By-product Of Biodiesel Production Research Articles

287 Effects of crude glycerin supplementation of beef cattle grazing wheat pasture on forage intake and characteristics of rumen fermentation

Abstract Crude glycerin (CG), mainly composed of glycerin, is a by-product of biodiesel production. Glycerin can be utilized as a substrate of gluconeogenesis by either rapid fermentation to propionate in the rumen or can be directly absorbed through the rumen epithelial wall, resulting in the conversion to glucose in the liver. Therefore, CG supplementation may increase the energy intake of cattle grazing wheat pasture. Ruminally cannulated Angus-crossbred cows [n = 9; 564.4 ±101.6 kg initial body weight (BW)] grazing wheat pasture were utilized in a split-plot design with the objective of evaluating the effects of CG supplementation and forage maturity on forage intake and rumen fermentation characteristics. Treatment was the main plot, and stage of forage maturity was the subplot. Treatments were unsupplemented control (CON) and crude glycerin supplementation (SUP; 37.2% glycerin, DM basis) dosed at 0.11% BW (DM basis). Supplementation levels correspond to 5% of the diet, assuming forage intake of 2.2% of BW on a DM basis. The stages of wheat maturity pasture were March (MAR; vegetative stage) and April (APR; early reproductive stage). Cows grazed a single wheat pasture and were supplemented directly through the rumen cannula twice daily at 0700 and 1900 h. Forage intake in kg/d and as % of BW was greater (P = 0.04) for SUP than CON. Ruminal pH, ammonia, and VFA concentrations, as well as proportions of VFAs, were not affected by CG supplementation (P ≥ 0.34; Table 1). However, ruminal pH (5.77 and 5.99 ± 0.049) and ammonia concentration (0.67 and 3.37 ± 0.307 mM) were greater, while total VFA concentration (136.3 and 110.8 ± 5.23 mM) was less (P = 0.01) for APR compared with MAR. Acetate, propionate, and butyrate molar proportions, as well as acetate: propionate ratio, were not affected (P ≥ 0.27) by the stage of wheat pasture maturity. Results indicate that crude glycerin used as an ingredient in supplementation strategies for cattle grazing wheat pasture may increase cattle energy intake without negatively affecting forage intake and ruminal fermentation.

Synthesis and Characterisation of Graphene Oxide Catalysts for Glycerol Acetylation

Glycerol in large quantities as a by-product of biodiesel production is a promising feedstock to be converted into more valuable products such as acetin. In this work, acetin converted from glycerol acetylation with acetic acid was performed over graphene oxide as a catalyst in a batch reactor. The study's objective was to evaluate the effect of sodium nitrate amount in the catalyst preparation on the catalyst's characteristics and catalytic performance. The graphene oxide (GO) catalysts were charac­terised by various tests, such as SEM-EDX for their morphology, the nitrogen adsorption capacity using Breneur-Emmet Teller (BET), structural analysis using XRD, functional group us­­ing FTIR, and catalytic activity on glycerol acetylation. The GO1, GO2, and GO3 catalysts were varied based on the NaNO3 amount in the modified Hummer method. The experiments found that the NaNO3 amount in catalyst preparation plays a vital role in GO structure formation. The GO2 catalyst has the highest performance, as indicated by the highest surface area, pore volume, and size. High glycerol conversion (94 %) and selectivity toward the interest products of triacetin (24 %) and diacetin + triacetin (83 %) were reached in 2 h of reaction using three wt.% catalysts, 110 °C reaction temperature, and 1:9 molar ratio of glycerol to acetic acid. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Hierarchical EMT structured zeolites as improved catalysts for glycerol dehydration

A fast and simple post-synthesis method for creating secondary mesoporosity in EMT zeolites was developed using an ammonium fluoride / cetyltrimethylammonium bromide (NH4F/CTAB) solution at low temperature with ultrasound irradiation. This strategy is shown to be highly effective for producing hierarchical EMT structured zeolites through the etching of both Si and Al species. The catalytic performance of these materials were assessed using glycerol dehydration as a reaction test, which is in addition a relevant reaction due to the high amounts of glycerol generated as a by-product of biodiesel production. The resulting hierarchical EMT structured zeolites exhibited improved catalytic activity and high selectivity towards acrolein (around 80 %). This innovative approach creates new opportunities for using hierarchical EMT structured zeolites in processes related with biodiesel manufacture.

