Liquid Hot Water Pretreatment Research Articles

Enhanced bioethanol production from sugarcane bagasse: combination of liquid hot water and deep eutectic solvent pretreatment for optimized enzymatic saccharification

Enhanced bioethanol production from sugarcane bagasse: combination of liquid hot water and deep eutectic solvent pretreatment for optimized enzymatic saccharification

Use of scrap particleboard to produce recycled particleboard

Recycling is presently the most environmentally friendly approach that deals with wood waste. Each year a huge amount of particleboard completes its service life and needs to be disposed of or recycled. Scrap particleboard has the potential to be reused as raw material for particleboard production. A crucial step for producing particleboards using scrap particleboards is to break down urea-formaldehyde (UF) resins in the scrap particleboards to obtain separated particles. In this study, liquid hot water (LHW) pretreatment was employed to decompose the UF resins to detach and recover wood particles from the scrap particleboards. The recovered wood particles and fresh industrial wood particles in different proportions were used as the raw material for the particleboard. The physical and mechanical properties of the recycled particleboards were evaluated. The modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond (IB) of the recycled particleboards were lower than those of the particleboards made with fresh wood particles. However, the 2 h thickness swelling (TS) of the recycled particleboards was better than that of the fresh particleboards, indicating that the recycled particleboards were more dimensionally stable. The mechanical properties of the particleboards containing up to 40% recycled wood particles met the minimum Chinese National Standard requirements for general-purpose particleboards. Conclusively, scrap wood particleboards could be utilized as raw material in particleboard production.

Improving performance of bamboo fluff pulp by liquid hot water pretreatment and combination with longer fibers

Bamboo has several disadvantages as a raw material for the preparation of fluff pulp, including short fiber length, a high proportion of hemicellulose and high levels of fines and non-fibrous cells. Here, the proportion of hemicellulose was reduced by liquid hot water (LHW) pretreatment. The bamboo was then kraft cooked, screened through a 100 mesh screen plate to remove fines and non-fibrous cells, and bleached to prepare bamboo pulp fibers. Changes in the functional groups and crystallinity after LHW pretreatment were investigated by Fourier-transform infrared spectroscopy and X-ray diffraction. Analysis of the cross-sectional and surface morphology of the bamboo before and after pretreatment and of the surface morphology of the fluff pulp by field emission scanning electron microscopy showed that LHW pretreatment effectively removes hemicellulose from the bamboo. Combination of the bamboo pulp fibers with softwood fiber or cotton linter fiber produced a fluff pulp fiber with improved strength and water absorption. The new bamboo-cotton and bamboo-wood mixed fiber fluff pulps outperformed a branded commercial fluff pulp.

Bioconversion of spray corn husks into L-lactic acid with liquid hot water pretreatment

Agricultural by-products like rice husk, bran, and spray corn husks, often utilized as feed, are considered less desirable. This study aims to enhance the utilization rate of these materials by subjecting then to liquid hot water (LHW) pretreatment, followed by enzymatic hydrolysis to produce fermentable sugars. We investigated the production of L-lactic acid using two methods: simultaneous saccharification fermentation (SSF) and separate hydrolysis fermentation (SHF), following varying intensities of LHW pretreatment. The results showed that the optimal enzymatic hydrolysis efficiency was achieved from spray corn husks under the pretreatment conditions of 155 °C and 15 min. SHF was generally more effective than SSF. The glucose L-lactic acid conversion rate in SHF using spray corn husks can reach more than 90 %. Overall, this work proposed a novel, environmental-friendly strategy for efficient and for L- lactic acid production from spray corn husks.

