Liquid Hot Water Research Articles

Biorefinery concept for the valorization of grapevine shoots: Study case for the Austrian variety Grüner Veltliner

Identifying feedstocks and their integral valorization is essential for the sustainable production of chemicals, materials, fuels, and energy. Waste materials from different agricultural activities can be a potential source. Specifically, winemaking and grape crops are a source of both the large amounts and variety of residues. The grapevine shoots are the primary residue resulting from the pruning of grape crops, consisting of the stems and leaves. More than 46 thousand hectares in Austria are dedicated to grape crops, and almost half of this area corresponds to the variety Grüner Veltliner. Italian, Portuguese, and Spanish grapevine residues have been studied to produce bioactive compounds; however, the most important Austrian grape variety has not been thoroughly studied for this purpose. The grapevine shoots offer different lignocellulosic platforms and valorization strategies if the leaves and stem are evaluated separately. This work evaluated the extraction of bioactive compounds and the production of hemicellulosic sugars, lignin, and a cellulose-enriched pulp from Grüner Veltliner's grapevine shoots under a biorefinery concept. Pressurized Liquid Extraction was the selected technology for extracting bioactive compounds, and Liquid Hot Water and Organosolv were chosen for hemicellulose and lignin hydrolysis. Quercetin was the flavonoid found in higher concentrations in the leaves (10.6 mg/g of dry feedstock) and resveratrol in the stems (1.9 mg/g of dry feedstock); both components were found in higher yields than other grape varieties reported in the literature. In addition, hemicellulose and lignin hydrolysis reached yields (0.18 and 0.08 g/g of dry feedstock, respectively) in the same order of magnitude as other feedstock used for hemicellulose and lignin valorization (e.g., wheat straw). These results clearly show the potential of this under-valorized feedstock and encourage further study of the downstreaming of the intermediate products and a deeper study of the production cycle of the shoots to determine the actual available amount to be used.

Xylooligosaccharide production by optimized sulfuric, acetic acid, and liquid hot water treatment of sugarcane leaves

Xylooligosaccharide production by optimized sulfuric, acetic acid, and liquid hot water treatment of sugarcane leaves

Combinatorial pretreatments of reed straw using liquid hot water and lactic acid for fermentable sugar production

A green combinatorial pretreatment using liquid hot water (LHW) and lactic acid (LA) was used to treat reed straw for effective lignocellulose digestibility and xylose recovery. The reeds were first treated with LHW at 180 °C for 60 min, followed by LA treatment at 170 °C for 45 min. Using 37.5 g/L lactic acid, the lignocellulose digestibility was 80.6 % and glucose yield was 56.0 %, which was much higher than that for one-step LHW pretreatment (the lignocellulose digestibility was 27.3 % and the glucose yield was 26.3 %). These data demonstrated that LHW-LA pretreatment increased lignocellulose digestibility and glucose yield by 1.95-fold and 1.13-fold, respectively. The highest total sugar yielded 39.2 g/100 g-substrate. The results revealed that LHW-LA pretreatment removed most hemicellulose and partial lignin from the reed straw and prompted cellulase binding to reed cellulose, which enhanced lignocellulose enzymatic saccharification. The high fermentable glucose yielded from the combinatorial pretreatment as presented in this study highlighted the great potential of our pretreatment technology to be applied in the biorefinery, which could lay down the cost and sustainability of current biorefinery industry.

Xylooligosaccharides from Industrial Fruit and Restaurant Waste Produced by Liquid Hot Water Treatment

Xylooligosaccharides from Industrial Fruit and Restaurant Waste Produced by Liquid Hot Water Treatment

Establishment of Narrow Root Fracture Models Using Modified Temperature Cycling Method and Diagnosis Using Different Cone-Beam CT Units.

Aim Using a modified thermal cycling method to establish narrow root fracture models and evaluate the diagnosis efficiency of them using four different cone-beam CT (CBCT) units. Methodology. Fifty-six intact teeth were selected, and the crowns of the teeth were embedded using general purpose acrylic resin. 50 root fracture models were established by soaking these teeth in liquid nitrogen and hot water cyclically; 6 teeth were used as the negative control. All the 56 teeth were scanned with the smallest voxel size of four different CBCT units (NewTom VGi, Planmeca Promax 3D Max, Kavo 3D eXam, and Soredex Scanora3D). 10 teeth were randomly selected, and the roots were sliced using slow-speed saw to obtain horizontal root sections. Scanning electron microscope (SEM) was used to measure the width of the fracture lines (FLs). The CBCT images were evaluated for the presence or absence of fracture lines. Accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated for the diagnosis of FLs using the four CBCT units. Results Fifty narrow root fracture models were successfully established, and 25 root sections with 45 FLs were acquired. The width of FLs was from 3.43 μm to 143 μm; 32.2% of the points had width under 25 μm, while only 9.6% of them had width over 75 μm. The accuracy was 0.41, 0.54, 0.41, and 0.30 for NewTom VGi, Planmeca Promax 3D Max, Kavo 3D eXam, and Soredex Scanora3D, respectively. Conclusions The modified temperature cycling method is a simple and effective method to establish narrow root fracture models, and the diagnosis efficiency for these narrow fracture lines was quite poor using all the four different CBCT units.