Optimization of crude glycerol purification from grease trap waste biodiesel production: exploring the synergistic effect of mixed extraction alcohols on enhanced glycerol purity

AbstractBACKGROUNDThe purification of crude glycerol, a byproduct of biodiesel production and grease trap waste, is essential for its utilization in high‐value applications. Achieving exceptionally pure glycerol without relying on energy‐intensive vacuum distillation during transesterification is of substantial economic interest.RESULTSThis investigation focuses on crafting a purification process involving chemical treatment (neutralization), adsorption and extraction. The assessment of the neutralization process using sodium hydroxide (NaOH) and potassium hydroxide (KOH) revealed their comparative efficacy. Activated carbon adsorption was used to reduce coloration in crude glycerol, with weights set at 4 and 8 wt%. Efficient salt extraction from crude glycerol was explored using solvents such as methanol, ethanol and isopropyl alcohol in varying mass ratios to crude glycerol (1:1 and 2:1). The study also examined the synergistic effects and impact of mixing alcohol solvents. Optimal conditions for achieving high purity (92.44%) were identified as the combination of KOH, 8 wt% activated carbon and a 2:1 ratio of a mixture of the three alcohols.CONCLUSIONThe combined effects of employing a mixture of alcohols significantly enhance the extraction process, resulting in the efficient and successful purification of glycerol. These outcomes offer valuable insights into improving the extraction process in industrial settings, leading to the production of high‐quality glycerol products. © 2024 Society of Chemical Industry (SCI).

Structural study of mixed metal oxide catalysts comprising Mg, Ca, and Al used for upgrading biodiesel byproduct glycerol to glycerol carbonate

Glycerol is a by-product in biodiesel production. It is possible to convert glycerol to glycerol carbonate by carbonylation with CO2. In this work, novel mixed metal oxides of Mg-Ca, Mg-Al, and Ca-Al were prepared by co-precipitation method, and used as catalysts for this reaction for the first time. Catalysts were characterized through XRD, BET surface area analyzer, XPS, ICP-OES, SEM, and CO2-TPD analyses. Mg0.75Ca0.25O catalyst showed the highest glycerol conversion of 18.2±0.7%, and glycerol carbonate yield of 12% at initial conditions. Reaction parameters including pressure, temperature, and catalyst loading were optimized, when Mg0.75Ca0.25O catalyst was used, to achieve the highest glycerol carbonate yield. The optimal reaction parameters were pressure of 7 MPa, temperature of 180 ⁰C, and catalyst loading of 8.5%. Glycerol conversion was 25.7% and the glycerol carbonate yield was 16% at optimized condition. Morphology and chemical structure of Mg-Ca catalyst were also investigated.

Hydrogenolysis of Glycerol over NiCeZr Catalyst Modified with Mg, Cu, and Sn at the Surface Level.

Biomass valorization is an essential strategy for converting organic resources into valuable energy and chemicals, contributing to the circular economy, and reducing carbon footprints. Glycerol, a byproduct of biodiesel production, can be used as a feedstock for a variety of high-value products and can contribute to reducing the carbon footprint. This study examines the impact of surface-level modifications of Mg, Cu, and Sn on Ni-Ce-Zr catalysts for the hydrogenolysis of glycerol, with in situ generated hydrogen. The aim of this approach is to enhance the efficiency and sustainability of the biomass valorization process. However, the surface modification resulted in a decrease in the global conversion of glycerol due to the reduced availability of metal sites. The study found that valuable products, such as H2 and CH4 in the gas phase, and 1,2-PG in the liquid phase, were obtained. The majority of the liquid fraction was observed, particularly for Cu- and Sn-doped catalysts, which was attributed to their increased acidity. The primary selectivity was towards the cleavage of the C-O bond. Post-reaction characterizations revealed that the primary causes of deactivation was leaching, which was reduced by the inclusion of Cu and Sn. These findings demonstrate the potential of Cu- and Sn-modified Ni-Ce-Zr catalysts to provide a sustainable pathway for converting glycerol into value-added chemicals.

