubingensis TSIP9 could form sphere-shape and packed pellets using either fungal fresh spores or those stored in liquid medium for 6 weeks at 4 °C. The fungus was used to immobilize yeast Saccharomyces cerevisiae FAI via adsorption and co-cultivation methods. Scanning electron microscopy images revealed that the bioencapsulated yeast cells via co-cultivation seemed to be more tightly adhered on fungal mycelia and surrounded by extracellular polymeric substances. The yeast biocapsules also exhibited higher stability and maintained their structural integrity during repeated-batch fermentation while the immobilized yeast cells by adsorption gradually degraded during their repeated uses. The bioethanol production from glucose by yeast biocapsules were in the range of 95–98 g/L with the bioethanol yield of 0.49–0.54 g-ethanol/g-consumed glucose. The yeast biocapsules could produce bioethanol well when using enzymatic hydrolysate of lignocellulosic palm waste, as alternative cheap carbon source, with the comparable bioethanol yield of 0.49 ± 0.17 g-ethanol/g-consumed glucose. The spontaneous and inter-species bioencapsulation show the perspectives as active biocatalysts with high cell retention for repeated uses.

Methyl red dye decolourization by the photosynthetic bacteria, Rhodopseudomonas palustris and Afifellamarina

Anoxygenic photosynthetic bacteria are common inhabitants of wastewater: we found that Rhodopseudomonas palustris and Afifella marina in eutrophic conditions only partially degraded the azo dye (50 mmol m−3), Methyl Red, but completely degraded it under specially defined conditions. The azo dye is potentially a source of both carbon and fixed nitrogen. Rhodopseudomonas palustris and Afifella marina can live heterotrophically, photoheterotrophically or photoautotrophically under anoxic conditions where they can fix N2 if no organic nitrogen or NH3 is available. If organic carbon sources are available or if NH3 is present, the cells again only partially catabolised Methyl Red. In the absence of no alternative organic carbon sources and no NH3, the cells almost completely spectroscopically decolourised Methyl Red in 4 days. In sewage ponds the ready availability of alternative organic carbon and NH3 would result in only partial removal of Methyl Red. Rhodopseudomonas cells responded to the availability of Methyl Red in N-free media, by increasing both Optimum irradiance and maximum ETR (Eopt 276.3 μmol quanta m−2 s−1; ETRmax 391.4 μmol e− g−1 BChl a s−1) compared to control cells incubated in PM media with no organic carbon source and no fixed N-source (Eopt 115.2 μmol quanta m−2 s−1; ETRmax = 153.0 μmol e− g−1 BChl a s−1. If no alternative C or N sources are available, Rhodopseudomonas embedded in alginate biobeads will completely and repeatedly break down Methyl Red. The marine Afifella readily broke down Methyl Red but again breakdown was only complete if alternative carbon and no fixed nitrogen sources were available. The toxicity of the breakdown products produced by photosynthetic bacteria from azo-dyes needs to be followed up. Photosynthetic bacterial-alginate biobeads have long lifetimes (Rhodopseudomonas ≈ 2 months, Afifella > 6 months) making them of great biotechnological potential.

Metagenomic survey reveals hydrocarbon biodegradation potential of Canadian high Arctic beaches

BackgroundDecreasing sea ice coverage across the Arctic Ocean due to climate change is expected to increase shipping activity through previously inaccessible shipping routes, including the Northwest Passage (NWP). Changing weather conditions typically encountered in the Arctic will still pose a risk for ships which could lead to an accident and the uncontrolled release of hydrocarbons onto NWP shorelines. We performed a metagenomic survey to characterize the microbial communities of various NWP shorelines and to determine whether there is a metabolic potential for hydrocarbon degradation in these microbiomes.ResultsWe observed taxonomic and functional gene evidence supporting the potential of NWP beach microbes to degrade various types of hydrocarbons. The metagenomic and metagenome-assembled genome (MAG) taxonomy showed that known hydrocarbon-degrading taxa are present in these beaches. Additionally, we detected the presence of biomarker genes of aerobic and anaerobic degradation pathways of alkane and aromatic hydrocarbons along with complete degradation pathways for aerobic alkane degradation. Alkane degradation genes were present in all samples and were also more abundant (33.8 ± 34.5 hits per million genes, HPM) than their aromatic hydrocarbon counterparts (11.7 ± 12.3 HPM). Due to the ubiquity of MAGs from the genus Rhodococcus (23.8% of the MAGs), we compared our MAGs with Rhodococcus genomes from NWP isolates obtained using hydrocarbons as the carbon source to corroborate our results and to develop a pangenome of Arctic Rhodococcus. Our analysis revealed that the biodegradation of alkanes is part of the core pangenome of this genus. We also detected nitrogen and sulfur pathways as additional energy sources and electron donors as well as carbon pathways providing alternative carbon sources. These pathways occur in the absence of hydrocarbons allowing microbes to survive in these nutrient-poor beaches.ConclusionsOur metagenomic analyses detected the genetic potential for hydrocarbon biodegradation in these NWP shoreline microbiomes. Alkane metabolism was the most prevalent type of hydrocarbon degradation observed in these tidal beach ecosystems. Our results indicate that bioremediation could be used as a cleanup strategy, but the addition of adequate amounts of N and P fertilizers, should be considered to help bacteria overcome the oligotrophic nature of NWP shorelines.

