Integrated biorefinery approach for utilization of wood waste into levulinic acid and 2-Phenylethanol production under mild treatment conditions.

In a bid to explore the on-site biorefinery approach for conversion of forestry residues, lignocellulosic biomass into value-added products was studied. The bark white pine wood was subjected to the microwave technique of fast and slow hydrolysis under varying acid and biomass concentrations to produce levulinic acid (LA). The HCl (2% v/v) and plant biomass (1% w/v) were identified as the optimum conditions for fast wood hydrolysis (270 ºC for 12 sec), which led to maximum LA yield of 446.68 g/kgPB. The proposed sustainable approach is mild, quick, and utilized a very low concentration of the HCl for the production of LA. The hydrolysate was used as a medium for Kluyveromyces marxianus growth to produce 2-phenylethanol (2-PE). K. marxianus used 74-95% of furfural from hydrolysate as a co-substrate to grow. The proposed model of the integrated biorefinery is an affordable on-site approach of using forest waste into localized solutions to produce LA and 2-PE.

Production of levulinic acid from macroalgae by hydrothermal conversion with ionic resin catalyst.

Gracilaria verrucosa is red algae (Rhodophyta) that is particularly significant because of its potential for bioenergy production as a sustainable and environmentally friendly marine bioresource. This study focuses on the production of levulinic acid from G. verrucosa using hydrothermal conversion with an ionic resin Purolite CT269DR as the catalyst. By optimization of the conversion condition, a 30.3 % (22.58 g/L) yield of levulinic acid (LA) (based on carbohydrate content) was obtained at 200 °C for 90 min with 12.5 % biomass and 50 % catalyst loading of biomass quantity. Simultaneously, formic acid yielded 14.0 % (10.42 g/L). The LA yield increased with increasing combined severity (CS) levels under tested ranges. Furthermore, the relationship between CS and LA synthesis was effectively fitted to the nonlinear sigmoidal equation. However, as the yield of sugar decreased, LA yield was linearly increased. Thus, the use of ionic resin as a heterogeneous catalyst presents significant potential for the manufacture of platform chemicals, specifically LA, through the conversion of renewable marine macroalgae.

Metabolic Engineering of Escherichia coli for Production of Polyhydroxyalkanoates with Hydroxyvaleric Acid Derived from Levulinic Acid.

Polyhydroxyalkanoates (PHAs) are emerging as alternatives to plastics by replacing fossil fuels with renewable raw substrates. Herein, we present the construction of engineered Escherichia coli strains to produce short-chain-length PHAs (scl-PHAs), including the monomers 4-hydroxyvalerate (4HV) and 3-hydroxyvalerate (3HV) produced from levulinic acid (LA). First, an E. coli strain expressing genes (lvaEDABC) from the LA metabolic pathway of Pseudomonas putida KT2440 was constructed to generate 4HV-CoA and 3HV-CoA. Second, both PhaAB enzymes from Cupriavidus necator H16 were expressed to supply 3-hydroxybutyrate (3HB)-CoA from acetyl-CoA. Finally, PHA synthase (PhaCCv) from Chromobacterium violaceum was introduced for the subsequent polymerization of these three monomers. The resulting E. coli strains produced four PHAs (w/w% of dry cell weight): 9.1 wt% P(4HV), 1.7 wt% P(3HV-co-4HV), 24.2 wt% P(3HB-co-4HV), and 35.6 wt% P(3HB-co-3HV-co-4HV).

5-aminolaevulinic acid (5-ALA) accumulates in GIST-T1 cells and photodynamic diagnosis using 5-ALA identifies gastrointestinal stromal tumors (GISTs) in xenograft tumor models.

Gastrointestinal stromal tumor (GIST) diagnosis using conventional gastrointestinal endoscopy is difficult because such malignancies cannot be distinguished from other types of submucosal tumors. Photodynamic diagnosis (PDD) is based on the preferential uptake of photosensitizers by tumor tissues and its detection by fluorescence emission upon laser excitation. In this study, we investigated whether PDD using 5-aminolevulinic acid (5-ALA), a standard photosensitizer used worldwide, could be used for GIST diagnosis. 5-ALA is metabolized to endogenous fluorescent protoporphyrin IX (PpIX). We examined the accumulation of PpIX in GIST-T1 cells using flow cytometry and immunofluorescent staining. Furthermore, we established GIST-T1 xenograft mouse models and examined PpIX accumulation in the resultant tumors. PpIX accumulated in GIST-T1 cells and was localized mainly to lysosomes. PpIX accumulation was also observed in murine xenograft tumors. Moreover, tumor and normal tissues could be distinctly identified by relative PpIX fluorescence. Thus, our results demonstrated that PDD with 5-ALA has substantial clinical potential for GIST diagnosis.

