Cellulase Dosage Research Articles

The co-production of xylose, fermentable glucose and β-O-4 linkage-rich lignin through efficiently dismantling sugarcane bagasse.

As an "upstream" process in biorefinery, biomass dismantling can dismantle the natural stable structure of lignocellulosic biomass and separate its three major components. To increase the value of the entire biomass by fully utilizing the three main components (cellulose, lignin, and hemicellulose), this study proposes a two-step decomposition system combining formic acid (FA) pretreatment and ethylene glycol-NaOH (EGA) dismantling, aiming to effectively convert sugarcane bagasse into xylose, fermentable glucose, and high-value lignin. In the first step, FA pretreatment removed 79.85 % of hemicellulose at 140 °C for 90 min with 3 % FA. Based on the first step, further combination of EGA dismantling can achieve a hemicellulose removal rate of 92.05 % and a lignin removal rate of 95.90 %. In addition, the solid residue was hydrolyzed by enzymes, and the glucose conversion rate was close to 83.29 % when the cellulase dosage was 10 FPU/g. In addition, the lignin recovered by this system retained 83.62 % of the natural β-O-4 structure, which has the potential to catalyze the formation of aromatic monomers. In summary, this gentle two-step system simultaneously improves the efficiency of lignocellulose decomposition and produces different value-added products, demonstrating the potential for industrial-scale production.

Production of Sugars and Ethanol from Acid–Alkaline-Pretreated Agave sisalana Residue

Drylands in Brazil have been exploring sisal (Agave sisalana) as an essential source of income. However, the solid residues generated because of this activity still need suitable destinations; therefore, research has been carried out to transform them into added-value products. Therefore, the present study evaluated the potential of sisal or agave solid residue as a precursor feedstock for second-generation ethanol production. Acid and acid–alkaline pretreatments were carried out on sisal residues to enrich the biomass with cellulose and maximize enzymatic digestibility. Second-generation ethanol production was carried out using Semi-simultaneous saccharification and fermentation (SSSF). Regardless of catalyst dosage and incubation time, oxalic acid pretreatments generated samples with a similar chemical composition to those pretreated with sulfuric acid. However, samples pretreated with oxalic acid showed lower enzymatic digestibility. Samples pretreated with oxalic acid and sodium hydroxide obtained 14.28 g/L of glucose and cellulose conversion of 79.1% (at 5% solids), while 21.49 g/L glucose and 91.2% of cellulose conversion were obtained in the hydrolysis of pretreated samples with sulfuric acid and sodium hydroxide combined pretreatments. The pretreatment sequence efficiently reduced cellulase dosage from 20 to 10 FPU/g without compromising sugar release. SSSF achieved maximum production of 40 g/L ethanol and 43% ethanol conversion using 30% solids and gradually adding biomass and cellulases.

Optimizing Cellulase-Limosilactobacillus fermentum ZC529 Synergy Fermentation for Preserving Macadamia integrifolia Pericarp's Potential Use as Antioxidants.

Macadamia integrifolia pericarps (MIP) are byproducts of nut production which are rich in natural antioxidant compounds, making them an excellent source for extracting bioactive compounds. However, the antioxidant compounds in MIP are easily oxidized under natural storage conditions, resulting in significant biomass loss and resource wastage. To preserve the potential of MIP to be used as an antioxidant product, we employed cellulase and Limosilactobacillus fermentum ZC529 (L.f ZC529) fermentation and utilized response surface methodology to optimize the fermentation parameters for mitigating the antioxidant loss. Total antioxidant capacity (T-AOC) was used as the response variable. The fermented MIP water extract (FMIPE) was obtained via ultrasound-assisted extraction, and its biological activity was evaluated to optimize the best fermentation conditions. Results indicated that a cellulase dosage of 0.9%, an L.f ZC529 inoculation size of 4 mL/100 g, and a fermentation time of 7 days were the optimal conditions for MIP fermentation. Compared to spontaneous fermentation, these optimal conditions significantly increased the total phenolic and total flavonoid contents (p < 0.05). T-AOC was 160.72% increased by this optimal fermentation (p < 0.05). Additionally, supplementation with varying concentrations of FMIPE (6.25%, 12.5%, and 25%) increased the T-AOC, SOD activity, and GSH content, and reduced MDA levels of the oxidative-stressed Drosophila melanogaster (p < 0.05). Moreover, 12.5% and 25% of FMIPE treatments elevated CAT activity in the Drosophila melanogaster (p < 0.05). The effects of FMIPE on GSH and MDA in Drosophila melanogaster were equivalent to the 0.5% vitamin C (Vc) treatment. In summary, synergistic fermentation using cellulase and L.f ZC529 effectively preserves the antioxidant activity of the MIP, offering a simple, eco-friendly method to promote the utilization of MIP resources.