Optimized genome-wide CRISPR screening enables rapid engineering of growth-based phenotypes in Yarrowia lipolytica

CRISPR-Cas9 functional genomic screens uncover gene targets linked to various phenotypes for metabolic engineering with remarkable efficiency. However, these genome-wide screens face a number of design challenges, including variable guide RNA activity, ensuring sufficient genome coverage, and maintaining high transformation efficiencies to ensure full library representation. These challenges are prevalent in non-conventional yeast, many of which exhibit traits that are well suited to metabolic engineering and bioprocessing. To address these hurdles in the oleaginous yeast Yarrowia lipolytica, we designed a compact, high-activity genome-wide sgRNA library. The library was designed using DeepGuide, a sgRNA activity prediction algorithm and a large dataset of ∼50,000 sgRNAs with known activity. Three guides per gene enables redundant targeting of 98.8% of genes in the genome in a library of 23,900 sgRNAs. We deployed the optimized library to uncover genes essential to the tolerance of acetate, a promising alternative carbon source, and various hydrocarbons present in many waste streams. Our screens yielded several gene knockouts that improve acetate tolerance on their own and as double knockouts in media containing acetate as the sole carbon source. Analysis of the hydrocarbon screens revealed genes related to fatty acid and alkane metabolism in Y. lipolytica. The optimized CRISPR gRNA library and its successful use in Y. lipolytica led to the discovery of alternative carbon source-related genes and provides a workflow for creating high-activity, compact genome-wide libraries for strain engineering.

Climate neutrality of the French energy system: overview and impacts of sustainable aviation fuel production

CO2 emission reduction of sectors such as aviation, maritime shipping, road haulage, and chemical production is challenging but necessary. Although these sectors will most likely continue to rely on carbonaceous energy carriers, they are expected to gradually shift away from fossil fuels. In order to do so, the prominent option is to utilize alternative carbon sources—like biomass and CO2 originating from carbon capture—for the production of non-fossil carbonaceous vectors (biofuels and e-fuels). However, the limited availability of biomass and the varying nature of other carbon sources necessitate a comprehensive evaluation of trade-offs between potential carbon uses and existing sources. Then, it is primordial to understand the origin of carbon used in sustainable aviation fuel (SAF) to understand the implications of defossilizing aviation for the energy system. Moreover, the production of SAF implies deep changes to the energy system that are quantified in this work. This study utilizes the linear programming cost optimization tool EnergyScope TD to analyze the holistic French energy system, encompassing transport, industry, electricity, and heat sectors while ensuring net greenhouse gas neutrality. A novel method to model and quantify carbon flows within the system is introduced, enabling a comprehensive assessment of greenhouse gas neutrality. This study highlights the significance of fulfilling clean energy requirements and implementing carbon dioxide removal measures as crucial steps toward achieving climate neutrality. Indeed, to reach climate neutrality, a production of 1,046 TWh of electricity by non-fossil sources is needed. Furthermore, the findings underscore the critical role of efficient carbon and energy valorization from biomass, providing evidence that producing fuels by combining biomass and hydrogen is optimal. The study also offers valuable insights into the future cost and impact of SAF production for air travel originating from France. That is, the European law ReFuelEU would increase the price of plane tickets by +33% and would require 126 TWh of hydrogen and 50 TWh of biomass to produce the necessary 91 TWh of jet fuel. Finally, the implications of the assumption behind the production of SAF are discussed.

Decapping activators Edc3 and Scd6 act redundantly with Dhh1 in post-transcriptional repression of starvation-induced pathways.

