Liquid Hot Water Research Articles

Cytotoxicity and biological capacity of sulfur-free lignins obtained in novel biorefining process

Lignin is one of the most promising and versatile products obtained in biorefineries due to its diverse therapeutic properties such as antimicrobial, antioxidant and anti-inflammatory activity. However, these properties depend on the source of lignin and the way it was isolated from the biomass. In this study, four different lignins are compared (extracted with Aquasolv (ASL1, ASL2), Organosolv (OSL) and Alkali (ALK) processes) for their cellular antioxidant capacity, anti-diabetic activity, free radical scavenging and cytotoxicity. Alkali and Organosolv lignins showed the highest antioxidant capacity 1159.815 μmol TE g−1 and 1463.415 μmol TE g−1, respectively, in agreement with their highest amount of free –OH groups. Additionally, OSL showed the highest inhibition in the antidiabetic assay followed by ASL1 with values for α–amylase of 3.6 mg/ml and 4.3 mg/ml respectively, and α–glucosidase 1.6 mg/ml and 2.5 mg/ml correspondingly. Nevertheless, cell-based assays revealed that ASL has the lowest cytotoxic effect in Caco-2 cells and, thus, is 10 times less cytotoxic than Alkali and OSL. This work suggests the applicability of ASL for high value applications such as cosmetics or pharmaceuticals. Industrial relevanceIndustrially, Liquid Hot Water (LHW) and Organosolv processes may appear as promising biorefining technologies in the following years. Lignin produced is free of sulfur, can be labelled as clean and environmentally-friendly and in this study, was proven that LHW lignin is non cytotoxic. The findings in this paper showed that different sources of lignin can be used in product formulation for life science purposes, thus opening a broad spectrum of possibilities for lignin valorisation in biorefineries.

Single cell protein production by a local Aspergillus niger in solid state fermentation using rice straw pulp as carbon source: effects of fermentation variables

In this study, solid-state fermentation was carried out to produce single cell protein by local Aspergillus niger. Rice straw pulp produced from the pretreatment by liquid hot water at temperature 121 °C for 60 minutes of cooking time was used as carbon source. The effects of nitrogen sources, initial medium pH, C/N ratios of substrates and fermentation time on SCP production were evaluated in these experiments. The single cell protein was measured as crude protein content in the fermentation product by the Kjeldahl analysis method. The maximum crude protein of 18.9 % (w/w) contained in the fermentation product occurred at the fermentation condition with C/N ratio 30:1, the initial medium pH 4, temperature 30 °C, moisture content 75 % and relative humidity 95 %.

Effects of press- mud pre-treatment on the feasibility of biogas production

In this study, an energetic, economic and environmental feasibility for the anaerobic digestion (AD) of press mud previously pretreated with liquid hot water (LHW) or thermo-alkaline (TA) methods were assessed. A typical Cuban sugar mill was selected as ¨Case Study¨. The sugar mill has a potential capacity to process 4600 t d-1of sugar cane and operates 130 days per year. The biogas produced can be used to feed an internal combustion engine to produce electricity and heat. It was assumed that the electricity will be sold to the national electric grid and the heat recovered from the exhaust gases will be used as energy source to supply the thermal demand for press mud pre-treatments. The thermal requirements for pre-treatments (9.4 and 12.1 MWh d-1) were energy sufficient by recovering the heat from the engine exhaust. For the alternatives considered, an improvement of the environmental profile with respect to the reference scenario was obtained. The profitability of methane production also increased for alternatives considering pre-treatment. In general, the economical, energetic and environmental assessment showed the best indicators for the AD of press mud using LHW pre-treatment.