The effects of crude glycerol addition on biogas production

Crude glycerol is a by-product of biodiesel production in which the number increases every year and is quite an expensive purification process to meet the technical standards required by consumer industries. To overcome this, it is important to find alternatives for crude glycerol utilization to increase the economic feasibility of the biodiesel industry. This study aimed to evaluate the technical feasibility of biogas production with the addition of crude glycerol from a Palm Oil Plant. The glycerol was introduced into 500mL Anaerobic Digester (AD) as a carbon source and energy source for the growth of methanogenic bacteria along with cow dung and Distilled Water with a ratio of 1:1. The addition of crude glycerol was 5% wt (GL5), 10% wt (GL10) dan 15% wt (GL15), and one control reactor without crude glycerol addition (GL0). AD was operated in a batch system at mesophilic conditions for 30 days. The highest biogas yield was obtained in the experimental set GL10 as much as 380 mL/g VS and was formed on the 3rd day but the highest percentage of methane gas (CH4) was obtained from the control set GL0 as much as 60.2%. In addition to the identification of bacteria, it was found that the type of Bacillus sp in the GL10 treatment was the most biogas producer, and based on the results of its bio-slurry analysis it could be used as organic fertilizer and soil improvement for agriculture and degraded soil.

H2 production based on a ternary mixture of commercial CuO-NiO-TiO2 in a solar pilot plant

Glycerol is a by-product in biodiesel production (in the range of g·L−1), so its photoreforming by photocatalysis is a way of valorising it. TiO2 in photocatalysis has been widely studied, although its efficiency is limited by the high energy band gap, and the electron-hole recombination. Its combination with different semiconductors should improve charge separation, extending also the absorption from UV to visible light. Cu and Ni oxides are two of the most efficient low-cost transition metal oxide catalysts. Experiments were carried out in a 25 L pilot plant connected to a compound parabolic solar collector. Different combinations of the three semiconductors, based on the concentration of each metal on TiO2 (Me, 5%, 7.2% and 10%) were evaluated. Evonik P25-TiO2, CuO and NiO were combined by mechanical mixing. Hydrogen was quantified by a micro gas chromatograph, and copper and nickel leaching by ICP-MS. The best hydrogen production (0.060 mMol kJ−1) was attained with a proportion of 10:1 of TiO2:MeO, that corresponds to a total metal concentration of 7.2 wt%, being Cu and Ni in the same proportion. Metal content in solution increased as the reaction progressed, but Ni lixiviation of <0.012 mg L−1 was not significant. Significant Cu leaching (>1 mg L−1) was observed. This article presents novel results, in a solar pilot plant, for determining which ternary mixture can give better results, as well as metal leaching into water. Handling relevant volume of water in anoxic conditions can help to understand the application of this technology for the production of hydrogen.

Effects of Heterogeneous Sulfated Acid Photocatalysts and Irradiation of Ultraviolet Light on the Chemical Conversion and Characteristics of Antifreeze from Bioglycerol

The purity of crude glycerol, a by-product of biodiesel production, may be as low as 50%. Thus, it has relatively low economic value without previously applying adequate physical purification or chemical conversion processes. A solid-state sulfated acid photocatalyst, TiO2/SO42− was prepared in this study to catalyze the chemical conversion of bioglycerol with acetic acid to produce an antifreeze of glycerine acetate to improve the low-temperature fluidity of liquid fuel. The experimental results show that similar X-ray intensity structures appeared between the catalysts of TiO2/SO42− and SO42−. An infrared spectra analysis using a Fourier transform infrared (FTIR) spectrometer confirmed the successful sintering of SO42− and ligating with TiO2 for preparing TiO2/SO42−. The effects of the photocatalyst were further excited by the irradiation of ultraviolet light. The highest weight percentage of glycerine acetate was obtained under a reaction time and reaction temperature of 10 h and 120 °C, respectively. In addition, it was observed that the glycerol conversion ratio reached 98.65% and the triacylglycerols compound amounted to 40.41 wt.% when the reacting molar ratio was 8. Moreover, the freezing point of the product mixture of glycerine acetate under the same molar ratio reached as low as −46.36 °C; the lowest among the products made using various molar ratios of acetic acid/glycerol. The UV light irradiation rendered higher triacylglycerols and diacylglycerols with lower diacylglycerol formation ratios than those without light irradiation.

