High Value-added Products Research Articles

Mechanism insight into esterification of levulinic acid with methanol on H-Beta Zeolite: A DFT study

The esterification of levulinic acid (LA) to alkyl levulinate esters from biomass by heterogeneous acid catalysis is a potential chemical route for the sustainable production of high value-added products. Acidic zeolites are promising catalysts for this conversion due to their unique pore structures, high selectivity and strong acidity. In this work, we use Density Functional Calculations (DFT) to study the reaction mechanisms for the esterification of LA with MeOH on H-Beta zeolite. We have studied two mechanisms that we consider relevant to the formation of methyl levulinate in acidic zeolites, one involving an Eley-Rideal type mechanism and the other a Langmuir-Hinshelwood type mechanism. Since the activation energies of the rate-determining steps are quite similar, our results suggest that both mechanisms are favourable for this reaction, depending on how the LA and MeOH molecules are initially adsorbed.

Sustainable Production of Ulva Oligosaccharides via Enzymatic Hydrolysis: A Review on Ulvan Lyase.

Ulvan is a water-soluble sulfated polysaccharide extracted from the green algae cell wall. Compared with polysaccharides, oligosaccharides have drawn increasing attention in various industries due to their enhanced biocompatibility and solubility. Ulvan lyase degrades polysaccharides into low molecular weight oligosaccharides through the β-elimination mechanism. The elucidation of the structure, catalytic mechanism, and molecular modification of ulvan lyase will be helpful to obtain high value-added products from marine biomass resources, as well as reduce environmental pollution caused by the eutrophication of green algae. This review summarizes the structure and bioactivity of ulvan, the microbial origin of ulvan lyase, as well as its sequence, three-dimensional structure, and enzymatic mechanism. In addition, the molecular modification of ulvan lyase, prospects and challenges in the application of enzymatic methods to prepare oligosaccharides are also discussed. It provides information for the preparation of bioactive Ulva oligosaccharides through enzymatic hydrolysis, the technological bottlenecks, and possible solutions to address these issues within the enzymatic process.

Dual Polarization of Ni Sites at VOx-Ni3N Interface Boosts Ethanol Oxidation Reaction.

Substituting thermodynamically favorable ethanol oxidation reaction (EOR) for oxygen evolution reaction (OER) engenders high-efficiency hydrogen production and generates high value-added products as well. However, the main obstacles have been the low activity and the absence of an explicit catalytic mechanism. Herein, a heterostructure composed of amorphous vanadium oxide and crystalline nickel nitride (VOx-Ni3N) is developed. The heterostructure immensely boosts the EOR process, achieving the current density of 50mA cm-2 at the low potential of 1.38V versus reversible hydrogen electrode (RHE), far surpassing the sluggish OER (1.65V vs RHE). Electrochemical impedance spectroscopy indicates that the as-fabricated heterostructure can promote the adsorption of OH- and the generation of the reactive species (O*). Theoretical calculations further outline the dual polarization of the Ni site at the interface, specifically the asymmetric charge redistribution (interfacial polarization) and in-plane polarization. Consequently, the dual polarization modulates the d-band center, which in turn regulates the adsorption/desorption strength of key reaction intermediates, thereby facilitating the entire EOR process. Moreover, a VOx-Ni3N-based electrolyzer, coupling hydrogen evolution reaction (HER) and EOR, attains 50mA cm-2 at a low cell voltage of ≈1.5V. This work thus paves the way for creating dual polarization through interface engineering toward broad catalysis.

Ionic Liquids toward Enhanced Carotenoid Extraction from Bacterial Biomass.