Combined biofuel production from cotton stalk and seed with a biorefinery approach

Due to usage of fossil fuels, the depletion of world crude oil reserves and increased deteriorating climate conditions have reached a high level. These circumstances have led researches to search for alternative and efficient fuels. The main biofuels considered are bioethanol and biodiesel. In this study, ethanol and biodiesel production from cotton stalk and seed were aimed using liquid hot water (LHW) along with consecutive processes, where separate saccharification and fermentation (SHF) process was carried out. The maximum ethanol concentrations of 0.348 g/L and 0.721 g/L were achieved at 24 h and 72 h, respectively. For biodiesel conversion, cottonseed oil was subjected to transesterification, where the main interest was to utilize the by-product, glycerol. Three different glycerol concentrations were investigated in terms of ethanol fermentation using Escherichia coli K1 active culture. The maximum ethanol concentration of 0.415 g/L was achieved at 20 mL glycerol concentration for 48 h. Overall, cotton stalk and seed have the potential to be utilized on an industrial scale.

Liquid hot water extraction followed by mechanical extrusion as a chemical-free pretreatment approach for cellulosic ethanol production from rigid hardwood

To alleviate the heavy dependence on chemical input of chemical pretreatments and make a better use of current idle thermo-mechanical pretreatment plant for mechanical pulp, a sequential chemical-free pretreatment approach, i.e., liquid hot water extraction followed by mechanical extrusion was investigated in this work. Its ability to fractionate hemicellulose while facilitating cellulose hydrolysis of rigid eucalyptus and aspen hardwood was assessed. The structural changes of lignin during liquid hot water extraction were elucidated using spectrum analysis. Cellulose accessibility to hydrolytic enzymes, cellulose hydrolysis yields and fermentation potential were also assessed. Results showed that the mild liquid hot water extraction recovered 54.0% and 38.1% of xylan hemicellulose from eucalyptus and aspen hardwood respectively, while causing limited lignin condensation reactions. Extending liquid hot water extraction time from 45 to 90 min significantly facilitated the subsequent mechanical deconstruction of both wood substrates without compromising their overall carbohydrate recovery. A maximum cellulose hydrolysis yield of 79.6% and nearly 100% (10 w/v solids loading, enzyme dosage, 20 mg g−1 cellulose) was observed on eucalyptus and aspen substrate respectively, which were feasible for further fermentation process. This work showed liquid hot water extraction followed by mechanical extrusion was a feasible pretreatment strategy for bioethanol production even the starting wood chip substrate was highly rigid.

A finalized determinant for complete lignocellulose enzymatic saccharification potential to maximize bioethanol production in bioenergy Miscanthus

BackgroundMiscanthus is a leading bioenergy crop with enormous lignocellulose production potential for biofuels and chemicals. However, lignocellulose recalcitrance leads to biomass process difficulty for an efficient bioethanol production. Hence, it becomes essential to identify the integrative impact of lignocellulose recalcitrant factors on cellulose accessibility for biomass enzymatic hydrolysis. In this study, we analyzed four typical pairs of Miscanthus accessions that showed distinct cell wall compositions and sorted out three major factors that affected biomass saccharification for maximum bioethanol production.ResultsAmong the three optimal (i.e., liquid hot water, H2SO4 and NaOH) pretreatments performed, mild alkali pretreatment (4% NaOH at 50 °C) led to almost complete biomass saccharification when 1% Tween-80 was co-supplied into enzymatic hydrolysis in the desirable Miscanthus accessions. Consequently, the highest bioethanol yields were obtained at 19% (% dry matter) from yeast fermentation, with much higher sugar–ethanol conversion rates by 94–98%, compared to the other Miscanthus species subjected to stronger pretreatments as reported in previous studies. By comparison, three optimized pretreatments distinctively extracted wall polymers and specifically altered polymer features and inter-linkage styles, but the alkali pretreatment caused much increased biomass porosity than that of the other pretreatments. Based on integrative analyses, excellent equations were generated to precisely estimate hexoses and ethanol yields under various pretreatments and a hypothetical model was proposed to outline an integrative impact on biomass saccharification and bioethanol production subjective to a predominate factor (CR stain) of biomass porosity and four additional minor factors (DY stain, cellulose DP, hemicellulose X/A, lignin G-monomer).ConclusionUsing four pairs of Miscanthus samples with distinct cell wall composition and varied biomass saccharification, this study has determined three main factors of lignocellulose recalcitrance that could be significantly reduced for much-increased biomass porosity upon optimal pretreatments. It has also established a novel standard that should be applicable to judge any types of biomass process technology for high biofuel production in distinct lignocellulose substrates. Hence, this study provides a potential strategy for precise genetic modification of lignocellulose in all bioenergy crops.