Prospecting Biochemical Pathways to Implement Microbe-Based Production of the New-to-Nature Platform Chemical Levulinic Acid.

Levulinic acid is a versatile platform molecule with potential to be used as an intermediate in the synthesis of many value-added products used across different industries, from cosmetics to fuels. Thus far, microbial biosynthetic pathways having levulinic acid as a product or an intermediate are not known, which restrains the development and optimization of a microbe-based process envisaging the sustainable bioproduction of this chemical. One of the doors opened by synthetic biology in the design of microbial systems is the implementation of new-to-nature pathways, that is, the assembly of combinations of enzymes not observed in vivo, where the enzymes can use not only their native substrates but also non-native ones, creating synthetic steps that enable the production of novel compounds. Resorting to a combined approach involving complementary computational tools and extensive manual curation, in this work, we provide a thorough prospect of candidate biosynthetic pathways that can be assembled for the production of levulinic acid in Escherichia coli or Saccharomyces cerevisiae. Out of the hundreds of combinations screened, five pathways were selected as best candidates on the basis of the availability of substrates and of candidate enzymes to catalyze the synthetic steps (that is, those steps that involve conversions not previously described). Genome-scale metabolic modeling was used to assess the performance of these pathways in the two selected hosts and to anticipate possible bottlenecks. Not only does the herein described approach offer a platform for the future implementation of the microbial production of levulinic acid but also it provides an organized research strategy that can be used as a framework for the implementation of other new-to-nature biosynthetic pathways for the production of value-added chemicals, thus fostering the emerging field of synthetic industrial microbiotechnology.

Protein 4.1R affects photodynamic therapy for B16 melanoma by regulating the transport of 5-aminolevulinic acid.

Melanoma is the most aggressive malignant tumor of skin cancer as it can grow rapidly and metastasize. Photodynamic therapy (PDT) is a promising cancer ablation method for skin tumors, although it lacks efficiency owing to factors such as tumor characteristics, delivery of photosensitizers, immune response in vivo etc. Extensive investigation of molecules that can potentially modulate treatment efficacy is required. Protein 4.1R is a cytoskeletal protein molecule. Previous studies have shown that protein 4.1R knockdown reduces PDT sensitivity in mouse embryonic fibroblast cells. However, the functional role of protein 4.1R in melanoma is unclear. In this study, we aimed to elucidate the effect of protein 4.1R on PDT for melanoma in mice and the mechanism of anti-tumor immunity. Our results indicated that CRISPR/Cas9-mediated protein 4.1R knockout promotes the proliferation, migration, and invasion of B16 cells. We further investigated the potential mechanism of protein 4.1R on tumor cell PDT sensitivity. Our results showed that protein 4.1R knockout reduced the expression of membrane transporters γ-aminobutyric acid transporter (GAT)-1 and (GAT)-2 in B16 cells, which affected 5-ALA transmembrane transport and reduced the efficiency of PDT on B16 cells. Protein 4.1R knockout downregulated the anti-tumor immune response triggered by PDT in vivo. In conclusion, our data suggest that protein 4.1R is an important regulator in PDT for tumors and may promote the progress and efficacy of melanoma treatment.

Catalytic Conversion of Glucose into Levulinic Acid Using 2-Phenyl-2-Imidazoline Based Ionic Liquid Catalyst.

Levulinic acid (LA) is an industrially important product that can be catalytically valorized into important value-added chemicals. In this study, hydrothermal conversion of glucose into levulinic acid was attempted using Brønsted acidic ionic liquid catalyst synthesized using 2-phenyl-2-imidazoline, and 2-phenyl-2-imidazoline-based ionic liquid catalyst used in this study was synthesized in the laboratory using different anions (NO3, H2PO4, and Cl) and characterized using 1H NMR, TGA, and FT-IR spectroscopic techniques. The activity trend of the Brønsted acidic ionic liquid catalysts synthesized in the laboratory was found in the following order: [C4SO3HPhim][Cl] > [C4SO3HPhim][NO3] > [C4SO3HPhim][H2PO4]. A maximum 63% yield of the levulinic acid was obtained with 98% glucose conversion at 180 °C and 3 h reaction time using [C4SO3HPhim][Cl] ionic liquid catalyst. The effect of different reaction conditions such as reaction time, temperature, ionic liquid catalyst structures, catalyst amount, and solvents on the LA yield were investigated. Reusability of [C4SO3HPhim][Cl] catalyst up to four cycles was observed. This study demonstrates the potential of the 2-phenyl-2-imidazoline-based ionic liquid for the conversion of glucose into the important platform chemical levulinic acid.