Carotenoids are high added-value products primarily known for their intense coloration and high antioxidant activity. They can be extracted from a variety of natural sources, such as plants, animals, microalgae, yeasts, and bacteria. Gordonia alkanivorans strain 1B is a bacterium recognized as a hyper-pigment producer. However, due to its adaptations to its natural habitat, hydrocarbon-contaminated soils, strain 1B is resistant to different organic solvents, making carotenoid extraction through conventional methods more laborious and inefficient. Ionic liquids (ILs) have been abundantly shown to increase carotenoid extraction in plants, microalgae, and yeast; however, there is limited information regarding bacterial carotenoid extraction, especially for the Gordonia genus. Therefore, the main goal of this study was to evaluate the potential of ILs to mediate bacterial carotenoid extraction and develop a method to achieve higher yields with fewer pre-processing steps. In this context, an initial screening was performed with biomass of strain 1B and nineteen different ILs in various conditions, revealing that tributyl(ethyl)phosphonium diethyl phosphate (IL#18), combined with ethyl acetate (EAc) as a co-solvent, presented the highest level of carotenoid extraction. Afterward, to better understand the process and optimize the extraction results, two experimental designs were performed, varying the amounts of IL#18 and EAc used. These allowed the establishment of 50 µL of IL#18 with 1125 µL of EAc, for 400 µL of biomass (cell suspension with about 36 g/L), as the ideal conditions to achieve maximal carotenoid extraction. Compared to the conventional extraction method using DMSO, this novel procedure eliminates the need for biomass drying, reduces extraction temperatures from 50 °C to 22 ± 2 °C, and increases carotenoid extraction by 264%, allowing a near-complete recovery of carotenoids contained in the biomass. These results highlight the great potential of ILs for bacterial carotenoid extraction, increasing the process efficiency, while potentially reducing energy consumption, related costs, and emissions.

Candida antartica lipase-catalyzed esterification for efficient partial acylglycerol synthesis in solvent-free system: Substrate selectivity, molecular modelling and optimization

Partial acylglycerols are valued for their emulsifying and stabilizing properties, yet precise green synthesis remains challenging due to low yield and selectivity. This study aimed to elucidate the “lipase selectivity-substrate structure-product composition” relationship to enhance the yield of targeted partial acylglycerol. The results showed that lipase exhibited a greater selectivity towards fatty acids with shorter chain lengths and higher unsaturation. Hydroxyl donors also affected the esterification process, with the enzyme-acyl complex exhibiting selectivity towards hydroxyl donors as follows: glycerol > monoacylglycerol > diacylglycerol. Substrate ratio significantly influenced enzymatic reactions; a 10:1 ratio favored triacylglycerol formation (>80 %), while a 1:1 ratio produced > 90 % partial acylglycerols. Molecular docking simulations revealed that substrates primarily interacted with lipase through hydrogen bonding and hydrophobic interactions. A comprehensive understanding of lipase selectivity patterns could facilitate the design of more efficient reaction systems, enabling the conversion of basic lipid resources into desired high value-added products.

Low-energy thermo-chemical conversion processes of municipal wet waste

Hydrothermal carbonization (HTC) is a low-energy thermochemical process that converts wet biomass into a carbon-rich solid, commonly called hydrochar, for use in a variety of areas, such as soil amendment, biofuels or to produce carbon-based materials. The purpose of this paper is to increase knowledge for the economic valorization of municipal wet waste, considered as a raw material to obtain high value-added products through an HTC process and an additional chemical activation procedure. In the first part of the work, a 4.5-liter batch reactor was designed, built, and used in the HTC experimental campaign by varying the main process parameters, namely reaction time, amount and type of organic waste (e.g. vegetables, fruits, bread, pasta), water concentration, temperature and pressure. In addition, some experiments were conducted by applying the steam explosion technique at the end of the HTC process. The HTC results showed that in biomass with high water content, increasing residence time decreases the hydrochar yield. Considering a dry heterogeneous waste with high carbon content, the yields at the end of the process are much higher. In the second part of this work, the hydrochar samples were treated with a high-temperature activation process based on the use of KOH, obtaining activated carbon. Particularly, the best results were achieved by using high KOH: hydrochar ratios, resulting in high-quality activated carbons with good porosity and a high surface area of 2890 m2/g. Finally, an energy analysis was carried out to evaluate how to make the whole process cost-effective.