Comparison of liquid hot water and saturated steam pretreatments to evaluate the enzymatic hydrolysis yield of elephant grass

Comparison of liquid hot water and saturated steam pretreatments to evaluate the enzymatic hydrolysis yield of elephant grass

Co-production of levulinic acid and lignin adsorbent from aspen wood with combination of liquid hot water and green-liquor pretreatments

Efficient lignocellulosic fractionation and conversion into platform chemicals provide a considerable opportunity for the industrial operation of a lignocellulosic biorefinery. However, single-step pretreatments are often insufficient to overcome biomass recalcitrance as the existence of insoluble lignin generally restricts component fractionation and conversion. This study performed a two-step pretreatment, consisting of sequential liquid hot water (LHW) and green-liquor (GL), for bioprocessing of aspen biomass into bioproducts such as glucose, levulinic acid (LA), and lignin adsorbent. The two-step pretreated glucan-rich solid displayed high cellulose accessibility, which is responsible for 94% of the glucose yield. The optimized LHW pretreatment (200 °C, 40 min) solubilized 91% of the hemicellulose, which together with monomeric sugars in the hydrolysate solution was straightly heated at 190 °C for 80 min and yielded 72.49% of LA in the presence of sulfuric acid as a catalyst. Moreover, GL post-treatment (Na2CO3+Na2SO3) solution maximized the delignification at 78% from LHW pretreated substrate. The isolated lignin possessed a remarkable ability for Cd2+ and Pb2+ uptake with maximized adsorption values of 250 mg/g and 228 mg/g, respectively. Finally, energy analyses showed that moderate lignocellulosic conversion could obtain an energy recovery of 85%, providing a sustainable pathway for biorefinery approaches.

Performance Evaluation of Combined Hydrothermal-Mechanical Pretreatment of Lignocellulosic Biomass for Enzymatic Enhancement.

Pretreatment is a crucial process in a lignocellulosic biorefinery. Corncob is typically considered as a natural renewable carbon source to produce various bio-based products. This study aimed to evaluate the performance of the hydrothermal-mechanical pretreatment of corncob for biofuels and biochemical production. Corncob was first pretreated by liquid hot water (LHW) at different temperatures (140–180 °C) and duration (30, 60 min) and then subjected to centrifugal milling to produce bio-powders. To evaluate the performance of this combined pretreatment, the energy efficiency and waste generation were investigated. The results indicated that the maximum fermentable sugars (FS) were 0.488 g/g biomass obtained by LHW at 180 °C, 30 min. In order to evaluate the performance of this combined pretreatment, the energy efficiency and waste generation were 28.3 g of FS/kWh and 7.21 kg of waste/kg FS, respectively. These obtained results indicate that the combined hydrothermal-mechanical pretreatment was an effective pretreatment process to provide high energy efficiency and low waste generation to produce biofuels. In addition, the energy efficiency and waste generation will be useful indicators for process scaling-up into the industrial scale. This combined pretreatment could be a promising pretreatment technology for the production of biofuels and biochemicals from lignocellulosic valorization.

Sequential Pretreatment of Wheat Straw: Liquid Hot Water Followed by Organosolv for the Production of Hemicellulosic Sugars, Lignin, and a Cellulose-Enriched Pulp