Biodegradable dust suppressants prepared from biomass-based materials: The role of viscosity and suppressed particles

ABSTRACT In this study, biodegradable dust suppressants were prepared using glycerol and biomass-based oily compounds, including palm oil, biodiesel, and soybean oil. The suppressing ability of the glycerol and the oily compound mixture was evaluated using wind tunnel tests, and factors affecting the suppression of the particles were determined. The replacement of sodium dodecyl sulfate with coco glucoside and lauryl glucoside significantly enhanced the biodegradability of the suppressants (2.02 vs. 9.01 and 8.54 mg/L of BOD5). The glycerol and soybean oil mixture exhibited excellent performance owing to the relatively high viscosity of the suppressants, and the optimal dilution ratio was 1:50 and 1:1000 for sand and granite-weathered soil, respectively. More than 98% of suppression was obtained under the optimal conditions. The effect of the particle properties (particularly permeability) was significant, even though the viscosity of the suppressants was responsible for the suppression of the particles. Our results suggest that the mixture of glycerol and biomass-based oily compounds could be a promising suppressant for reducing the mobility of ultrafine particles in the atmosphere. Implications Since the early 2010s, anthropogenic fugitive dust from industrial activities has become a serious environmental issue due to its serious hazards to the environment and human health in South Korea. So far, several dust suppressants (mostly salts) were made and used for field application. However, due to their toxic effects, it is necessary to develop a new eco-friendly suppressant that can be biodegraded in the soil and that is not hazardous to human health or the environment. Previously we have developed an eco-friendly dust suppressant with low toxicity and high suppression ability using ingredients and by-products of biodiesel production, marine biomass, and commercial vegetable oils (Tsgot and Oh, 2021, J. Air Waste Manag. Assoc. 71:1386–1396). However, due to the low biodegradability of surfactant, the synthesized dust suppressants showed limited biodegradability. As a follow-up to our previous study, we employed readily biodegradable surfactants as additives to enhance the biodegradability of the dust suppressants with the same excellent suppressing ability. To determine the optimal conditions, the synthesis and preparation of the dust suppressants was conducted using biodegradable surfactants, including coco glucoside and lauryl glucoside. The factors affecting the suppressing ability of the suppressants were examined via wind tunnel tests. These factors include the dilution factors, the viscosity of the suppressants, and the type of suppressed particles. Possible suppressing mechanisms were also discussed.

Selective Photoelectrochemical Oxidation of Glycerol to Glyceric Acid on (002) Facets Exposed WO3 Nanosheets

AbstractGlycerol is a byproduct of biodiesel production. Selective photoelectrochemical oxidation of glycerol to high value‐added chemicals offers an economical and sustainable approach to transform renewable feedstock as well as store green energy at the same time. In this work, we synthesized monoclinic WO3 nanosheets with exposed (002) facets, which could selectively oxidize glycerol to glyceric acid (GLYA) with a photocurrent density of 1.7 mA cm−2, a 73 % GLYA selectivity and a 39 % GLYA Faradaic efficiency at 0.9 V vs. reversible hydrogen electrode (RHE) under AM 1.5G illumination (100 mW cm−2). Compared to (200) facets exposed WO3, a combination of experiments and theoretical calculations indicates that the superior performance of selective glycerol oxidation mainly originates from the better charge separation and prolonged carrier lifetime resulted from the plenty of surface trapping states, lower energy barrier of the glycerol‐to‐GLYA reaction pathway, more abundant active sites and stronger oxidative ability of photogenerated holes on the (002) facets exposed WO3. Our findings show great potential to significantly contribute to the sustainable and environmentally friendly chemical processes via designing high performance photoelectrochemical cell via facet engineering for renewable feedstock transformation.

Selective Photoelectrochemical Oxidation of Glycerol to Glyceric Acid on (002) Facets Exposed WO3 Nanosheets.