Insight into pyrolysis characteristic and mechanism of natural rubber using rapid infrared-heating fixed bed combined with pyrolysis kinetics

Pyrolysis is a potential approach to treat post-consumer waste natural rubber (NR), however, unclear pyrolysis mechanism restricts its actual utilization. In this work, thermal degradation of NR was investigated combining dynamical method with pyrolysis on the infrared-heating fixed-bed reactor. Results show that thermal degradation of NR is an apparently exothermic and multistep reaction, tar yield reaches up to 96.59 wt%. Pyrolysis tar mainly consists of cycloolefin with a small quantity of chain olefins and mono-ring aromatic hydrocarbons. High temperature reduces the cycloolefin yield but promotes the generation of mono-ring aromatic hydrocarbons. Tar is mainly composed of dimer (C10) or trimer (C15) of isoprene with different structures. H type in tar is mainly aliphatic hydrogen. Besides, a possible pyrolysis mechanism based on the β bond breakage was proposed. The work can provide a theoretical basis for direct control of high value-added products during NR pyrolysis and achieve high efficiency pyrolysis of NR.

Exploiting UPO versatility to transform rutin in more soluble and bioactive products

The discovery of unspecific peroxygenases (UPOs) completely changed the paradigm of enzyme-based oxyfunctionalization reactions, as these enzymes can transform a wide variety of substrates with a relatively simple reaction mechanism. The fact that UPO can exert both peroxygenative and peroxidative activity in either aromatic or aliphatic carbons, represents a great potential in the production of high value-added products from natural antioxidants. In this work, the flavonoid rutin has been considered as possible substrate for UPO from Agrocybe aegerita, and its peroxygenation or its peroxidation and successive oligomerization have been studied. Different experiments were performed in order to reduce the range of process variables involved and gaining insight on the behavior of this enzyme, leading to a multivariable optimization of UPO-based rutin modification. While trying to preserve enzyme activity this optimization aimed for maximizing the production of more soluble antioxidants. Reusability of the enzyme was evaluated recovering UPO using an enzymatic membrane reactor, revealing challenges in enzyme stability due to inactivation during the filtration stages. The influence of the radical scavenger ascorbic acid on product formation was investigated, revealing its role in directing the reaction towards hydroxylated rutin derivatives, hence indicating a shift towards more soluble and bioactive products.

High value-added chemical production through anaerobic codigestion of corn straw with a microbial consortium, cow manure and cow digestion solution

ObjectivesThis study investigated the codigestion of corn straw (CS) with cow manure (CM), cow digestion solution (CD), and a strain consortium (SC) for enhanced volatile fatty acid (VFA) production. The aims of this study were to develop a sustainable technique to increase VFA yields, examine how combining microbial reagents with CS affects VFA production by functional microorganisms, and assess the feasibility of improving microbial diversity through codigestion. MethodsBatch experiments evaluated VFA production dynamics and microbial community changes with different combinations of CS substrates with CM, CD, and SC. Analytical methods included measuring VFAs by GC, ammonia and chemical oxygen demand (COD) by standard methods and microbial community analysis by 16S rRNA gene sequencing. ResultsCodigesting CS with the strain consortium yielded initial VFA concentrations ranging from 0.6 to 1.0 g/L, which were greater than those of the other combinations (0.05–0.3 g/L). Including CM, and CD further increased VFA production to 1.0–2.0 g/L, with the highest value of 2.0 g/L occurring when all four substrates were codigested. Significant ammonium reduction (194–241 mg/L to 29–37 mg/L) and COD reduction (3310–5250 mg/L to 730–1210 mg/L) were observed. Codigestion with CM and CD had greater Shannon diversity indices (3.19–3.24) than did codigestion with the other consortia (2.26). Bacillota dominated (96.5–99.6 %), with Clostridiales playing key roles in organic matter breakdown. ConclusionsThis study demonstrated the feasibility of improving VFA yields and harnessing microbial diversity through anaerobic codigestion of lignocellulosic and animal waste streams. Codigestion substantially enhanced VFA production, which was dominated by butyrate, reduced ammonium and COD, and enriched fiber-degrading and fermentative bacteria. These findings can help optimize codigestion for sustainable waste management and high-value chemical production.