An optimum combined severity factor improves both the enzymatic saccharification yield and the functional lignin structure

Liquid hot water (LHW) pretreatment has become an interesting alternative among the known pretreatment approaches. In this study, an extended combined severity factor (CSF) as LHW pretreatment severity was used to make a balance between the enzymatic hydrolysis of cellulose and the potential application value of lignin. The results, mainly from the degradation of carbohydrates, the enzymatic saccharification of cellulose, and the characterization of lignin by FTIR, TGA, 31P NMR, and 2D HSQC NMR, demonstrated that a CSF of approximately 8.37 was the optimum pretreatment severity to facilitate the cellulose enzymatic hydrolysis and obtain functional lignin. Hemicellulose was removed for > 74.7% with a negligible glucose concentration of 1.19 g/L. The pretreated substrates were subsequently enzymatically hydrolyzed reaching a saccharification yield of 83.92%. The obtained lignin exhibited excellent structural properties, such as a higher hydroxyl (OH) content (2.34 mmol/g of aliphatic hydroxyl and 2.43 mmol/g of phenolic OH) and more β-O-4 aryl ether linkages (27.86%). In a word, this study hence provides useful guidance for the enzymatic saccharification of cellulose and the extraction of functional lignin using LHW pretreatment.

Enzymatic Hydrolysis of Liquid Hot Water-Pretreated Switchgrass at High Solid Content

Experimental assays were performed to evaluate the cellulose enzymatic hydrolysis of liquid hot water-pretreated switchgrass at high solid content. Liquid hot water pretreatment (200 °C, 5 min), fo...

Novel process for the coproduction of xylo-oligosaccharide and glucose from reed scraps of reed pulp mill

Current utilization of reed scraps (RS) from reed pulping mills is just burning and burying, remaining the unused RS a major industry waste. The aim of this study was to valorize RS by utilizing it as feedstock for xylo-oligosaccharide (XOS) production. The RS was subjected to dilute acid, alkaline, and liquid hot water (LHW) pretreatments to get the pretreated RS, which was then subjected to xylanase and subsequently cellulase enzymatic to produce XOS and glucose as well. The highest yield of XOS and glucose were 0.144 g and 0.304 g / g of RS, respectively, which were obtained from the LHW pretreatment under the optimized conditions of 170 °C, 1:8 solid loadings and 30 min duration. Overall, by upgrading RS waste into XOS and glucose as value-added products of reed pulp production, we thereby paved a new way in this research to valorize the waste from reed pulping mills.

Impact of protein blocking on enzymatic saccharification of bagasse from sugarcane clones.

Lignin plays an important functional and structural rolein plants, but also contributes to the recalcitrance of lignocellulosic biomass to hydrolysis. This study addresses the influence of lignin in hydrolysis of sugarcane bagasse from conventional bred lines (UFV260 and UFV204) that were selected from 432 field-grown clones. In addition to higher sugar production, bagasse clone UFV204 had a small, but statistically significant, lower insoluble lignin content compared with clone UFV260 (15.5% vs, 16.6%) and also exhibited a significantly higher cellulose conversion to glucose (81.3% vs. 63.3%) at a cellulase loading of 5 (filter paper unit) FPU/g of glucan or 3 FPU/g total solids for liquid hot water pretreated bagasse (200°C, 10 min). The enzyme loading was further decreased by 50% to 2.5 FPU/g glucan and resulted in a similar glucan conversion (88.5%) for clone UFV204 when the bagasse was preincubated with bovine serum albumin at pH 4.8 and nonproductive binding of cellulase components was blocked. Comparison of Langmuir adsorption isotherms and differential adsorption of the three major cellulolytic enzyme components endoglucanase, cellobiohydrolase, and β-glucosidase help to explain differences due to lignin content.

