Search

[Display omitted] • Autohydrolysis enhanced the delignification of p -TsOH post-treatment of poplar. • Unexpectedly, the glucose yields of combined pretreated poplar decreased. • The intensified surface lignin coverage hindered the enzymatic hydrolysis. • Tween 80 enabled the excellent enzymatic hydrolysis of combined pretreated poplars. In this study, a combined pretreatment involving autohydrolysis and p -toluenesulfonic acid (p -TsOH) was performed on poplar to coproduce xylooligosaccharides (XOSs) and monosaccharides. The autohydrolysis (180 °C, 30 min) yielded 53.2 % XOS and enhanced the delignification efficiency in the subsequent p -TsOH treatment. Furthermore, considerably high glucan contents (64.1 %∼83.1 %) were achieved in the combined pretreated substrates. However, their enzymatic digestibilities were found to be extremely poor (9.6 %∼14.2 %), which were even lower than the single p -TsOH pretreated substrates (10.2 %∼35.8 %). The underlying reasons were revealed by systematically investigating the effects of the single and combined pretreatment strategies on substrate properties. Moreover, the Tween 80 addition successfully reversed the adverse effects of combined pretreatment on the enzymatic hydrolysis, achieving a high glucose yield of 99.3 % at an enzyme loading of 10 filter paper units/g (FPU/g) glucan. These results deepen the understanding of the synergy of combined pretreatment on biomass fractionation and enzymatic saccharification. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel combined H 2 SO 4 -ChCl/Gly pretreatment of reed stalks was developed. • Synergistic effect of H 2 SO 4 and ChCl/Gly eliminated xylan and lignin effectively. • H 2 SO 4 -ChCl/Gly-treated reed stalk was converted to glucose in a high yield of 91.1%. • High saccharification was due to enhanced accessibility and reduced lignin surface. In this study, an efficient combination of pretreatment solvents involving Choline chloride/Glycerol (ChCl/Gly) and H 2 SO 4 was firstly developed to assess the pretreatment performance and determine optimal pretreatment conditions. The results illustrated that the H 2 SO 4 -[ChCl/Gly] combination efficiently removed lignin (52.6%) and xylan (80.5%) from the pretreated reed stalk, and subsequent enzymatic hydrolysis yielded 91.1% of glucose. Furthermore, several characterizations were conducted to examine the structural and morphological changes of the reed stalk, revealing apparently enhanced accessibility (128.4 to 522.6 mg/g), reduced lignin surface area (357.9 to 229.5 m2/g), and substantial changes on biomass surface. Based on the aforementioned study, possible mechanisms for the H 2 SO 4 -[ChCl/Gly] pretreatment of reed stalks were proposed. The comprehensive understanding of combined H 2 SO 4 -[ChCl/Gly] pretreatment system for enhancing the saccharification of the reed stalk was interpreted in this work. Overall, this novel approach could be efficiently applied to pretreat and saccharify reed stalks, empowering the biomass refining industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • The impacts of water-washing and freeze-drying pretreatment on biochar are studied. • Biochar with combined pretreatments (W-FD-PB) has a large surface area (212.69 m2/g). • Q m of Pb2+ on W-FD-PB is 406.99 mg/g, 1.53-fold of W-PB and 2.19-fold of PB. • Precipitation and ion exchange were enhanced during Pb2+ adsorption by W-FD-PB. • The addition of biochar significantly reduced DTPA-Pb concentrations in soil. This paper examined the impacts of different pretreatments on the characteristics of biochar and its adsorption behavior for Pb2+. Biochar with combined pretreatment of water-washing and freeze-drying (W-FD-PB) performed a maximum adsorption capacity for Pb2+ of 406.99 mg/g, higher than that of 266.02 mg/g on water-washing pretreated biochar (W-PB) and 188.21 mg/g on directly pyrolyzed biochar (PB). This is because the water-washing process partially removed the K and Na, resulting in the relatively enriched Ca and Mg on W-FD-PB. And the freeze-drying pretreatment broke the fiber structure of pomelo peel, favoring the development of a fluffy surface and large specific surface area during pyrolysis. Quantitative mechanism analysis implied that cation ion exchange and precipitation were the driving forces in Pb2+ adsorption on biochar, and both mechanisms were enhanced during Pb2+ adsorption on W-FD-PB. Furthermore, adding W-FD-PB to Pb-contaminated soil increased the soil pH and significantly reduced the availability of Pb. [ABSTRACT FROM AUTHOR]