Different Reactivity of Raw Starch from Diverse Potato Genotypes.

Potato starch is one of the most important renewable sources for industrial manufacturing of organic compounds. Currently, it is produced from mixed potato varieties that often are harvested from different fields. Meanwhile, tuber starches of various potato breeds differ in their crystallinity, granule morphology, and other physical and chemical parameters. We studied the reactions of raw potato starches of different origins to chemical and biochemical reactions typically used for industrial starch modification. The results clearly demonstrate that there is a significant difference in the reactivity of the starches of different potato genotypes. While the main products of the transformations are the same, their preparative yields differ significantly. Thus, tuber starch of certain potato varieties may be more suitable for specific industrial purposes. Starch reactivity may potentially be a phenotypical trait for potato breeding to obtain potato starches for various industrial applications.

Macroscopic fluorescence-lifetime imaging of NADH and protoporphyrin IX improves the detection and grading of 5-aminolevulinic acid-stained brain tumors.

Maximal safe tumor resection remains the key prognostic factor for improved prognosis in brain tumor patients. Despite 5-aminolevulinic acid-based fluorescence guidance the neurosurgeon is, however, not able to visualize most low-grade gliomas (LGG) and infiltration zone of high-grade gliomas (HGG). To overcome the need for a more sensitive visualization, we investigated the potential of macroscopic, wide-field fluorescence lifetime imaging of nicotinamide adenine dinucleotide (NADH) and protoporphyrin IX (PPIX) in selected human brain tumors. For future intraoperative use, the imaging system offered a square field of view of 11 mm at 250 mm free working distance. We performed imaging of tumor tissue ex vivo, including LGG and HGG as well as brain metastases obtained from 21 patients undergoing fluorescence-guided surgery. Half of all samples showed visible fluorescence during surgery, which was associated with significant increase in PPIX fluorescence lifetime. While the PPIX lifetime was significantly different between specific tumor tissue types, the NADH lifetimes did not differ significantly among them. However, mainly necrotic areas exhibited significantly lower NADH lifetimes compared to compact tumor in HGG. Our pilot study indicates that combined fluorescence lifetime imaging of NADH/PPIX represents a sensitive tool to visualize brain tumor tissue not detectable with conventional 5-ALA fluorescence.

Effectiveness of Photodynamic Screening Using 5-Aminolevulinic Acid for the Diagnosis of Pancreatic Cancer.

BACKGROUND/AIM: We evaluated urinary levels of porphyrin metabolites, such as uroporphyrin (UP) and coproporphyrin (CP), after 5-Aminolevulinic acid (ALA) administration in patients with or without pancreatic cancer (PaC). PATIENTS AND METHODS: Sixty-seven subjects with PaC, 11 with pancreatitis, and 9 with normal pancreas (NP) were enrolled. Urine samples from all subjects were collected prior to ALA administration and at more than 4 hours after ALA administration. We measured the urinary levels of UP and CP by high-performance liquid chromatography analysis. RESULTS: The PaC group showed significantly higher UP levels compared to NP groups (104.9 nmol/g Cre vs. 53.4 nmol/g Cre, p=0.014). Moreover, PaC patients with long-term survival had significantly lower urinary levels of UP at diagnosis (98.8 nmol/gCre) than the short-term survival group (125.2 nmol/gCre) (p=0.042). CONCLUSION: The urinary levels of UP after ALA administration might serve as a promising biomarker for diagnosis and prognosis prediction of PaC.

The iTRAQ-based chloroplast proteomic analysis of Triticum aestivum L. leaves subjected to drought stress and 5-aminolevulinic acid alleviation reveals several proteins involved in the protection of photosynthesis.