Separation and extraction of iron resources from hazardous electric arc furnace (EAF) steel slag: Aggregation of Fe-rich layers, magnetic separation, powder characterization

China's electric arc furnace (EAF) slag reserves are huge, the problems of EAF slag resource application need to be solved urgently. In this study, high temperature holding and slow cooling treatment were used to treat the slag. The phase and structure of the slag were analysed by means of X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. To analyse the migration pattern of iron elements and to study the interaction between EAF slag basicity and magnetic separation efficiency. The results show that, there is an obvious layering phenomenon during the cooling slag, and the top layer is the Fe-rich layer. The slow cooling treatment makes the Fe-rich phase grow sufficiently and improves the dissociation efficiency of the Fe-rich phase in the crushing process. As the basicity increases, the thickness of the iron-rich layer gradually decreases and the iron element is transferred to the RO phase, while the concentrate yield decreases. Multi-stage wet weak magnetic separation of treatment slag resulted in the highest concentrate yield of 49.05 % at an basicity of 1, with a T.Fe content of 56.711 %, and 70.32 % of the iron component entering the concentrate. The concentrate can be returned to the steelmaking process instead of the charge, and the tailings can be used to make high value-added products.

New mechanistic insights into CO2 electroreduction to methane on penta-octa-graphene catalyst

Electrocatalytic reduction of CO2 to produce high value-added products is an important way to achieve sustainable production of green energy, but it is limited by high complexity of the catalyst structure and reaction process, making the rational design of the catalyst and the targeted generation of specific products a huge challenge. Herein, based on the penta-octa-graphene (POG) with sp2 and sp3 hybrid as the prototype, we theoretically guide the design of CO2 electrocatalytic reduction (CO2RR) catalyst over pure POG and TM doping POG (TM@POG). Our mechanistic study highlights two key factors in new pathway for CH4 production and catalytic performance, i.e., TM provides electron transfer for the key intermediate *CHO, promoting the activation of CO2, and the type of protonation for CO2RR is determined by the charge accumulation on the O atom of the intermediates. This reduces the complexity of the reaction and provides a predictive effect on the formation of intermediates. More importantly, the proper values of the Gibbs free energy indicate that TM@POG is an ideal catalyst candidate, especially the Fe@POG, which is superior to Cu (211) material. On this basis, three simple descriptors (Bader charge, d-band center εd and descriptor φ) based on the inherent properties of atoms were constructed to reveal the underlying causes of the improvement of catalytic activity. Our results provide a new understanding of the ’structure-performance’ relationship of carbon-based electrocatalysts, thus providing a useful strategy for the design of catalysts for CO2RR.

A Light-Powered In Vitro Synthetic Enzymatic Biosystem for the Synthesis of 3-Hydroxypropionic Acid via CO2 Fixation.

3-Hydroxypropionic acid (3-HP) is a highly sought-after platform chemical serving as a precursor to a variety of high value-added chemical products. In this study, we designed and constructed a novel light-powered in vitro synthetic enzymatic biosystem comprising acetyl-CoA ligase, acetyl-CoA carboxylase, malonyl-CoA reductase, and phosphotransferase to efficiently produce 3-HP through CO2 fixation from acetate, a cost-effective and readily available substrate. The system employed natural thylakoid membranes (TMs) for the regeneration of adenosine triphosphate and nicotinamide adenine dinucleotide phosphate. Comprehensive investigations were conducted on the effects of buffer solutions, substrate concentrations, enzyme loading levels, and TMs loading levels to optimize the yield of 3-HP. Following optimization, a production of 0.46 mM 3-HP was achieved within 6 h from an initial 0.5 mM acetate, with a yield nearing 92%. This work underscores the simplicity of 3-HP production via an in vitro biomanufacturing platform and highlights the potential for incorporating TMs as a sustainable and environmentally friendly approach in biomanufacturing processes.

Highly selective aerobic oxidation of cyclohexane by flower-like MoO3-x microspheres-nitrogen-doped carbon dots heterojunction

Due to the higher susceptibility of alcohols and ketones to oxidation compared to alkanes, converting inert C-H bonds in alkanes into high value-added product KA oil with high selectivity is still a significant obstacle. In this study, flower-like microspheres of MoO3-x, featuring aligned nanosheets and oxygen vacancies, were combined with nitrogen doped carbon dots (NCDs) to fabricate S-scheme heterojunctions of MoO3-x-NCDs for boosting the photocatalytic efficiency in oxidizing cyclohexane. Because of the oxygen vacancies-triggered localized surface plasmon resonance (LSPR) and the S-scheme charge transfer mechanism, there was a significant improvement in the absorption of visible light and an enhancement in the efficiency of charge separation. The MoO3-x-NCDs composites exhibited a notably improved catalytic performance in cyclohexane oxidation. The MoO3-x-NCDs composite exhibited remarkable selectivity of KA oil in catalyzing cyclohexane oxidation under light exposure, attributed to the substantial increase in cyclohexane adsorption capacity. The highest cyclohexane transformation rate of 9.98 % was achieved by MoO3-x-NCDs-2 composites with a MoO3-x/NCDs ratio of 50:1, outperforming bare MoO3-x by 1.81 times, while exhibiting a KA oil selectivity reaching 93.75 %. The mechanism of selective photocatalytic oxidation was explored using photoelectric examination, analysis of energy bands, and evaluation of active radicals. In this research, green photocatalysts were fabricated through the utilization of NCDs, enabling efficient conversion and selective oxidation of cyclohexane in gentle environments. This innovative approach holds great potential for advancing the field of photocatalysis.