Mild γ-Butyrolactone/Water Pretreatment for Highly Efficient Sugar Production from Corn Stover.

In this study, γ-butyrolactone/water (GBL/H2O) was explored as a mild, efficient, and cost-effective binary solvent pretreatment to enhance hydrolyzability of corn stover (CS). Key pretreatment parameters-reaction time, temperature, and H2SO4 concentration-were systematically investigated for their effects on the physicochemical properties of CS. Specifically, increased temperature and acid concentration significantly decreased cellulose crystallinity (from 1.39 for untreated CS to 1.04 for CS pretreated by GBL/H2O with 100 mM H2SO4 at 120°C for 1h) and promoted lignin removal (47.3% for CS pretreated by GBL/H2O with 150 mM H2SO4 at 120°C for 1h). Acknowledging the cellulase's limited hydrolysis efficiency, a dual-enzyme scheme using a low cellulase dosage (10 FPU/g) supplemented with β-glucosidase or xylanase was tested, enhancing hydrolysis of CS pretreated under low temperature-long duration and high temperature-short duration conditions, respectively. Optimum sugar release was obtained from CS pretreated with GBL/H2O and 150 mM H2SO4 at 120°C for 1h, achieving 98% glucan and 82.3% xylan conversion, compared with 53.9% and 17% of glucan and xylan conversion from untreated CS. GBL/H2O pretreatment outperformed other binary systems in literature, achieving the highest sugar conversions with lower enzyme loading. These results highlight the potential of GBL/H2O pretreatment for efficient biomass conversion, contributing to the goals of the green economy.

Ultrasound-assisted enzymatic extraction of polysaccharides from Paulownia flowers: process optimization, structural characterization, antioxidant and hypoglycemic activities

This study aimed to optimize the ultrasound-assisted enzymatic extraction (UAEE) process of Paulownia flowers polysaccharides (PFP) and investigate its antioxidant and hypoglycemic activities. The optimal extraction conditions were cellulase dosage 1.6 mg/g, liquid-solid ratio 27:1mL/g, ultrasonic power 230 W, temperature 51 °C, the PFP yield reached 5.50 % which was close to the predicted value of 5.59 %. Furthermore, the PFP was isolated and purified by DEAE-52 cellulose column and sephadex G-200 column to obtain two polysaccharide fractions, PFP1-1 and PFP2-1. The characteristics, antioxidant activity and hypoglycemic activity of PFP1-1 and PFP2-1 were analyzed. PFP1-1 with a molecular weight of 52.8 kDa was mainly composed of mannose and glucose (molar ratio1.00:5.05), and PFP2-1 with a molecular weight of 8.768 kDa was consisted of mannose, rhamnose, glucuronic acid, glucose (molar ratio 1.00:7.41:8.09:11.30). Compared to PFP1-1, the antioxidant activity assays showed that PFP2-1 exhibited stronger DPPH radical, hydroxyl radical and superoxide radical scavenging capacity and the inhibitory activities revealed that PFP2-1 could more effectively inhibit α-amylase and α-glucosidase, which might be attributed to the uronic acid and low molecular weight in PFP2-1. This work will provide a foundation for the efficient extraction of PFP and utilization for antioxidant agent and digestive enzymes inhibitor of diabetes.