Degradation of many yeast mRNAs involves decapping by the Dcp1:Dcp2 complex. Previous studies on decapping activators Edc3 and Scd6 suggested their limited roles in mRNA decay. RNA-seq analysis of mutants lacking one or both proteins revealed that Scd6 and Edc3 have largely redundant activities in targeting numerous mRNAs for degradation that are masked in the single mutants. These transcripts also are frequently targeted by decapping activators Dhh1 and Pat1, and the collective evidence suggests that Scd6/Edc3 act interchangeably to recruit Dhh1 to Dcp2. Ribosome profiling shows that redundancy between Scd6 and Edc3 and their functional interactions with Dhh1 and Pat1 extend to translational repression of particular transcripts, including a cohort of poorly translated mRNAs displaying interdependent regulation by all four factors. Scd6/Edc3 also participate with Dhh1/Pat1 in post-transcriptional repression of proteins required for respiration and catabolism of alternative carbon sources, which are normally expressed only in limiting glucose. Simultaneously eliminating Scd6/Edc3 increases mitochondrial membrane potential and elevates metabolites of the tricarboxylic acid and glyoxylate cycles typically observed only during growth in low glucose. Thus, Scd6/Edc3 act redundantly, in parallel with Dhh1 and in cooperation with Pat1, to adjust gene expression to nutrient availability by controlling mRNA decapping and decay.

Progress and perspectives of natural cell factories for chemical production from methanol

Methanol has been considered one of the most important alternative carbon sources for the next-generation biomanufacturing due to its low price, mature production processes, and potential sustainability. Constructing microbial cell factories for methanol to chemical biotransformation has become a research hotspot in the green biomanufacturing industry. Focusing on the microorganisms that can naturally use methanol, we compare them with non-natural cell factories for chemical production from methanol. We discuss the key issues and challenges associated with natural cell factories for chemical production from methanol, summarize recent research progress surrounding these issues, and propose possible solutions to these challenges. This review helps to generate feasible guidelines and research strategies for the modification of natural cell factories for efficient methanol to chemical production in the future.

Enhanced Electrohydrogenation of Cis,Cis-Muconic Acid to Trans-3-Hexenedioic Acid Using Hybrid Metal/Carbon Fiber Cathodes

Organic electrosynthesis is a long-known technique for diverse product development and efficient synthesis. With the recent rise of biomass as an alternative carbon and energy source, electrochemistry is further gaining popularity due to its inherently green and environmentally benign operating conditions. Electrochemical hydrogenation (ECH) reactions are particularly attractive for biomass conversion due to their ability to abstract hydrogen from water, tolerate biogenic impurities, and utilize Earth-abundant base metal electrodes. Moreover, the rate and selectivity of the reaction can be tubed by controlling the electrode material, operating potential/current density, and reactor design. However, the implementation of this decarbonized technology for chemical production is still hampered by low productivity and, as a result, unfavorable economics. cis,cis-Muconic acid (ccMA), a bioderived C6 diunsaturated diacid platform molecule, can be converted into commodity chemicals like caprolactam, adipic acid (AA), and terephthalic acid, with AA being of particular interest for the synthesis of nylon 6,6.1 Apart from various drop-in chemicals, ccMA can also be electrochemically upgraded to trans-3-hexenedioic acid (t3HDA), a potential bio-advantaged substitute for AA as the additional C=C bond in t3HDA can be leveraged to synthesize performance-advantaged polyamides.2,3 In this work, we investigated the electrohydrogenation of ccMA to t3HDA over Pb cathodes. We demonstrate that the reaction follows a radical-based pathway involving sequential electron transfer and hydrogen addition in solution to selectively produce t3HDA (100% selectivity). Next, we contacted the cathode with carbon felts (CF) to increase productivity. CF are often used in fuel cells and H2O2 electrolyzers due to their excellent conductivity, porosity for enhanced turbulence, and ability to tune the gas-liquid-solid three-phase interface. Following similar principles, we placed a CF (3mm. thickness) in contact with the Pb cathode to lower the charge transfer resistance (~3Ω) at the interface. The surface functionalities of carbon allowed us to further tune the hydrophobicity/hydrophilicity of our hybrid electrode. Molecular dynamics (MD) calculations provided critical insights into the role of surface functionalities and guided the optimal functionalization of CF’s surface. Combining reactor configuration with fine-tuning of the electrode’s microenvironment, we were able to achieve a 50x increase in t3HDA productivity reaching up to 20 g/cm2/day at a current density of 200 mA/cm2. We further replaced the kinetically sluggish oxygen-evolution reaction with the glucose oxidation reaction at the anode, allowing us to operate the electrolyzer at a lower cell potential.Overall, ECH represents a valuable alternative to thermochemical transformations for biomass upgrading. This work provides critical insights into reactor modifications for the scaled-up synthesis of bio-derived performance monomers via hybrid microbial electrosynthesis (HMES).