Nanoparticulated Vanadium Oxide on BiVO4 for Boosting Photoelectrochemical Glycerol Oxidation

Hydrogen (H2) has been spotlighted as ideal energy carrier due to its relatively higher energy density compared to fossil fuel and no carbon emissions during the energy generation. However, most of current produced H2 comes from as byproducts in fossil fuel reforming processes. To reduce dependence on fossil fuel in the H2 production process, photoelectrochemical (PEC) water splitting is considered as promising strategy for producing H2 using sustainable resources. Nevertheless, the insufficient efficiency in PEC water oxidation oxygen evolution reaction (OER) has limited overall PEC water splitting system efficiency due to its relatively high oxidation potential and sluggish catalytic kinetics. Furthermore, the low value of generated oxygen has been pointed out as obstacle from an economic perspective. To overcome these challenges, glycerol, byproduct of biodiesel, has been attracted numerous attentions as PEC oxidation resource since it has three hydroxyl groups and relatively lower oxidation potential than OER. Furthermore, glycerol oxygenated value-added products like dihydroxyacetone (DHA) can improve economics of PEC hydrogen production system. Upon these strengths, PEC glycerol oxidation reaction (GOR) provides improved strategy that generates value-added products in anodic part and green energy source (H2) in cathodic part simultaneously, which can replace PEC water splitting. Bismuth vanadate (BiVO4) is one of the most promising transition metal oxide based catalyst for PEC GOR due to its relatively narrow bandgap, high theoretical photocurrent density and deep positive valence band maximum (VBM) position. Additionally, although the surface kinetics of BiVO4 for OER has been sluggish, it potentially would be advantage for GOR with high production rate. However, the relatively instability of BiVO4 in acidic electrolyte during operation and lower selectivity of oxygenated products has hindered their practical application in PEC GOR. To solve these problems, introduction of nanoparticles as cocatalysts has been much studied for ameliorating surface kinetics and passivation the surface of photoanode. However, the interface between nanoparticles and photoanode with poor chemical interaction can induce the higher interfacial resistance and slow charge transfer efficiency rather. In this study, we present in-situ vanadium oxide (VOx) nanoparticle decoration on the surface of BiVO4 (VOx/BiVO4) via selective etching process using alkaline treatment for enhancing PEC GOR and we report the world best photocurrent density based on BiVO4 photoanode for GOR with high selective DHA production. VOx nanoparticles with an average size of 5 nm by selective etching process using alkaline treatment is decorated on the surface of BiVO4. The VOx promotes the surface reaction kinetics via modulating the fermi level and enhanced photovoltage of BiVO4 and improves long-term stability for GOR by compensation of V5+ and Bi3+, which combines both efficiency and stability. Furthermore, the surface decorated photoanode presents a 6.82 mA/cm2 (1.34-fold improvement) photocurrent density at 1.23 V versus the reversible hydrogen electrode (RHE) under 1 sun illumination, which has been attributed enhanced catalytic kinetics with upshifted fermi level and photovoltage of BiVO4. Moreover, the long-term stability of VOx/BiVO4 has been exhibited over 10 hours and the high selectivity for DHA is achieved. This study presents insight into the role vanadium of selective etched VOx on the surface of BiVO4 with low valence state than that of BiVO4 and improving the potential of BiVO4 based catalyst as GOR photoanode for high selective value-added DHA production using solar energy.

Catalytic Approaches to Tackle Mixed Plastic Waste Challenges: A Review.