Glycerol is a byproduct of biodiesel production. Selective photoelectrochemical oxidation of glycerol to high value-added chemicals offers an economical and sustainable approach to transform renewable feedstock as well as store green energy at the same time. In this work, we synthesized monoclinic WO3 nanosheets with exposed (002) facets, which could selectively oxidize glycerol to glyceric acid (GLYA) with a photocurrent density of 1.7 mA cm-2 , a 73 % GLYA selectivity and a 39 % GLYA Faradaic efficiency at 0.9 V vs. reversible hydrogen electrode (RHE) under AM 1.5G illumination (100 mW cm-2 ). Compared to (200) facets exposed WO3 , a combination of experiments and theoretical calculations indicates that the superior performance of selective glycerol oxidation mainly originates from the better charge separation and prolonged carrier lifetime resulted from the plenty of surface trapping states, lower energy barrier of the glycerol-to-GLYA reaction pathway, more abundant active sites and stronger oxidative ability of photogenerated holes on the (002) facets exposed WO3 . Our findings show great potential to significantly contribute to the sustainable and environmentally friendly chemical processes via designing high performance photoelectrochemical cell via facet engineering for renewable feedstock transformation.

Fenton oxidation of glycerin: A sustainable approach for byproduct treatment

This article explores the application of Fenton oxidation as a sustainable and efficient method for the treatment of glycerol, a major byproduct in biodiesel production. Glycerol, rich in impurities, poses environmental challenges if not properly managed. The research aims to contribute to the understanding of Fenton oxidation mechanisms specific to glycerol transformation into dl-glyceraldehyde and to highlight its potential as a sustainable solution. Glycerol, a trihydroxy sugar alcohol, is a versatile compound derived primarily from the hydrolysis of triglycerides and has found applications in various industries, including pharmaceuticals, cosmetics, and food production. One intriguing aspect of glycerol is its potential conversion to dl-glyceraldehyde, a key intermediate with significant importance in various biological processes. Employing Fenton oxidation emerges as beneficial approach in glycerol processing, considering the tenets of environmental sustainability.

Production of glycerol carbonate from glycerol and carbon dioxide using metal oxide catalysts

This work is focused on a green production of glycerol carbonate through converting glycerol, as a by-product of biodiesel production, and a greenhouse gas, carbon dioxide, using metal oxide catalysts of MgO, CaO, and Al2O3. The catalysts were prepared by precipitation method and characterized by surface area and pore size, TGA, XRD, CO2-TPD, and SEM analyses. The catalysts’ performance was mostly influenced by the number of basic sites and the BET surface area of the catalysts. The catalysts’ activity results displayed that MgO showed the highest glycerol conversion of 22.7% and the highest yield of 10.6% among the investigated catalysts. The turnover number of the optimum catalyst was 14.9 μmol glycerol carbonate/μmol CO2. The effect of reaction parameters on the performance of the reaction was also investigated and the highest glycerol carbonate yield of 12.76 % was achieved at a catalyst loading of 5.5 wt% of glycerol amount, the temperature of 150 ⁰C, and pressure of 8 MPa. The physicochemical properties of catalysts were correlated with their activities and abilities for CO2 activation.

Glycerol Electrooxidation in Flow Reactors

Transitioning away from fossil-fuel-based chemical manufacturing is critical in advancing towards a carbon-neutral society. Chemical manufacturing processes that can be driven by renewable energy and use renewable feeds or waste products from other processes are of particular interest. This talk focuses on utilization of glycerol, a byproduct of biodiesel production and other processes, as a platform chemical for electro-organic synthesis of a number of value-added intermediates.Oxidation of glycerol can result in ten or more different products. Processes are needed to synthesize specific products of interest selectively. Based on market size and value, the four most promising oxidation products of glycerol are lactic acid, glycolic acid, oxalic acid, and dihydroxyacetone. Electrochemical reduction and oxidation processes can, in principle, be directed to produce different products by tuning reactor and reaction conditions such as catalyst identity, electrolyte/analyte concentration, flow/stir rates, electrolyte composition, etc. While a significant body of work has studied glycerol electrooxidation (GEOR) in electrochemical cells with the goals of unraveling mechanisms and identifying better catalysts (higher rates/selectivities), transitioning some of the most promising GEOR approaches to larger scales has received limited attention.In our work, we pursue glycerol electrooxidation in flow reactor configurations that could be scaled to industrial levels. Flow electrolysis approaches, in addition to providing a scalable chemical manufacturing platform, enhance mass transfer and kinetics while retaining the ability to tune key operational parameters that determine rates and selectivities. In this talk, we will report on two aspects: (i) Product speciation: what parameters can be used to optimize product selectivity towards key desired products (e.g., lactic acid, glycolic acid), and (ii) Feedstock composition: how to utilize raw glycerol (so-called ‘crude’ glycerol, containing varying amounts of water, NaOH, and methanol), available as a byproduct from a wide variety of plants, as the feedstock. For the former, we employ a systematic design approach that seeks to optimize the interplay between the different parameters that determine current density (conversion rate) and Faradaic efficiency (selectivity). For the latter, we explore which of the other ingredients (methanol, NaOH, water) of crude glycerol needs to be controlled or adjusted for reproducible, desired outcomes of flow glycerol electrolysis.