Effect of Biological and Liquid Hot Water Pretreatments on Ethanol Yield from Mengkuang (Pandanus artocarpus Griff)

This study aimed to increase the sugar and ethanol yield from the mengkuang plant biomass through biological and liquid hot water (LHW) pretreatment and their combination. The results showed that biological pretreatments with 5% inoculum of the fungus Trametes versicolor resulted in the highest alpha cellulose content incubated for 30 days, and 10% inoculum resulted in the lowest lignin content. LHW pretreatment decreased the hemicellulose content of pulps from 10.17% to 9.99%. T. versicolor altered the structure of the mengkuang pulp by degrading the lignin and lignocellulose matrix. The resulting delignification and cellulose degradation facilitate the hydrolysis of cellulose into sugars. The alpha cellulose content after biological-LHW pretreatment was higher (78.99%) compared to LHW-biological pretreatment (76.85%). Scanning electron microscopy analysis showed that biological–LHW combinated treatment degrades the cell wall structures. The ethanol yield for biological–LHW pretreated sample was observed 43.86% (13.11 g/L ethanol by weight of the substrate, which is much higher than that of LHW–biological pretreatment (34.02%; 9.097 g/L). The highest reducing sugar content about 45.10% was observed with a resulting ethanol content of 15.5 g/L at LHW pretreatment temperature of 180°C for 30 min.

Enhancing Lignocellulosic Biomass Hydrolysis by Hydrothermal Pretreatment, Extraction of Surface Lignin, Wet Milling and Production of Cellulolytic Enzymes.

Acetone and ethanol extraction of lignin deposits from the surface of hydrothermally (liquid hot water) pretreated beech wood biomass alleviates the lignin inhibitory effects during enzymatic hydrolysis of cellulose to glucose and boosts the enzymatic digestibility to high values (≈70 %). Characterization of the extracted lignins (FTIR, pyrolysis/GC-MS, differential thermogravimetry, gel permeation chromatography) indicated high purity, low molecular weight, and features that suggest that it consists mainly of fragments of the native wood lignin partially depolymerized and recondensed on the biomass surface during the hydrothermal pretreatment. The pyrolysis products of the extracted surface lignins suggest their high potential as a feedstock for the production of high added value phenolic compounds. When the enzymatic hydrolysis of the pretreated and extracted biomass solids was assisted by mild wet milling, near complete cellulose digestibility (≥95 %) could be achieved. In the context of the biorefinery and whole-biomass valorization concept, it was also shown that the hydrothermally (hemicellulose-deficient) pretreated and delignified biomass solids could be also successfully used for the production of crude cellulase from Trichoderma reesei cultures, providing a simple and low-cost method for the complementary production of cellulases by utilizing fractions of the integrated hydrolysis process.

Comparative evaluations of lignocellulose reactivity and usability in transgenic rice plants with altered lignin composition

The aromatic composition of lignins is considered an important trait that affects the physico-chemical properties of lignocellulosic biomass. However, our knowledge of the relationship between lignin structure and biomass utilization properties remains limited, especially in monocotyledonous grass species, despite their potential as biomass feedstocks. In this study, we used recently produced rice transgenic lines with distinct lignin monomer compositions, i.e., guaiacyl (G)/syringyl (S)/p-hydroxyphenyl (H) aromatic unit ratios, to study the impact of lignin composition on the chemical reactivity, enzymatic saccharification efficiency and calorific value of rice lignocellulose. The H-lignin-enriched rice transgenic line showed significantly enhanced biomass saccharification efficiency after alkali and acid pretreatments and even without any pretreatment, whereas the S-lignin-enriched rice transgenic line displayed enhanced saccharification efficiency after liquid hot water pretreatment. While we detected no significant differences in biomass heating values between the transgenic rice materials tested, analysis of synthetic lignins comprising only G, S or H units suggested that increased ratios of G or H units could increase the heating value of lignin-based solid biofuels.