Highlights • Combined ultrasound-acid pretreatment improved H 2 yield of grass by 311.7%. • The combined pretreatment improved the substrate utilization efficiency. • The combined pretreatment induced a more efficient fermentation pathway. • More enrichment of Clostridium contributed to the improvement in H 2 production. Abstract In this study, the dilute acid pretreatment combined with ultrasound was applied to improve fermentative hydrogen production from grass. The experimental results indicated that SCOD and soluble carbohydrate contents of grass was improved by 98.6% and 236.9% after the combined treatment, respectively. Surface morphology (SEM and AFM) and crystallinity analysis revealed that the combined pretreatment process could effectively destroyed the biomass structure and increased their surface area. Owing to the increased soluble organics proportion and better enzymatic accessibility of residual solids, the hydrogen yield reached 42.2 mL/g-dry grass after the combined treatment, which was 311.7%, 190.0% and 35.0% higher in comparison with the control, individual ultrasound and acid pretreated groups, respectively. Meanwhile, the combined treatment also increased the substrate utilization efficiency and induced a more efficient fermentation pathway. Bacterial community analysis revealed that more enrichment of Clostridium and less enrichment of Enterococcus contributed to the improved hydrogen production. [ABSTRACT FROM AUTHOR]

A thorough assessment of the microstructural changes and synergistic effects of hydrothermal and/or ultrafine grinding pretreatment on the subsequent enzymatic hydrolysis of corn stover was performed in this study. The mechanism of pretreatment was elucidated by characterizing the particle size, specific surface area (SSA), pore volume (PV), average pore size, cellulose crystallinity (CrI) and surface morphology of the pretreated samples. In addition, the underlying relationships between the structural parameters and final glucose yields were elucidated, and the relative significance of the factors influencing enzymatic hydrolyzability were assessed by principal component analysis (PCA). Hydrothermal pretreatment at a lower temperature (170 °C) combined with ultrafine grinding achieved a high glucose yield (80.36%) at a low enzyme loading (5 filter paper unit (FPU)/g substrate) which is favorable. The relative significance of structural parameters in enzymatic hydrolyzability was SSA > PV > average pore size > CrI/cellulose > particle size. PV and SSA exhibited logarithmic correlations with the final enzymatic hydrolysis yield. [ABSTRACT FROM AUTHOR]

In this study, the combined ionizing radiation-acid pretreatment process was firstly applied to enhance hydrogen fermentation of grass waste. Results showed that the combined pretreatment synergistically enhanced hydrogen fermentation of grass waste. The SCOD and soluble polysaccharide contents of grass waste increased by 1.6 and 2.91 times after the combined pretreatment, respectively. SEM observation and crystallinity test showed the combined pretreatment effectively disrupted the grass structure. Owing to the more favorable substrate conditions, the hydrogen yield achieved 68 mL/g-dry grass added after the combined pretreatment, which was 161.5%, 112.5% and 28.3% higher than those from raw, ionizing radiation pretreated and acid pretreated grass waste, respectively. The VS removal also increased from 13.9% to 25.6% by the combined pretreatment. Microbial community analysis showed that the abundance of dominant hydrogen producing genus Clostridium sensu stricto 1 increased from 37.9% to 69.4% after the combined pretreatment, which contributed to more efficient hydrogen fermentation. [ABSTRACT FROM AUTHOR]

To enhance the cellulose digestibility of energy grass hybrid Pennisetum ( P. americanum × P. purpureum , HP) with low energy-consumption and high efficiency, a novel combinatorial pretreatment of oxygen-aqueous alkaline ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate ([Emim]Ac) media (OEA) was developed in this work. The combinatorial pretreatment was performed under the relatively low temperature (120 °C), short retention time (30 min), and 12 bar oxygen pressure. The combinatorial pretreatment of OEA was demonstrated effectively for pretreatment of hybrid Pennisetum , which evidenced by the removal of lignin, degradation of carbohydrate, and porosity property of the regenerated biomass. Subsequently, a higher glucose recovery (96.9%) at a low enzyme loading (20 FPU/g substrate) was obtained by the OEA pretreatment, and it was 9.1 times as much as the untreated samples. Overall, the novel OEA combinatorial pretreatment has the advantages of low thermal energy input and enzyme usage, and short retention time. [ABSTRACT FROM AUTHOR]