Enhancement of Liquid Hot Water Pretreatment on Corn Stover with Ball Milling to Improve Total Sugar Yields

Conversion of the lignocellulosic biomass to bioethanol contributes to the reduction of greenhouse gas emissions, enhancement of energy security, utilization of waste materials, and the promotion of sustainable agricultural practices. In this study, we report the effect of combining ball milling followed by liquid hot water (LHW) pretreatment of corn stover to lower the amount of enzyme required while also greatly increasing the recovery of xylose in fermentable form compared to either pretreatment alone. Short-duration ball milling for 60 min reduces the particle size of corn stover to 37.3 μm; however, the glucose only increased to 47% compared to 32% for unpretreated corn stover. In contrast, liquid hot water pretreatment alone can achieve increasing enzyme hydrolysis yields of cellulose from 49% to 93% as the pretreatment severity factor is increased from 3.24 to 4.41. However, the xylose yield decreased to 36% due to the fact that a considerable part of the xylose was degraded into furfural and humins. Surprisingly, the combination of mild ball milling (30 min) followed by mild liquid hot water pretreatment (190 °C, 15 min) could achieve both high glucose (83%) and xylose (72%) yields for a total sugar yield of 79%, theoretically. Thus, combining ball milling with liquid hot water pretreatment allows for milder conditions for both processes that lead to enhanced cellulose conversion without sacrificing xylose to degradation, which hinders enzymatic hydrolysis.

Optimizing monosaccharide production from liquid hot water pretreatment and enzymatic hydrolysis of grass-clover press cake

In the present study, clover-grass press cake was treated by liquid hot water at temperatures of 180–200 °C for a reaction time of 5–10 min. Evaluation of pretreatments was based on the monosaccharide yield after enzymatic hydrolysis of the pretreated slurry and solid fraction, respectively. Extraction of up to 48% hemicellulose and 4% cellulose was observed during pretreatment. The optimal pretreatment conditions were identified as 190 °C and 10 min resulting in monosaccharide yields of 90% and 73% of the theoretical maximum by slurry and solid conversion, respectively. At optimal conditions, the C6 monosaccharide yield (83–90%) was fairly equal compared to the C5 monosaccharide yield (56–89%), which increased by slurry conversion due to near-complete monomerization of soluble xylo-oligosaccharides. In this study, we showed that clover-grass press cake possesses considerable potential as feedstock for production of fermentable sugars in a biorefinery context.

Detoxification of high solid-liquid hydrothermal pretreated sugar cane bagasse by chromatographic adsorption for cellulosic ethanol production

The conversion of sugar cane bagasse (SCB) into cellulosic ethanol by microorganism becomes challenging at high solid liquid ratio (SLR) due to high concentration of inhibitors in the liquid hot water pretreatment. Therefore, this study aims to produce cellulosic ethanol by detoxifying the high SLR hydrolysate (1:6, w/v) using SY-01 resin. The detoxification effects of SY-01 resin dosage and adsorption modes were systematically investigated. The resulting detoxified hydrolysate was successfully fermented, and the highest ethanol concentration achieved was 30.94 ± 0.13 g/L. Additionally, the ethanol yield was 102.51 ± 0.94%, and the ethanol production from SCB was 210 ± 1 mg/g SCB. Our findings confirm that SY-01 resin is effective in detoxifying lignocellulosic enzymatic hydrolysate, providing an economical and feasible method for the high-value utilization of biomass resources.

Integrated pretreatment of poplar biomass employing p-toluenesulfonic acid catalyzed liquid hot water and short-time ball milling for complete conversion to xylooligosaccharides, glucose, and native-like lignin

This work aimed to study an integrated pretreatment technology employing p-toluenesulfonic acid (TsOH)-catalyzed liquid hot water (LHW) and short-time ball milling for the complete conversion of poplar biomass to xylooligosaccharides (XOS), glucose, and native-like lignin. The optimized TsOH-catalyzed LHW pretreatment solubilized 98.5% of hemicellulose at 160 °C for 40 min, releasing 49.8% XOS. Moreover, subsequent ball milling (20 min) maximized the enzymatic hydrolysis of cellulose from 65.8% to 96.5%, owing to the reduced particle sizes and cellulose crystallinity index. The combined pretreatment reduced the crystallinity by 70.9% while enlarging the average pore size and pore volume of the substrate by 29.5% and 52.4%, respectively. The residual lignin after enzymatic hydrolysis was rich in β-O-4 linkages (55.7/100 Ar) with less condensed structures. This lignin exhibited excellent antioxidant activity (RSI of 66.22) and ultraviolet absorbance. Thus, this research suggested a sustainable waste-free biorefinery for the holistic valorization of biomass through two-step biomass fractionation.