The effect of different pre-treatments to improve delignification of eucalypt stumps in a biorefinery context

E. globulus stumps are recently considered as feedstock for pulp industries. Pre-treatments may improve delignification, increase pulp quality and promote other cellulosic applications. Five environmentally friendly pre-treatments were studied: liquid hot water (LHW), oxalic acid (OA), alkaline peroxide (AHP), sodium xylenesulfonate (SXS) and iron (III) chloride (FeCl3). The pre-treatments presented different yields: 94.7% (LHW), 92.7% (OA), 79.0% (AHP), 74.8% (SXS) and 78.9% (FeCl3). The chemical composition and FTIR analysis, including infrared structural ratios, of the pre-treated solids showed changes in cell wall structure. OA, SXS and FeCl3 pre-treatments were more selective for hemicelluloses extraction. Mass loss and pulp yield occurred considerably with AHP (21.0%; 53.9%), SXS (25.2%; 46.0%) and FeCl3 (21.1%; 30.7%). The pre-treated material was delignified by the kraft process, bleached using an ECF sequence (D0E1D1E2D2), and the pulp properties were evaluated. LHW improved the pulp physical properties while OA, AHP and SXS showed potential for production of dissolving pulps.

Preparation of Gelatin/Carrageenan Blend Film and Reinforced by Bagasse Hemicelluloses Extracted by Liquid Hot Water

Preparation of Gelatin/Carrageenan Blend Film and Reinforced by Bagasse Hemicelluloses Extracted by Liquid Hot Water

Integration of Pretreatment With Simultaneous Counter-Current Extraction of Energy Sorghum for High-Titer Mixed Sugar Production

Sorghum (Sorghum bicolor L. Moench) offers substantial potential as a feedstock for the production of sugar-derived biofuels and biochemical products from cell wall polysaccharides (i.e., cellulose and hemicelluloses) and water-extractable sugars (i.e., glucose, fructose, sucrose, and starch). A number of preprocessing schemes can be envisioned that involve processes such as sugar extraction, pretreatment, and densification that could be employed in decentralized, regional-scale biomass processing depots. In this work, an energy sorghum exhibiting a combination of high biomass productivity and high sugar accumulation was evaluated for its potential for integration into several potential biomass preprocessing schemes. This included counter-current extraction of water-soluble sugars followed by mild NaOH or liquid hot water pretreatment of the extracted bagasse. A novel processing scheme was investigated that could integrate with current diffuser-type extraction systems for sugar extraction. In this approach, mild NaOH pretreatment (i.e., 8%) at high metabolic yields without detoxification using a Saccharomyces cerevisiae strain metabolically engineered and evolved to ferment xylose.

Addition of Soybean Protein Improves Saccharification and Ethanol Production from Hydrothermally Pretreated Sugarcane Bagasse

The bioconversion yield of ethanol from lignocellulosic feedstocks is negatively affected by the unproductive adsorption of cellulolytic enzymes onto lignin. In this work, soybean protein was used as a lignin-blocking additive, with the aim of improving the production of ethanol from enzymatic hydrolysates of pretreated sugarcane bagasse. Investigation was made of the effects of the type of hydrothermal pretreatment process—steam explosion (SE) or liquid hot water (LHW), loadings of solids and enzymes, and bioreactor type. The addition of soybean protein led to a exceptional 76% increase of glucose released using the LHW pretreated bagasse, after 24 h of reaction, employing a high-solids loading (15%, w/v) and a low enzyme dosage (5 FPU/g dry biomass). A significant improvement was also achieved for industrial-like mixing conditions in a bench-scale stirred tank reactor, increasing the glucose released by 61 and 42% for the LHW and SE processes, respectively. Ethanol production was also positively affected by the presence of soybean protein, with increases of up to 86 and 65% for the LHW and SE hydrolysates, compared to the control experiment. Characterization of the sugarcane bagasse after the adsorption of soybean protein, using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), corroborated the higher affinity of the additive for the LHW bagasse. These findings suggest that soybean protein supplementation during enzymatic hydrolysis by commercially available enzymes is an effective strategy for achieving higher saccharification yields from hydrothermally pretreated biomass, hence improving ethanol production.