[Display omitted] • Waste activated sludge is an efficient feedstock for biohydrogen production. • Synergetic disintegration were emphasized by thermo-chemo disperser pretreatment. • Solubilization and SS reduction fostered at 2081.82 kJ/kg TS specific energy. • About 116.9 mL H 2 /g COD achieved at TCD pretreated samples. Generation of excess sludge in large quantities from wastewater treatment plant face huge problem in terms of handling and management, whereas it possess higher organic and inorganic constituents and thus it can be used as a feedstock for the generation of biofuel with proper disintegration techniques. In this regard, an effort has been made in this study to combine thermo-chemo-disperser pretreatment for the disintegration of paper mill waste activated sludge for the production of biohydrogen in an energy efficient way. These combinations of thermo-chemo-disperser (TCD) tend to be effective in disintegration and possess 24.3% COD solubilization and higher suspended solid reduction of 18.8% at the specific energy usage of 2081.82 kJ/kg TS. The pretreatment with TCD technique shows the biohydrogen production of 120.2 mLH 2 /gCOD as compared to thermochemically pretreated alone (73.6 mLH 2 /gCOD) sample. Thus, the combined process was considered to be potentially effective in sludge disintegration. [ABSTRACT FROM AUTHOR]

Combined pretreatment with hot compressed water and wet disk milling was performed with the aim to reduce the natural recalcitrance of oil palm biomass by opening its structure and provide maximal access to cellulase attack. Oil palm empty fruit bunch and oil palm frond fiber were first hydrothermally pretreated at 150–190 °C and 10–240 min. Further treatment with wet disk milling resulted in nanofibrillation of fiber which caused the loosening of the tight biomass structure, thus increasing the subsequent enzymatic conversion of cellulose to glucose. The effectiveness of the combined pretreatments was evaluated by chemical composition changes, power consumption, morphological alterations by SEM and the enzymatic digestibility of treated samples. At optimal pretreatment process, approximately 88.5% and 100.0% of total sugar yields were obtained from oil palm empty fruit bunch and oil palm frond fiber samples, which only consumed about 15.1 and 23.5 MJ/kg of biomass, respectively. [ABSTRACT FROM AUTHOR]

Abstract: In this study, individual pretreatments (acid and ultrasonic) and a combination of these pretreatments were optimized to enhance the efficiency of dark fermentative hydrogen production (DFHP) from microalgal biomass. The experimental results show that the maximum H2 production performance of 42.1mL H2/g dry cell weight (dcw) was predicted at 0.79% (v/w) HCl and at a specific energy input (SEI) of 49,600kJ/kg dcw in the combined pretreatment, while it was limited in both individual pretreatments. Repeated batch testing of the predicted optimal conditions revealed that the combined pretreatment conditions for DFHP from microalgal biomass were successfully optimized by increasing the solubilization of the feedstock and by reducing the formation of the toxic 5-hydroxymethylfurfural (HMF). [Copyright &y& Elsevier]

Abstract: Pretreatment technology is a prerequisite to facilitate the release of sugars from a lignocellulosic biomass prior to fermentation. Recently, some pretreatment methods have been tried with ionic liquids, but they were still expensive and unpractical. In this study, an efficient pretreatment method using ammonia and ionic liquid was developed for the recovery of bio-digestible cellulose from a lignocellulosic byproduct, rice straw, and the increase of ionic liquid utilization. The combined use of ammonia and ionic liquid ([Emim]Ac) treatment exhibited a synergy effect for rice straw with 82% of the cellulose recovery and 97% of the enzymatic glucose conversion. This cooperative effect showed over 90% of the glucose conversion even with a reduced enzyme usage and incubation time. The ionic liquid was successfully recycled more than 20 times. The 20th-recycled ([Emim]Ac) showed 74% of the cellulose recovery and 78% of the glucose conversion to rice straw. Compared with the conventional pretreatment, our combined method for lignocellulosic biomass pretreatment was an economical and eco-friendly. [Copyright &y& Elsevier]

Abstract: Two novel two-step pretreatments for enzymatic hydrolysis of rice hull (RH) were proposed to lower the severity requirement of fungal pretreatment time. They consisted of a mild physical or chemical step (ultrasonic and H2O2) and a subsequent biological treatment (Pleurotus ostreatus). The combined pretreatments led to significant increases of the lignin degradation than those of one step pretreatments. After enzymatic hydrolysis of the pretreated RH, the net yields of total soluble sugar (TS) and glucose (G) increased greatly. The combined pretreatment of H2O2 (2%, 48h) and P. ostreatus (18d) was more effective than sole pretreatment of P. ostreatus for 60d. It could remarkably shorten the residence time and reduce the losses of carbohydrates. Ligninase analyses and SEM observations indicated that the enhancing of the efficiency could possibly attribute to the structure disruption of the RH during the first pretreatment step. So, the combined pretreatment could be recommended to different lignocellulosic materials for enzyme based conversions. [Copyright &y& Elsevier]