Low-temperature pretreatment by AlCl3-catalyzed 1,4-butanediol solution for producing ‘ideal’ lignin with super-high content of β-O-4 linkages

High contents of internal β-O-4 linkages in lignin are critical for high-yield production of high-value aromatic monomers by depolymerization. However, it remains great challenge due to lack of suitable protection strategy. In this work, a very effective lignin-first strategy was developed to produce ideal lignin with a super high content of β-O-4 linkages (up to 72 %) from poplar, in which the pretreatment was undertaken at low temperatures of 90–130 °C with the use of AlCl3-catalyzed 1, 4-butanediol solution. 2D-HSQC NMR spectra revealed that lignin β-O-4 linkages were protected from etherification of the OH group by 1, 4-butanediol at the α position of lignin aliphatic chains. Besides, the OH groups at the γ position of lignin was also etherified, leading the formation of a structure of Ph-CH=CHCH2O(CH2)4OH. Interestingly, structure protection facilitated the formation of lignin nanoparticles via self-assembly (<100 nm). In addition, it was observed from pyrolysis results that addition of 1, 4-butanediol remarkably protected the structure of lignin by avoiding condensation, promoting the production of aromatics. The cellulose-rich fraction possessed a high cellulose digestibility of 91.64 % by enzymatic hydrolysis at a cellulase dosage of 15 FPU/g cellulose, approximately 6-fold untreated poplar (15.91 %). This low-temperature lignin-first strategy was of great importance for multi-products biorefining lignocellulose because it leads to the production of both lignin with super high content of β-O-4 linkages for depolymerization and highly digestible cellulose for sugar production.

Microwave and enzyme co-assisted extraction of anthocyanins from Purple-heart Radish: Process optimization, composition analysis and antioxidant activity

Purple-heart Radish named “Xinlinmei” is rich in anthocyanins by specific cultivation. In this work, a novel method for synergistic extraction of anthocyanins from Purple-heart Radish was developed by combining microwave-assisted extraction (MAE) with enzyme-assisted extraction (EAE). Integration of MAE and EAE was optimized by screening various enzymes and combination approaches, followed by investigation of process parameters with single-factor experiments and response surface methodology (RSM). The optimized conditions by RSM were as follow: 25.0 g/100 g cellulase dosage, 60 mL/100 mL ethanol concentration, pH 4.0, 50 °C temperature, 7.15 min extraction time, 80 mesh particle size and 60:1 mL/g liquid-to-material ratio, yielding a maximum response predicted and experimental values of 6.292 and 6.125 ± 0.034 mg/g respectively. Based on the synergistic effect, MAE-EAE achieved higher extraction efficiency compared to the other extraction methods such as MAE, UAE and EAE etc. By means of HPLC-Q-Orbitrap/MS and HPLC, 11 anthocyanins extracted were identified and quantified as pelargonins with different glucosides, exhibiting quite homologous fragmentation pattern, biometabolic products and satisfactory yield. The antioxidation capacity of the extracted and purified products was evaluated by DPPH, ABTS and anti-lipid peroxidant assays, suggesting that the anthocyanins purified by the macroporous resin had stronger antioxidant activity. This study provided an efficient and promising approach to improve extraction of the anthocyanins from Purple-heart Radish, and a new source of pelargonins as a powerful antioxidant to be developed.

Dietary fiber extraction from citrus peel pomace: Yield optimization and evaluation of its functionality, rheological behavior, and microstructure properties.

Citrus fruits were widely used in processing and production, generating a large amount of peel pomace and a low utilization rate, resulting in substantial economic losses and environmental risks. It was important to extract compounds from citrus peel pomaces and find suitable preparation methods to improve their yield and physicochemical properties. Grapefruit peel pomace (GP) and navel orange peel pomace (OP) were used as raw materials in this study to prepare green and edible soluble dietary fiber (SDF) and insoluble dietary fiber (IDF). Analysis was done on the effects of solid-liquid ratio, cellulase hydrolysis time, cellulase dosage, and ultrasonic time on dietary fiber (DF) yield. To obtain the best DF preparation conditions, we used range analysis, variance analysis, and orthogonal experimental design. We also analyzed the structural, physicochemical, and rheological characteristics of SDF and IDF. According to the study's findings, SDF and IDF showed a loose and expansive structure with reduced particle size, higher specific surface area, and noticeably better physical and chemical properties after treating GP and OP with ultrasound-assisted composite enzyme method. Both SDF solution and IDF suspension were discovered through rheological analysis to be non-Newtonian pseudoplastic fluids, which was advantageous for expanding their applications in the field of food packaging. In conclusion, DF prepared using the ultrasound-assisted composite enzyme method was an excellent source of edible packaging materials, offering a benchmark for the recycling of other citrus peel wastes and ultimately paving the way for new methods of recycling citrus waste.