Plastics are widely used materials in our daily lives and various industries due to their affordability and versatility. The massive production of plastic waste, however, has recently emerged as a pressing environmental concern across all media. To address this, emerging technologies are being explored for the sustainable valorization of postconsumer plastic wastes including thermochemical, physical, and catalytic processes aimed at transforming them into higher value-added products. However, the chemical recycling of mixed plastic wastes poses a formidable challenge due to the diverse array of monomers and catalyst systems involved, each employing distinct mechanisms. Complicating matters further is that contaminants reduce catalytic efficacy, requiring rigorous and labor-intensive separation and purification processes to extract individual plastic streams from practical plastic waste mixtures. Consequently, the majority of such mixtures often end up in incineration and landfills, perpetuating environmental and societal challenges, such as leachate, carbon dioxide emissions, and other air pollutants. This review will introduce current technical developments available for recycling practical plastic waste mixtures through catalytic processes. The current challenges in process performance, low selectivity of the desired products, and catalyst deactivation from the catalysis of plastic waste mixtures are also discussed. Promising approaches to overcome the problems are suggested in future research directions.

Integrated production of xylose and docosahexaenoic acid from hemicellulose and cellulose in corncob

Exploring efficient and comprehensive utilization of agricultural waste to produce high value-added products has been global research hotspot. In this study, a novel process for integrated production of xylose and docosahexaenoic acid (DHA) from hemicellulose and cellulose in corncob was developed. Corncob was treated with dilute H2SO4 at 121 °C for 1 h and xylose was readily produced with a recovery yield of 79.35 %. The corncob residue was then subject to alkali pretreatment under optimized conditions of 0.1 g NaOH/g dry solid, 60 °C for 2 h, and the contents of cellulose, hemicellulose, and lignin in the resulting residue were 87.49 %, 7.58 % and 2.31 %, respectively. The cellulose in the residue was easily hydrolyzed by cellulase, yielding 74.87 g/L glucose with hydrolysis efficiency of 77.02 %. Remarkably, the corncob residue hydrolysate supported cell growth and DHA production in Schizochytrium sp. ATCC 20888 well, and the maximum biomass of 32.71 g/L and DHA yield of 4.63 g/L were obtained, with DHA percentage in total fatty acids of 36.89 %. This study demonstrates that the corncob residue generated during xylose production, rich in cellulose, can be effectively utilized for DHA production by Schizochytrium sp., offering a cost-effective and sustainable alternative to pure glucose.

COMPARATIVE ANALYSIS OF CURRENT BIOMASS UTILISATION BY PALM OIL MILLS IN PENINSULAR MALAYSIA

Oil palm biomass, which includes empty fruit bunches (EFB), mesocarp fibres (MF), palm kernel shells (PKS), and palm oil mill effluent (POME), are no longer seen as low-value residue, but as valuable economic resources that may contribute positively to national wealth. These oil palm biomasses can be converted into high value-added products, which can in turn generate additional revenue for the country. This study aims to identify the current biomass utilisation by palm oil mills in Peninsular Malaysia and examine the economic viability of biomass products generated by these mills across different categories. This study uses primary data obtained through a census of all 242 Malaysian Palm Oil Board-licensed palm oil mills in Peninsular Malaysia. The data were analysed using descriptive analysis and independent samples t-test. The study found that incineration is the most profitable approach for EFB, followed by selling EFB to other parties. However, due to environmental regulation and the lack of market for EFB, most of the resources (62.4%) were either returned to plantations or sent to landfills. In addition, 92.4% of MF generated were utilised for electricity generation through in-house boilers and this alternative has been proven to provide maximum profit to palm oil mills. The study also found that although selling PKS to other parties was proven to provide better profits to the palm oil mills, the PKS were mostly utilised for electricity generation through in-house boilers. Lastly, for the sludge from POME, there was no significant difference in the utilisation of the sludge, either if it was used for plantations or sold to other parties.