BACKGROUNDS: The perturbance of chloroplast proteins is a major cause of photosynthesis inhibition under drought stress. The exogenous application of 5-aminolevulinic acid (ALA) mitigates the damage caused by drought stress, protecting plant growth and development, but the regulatory mechanism behind this process remains obscure. RESULTS: Wheat seedlings were drought treated, and the iTRAQ-based proteomic approach was employed to assess the difference in chloroplast protein content caused by exogenous ALA. A total of 9499 peptides, which could be classified into 2442 protein groups, were identified with ≤0.01 FDR. Moreover, the contents of 87 chloroplast proteins was changed by drought stress alone compared to that of the drought-free control, while the contents of 469 was changed by exogenous ALA application under drought stress compared to that of drought stress alone. The Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis results suggested that the ALA pretreatment adjusted some biological pathways, such as metabolic pathways and pathways involved in photosynthesis and ribosomes, to enhance the drought resistance of chloroplasts. Furthermore, the drought-promoted H2O2 accumulation and O2- production in chloroplasts were alleviated by the exogenous pretreatment of ALA, while peroxidase (POD) and glutathione peroxidase (GPX) activities were upregulated, which agreed with the chloroplast proteomic data. We suggested that ALA promoted reactive oxygen species (ROS) scavenging in chloroplasts by regulating enzymatic processes. CONCLUSIONS: Our results from chloroplast proteomics extend the understanding of the mechanisms employed by exogenous ALA to defend against drought stress in wheat.

Quantification, regulation and production of 5-aminolevulinic acid by green fluorescent protein in recombinant Escherichia coli.

5-Aminolevulinic acid (5-ALA) is an unnatural amino acid and has been approved as a biodegradable, non-toxic pesticide and herbicide with applications in sustainable agriculture. 5-ALA can also be applied for cancer targeting via tumor localization and photodynamic therapy. Herein, we developed a feasible quantification, regulation and production method of 5-ALA in Escherichia coli is based on the chimera of 5-ALA synthetase from Rhodobacter sphaeroides (RshemA) and super-fold green fluorescent protein (sfGFP) under the control of dual promoters/double plasmids. 5-ALA production based on quantification with the reporter sfGFP was unsuccessfully for the RshemA-sfGFP fusion protein owing to a steric hindrance effect, but was effective using dual constitutive promoters (i.e., J23100 and PLacI) for RshemA and sfGFP independently. Moreover, a simple quantification method based on the linear relationship between 5-ALA concentration and the change in sfGFP intensity was calculated with the Hill equation according to the results of dual plasmids which composed of RshemA-threonine/homoserine exporter (RhtA) and the sensing plasmid pSU-T7-sfGFP. Compared with the conventional detection method for 5-ALA using Ehrlich's reagent, our proposed method is advantages in effectiveness, real-time detection, and outstanding sensitivity. Finally, the highest yield of 5-ALA was obtained in E. coli D2TT strain, reaching 2.46 g/L of 5-ALA produced in a 2.5-L baffle flask fermentation. Hence, this approach shows strong potential for improving 5-ALA production with appropriate regulation and detection based on the fluorescent signal.

Production of 5-aminolevulinic acid from glutamate by overexpressing HemA1 and pgr7 from Arabidopsis thaliana in Escherichia coli.

The important metabolic intermediate 5-aminolevulinic acid (ALA) is useful for cancer treatment or plant growth regulation and has consequently received much attention. In this study, we introduced the HemA1 and pgr7 genes from the higher plant Arabidopsis thaliana into recombinant Escherichia coli to overproduce extracellular 5-aminolevulinic acid via the C5 pathway. In the E. coli BL21 (DE3) strain background, the ALA concentration of the strain expressing both HemA1 and pgr7 was the highest and reached 3080.62 mg/L. Among the 7 tested hosts, ALA production was the highest in E. coli Transetta (DE3). In E. coli Transetta GTR/GBP, the expression levels of zwf, gnd, pgl and RhtA were upregulated. Glutamate induced the expression of the GltJ, GltK, GltL and GltS genes that are in involved in glutamate uptake. The recombinant E. coli Transetta GTR/GBP was able to produce 7642 mg/L ALA in modified minimal medium supplemented with 10 g/L glutamate and 15 g/L glucose after 48 h of fermentation at 22 °C. The results provide persuading evidence for the efficient production of ALA from glucose and glutamate in E. coli expressing A. thaliana HemA1 and pgr7. Further optimization of the fermentation process should be done to improve the ALA production to an industrially relevant level.

5-Aminolevulinic acid fermentation using engineered Saccharomyces cerevisiae.