Achieving high enzymatic hydrolysis sugar yield of sodium hydroxide-pretreated wheat straw with a low cellulase dosage by adding sulfomethylated tannic acid

Sulfonated lignin can significantly enhance the enzymatic hydrolysis of lignocellulose substrates. Lignin is a type of polyphenol, therefore, sulfonated polyphenol, such as tannic acid, is likely to have similar effects. In order to obtain a low-cost and high-efficiency additive to improve enzymatic hydrolysis, sulfomethylated tannic acids (STAs) with different sulfonation degrees were prepared and their impact on enzymatic saccharification of sodium hydroxide-pretreated wheat straw were investigated. Tannic acid strongly inhibited, while STAs strongly promoted the substrate enzymatic digestibility. While adding 0.04 g/g-substrate STA containing 2.4 mmol/g sulfonate group, the glucose yield increased from 60.6% to 97.9% at a low cellulase dosage (5 FPU/g-glucan). The concentration of protein in enzymatic hydrolysate significantly increased with the added STAs, indicating that cellulase preferentially adsorbed with STAs, thereby reducing the amount of cellulase nonproductively anchored on substrate lignin. This result provides a reliable approach for establishing an efficient lignocellulosic enzyme hydrolysis system.

Extraction and functional properties of pigment from pumpkin peels by a novel green deep eutectic alcohol two-phase system

Pumpkin peel pigments contain a variety of natural antioxidants carotenoids including α-carotene, β-carotene, β-cryptoflavin, and xanthine, etc.. Conventional extraction methods generally have low yields and high energy consumption. To explore a green and efficient extraction process, firstly, different kinds and proportions of deep eutectic solvent (DES) alcohol two-aqueous phase system were prepared, and then ultrasound-assisted cellulase was used to optimize the parameters by Box-Behnken design (BBD) on the basis of single factor experiment. The results showed that the extraction solvent was determined as DES (choline chloride: triethylene glycol = 1 : 3) and ethanol = 6 : 4, the yield of the pigments was 2.460% ± 0.037% at cellulase dosage of 2.10%, solid-liquid ratio of 1 : 40 g/mL, ultrasonic power of 300 W for 40 min. The inhibition rate of the pigments to α-amylase and sucrase was 82.20% ± 0.90% and 75.63% ± 1.19%, respectively, at the concentration of 100 μg/mL. They could significantly prolong the survival rate of Caenorhabditis elegans under hydrogen peroxide stress (p < 0.05), and the mean lifespans of C. elegans reach 9.047 ± 0.296 h, which was significantly higher than that of the negative control (2.717 ± 0.125 h) and the positive control group (5.067 ± 0.327 h). They also significantly enhanced the activities of T-SOD (>77.17%) and CAT (>112.09%) and reduced the level of MDA (p < 0.05), indicating that the pigments played an important role in alleviating oxidative stress damage, and with great development value as a recyclable resource.

A Comparative Study on Extraction and Physicochemical Properties of Soluble Dietary Fiber from Glutinous Rice Bran Using Different Methods