Simultaneous Lipid and Carotenoid Production via Rhodotorula paludigena CM33 Using Crude Glycerol as the Main Substrate: Pilot-Scale Experiments.

Rhodotorula paludigena CM33 is an oleaginous yeast that has been demonstrated to accumulate substantial quantities of intracellular lipids and carotenoids. In this study, crude glycerol, a by-product of biodiesel production, was used as a carbon source to enhance the accumulation of lipids and carotenoids in the cells. The culture conditions were first optimized using response surface methodology, which revealed that the carotenoid concentration and lipid content improved when the concentration of crude glycerol was 40 g/L. Different fermentation conditions were also investigated: batch, repeated-batch, and fed-batch conditions in a 500 L fermenter. For fed-batch fermentation, the maximum concentrations of biomass, lipids, and carotenoids obtained were 46.32 g/L, 37.65%, and 713.80 mg/L, respectively. A chemical-free carotenoid extraction method was also optimized using high-pressure homogenization and a microfluidizer device. The carotenoids were found to be mostly beta-carotene, which was confirmed by HPLC (high pressure liquid chromatography), LC-MS (liquid chromatography-mass spectrometry), and NMR (nuclear magnetic resonance). The results of this study indicate that crude glycerol can be used as a substrate to produce carotenoids, resulting in enhanced value of this biodiesel by-product.

Environmentally friendly process for phytosterols recovery from residues of biodiesel production.

Phytosterols are naturally occurring plant sterols found in various foods of plant origin, such as fruits, vegetables, nuts, and whole grains. Phytosterols have been shown to have potential beneficial effects on human health, particularly in reducing the risk of cardiovascular disease.Insoluble tank precipitates, predominantly composed of sterylglucosides (SG), are recognized as a by-product of biodiesel production. These SG glucosides can be hydrolyzed using mineral acids to yield valuable phytosterols. In this study, we developed an efficient method for preparing phytosterols from SG recovered from soybean biodiesel insoluble precipitates. Instead of traditional mineral acids, we employed aqueous solutions of Methanesulphonic acid (MSA), which is an environmentally friendly alternative. By optimizing temperature, reaction time, and MSA concentration using a Central Composite design, we accurately predicted the phytosterol yield with a resulting model. Validation experiments confirmed the model's accuracy, demonstrating the effectiveness of the optimized method in preparing phytosterols. Notably, this developed and optimized method offers a greener approach in terms of E factor and energy consumption, as well as improved safety.The development of a simple and efficient method for producing phytosterols from a biodiesel by-product has important implications for the food and nutraceutical industries, which are increasingly focused on using renewable and eco-friendly sources.

Biochemical and molecular characterization of a novel glycerol dehydratase from Klebsiella pneumoniae 2e with high tolerance against crude glycerol impurities