Recycling potato waste for the production of blue pigments by Streptomyces lydicus PM7 through submerged fermentation

BackgroundDiscarded potato is the most abundant potato waste and represents a worldwide disposal problem to the potato industry. This agricultural waste contains valuable nutrients that could be used as substrate to obtain diverse high value-added microbial products, such as biopigments. The aim of this work was to evaluate the use of discarded potato as a sole substrate source for producing blue pigments by Streptomyces lydicus PM7 through submerged fermentation.ResultsInitially, the traditional culture medium ISP2 was established as suitable for inoculum preparation, as it allowed high growth rates and consumption of ~ 75% reducing sugar, leading to 1.3 g L−1 dry biomass at 72 h of incubation. The formulated discarded potato broth (DPB) medium was evaluated together with five other traditional liquid culture media (potato dextrose broth, ISP2, ISP3, ISP4, and ISP5) for producing blue pigments by S. lydicus PM7. The highest blue pigment production was obtained by using DPB medium, reaching ~ 0.97 g L−1, followed by ISP5 (~ 0.36 g L−1). In terms of evaluating the concentration of discarded potato powder, the highest concentration of blue pigments was obtained with 16 g L−1, compared to concentrations of 4, 8, and 32 g L−1. In general, a notable increase in total proteins (~ 14 g L−1 in biomass; ~ 8 g L−1 in medium) and reducing sugars (~ 5 g L−1) on the fifth day of DPB fermentation was observed, at which time the production of blue pigments began. These data proved that S. lydicus PM7 is able to degrade potato wastes during submerged fermentation and to direct metabolism towards the formation of biopigments. Chromatographic analysis revealed that the main blue pigment produced by new strain in this complex medium is actinorhodin.ConclusionsDiscarded potato favored the production of blue pigments by S. lydicus PM7 under submerged fermentation, leading to final product concentration almost three times higher than others traditional Streptomyces culture media. To the best of our knowledge, this is the first report on the production of actinorhodin by the specie S. lydicus, as well as on this pigment synthesis based on an agricultural waste as a sole nutrient source for fermentation process. The findings showed that potato waste could be a potential byproduct for replacement of commercial culture media using for this same purpose.Graphical

Development of Leptolyngbya sp. BL0902 into a model organism for synthetic biological research in filamentous cyanobacteria.

Cyanobacteria have great potential in CO2-based bio-manufacturing and synthetic biological studies. The filamentous cyanobacterium, Leptolyngbya sp. strain BL0902, is comparable to Arthrospira (Spirulina) platensis in commercial-scale cultivation while proving to be more genetically tractable. Here, we report the analyses of the whole genome sequence, gene inactivation/overexpression in the chromosome and deletion of non-essential chromosomal regions in this strain. The genetic manipulations were performed via homologous double recombination using either an antibiotic resistance marker or the CRISPR/Cpf1 editing system for positive selection. A desD-overexpressing strain produced γ-linolenic acid in an open raceway photobioreactor with the productivity of 0.36 g·m-2·d-1. Deletion mutants of predicted patX and hetR, two genes with opposite effects on cell differentiation in heterocyst-forming species, were used to demonstrate an analysis of the relationship between regulatory genes in the non-heterocystous species. Furthermore, a 50.8-kb chromosomal region was successfully deleted in BL0902 with the Cpf1 system. These results supported that BL0902 can be developed into a stable photosynthetic cell factory for synthesizing high value-added products, or used as a model strain for investigating the functions of genes that are unique to filamentous cyanobacteria, and could be systematically modified into a genome-streamlined chassis for synthetic biological purposes.

Atomic-level rhodium doping into NiO for boosting the selective electrooxidation of HMF to FFCA in neutral electrolyte

The oxidation reaction of the biomass derivative 5-hydroxymethylfurfural (HMF) holds immense promise for the sustainable synthesis of high-value chemicals. Nevertheless, achieving the selective electrooxidation of HMF to generate high value-added formyl-2-furan carboxylic acid (FFCA) intermediate remains a serious challenge. Here, the V-NiO-Rh catalyst was constructed and demonstrates an impressive FFCA selectivity of 71 % for HMF electrooxidation reaction (HMFOR) in neutral electrolyte. The designed experiments elucidate that the HMFOR mechanism is the co-adsorption of OH* and HMF* on Ni active sites. Furthermore, the theoretical calculations prove that the modulation of Ni electronic structure by single atom Rh promotes the ability of HMF adsorption and the water electrolysis to release OH*. This paper establishes a theoretical foundation for the selective synthesis of high value-added intermediates products that are challenging to obtain in alkaline media.