The methods of hot water extraction and ultrasound-assisted enzymatic treatment were applied for extracting the soluble dietary fiber from the glutinous rice bran in the study. Based on the single factor experiment for the hot water method, the optimum parameters of the extraction time of 120 min, solid-liquid ratio 1:20 (w/v), and pH 8.0, as well as the extraction temperature 80 °C, were obtained, while the yield and purity of SDF reached 31.83 ± 0.06% and 93.28 ± 0.27%, respectively. Furthermore, the SDF yield was improved to 34.87 ± 0.55% by using the ultrasound-assisted enzymatic treatment under the optimum conditions of cellulase dosage 9 × 103 U/g and ultrasonic temperature of 50 °C. Similar polysaccharide compositions were detected based on the infrared spectroscopic analysis. Compared with the SDF obtained from hot water extraction, the whiteness, solubility, water holding capacity, and swelling properties of SDF extracted by ultrasound-assisted enzymatic method improved significantly. These results demonstrated that both two strategies could be applied to SDF extraction in practical production, and the ultrasound-assisted enzymatic method might be an effective tool to improve the functional properties of SDF.

Two-Stage Pretreatment of Jerusalem Artichoke Stalks with Wastewater Recycling and Lignin Recovery for the Biorefinery of Lignocellulosic Biomass

Jerusalem artichoke (Helianthus tuberosus L.) is emerging as one of the energy plants considered for biofuel production. Alkali and alkali-involved pretreatment methods have been widely used for the bioconversion of cellulosic materials due to their high sugar yield and low inhibitor release. However, the recovery and treatment of wastewater (black liquor) have been poorly studied. Here, we present a novel two-stage pretreatment process design for recycling black liquor. Jerusalem artichoke stalk (JAS) was first treated with 2% (w/v) NaOH, after which lignin was recovered by H2SO4 at pH 2.0 from the black liquor. The recycled solutions were subsequently used to treat the NaOH-pretreated JAS for the second time to dissolve hemicellulose. CO-pretreated JAS, hydrolysates, and acid-insoluble lignin were obtained after the above-mentioned two-stage pretreatment. A reducing sugar yield of 809.98 mg/g Co-pretreated JAS was achieved after 48 h at 5% substrate concentration using a cellulase dosage of 25 FPU/g substrate. In addition, hydrolysates containing xylose and acid-insoluble lignin were obtained as byproducts. The pretreatment strategy described here using alkali and acid combined with wastewater recycling provides an alternative approach for cellulosic biorefinery.

Comprehensive analysis of ethanol production from coffee mucilage under sustainability indicators

This article shows the results obtained by analyzing an emerging technology to produce bioethanol from coffee mucilage under sustainable development constraints. The investigation showed that the addition of an antibiotic is important to avoid contamination of the mucilage related to the presence of bacteria since these microorganisms can eat the sugars present in the biomass for their metabolism. On the other hand, for the conversion of cellulose and hemicellulose into simple reducing sugars present in coffee mucilage, the addition of the enzyme pectinase was necessary. The ANOVA analysis showed that the cellulase dose is the most significant factor in the hydrolysis process. The adequate doses of enzymes for the enzymatic hydrolysis process of coffee mucilage were obtained by the response surface method, finding an optimal value of 0,352 mL and 0,134 mL of cellulase and hemicellulase, respectively, per 100 mL of mucilage. From the logistics approach, the supply of coffee mucilage to a second-generation ethanol pilot plant with an installed capacity of 15.000 liters of mucilage per week was considered. Ideally, the pulping process must be carried out mechanically without water, ensuring a mucilage Brix content between 16 and 21, which would favor an ethanol yield close to 8% (v/v) in the must. A potential production of 4,137 liters of ethanol could be achieved with a total logistics cost of USD 305 if the available mucilage is collected. A potential reduction of 7,650 kg of carbon dioxide is possible if the ethanol produced is used to replace the same amount of gasoline in the transportation industry.

Enhancement of sugar release from sugarcane bagasse through NaOH-catalyzed ethylene glycol pretreatment and water-soluble sulfonated lignin