Graphene oxide synthesis from coconut fiber powder using triple superphosphate catalyst and its potency for secondary battery electrode

Coconut fiber, considered an organic waste, emerges as a promising alternative carbon source for graphene oxide production—a material characterized by its conductive nature due to oxidation and the introduction of functional groups. The synthesis process involves carbonization with varied holding times (10, 20, and 30 minutes) and the utilization of Triple Superphosphate (TSP) and Ferrocene catalysts at concentrations of 10 wt.% and 20 wt.%. Subsequently, the sonication method is employed to enhance the electrical conductivity of graphene oxide post-carbonization. Notably, the electrical conductivity tests, conducted using a sourcemeter, revealed the optimum performance at 20 minutes of carbonization duration and a 20 wt.% TSP catalyst concentration, yielding an impressive electrical conductivity of 11,489.86 S/m. These findings underscore the significance of tailored parameters in optimizing graphene oxide synthesis for applications such as high-conductivity battery anodes.

Bacterial cellulose biosynthesis: Optimization strategy using iranian nabat industry waste

Bacterial cellulose (BC) is a biopolymer has found extensive applications across different fields due to its nanostructure and biomaterial performance. This study focused on optimizing yield of BC produced by Komagataeibacter xylinus CH1, isolated from kombucha SCOBY. The study aimed to use Nabat industry waste (NIW) as a cost-effective alternative carbon source for submerged fermentation. To optimize the fermentation criteria, the central composite design was used with the inoculation amount (1.5–4.5 % VV−1), NIW (0–1%), and fermentation time (3–7 days) as independent variables. The impressive results indicated the yield was enhanced up to 45.543 gL-1 at 3.013 % VV−1 of inoculation, 0.516 % NIW, and 7 days of stirred fermentation. SEM, XRD, FTIR, and TGA were applied to evaluate the characteristics of freeze-dried BC, such as the three-dimensional, porous structure, crystalline peaks, amorphous haloes, and thermal stability. The physicochemical properties of BC including high moisture content (93.022 ± 0.472 %), water absorption rate (569.473 ± 3.739 %), water-holding capacity (1333.016 ± 3.680 %), porosity (166.247 ± 2.055 %), and low water activity (0.296 ± 0.030 %) were achieved. Rheological properties of BC suspensions showed that G′ dominated over G″, with tan δ values lower than 1. These characteristics indicate NIW and stirred fermentation conditions are a promising method for producing BC in high yield.

Enhancing the environmental and economic sustainability of heterotrophic microalgae cultivation: Kinetic modelling and screening of alternative carbon sources

Heterotrophic microalgae cultivation has been suggested to reduce conventional photo-autotrophic microalgal biomass production costs. In heterotrophic cultivation, the most relevant operational costs are constituted by the supply of pure substrates used as carbon source (e.g., glucose), and the high energy request for culture aeration. In addition, suboptimal conditions of temperature and pH reduce the algal productivity, further increasing production costs. In this work, an attempt was made to define more sustainable and cost-effective strategies for the heterotrophic cultivation of Chlorellaceae and Scenedesmaceae. Several by-products from a local confectionery industry were thus screened as alternative carbon sources. Manufacturing residues from peppermint and liquorice candies production allowed to achieve comparable maximum growth rates (1.44 d-1), biomass yields (0.33 g COD·g COD-1) and biomass productivities (370 mg COD·L-1·d-1) as those achieved using glucose. A preliminary economic evaluation showed that the operational costs could be lowered of up to 85.6% by substituting glucose with the selected industrial by-products. As for fermentation conditions, high growth rates could be maintained at relatively low dissolved oxygen (DO) concentrations, and in a large range of temperature and pH values. In addition, optimal temperatures (37.0 – 37.2°C), pH values (6.8 – 7.4), and DO concentrations (> 0.5 – 1 mg O2·L-1) were identified. On the overall, the study demonstrated the possibility of achieving the reduction of operational costs for heterotrophic microalgae cultivation, while implementing circular economy principles in the framework of resource recovery during the bioremediation of organic waste.