The complete valorization of the lignocellulosic fractions plays a fundamental role in biorefineries’ sustainability. One of the major challenges is finding technological configurations that allow using cellulose, hemicellulose, and lignin simultaneously. Cellulose has been extensively studied, yet, hemicellulose and lignin remain as platforms to be valorized. Sequential pretreatments have shown an opportunity to valorize the latter two components into sugar-rich and lignin-rich fractions. After the sequential pretreatment, a solid fraction enriched in cellulose could still be used for paper production. This work consisted of pretreating wheat straw with a sequential Liquid-Hot-Water/Organosolv, characterizing the respective hemicellulosic sugar and lignin extracts, and evaluating the final cellulose-enriched pulp for papermaking. Different pretreated pulp/cellulose pulp formulations were used for paper production as a proof-of-concept. Tensile strength and bursting pressure of the papers were measured. After pretreatment, the calculated solid composition was 70%wt cellulose, 26%wt hemicellulose, and 4%wt lignin, with extraction yields of 5.1%, 51.3%, and 89.9%, respectively. The tested pulp formulations showed similar tensile index and bursting index values at 10/90 (77.1 Nm/g, 3189 kPa) and 20/80 (63 Nm/g, 2419 kPa) %wt pretreated pulp/pulp when compared to the pulp (77 Nm/g, 4534 kPa). This proof-of-concept of the papermaking showed the potential of the LHW-OS pretreated wheat straw as a replacement for pure cellulose pulp and encourages studying other substitutes such as unbleached pulp or further treating the LHW-OS pretreated wheat straw. In addition, the hemicellulosic sugars and lignin extract can be valorized, indicating an option for developing a biorefinery concept.Graphical

Enhanced enzymatic digestibility of water lettuce by liquid hot water pretreatment

Liquid hot water (LHW) pretreatment conditions were optimized from various severities using response surface methodology to convert water lettuce (WL; Pistia stratiotes) to fermentable sugars to enhance the enzymatic digestibility of pretreated WL. The LHW pretreatment was performed using a 2% (w/v) WL loading over a temperature range of 152–208 °C and pretreatment times of 9–51 min. The optimal conditions for the LHW pretreatment were determined to be 190.7 °C for 51 min [a severity factor (log R0) of 4.38], which gave the highest total reducing sugar yield (17.26 g/L) and a high removal level of hemicellulose (68.32%) in the subsequent cellulase digestion. The physical structure of WL after pretreatment revealed changes to the WL structure that increased its susceptibility to attack by enzymes; an increased crystallinity, surface area, and total pore volume together with a lower hemicellulose and lignin content compared to the untreated WL.

Two-Phase Flow, Heat and Mass Transfer and Tracer Transport to the Atmosphere from Underground Nuclear Cavities Through Fractured Porous Media

Underground nuclear explosions generate non-isothermal two-phase flow, heat and mass transfer, and tracer transport through fractured porous media. The governing equations of these coupled phenomena on the Darcy scale are presented and the corresponding numerical code is briefly described. Two configurations are considered. In the first one, the damaged zone generated by the explosion is replaced by equivalent macroscopic boundary conditions at the bottom of the medium. Vapor condensation at distance from this zone plays a crucial role and slows down the tracer transport to the ground surface, while the presence of hot liquid water and of hot rubble particles in it accelerates it. In the second configuration, the damaged zone itself is treated as a porous medium with specific properties and is integrated in the simulation domain. Several regions can be distinguished with different properties, such as the chimney, the cavity, the solidified magma, the fractured porous medium, and the intact porous medium. Phase change, heat transfer and tracer transport can be detailed in these regions and at the boundaries between them. Among the most important conclusions, the role of phase change, of the thermal properties and therefore of the temperature, is pointed out.

A Combination Method of Liquid Hot Water and Phosphotungstic Acid Pretreatment for Improving the Enzymatic Saccharification Efficiency of Rice Straw

Chemical pretreatment can significantly improve the enzymatic hydrolysis efficiency of lignocellulosic biomass, thereby improving the yield of sugar materials for the production of cellulosic ethanol, but commonly used acid–base catalysts are difficult to recover and reuse. In this work, a combination method of liquid hot water (LHW) and phosphotungstic acid (PTA) pretreatment was performed to improve the saccharification efficiency of rice straw, and we attempted to evaluate the reuse effect of PTA catalysts. The rice straw was first treated with LHW at 180 °C for 90 min, and then treated with 20 mM PTA at 130 °C for 60 min. After pretreatment, the cellulose hydrolysis efficiency and glucose recovery of the rice straw increased by 201.85% and 164.25%, respectively. Glucose accounted for 96.8% of the total reducing sugar in the final enzymatic hydrolysate. After each PTA pretreatment, approximately 70.8–73.2% of the PTA catalyst could be recycled. Moreover, the catalytic activity of the PTA catalyst that had been used five times did not decrease. The improved enzymatic saccharification efficiency was attributed to the removal of 89.24% hemicellulose and 21.33% lignin from the lignocellulosic substrate. The two-step LHW-PTA pretreatment could pretreat biomass in the field of cellulosic ethanol production.

Evaluation of the Hydrolysis Efficiency of Bacterial Cellulose Gel Film after the Liquid Hot Water and Steam Explosion Pretreatments.