Optimization of liquid hot water pretreatment for extraction of nanocellulose crystal from South African waste corncobs

This study extracted nanocellulose crystals from South African waste corncobs via liquid hot water pretreatment and alkali treatment. The pretreatment process was designed and optimized using Central Composite Design (CCD) and Response Surface Methodology (RSM), respectively setting temperature (150–200 °C), time (10–60 min), and solid loading rate (3–10% w/w) as input variables. After pretreatment, the residue was treated with sodium hydroxide (2%wt) at 90 °C for 90 min. The extracted nanocellulose crystal was filtered, washed with deionized water, and dried in an oven. The characterization of the nanocellulose crystal was carried out based on standard procedures. The positive correlations between the input variables were observed, whereby a rise in the pretreatment conditions improved the nanocellulose crystal yield. Hence, the study obtained an optimum yield of 55.5% at 200 °C, 10% w/w, and 60 min. The surface morphology showed a more porous and rougher surface, and the crystallinity analysis indicated that run 7 had the most crystalline nanocellulose crystal with a crystallinity index of 57.3%. The study revealed that nanocellulose crystals could be extracted from corncobs via liquid hot water pretreatment and alkali treatment.

Combined liquid hot water and sulfonation pretreatment of sugarcane bagasse to maximize fermentable sugars production

Sugarcane bagasse (SCB) is a widely available biomass feedstock currently used for ethanol production in various parts of the world. Here, we carried out a combined liquid hot water and neutral/alkaline sulfonation pretreatments of SCB at relatively low temperatures to maximize enzymatic hydrolysis yields. To describe multi-step pretreatments severities, analytical equations for modified combind severity factors (CSF´m) were introduced. Although the chemical composition of SCB after the liquid hot water pretreatment alone has not been significantly changed under tested conditions, this pretreatment led to an increase in the efficiency of its enzymatic hydrolysis. Furthermore, a combination of liquid hot water pretreatment (at 120 °C for 1 h) and sulfonation of SCB (at 120 °C for 2 h) resulted in excellent enzymatic hydrolysis yields. After alkaline sulfonation, glucose yields reached 99.6 ± 0.21% for autoclaved and alkaline sulfonated bagasse (AASB) and 97.47 ± 0.75% for boiled and alkaline sulfonated bagasse (BASB), whereas xylose yields were 86.9 ± 1.9% and 88.0 ± 1.8% for AASB and BASB, respectively. High enzymatic hydrolysis yields are in line with elevated CSF´m of the latter pretreatments. X-ray diffraction, confocal laser scanning microscopy, and solid-state 13C NMR spectroscopy analyses showed that the structural desorganization of bagasse after liquid hot water pretreatment associated to chemical modifications of lignin and its massive removal promoted by alkaline sulfonation led to efficient separation of carbohydrates and lignin, revealing underlying structural reasons of the observed efficient enzymatic hydrolysis.

Scale-up of hydrothermal processing: Liquid hot water and pilot-scale tubular steam explosion batch reactor for bioethanol production using macroalgae Sargassum spp biomass

Sargassum spp. is a biomass that can potentially use as an alternative for bioethanol production. Hydrothermal processes (liquid hot water and steam explosion pretreatment) were carried out at different operational conditions. Enzymatic hydrolysis performed a preliminary test with different ratios 1:1 and 1:2 (cellulases and hemicellulases) of enzyme loading, once selected 1:2 ratio was obtained conversion yield of 99.91% and therefore carried a scale-up in stirred bioreactor getting 95.92% saccharification yield. Pre-simultaneous saccharification and fermentation strategy was performed in a continuous stirred tank bioreactor (CSTBR), producing ethanol yield of 57.69%, and for simultaneous saccharification and fermentation strategy was performed in a bubble column reactor was 71.37% ethanol yield. The energy efficiency was analyzed in different scenarios; the best data was 30.19 (gsugar/MJ) in the bioreactor enzymatic hydrolysis process. This development allows for establishing the conditions for a third-generation biorefinery on a circular bioeconomy using Sargassum biomass.