BACKGROUND: 5'-Aminolevulinic acid (ALA) is widely used in the pharmaceutical industry, healthcare, and food production, and is a substrate for the biosynthesis of heme, which is required for respiration and photosynthesis. Enhancement of ALA biosynthesis has never been developed in Saccharomyces cerevisiae, which is a well-known model microorganism used for bioproduction of many value-added compounds. RESULTS: We demonstrated that metabolic engineering significantly improved ALA production in S. cerevisiae. First, we found that overexpression of HEM1, which encodes ALA synthetase, increased ALA production. Furthermore, addition of an optimal amount of glycine, a substrate for ALA biosynthesis, or levulinic acid, an inhibitor of ALA dehydrogenase, effectively increased ALA production. Next, we developed an assay for multiple metabolites including ALA and found that aconitase, encoded by ACO1 and ACO2, is the rate-limiting enzyme of ALA biosynthesis when sufficient glycine is supplied. Overexpression of ACO2 further enhanced ALA production in S. cerevisiae overexpressing HEM1. CONCLUSIONS: In this study, ALA production in S. cerevisiae was enhanced by metabolic engineering. This study also shows a strategy to identify the rate-limiting step of a target synthetic pathway by assay for multiple metabolites alongside the target product. This strategy can be applied to improve production of other valuable products in the well-studied and well-industrialized microorganism S. cerevisiae.

Characterization and Engineering of a Clostridium Glycine Riboswitch and Its Use To Control a Novel Metabolic Pathway for 5-Aminolevulinic Acid Production in Escherichia coli.

A riboswitch, a regulatory RNA that controls gene expression by specifically binding a ligand, is an attractive genetic element for the control of conditional gene expression and metabolic pathways. In this study, we identified a glycine riboswitch located in the 5'-untranslated regions of a glycine:proton symporter gene in Clostridium pasteurianum. The glycine riboswitch is shown to contain two tandem aptamers and to function as an activator of expression of genes fused to its expression platform. Results of singlet aptamer experiments indicated that aptamer-2 has a much higher impact on regulating gene expression than aptamer-1. Further, we successfully obtained synthetic glycine-OFF riboswitches using a dual selection approach, and one of them repressed gene expression up to 10.2-fold with an improved dynamic range. The specific glycine-OFF riboswitch can function as an independent repressor in the presence of glycine, and its repression mechanism is inferred from predicted secondary structure. The selected glycine-OFF riboswitch was used to dynamically control the biosynthesis of 5-aminolevulinic acid (5-ALA) in Escherichia coli with an unnatural 5-ALA synthetic pathway, in which glycine plays a key role. It is demonstrated that the use of a synthetic Clostridium glycine-OFF riboswitch can lead to a significant increase (11%) of 5-ALA in E. coli harboring an unnatural biosynthetic pathway.

High-Level Production of 4-Hydroxyvalerate from Levulinic Acid via Whole-Cell Biotransformation Decoupled from Cell Metabolism.

γ-Hydroxyvalerate (4HV) is an important monomer used to produce various valuable polymers and products. In this study, an engineered 3-hydroxybutyrate dehydrogenase that can convert levulinic acid (LA) into 4HV was co-expressed with a cofactor (NADH) regeneration system mediated by an NAD+-dependent formate dehydrogenase (CbFDH) in the Escherichia coli strain, MG1655. The resulting strain produced 23-fold more 4HV in a shake flask. The 4HV production was not dependent on ATP and required low aeration; all of these are considered beneficial characteristics for the production of target compounds, especially at an industrial scale. Under optimized conditions in a 5 L fermenter, the titer, productivity, and molar conversion efficiency for 4HV reached 100 g/L, 4.2 g/L/h, and 92%, respectively. Our system could prove to be a promising method for the large-scale production of 4HV from LA at low-cost and using a renewable biomass source.

A new GSH-responsive prodrug of 5-aminolevulinic acid for photodiagnosis and photodynamic therapy of tumors.

5-Aminolevulinic acid (5-ALA) and its two ester derivatives (5-ALA-OMe and 5-ALA-OHex) have been approved for photodiagnosis and photodynamic therapy (PDT) of tumors in the clinical. However, their pharmacological activities are limited by their instability under physiological conditions and lack of tumor selectivity. With the aim to overcome these shortcomings, a glutathione-responsive 5-ALA derivative (SA) was designed based on the fact that many types of tumor cells have higher intracellular glutathione level than normal cells. SA was synthesized by masking the 5-amion group of 5-ALA methyl ester (5-ALA-OMe) with a self-immolative disulfide linker. Compared with 5-ALA and 5-ALA-OMe, SA exhibited higher stability under physiological conditions, and it can efficiently release the parent compound 5-ALA-OMe in response to glutathione. In tumor cells, SA displayed excellent protoporphyrin IX (PpIX) production activity at low concentrations while 5-ALA and 5-ALA-OMe were ineffective at the same concentration. The SA-induced PpIX production was positively correlated with the intracellular glutathione level, and SA exhibited enhanced phototoxicity due to its excellent PpIX generation activity. This study indicates that modification of the amino group in 5-ALA derivatives with a self-immolative disulfide linker is an effective strategy to improve their chemical stability and pharmacological activities, and SA is a potential photosensitizer for photodiagnosis and PDT of tumors.