In this work, five different NaOH-catalyzed ethylene glycol (EG) pretreatments together with water-soluble sulfonated lignin (SL) were used for enhancing sugarcane bagasse (SCB) enzymatic digestion. The results showed that the coupling of NaOH and EG into a one-pot pretreatment (10%NaOH/EG) was more beneficial to improve SCB enzymatic hydrolysis than that of single 10%NaOH or EG pretreatment, or the two-step pretreatment of NaOH and EG in different sequence (10%NaOH+EG and EG + 10%NaOH, respectively). The highest glucose yield of this work was 91.2 %, mainly released from the SCB that pretreated with 10%NaOH/EG at 130 °C for 60 min and 72 h enzymatic hydrolysis. The adding of SL into the enzymatic hydrolysis step could significantly lower the cellulase dosage and hydrolysis time from 20 FPU/g and 72 h to 10 FPU/g and 24 h, respectively, meanwhile keeping a high glucose yield of 90.4 %. The characterization of various pretreated or un-pretreated SCB confirmed that the improvement of hydrolysis efficiency of SCB after 10%NaOH/EG pretreatment was closely related to the removal of various components barriers in SCB and the fragmentation of pretreated solid. It can be concluded that the developed NaOH-catalyzed ethylene glycol pretreatment was an efficiency way to enhance the sugar release from SCB.

Process strategies to reduce cellulase enzyme loading for renewable sugar production in biorefineries

Second-generation (2G) sugar is the principal building block in biorefineries producing sustainable fuels, green chemicals, and materials. Its production involves a pre-treatment strategy, which can remove either hemicellulose or lignin, followed by a cellulase cocktail-mediated hydrolysis of pre-treated biomass applying numerous modifications. The high production cost of sugar from biomass using high-solid loadings with the desired purity is the important limiting factor for their economic conversion into bio-renewables. Pre-treatment and cellulase-mediated enzymatic hydrolysis of recalcitrant biomass are among the major technical and economic impediments to the overall success of biorefineries. Critical parameters such as the high amount of cellulase required for biomass hydrolysis, high cellulase cost, unproductive binding of cellulase to lignin, inhibitive reactions, and lower substrate applicability directly influence the recovery of sugar at a competitive price. Understanding the interaction of the relationship of the enzymes and substrates with the interactions of the reducing cellulase amount and effective hydrolysis rate should be positioned for the recovery of 2G sugar at a competitive price. Thus, effective strategies are needed to minimize cellulase dosage to overcome the cost of the enzyme. Further, on-site enzyme production, the addition of pre-treated biomass in fed-batch mode, and the washing of pre-treated biomass can play a pivotal role in the economic production of 2G sugar. This review provides a comprehensive analysis of the specific strategies such as applying extraneous proteins and additives, enzyme recycling, and effect of washing pre-treated biomass on 2G sugar production at a large scales in lignocellulose biorefineries.

Cellulase pretreated palm decanter cake for feeding of black soldier fly larvae in triggering bioaccumulation of protein and lipid into biodiesel productions

For every ton of palm oil produced, approximately 0.2 tons of palm decanter cake (PDC) waste is generated. Hence, there is a huge opportunity to valorize this organic waste, i.e., via the deployment of black soldier fly larvae (BSFL), which has been widely employed to convert various organic wastes into larval proteins and lipids. However, the PDC is mainly made up of lignocellulosic materials that are hard to digest by the BSFL. Therefore, this work attempted to grow BSFL in cellulase-pretreated PDC; thereby, providing an alternative solution to manage PDC waste. Results had shown that the cellulase pretreatment was effective in breaking down cellulose into glucose molecules, especially with higher cellulase dosage and longer treatment duration of up until 48 h. Subsequently, the maximum BSFL growth was found at 6.56 ± 2.69 mg/larva when being fed with PDC pre-treated by 1.0 wt% of cellulase for 72 h; which was about 4 mg higher than the controlled larva. Using a similar substrate, the highest protein yield and lipid yield from BSFL were attained at 1.63 ± 0.11 mg/larva (22.4 wt%) and 5.12 ± 1.01 mg/larva (69.9 wt%), respectively. In terms of biodiesel quality, a huge presence of saturated fatty acids had made the BSFL-based biodiesel oxidatively stable.