Economic value and environmental impact analysis of lignocellulosic ethanol production: assessment of different pretreatment processes

Second-generation bioethanol represents an interesting alternative to liquid fuels in times of increased concerns over global warming and energy security. However, the recalcitrant structure of lignocellulosic biomass feedstock makes necessary a pretreatment process to increase the conversion of sugars. Diluted acid, liquid hot water, steam explosion, ammonia fiber explosion, and organosolv pretreatments are assessed using a combined economic value and environmental impact analysis under a full biorefinery setup in order to assess the best pretreatment process from a techno-economic-environmental point of view. Five process areas were identified within each process considered: pretreatment stage, conversion stage, product purification and separation stage, water treatment stage, and cogeneration stage. A process simulation software was used to consider material and energy balances of the biorefineries with different pretreatment processes and to optimize the separation and purification processes (e.g., distillation columns). For the considered biomass and scenarios, all processes resulted in positive gains in terms of economic feasibility and carbon dioxide emissions. In particular, diluted acid can be considered the best pretreatment process to produce lignocellulosic bioethanol thanks to the best techno-economic-environmental performances, with the largest economic and environmental margins of 39.2 M$/year and 83.9 kt CO2/year, respectively.

ZSM-5 decrystallization and dealumination in hot liquid water.

Zeolites have recently attracted attention for upgrading renewable resources in the presence of liquid water phases; however, the stability of zeolites in the presence of liquid-phase water is not completely understood. Accordingly, the stability of the ZSM-5 framework and its acid sites was studied in the presence of water at temperatures ranging from 250 to 450 °C and at pressures sufficient to maintain a liquid or liquid-like state (25 MPa). Treated samples were analyzed for framework degradation and Al content and coordination using a variety of complementary techniques, including X-ray diffraction, electron microscopy, N2 sorption, 27Al and 29Si NMR spectroscopy, and several different types of infrared spectroscopy. These analyses indicate that the ZSM-5 framework retains >80% crystallinity at all conditions, and that 300-400 °C are the most aggressive. Decrystallization appears to initiate primarily at crystal surfaces and share many characteristics in common with alkali promoted desilication. Liquid water treatment promotes ZSM-5 dealumination, following a mechanism analogous to that observed under steaming conditions: initiation by Al-O hydrolysis, Al migration to the surface, and finally deposition as extra framework Al or possibly complete dissolution under some conditions. As with the framework, dealumination is most aggressive at 300-400 °C. Several models were evaluated to capture the non-Arrhenius effect of temperature on decrystallization and dealumination, the most successful of which included temperature dependent values of the water auto-ionization constant. These results can help interpretation of previous studies on ZSM-5 catalysis in hot liquid water and suggest future approaches to extend catalyst lifetime.

Validation of cleaning procedures used in an Italian Hospital Pharmacy for antineoplastic drug decontamination: a new tool for industrial hygiene.

Background:Current Italian regulations and procedures for surface decontamination of antineoplastic drugs (ADs) are not clear. Therefore, most hospital pharmacies follow internal procedures as an interpretation of the recommended handling guidelines.Objectives:Our study compared 7 different cleaning procedures after controlled contamination of the work surface of a biological safety cabinet workbench in an Italian hospital oncology pharmacy (HOP) to determine which of them is more efficient and practical. Moreover, in order to approximate operative routine and improve risk awareness, cleaning procedures were carried out by the personnel that usually operate in the HOP.Methods:Measured quantities, i.e. a drop (100 μL) of 5-FluoroUracil, IPhosfamide, CycloPhosphamide and Gemcitabine, were deposited on the work surface within precisely delimited areas. Following the wipe-test analysis using UPLC-MS/MS, the cleaning efficacy was calculated based on the ratio of the residual concentration of the AD, after the cleaning procedure, to the concentration of each AD before the procedure.Results:Tested cleaning procedures were: 1) Hypo-Chlor®, hot water and Farmecol70®; 2) Hypo-Chlor® and hot water; 3) Farmecol70®; 4) Surfa’Safe SH® and hot water; 5) Amuchina® 10%, hot water and Farmecol70®; 6) Incidin® Oxyfoam and hot water; 7) liquid Marseille soap, hot water and Farmecol70®. Within the studied HOP, the Marseille soap was evaluated to be the optimal choice due to its efficacy, low cost, and the very short contact time needed before rinsing.Discussion:The application of the protocol for procedure validation suggested here could be used in every HOP as a reliable industrial hygiene tool to demonstrate the validity of the chosen cleaning procedure.