The influence of bacterial cellulose gel film pretreatment methods on the efficiency of enzymatic hydrolysis was investigated. An increase in the efficiency of enzymatic hydrolysis due to liquid hot water pretreatment or steam explosion was shown. The glucose yield of 88% was obtained from raw, non-purified, bacterial cellulose treated at 130 °C. The results confirm the potential of bacterial cellulose gel film as a source for liquid biofuel production.

THE POTENTIAL OF Azadirachta indica (NEEM TREE) LEAVES FOR BIOETHANOL PRODUCTION USING Zymomanas mobilis AS FERMENTING ORGANISMS

Bioethanol is a renewable energy produced from lignocellulosic biomass mainly by the fermentation process. It is used as an alternative to fossil fuel which doesn’t contribute to global warming. This research work was carried out to determining the potential of Neem tree leaves for bioethanol production. The process used in this study include pretreatment, hydrolysis fermentation and distillation. Hot water and Acid methods were used for the pretreatment. The hydrolysis of the substrate was carried out using Aspergillus niger for five days. Benedict test method was used to determine the reducing sugar concentration of the hydrolysate. The highest yield of 1500-2000 (mg/dl) was obtained equally for both the pre-treatment method. After hydrolysis, fermentation process was carried out for seven days using Zymomonas mobilis to ferment the hydrolysate. The fermented broth was separate using fractional distillation. Acid potassium dichromate was used to determine the concentration of the bioethanol produced. The results obtained shows that liquid hot water pretreatment produced the highest yield of 0.294±0.882 (mg/L) whereas alkaline method produced 0.282±.882 (mg/L) yield. Gas chromatography and mass spectroscopy analysis was also carried out to determine the presence of volatile compounds in the bioethanol produced. The highest volatile compound was Ethanol with 33.12% where Butyl Glycol was found to be least volatile compound with 6.22%. This result shows that Neem tree leaves is a good biomass for bioethanol production and pretreatment using Hot water method produced more bioethanol than Alkaline method of pretreatment.

Robust Superamphiphobic Fabrics with Excellent Hot Liquid Repellency and Hot Water Vapor Resistance.

Superamphiphobic surfaces progress rapidly but suffer from the issues of low repellency to hot liquids, complicated and nonaqueous preparation methods, and low durability. Here, a simple waterborne approach is developed to fabricate robust superamphiphobic fabrics with excellent hot liquid repellency and hot water vapor resistance. First, a perfluorodecyl polysiloxane (FD-POS) aqueous suspension was prepared by hydrolytic cocondensation of (3-glycidyloxy propyl)trimethoxysilane and 1H,1H,2H,2H-perfluorodecyltriethoxysilane with SiO2 particles. Then, the superamphiphobic fabrics were fabricated by dipping polyester fabrics in the suspension, which were then cured. The fabrics show excellent superamphiphobicity owing to the combination of the hierarchical micro-/nanostructure and FD-POS with very low surface energy. The superamphiphobic fabrics feature excellent hot liquid repellency even for a large volume of 130.0 °C soybean oil and condensed small droplets from ∼90.0 °C water vapor. This is attributed to its high superamphiphobicity, excellent hot water vapor resistance, and outstanding thermal durability. In addition, the superamphiphobic fabrics exhibit high mechanical and chemical durability against washing, abrasion, and immersion in corrosive or organic liquids. Thus, hot liquid repellent superamphiphobic fabrics may find applications in various fields such as antiadhesion of various hot liquids and in efficiently preventing scalding.

Optimization of Liquid Hot Water Pretreatment and Fermentation for Ethanol Production from Sugarcane Bagasse Using Saccharomyces cerevisiae

Sugarcane bagasse can be considered a potential raw material in terms of quantity and quality for the production of alternative biofuels. In this research, liquid hot water (LHW) was studied as a pretreatment process to enhance the digestibility of pretreated material for further conversion into bioethanol. Different variables (temperature, residual time, and acid concentration) were determined to predict the optimized condition. LHW pretreatment showed an impact on the hemicellulose structure. The optimized condition at 160 °C for 60 min with 0.050 M acid concentration reached the highest glucose yield of 96.86%. Scanning electron microscopy (SEM) showed conspicuous modification of the sugarcane bagasse structure. The effect of LHW pretreatment was also demonstrated by the changes in crystallinity and surface area analysis. FTIR techniques revealed the chemical structure changes of pretreated sugarcane bagasse. The prepared material was further converted into ethanol production with the maximized ethanol concentration of 19.9 g/L.