Hydrothermal pretreatment optimization of hemicellulose dissolution of sugar palm starch industrial waste

Lignocellulosic biomass is a renewable source containing three main components: cellulose, hemicellulose, and lignin. The three main components can be processed into products that have high added value. Sources of lignocellulosic biomass includes wood, grass, industrial waste, and agricultural residu. Compared to other source, industrial wastes have a higher potential to be utilized without competition for other needs and assist industry in waste treatment. The production of sugar palm starch generate biomass waste which is disposed into the environment which disturbs the surrounding community and is not utilized. To utilize lignocellulosic biomass, pretreatment is a very important step. Hydrothermal is an environmentally friendly pretreatment, without using harmful chemicals in the process. The purpose of this study was to determine the level of solubility of hemicellulose in the hydrothermal pretreatment process of sugar palm starch industrial waste. The hydrothermal method used is liquid hot water with temperature and time parameters, optimization analysis using response surface methodology (RSM). The result obtained is that the liquid hot water pretreatment method is effective in dissolving the hemicellulose from the sugar palm starch industrial waste. The relationship between variables on hemiselulosa response is modeled Y = 7.7-3.04 X1 – 5.67X2 + 0.4250 X1X2 + 1.06 X1 2 + 3.61 X2 2. The optimization results showed the optimum temperature at 195.91°C for 36.725 minutes, with a hemicellulose dissolution of 81.59% and the level of desirability is 0.852.

Liquid hot water pretreatment combined with high-solids enzymatic hydrolysis and fed-batch fermentation for succinic acid sustainable processed from sugarcane bagasse

In order to sustainable process of bio-succinic acid (SA), response surface methodology (RSM) was applied to optimize liquid hot water pretreatment pretreatment of sugarcane bagasse (SCB), followed by high-solids enzymatic hydrolysis of pretreated residual that without washing, then the hydrolysates and partial pretreatment liquid were used as carbon sources for SA fermentation. Results showed that the highest sugars yield could be achieved at pretreatment conditions of temperature 186 °C, time 25 min and solid-to-liquid ratio 0.08; enzymatic digestion the pretreated residuals at 20 % (w/v) solid content via enzymes reconstruction and fed-batch strategy, the obtained sugars reached to 121 g/L; by controlling the nutrition and conditions of the fermentation process, most of the C5 and C6 sugars in the hydrolysate and pretreatment liquid were converted into SA with a conversion rate high to 280 mg/g SCB. This study can provide a novel clue for clean and efficient biorefining of chemicals.

Bioconversion of cellulose and hemicellulose in reed sawdust to xylo-oligosaccharides and L-lactic acid

Much of the carbohydrate-rich reed sawdust (RS) produced from the reed pulping mills is burned or buried, causing a waste of resources. The aim of this work is to effectively bio-convert cellulose and hemicellulose of RS to L-lactic acid and xylo-oligosaccharide (XOS) after liquid hot water (LHW) pretreatment. The experiments were carried out via separation hydrolysis fermentation (SHF) and simultaneous saccharification fermentation (SSF) by optimizing the culture and fermentation conditions of a probiotics compound composed of a consortium of lactic acid bacteria. In the end, functional feed additives containing 69.33 wt% L-lactic acid and 26.82 wt% XOS can easily be obtained without additional handling by SSF configuration at 40 ℃ for 82 h with the initial fermentation pH 7.0. The conversion rate of glucose to L-lactic acid reached 72.33%. The bioconversion of available portion in RS into XOS and L-lactic acid paves a new way for high-value utilization of reed residue resources.

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.

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.

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.

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.