Mathematical morphology-based imaging of gastrointestinal cancer cell motility and 5-aminolevulinic acid-induced fluorescence.

The aim of this study was the quantitative evaluation of gastrointestinal cancer cell motility and 5-aminolevulinic acid (5-ALA)-induced fluorescence in vitro using mathematical morphology and structural analysis methods. The results of our study showed that MKN28 cells derived from the lymph node have the highest motility compared with AGS or HCT116 cells derived from primary tumors. Regions of single cells were characterized as most moving, and "tightly packed" cell colonies as nearly immobile. We determined the reduction of cell motility in late passage compared to early passage. Application of 5-ALA caused fluorescence in all investigated cells, and the fluorescence was different with regard to the cell type and application time. We observed higher fluorescence in MKN28 cells. Comprehensive image analysis did not reveal any statistically significant difference in fluorescence intensity between "tightly packed" cell regions, where nearly no motility was registered and loosely distributed cells, where the highest cell motility was registered. In conclusions, our study revealed that MKN28 cells derived from the lymph node have higher motility and 5-ALA-induced fluorescence than AGS or HCT116 derived from primary tumors. Moreover, image analysis based on a large amount of processed data is an important tool to study these tumor cell properties.

Growth-coupled bioconversion of levulinic acid to butanone.

Common strategies for conversion of lignocellulosic biomass to chemical products center on deconstructing biomass polymers into fermentable sugars. Here, we demonstrate an alternative strategy, a growth-coupled, high-yield bioconversion, by feeding cells a non-sugar substrate, by-passing central metabolism, and linking a key metabolic step to generation of acetyl-CoA that is required for biomass and energy generation. Specifically, we converted levulinic acid (LA), an established degradation product of lignocellulosic biomass, to butanone (a.k.a. methyl-ethyl ketone - MEK), a widely used industrial solvent. Our strategy combines a catabolic pathway from Pseudomonas putida that enables conversion of LA to 3-ketovaleryl-CoA, a CoA transferase that generates 3-ketovalerate and acetyl-CoA, and a decarboxylase that generates 2-butanone. By removing the ability of E. coli to consume LA and supplying excess acetate as a carbon source, we built a strain of E. coli that could convert LA to butanone at high yields, but at the cost of significant acetate consumption. Using flux balance analysis as a guide, we built a strain of E. coli that linked acetate assimilation to production of butanone. This strain was capable of complete bioconversion of LA to butanone with a reduced acetate requirement and increased specific productivity. To demonstrate the bioconversion on real world feedstocks, we produced LA from furfuryl alcohol, a compound readily obtained from biomass. These LA feedstocks were found to contain inhibitors that prevented cell growth and bioconversion of LA to butanone. We used a combination of column chromatography and activated carbon to remove the toxic compounds from the feedstock, resulting in LA that could be completely converted to butanone. This work motivates continued collaboration between chemical and biological catalysis researchers to explore alternative conversion pathways and the technical hurdles that prevent their rapid deployment.

Conversion of Furfuryl Alcohol into Ethyl Levulinate over Glucose-Derived Carbon-Based Solid Acid in Ethanol.

In this study, a carbon-based solid acid was created through the sulfonation of carbon obtained from the hydrothermal pretreatment of glucose. Additionally, ethyl levulinate, a viable liquid biofuel, was produced from furfuryl alcohol using the environmentally benign and low-cost catalyst in ethanol. Studies for optimizing the reaction conditions, such as reaction time, temperature, and catalyst loading, were performed. Under the optimal conditions, a maximum ethyl levulinate yield of 67.1% was obtained. The recovered catalyst activity (Ethyl levulinate yield 57.3%) remained high after being used four times, and it was easily regenerated with a simple sulfonation process. Moreover, the catalyst was characterized using FT-IR, XRD, SEM, elemental analysis, and acid-base titration techniques.