From liquid hot water pretreatment solution to lignin-based hydrophobic deep eutectic solvent for highly efficient extraction of Cr (VI)

Liquid hot water (LHW) pretreatment has been widely investigated attributed to its advantages, such as environmental friendliness, the potential application of dissolved hemicellulose, and no chemical addition. Expanding the portfolio of products that can be made from LHW pretreatment solutions will be critical to enabling a viable LHW-based economy. We provide a one-step method to separate and functionalize lignin from the LHW pretreatment solution. A hydrophobic deep eutectic solvent (hDES) was prepared by using methyltrioctylammonium chloride (MTAC) and the LHW pretreatment solution and directly applied to the extraction of Cr (VI) in an aqueous solution. In the process of forming hDES, the removal rate of liquid hot water lignin (LHWL) was reached 99%. The new LHW-hDES exhibited excellent extraction performance for Cr (VI), the extraction capacity was as high as 198.402 mg g−1, optimum extraction conditions at the mass of hDES 0.10 g, vortex time 90 s, room temperature, and natural pH. Notably, we have shown that the method of combining the separation and functionalization of lignin in the LHW pretreatment solution, which can provide a way of thinking for the application of the LHW pretreatment solution.

Coprocessing Corn Germ Meal for Oil Recovery and Ethanol Production: A Process Model for Lipid-Producing Energy Crops

Efforts to engineer high-productivity crops to accumulate oils in their vegetative tissue present the possibility of expanding biodiesel production. However, processing the new crops for lipid recovery and ethanol production from cell wall saccharides is challenging and expensive. In a previous study using corn germ meal as a model substrate, we reported that liquid hot water (LHW) pretreatment enriched the lipid concentration by 2.2 to 4.2 fold. This study investigated combining oil recovery with ethanol production by extracting oil following LHW and simultaneous saccharification and co-fermentation (SSCF) of the biomass. Corn germ meal was again used to model the oil-bearing energy crops. Pretreated germ meal hydrolysate or solids (160 and 180 °C for 10 min) were fermented, and lipids were extracted from both the spent fermentation whole broth and fermentation solids, which were recovered by centrifugation and convective drying. Lipid contents in spent fermentation solids increased 3.7 to 5.7 fold compared to the beginning germ meal. The highest lipid yield achieved after fermentation was 36.0 mg lipid g−1 raw biomass; the maximum relative amount of triacylglycerol (TAG) was 50.9% of extracted oil. Although the fermentation step increased the lipid concentration of the recovered solids, it did not improve the lipid yields of pretreated biomass and detrimentally affected oil compositions by increasing the relative concentrations of free fatty acids.

Lignin chemical controls on bioconversion of tropically grown C4 bioenergy grasses to biofuels and biobased products

Converting lignocellulose to bioenergy and biobased products requires targeted breakdown of complex plant polymers that protect structural sugars. To identify lignophenolic compounds that promote enzymatic hydrolysis, the lignophenolic composition of biomass across 12 species and varieties of the Poaceae (grass) family were measured using copper (II) oxide (CuO) oxidation and gas chromatography–mass spectrometry (GC–MS). The suite of C4 grasses allowed generalization of lignophenolic effects across two lignocellulosic bioconversion pathways: anaerobic digestion (AD) for methane production and liquid hot water pretreatment followed by enzymatic hydrolysis for ethanol production. Principal components analysis and simple linear statistical models showed ferulic acid (FER), syringaldehyde (SYR), and vanillin (VAN) ratios related to both bioconversion processes. Though methane production during AD was not well explained by linear models, more than 80% of variance across enzymatic breakdown of biomass during hydrolysis and ethanol production could be explained by FER, SYR, and VAN concentrations.

Evaluation of methane production from liquid hot water pretreated Paspalum atratum and Brachiaria ruziziensis as alternative energy substrates

Atratum and ruzi grasses have illustrated high potential for methane production through anaerobic digestion. To enhance the utilization of these grasses for the production of renewable biogas, liquid hot water pretreatment was applied to break down various lignocellulose matter, in particular, hemicellulose. After pretreatment under optimal conditions (200 °C for 15 min), more than 90% of hemicellulose was removed and solubilized in the form of a clear hydrolysate. Xylose was the primary sugar in the hydrolysate, appearing in several forms, and acting as the major substrate for methane production. Total xylose yields for the atratum and ruzi grasses were 58 and 74 mg/g TS respectively. The pretreated atratum and ruzi substrates were evaluated for methane production resulting in an increased methane yield of at least 14%, and more than 70% biodegradability. This work demonstrates the potential for atratum and ruzi grasses to be used as a viable alternative to other energy crops such as Napier grass.