Enhancement of glucose production from sugarcane bagasse through an HCl-catalyzed ethylene glycol pretreatment and Tween 80

In this work, an HCl-catalyzed ethylene glycol (EG) pretreatment was exploited for promoting sugar release from sugarcane bagasse (SCB). The results showed that the combination of HCl and EG could remove the xylan (∼100.0%) and lignin (∼61.3%) in SCB together, which finally resulted in the pretreated substrate having a good efficacy for follow-up enzymatic hydrolysis. The maximum glucose yield of this work was 93.9% and obtained after pretreatment at 130 °C for 60 min with 0.5% HCl and 72 h enzymatic digestion. The analysis of various pretreated or un-pretreated SCB indicated that the changes of surface morphology and internal compositions of SCB were the mainly reasons for its hydrolysis efficiency enhancement. The addition of Tween 80 into hydrolysis process could remarkably shorten hydrolysis time and cellulase dosage from 72 h to 36 h and 20 FPU/g substrate to 10 FPU/g substrate, respectively, meanwhile maintaining a relatively high glucose yield (91.4%).

Structural Properties and Hydrolysability of Paulownia elongate: The Effects of Pretreatment Methods Based on Acetic Acid and Its Combination with Sodium Sulfite or Sodium Sulfite.

The effects of CH3COOH and Na2SO3 pretreatment on the structural properties and hydrolyzability of fast-growing Paulownia elongate were investigated. Acetic acid increased cellulose’s crystallinity and hydrolyzability when combined with alkaline sodium sulfite and sodium hydroxide. The cellulose content increased by 21%, the lignin content decreased by 6%, and the product showed better enzymatic digestibility. With a cellulase dose of 30 FPU/g DM, after 72 h hydrolysis, the hydrolysis yields of glucose and xylose were 78% and 83%, respectively, which were 51% and 69% higher than those of untreated materials. When the enzyme dosage was 20 FPU/g DM, after 72 h hydrolysis, the hydrolysis yields of glucose and xylose were 74% and 79%, respectively. The high hydrolyzability, low enzyme loading, and high hydrolysis yield demonstrate the potential of the proposed system for producing platform sugars from fast-growing Paulownia elongate.

One-step sodium bisulfate hydrolysis for efficient production of xylooligosaccharides from poplar

Acid salts have been shown to catalyze xylan hydrolysis selectively and efficiently for xylooligosaccharides (XOS) production while using acid salts that are non-toxic and available as feed additives can avoid separation from resulting XOS-rich hydrolysates. There is no report on XOS production with sodium bisulfate (NaHSO4) hydrolysis, of significance is that NaHSO4 as feed additive does not need to be separated. In this work, NaHSO4 hydrolysis was firstly employed to produce XOS from poplar. XOS yield of 42.7% was reached under optimal conditions of 0.04 mol/L NaHSO4, 170 °C and 60 min. After hydrogen peroxide/acetic acid and sodium hydroxide treatments of NaHSO4-pretreated poplar, high yields of glucose (92.0%) and xylose (91.3%) were obtained at a low cellulase dose of 5 FPU/g dry mass. NaHSO4 hydrolysis was a novel strategy to prepare XOS efficiently with simple operation steps, and XOS-rich hydrolysates could be potentially used as feed additives without NaHSO4 separation.

Sufficient premixing enhances enzymatic hydrolysis efficiency of lignocellulose at high-solids loading

Low efficiency of the high-solids enzymatic hydrolysis process leads to a sharp increase in energy consumption and enzyme dosage, which hinders the development of lignocellulose biorefinery. Inhomogeneity of trace amounts of enzymes and bulk substrates mixing may be a main barrier to the efficiency. In this study, the mixing degree of enzyme and substrate at high-solids loadings were explored. The 30% solids loading group took 52.9 times longer to reach the same mixing degree as the 5% solids loading group. The mixing process is divided into two stages: reactor-scale mixing and pore-scale mixing, the latter being the rate-limiting step at high-solids loadings. Sufficient premixing improved pore-scale mass transfer, resulting in 194.25% enzymatic hydrolysis efficiency improvement at the enzyme dosage of 5 FPU/g dry matter, cellulase dosage decreased from 40 FPU/g dry matter to 5 FPU/g dry matter and earlier liquefaction at 20% solids loading. Periodic vibration as an efficient premixing method enhanced high-solids enzymatic hydrolysis efficiency. This study is a step forward to the industrial application of high-solids enzymatic hydrolysis.