BackgroundThe direct bioconversion of crude glycerol, a byproduct of biodiesel production, into 1,3-propanediol by microbial fermentation constitutes a remarkably promising value-added applications. However, the low activity of glycerol dehydratase, which is the key and rate-limiting enzyme in the 1,3-propanediol synthetic pathway, caused by crude glycerol impurities is one of the main factors affecting the 1,3-propanediol yield. Hence, the exploration of glycerol dehydratase resources suitable for crude glycerol bioconversion is required for the development of 1,3-propanediol-producing engineered strains.ResultsIn this study, the novel glycerol dehydratase 2eGDHt, which has a tolerance against crude glycerol impurities from Klebsiella pneumoniae 2e, was characterized. The 2eGDHt exhibited the highest activity toward glycerol, with Km and Vm values of 3.42 mM and 58.15 nkat mg−1, respectively. The optimum pH and temperature for 2eGDHt were 7.0 and 37 °C, respectively. 2eGDHt displayed broader pH stability than other reported glycerol dehydratases. Its enzymatic activity was increased by Fe2+ and Tween-20, with 294% and 290% relative activities, respectively. The presence of various concentrations of the crude glycerol impurities, including NaCl, methanol, oleic acid, and linoleic acid, showed limited impact on the 2eGDHt activity. In addition, the enzyme activity was almost unaffected by the presence of an impurity mixture that mimicked the crude glycerol environment. Structural analyses revealed that 2eGDHt possesses more coil structures than reported glycerol dehydratases. Moreover, molecular dynamics simulations and site-directed mutagenesis analyses implied that the existence of unique Val744 from one of the increased coil regions played a key role in the tolerance characteristic by increasing the protein flexibility.ConclusionsThis study provides insight into the mechanism for enzymatic action and the tolerance against crude glycerol impurities, of a novel glycerol dehydratase 2eGDHt, which is a promising glycerol dehydratase candidate for biotechnological conversion of crude glycerol into 1,3-PDO.

Layered double hydroxides modified by transition metals for sustainable glycerol valorization to glycerol carbonate

The surplus of glycerol generated as a by-product in biodiesel production increased interest in the investigation of the catalytic conversion of this platform molecule into valuable chemical products, such as glycerol carbonate. Therefore, the catalytic transesterification of glycerol and dimethyl carbonate for the synthesis of glycerol carbonate was studied using Cu-Zn-Mg-Al mixed oxide catalysts with different Cu-Zn atomic ratios. Layered double hydroxides were the precursors materials to obtain multi metallic oxides. They were synthesized by coprecipitation. The materials were physico-chemically characterized by XRD, MP-AES, N2 sorption, SEM, XPS and TPD-CO2. The addition of Cu and Zn to the Mg and Al matrix improved the catalytic behaviour of the solid materials. First, the highest glycerol carbonate yield was reached with the catalyst with the highest Zn load at 70 °C for 90 min. This result was taken as a basis to modify parameters and find the optimal reaction conditions. They were a temperature of 85 °C, a reaction time of 270 min, a DMC:glycerol molar ratio of 2:1, solvent free and 7.5 wt% of catalyst. The highest yield obtained (82%) was attributable to the synergistic effect of the Cu-Zn load promoted by an adequate distribution of basicity and textural properties. The reuses of the best catalyst were also investigated.

Effect of removal of inhibitors on microbial communities and biogas yield of Jatropha curcas seeds during continuous anaerobic digestion

Jatropha curcas seeds, as an abundant lignocellulosic biomass, offer a highly promising and ideal alternative for producing energy in the form of methane. Use of J. curcas seeds has the potential to significantly bolster the biofuel sector, fostering a more sustainable circular economy. In the current study, different fractions of processed J. curcas seeds were investigated for biogas production. J. curcas seed pressed cake, a by-product of biodiesel production, was subjected to methanolic extraction. The remaining solids, referred to as methanolic residues, yielded more biogas in batch experiments than pressed cake and residues from aqueous and n-hexane extractions. The compounds extracted with methanol inhibited hydrolysis and reduced biogas production by 35.5% compared to the same setup without extracts. In continuous reactors fed with methanolic residues, the highest biogas yield occurred at an organic loading rate (OLR) of 1 g VS L−1 day−1 and a hydraulic retention time (HRT) of 20 days. The relative abundance of acetogenic bacteria was higher in reactors fed with methanolic residues than in those fed with seed pressed cake, seed oil, and whole seed. Jatropha seed oil and whole seed did not inhibit methanogens. A higher relative abundance of methanogenic communities was observed in all reactors at HRT of 20 days compared to those at HRTs at 15 and 10 days. These findings can be used to increase biogas production during anaerobic digestion of J. curcas seed components and suggests a zero-waste biorefinery production route for value added compounds derived from the removal of biogas-inhibiting components.