• Pretreatment is an essential step for the breakdown of lignocellulosic biomass. • Combining pretreatment helps to lower the severity of the drawbacks of a single step. • Biological-chemical/physicochemical combined pretreatment strategies were reviewed. • The order of pretreatment in the combined studies affects the overall efficiency. Sustainable biorefinery concepts based on lignocellulosic biomass are gaining worldwide research interest because of their inexpensiveness and abundance. The recalcitrance of lignocellulosic biomass poses a major hindrance to enhance biofuel production. Therefore, a pretreatment step is critical to prepare the substrates for the downstream process. Combining pretreatment steps help to lower the severity of the drawbacks of a single pretreatment step. This paper systematically reviews the combined biological and chemical/physicochemical pretreatment based on fiber degradation and sugar yield. An energy-efficient biological pretreatment method combined with a chemical pretreatment that accelerates the pretreatment times has been seen to be efficient for fiber degradation and sugar yields. However, fungal species, culture conditions, biomass type, the severity of chemical pretreatment and the order of sequential pretreatment influences the relative component contents and sugar yield. Even the same biomass from different sources undergoing similar pretreatment conditions could result in a varying amount of digestibility. [ABSTRACT FROM AUTHOR]

• In-situ lignin modification improved enzymatic hydrolysis of acid-pretreated larch. • Lignin modification with 2-naphthol suppressed lignin repolymerization. • Lignin modification with PEGDE lowered the enzyme non-productive binding on lignins. • 2-Naphthol and PEGDE modification synergistically facilitated enzymatic hydrolysis. To overcome the recalcitrance of residual lignins in acid-pretreated larch (AL), a combined acid and alkali pretreatment with in-situ lignin modification was developed in this study. The results showed that introducing in-situ lignin modification with 2-naphthol to acid pretreatment (160 and 180 oC) improved the enzymatic digestibility of AL by 12.7-14.4%, through suppressing lignin repolymerization. The obviously higher improvement (57.8-88.3%) was achieved by applying alkali post-treatment (90 oC) with poly (ethylene glycol) diglycidyl ether (PEGDE) on AL, mainly due to the function of in-situ lignin modification with PEGDE for reducing enzyme non-productive binding on lignins. More importantly, the synergism of 2-naphthol and PEGDE modification facilitated the enzymatic hydrolysis of AL more significantly. Its beneficial mechanism was explored by investigating the effects of in-situ lignin modification on lignin properties, including extraction yields, functional groups, and enzyme affinity of lignins. Results will give insights into establishing an efficient pretreatment of softwood biomass. [ABSTRACT FROM AUTHOR]

• The first report on bioethanol production from sesame plant residues. • Three combined pretreatments including physical, microbial, and chemical were done. • Kinetic modeling of pretreatment and bioethanol production process was done. • The maximum bioethanol yield was 1.90 g·L−1 in the finest (400 µm) particle size. This study explored the potential of sesame (Sesamum indicum L.) plant residue (SPR) for bioethanol production. Three particle sizes, including 400, 850 and 1300 µm of SPR, were subjected to microbial degradation by Phanerochaete chrysosporium followed by 1% H 2 SO 4 pretreatments. FTIR and HPLC analyses showed that the combined pretreatment which begins with microbial followed up by acid degraded SPR in the finest particle size (400 µm) resulted in the maximum contents of reducing sugars (370.23 mg·g−1). Kinetics studies of the pretreatment process also confirmed the maximized rate of hemicellulose and lignin reduction with reducing sugars production. The logistic model had better fitness as compared to the modified Gompertz model to predict bioethanol production. SPR gave a maximum of 1.90 g·L−1 bioethanol yield after 60 h of fermentation using Saccharomyces cerevisiae. This study is the first report on bioethanol production from SPR, which proposed its suitability for sustainable energy production. [ABSTRACT FROM AUTHOR]

• A combined pretreatment was established based on acetic acid and alkali treatment. • The combined pretreatment coproduced XOS and fermentable sugars from poplar sawdust. • Cellulose accessibility was significantly increased during the combined pretreatment. • In-situ lignin modification with PEGDE reduced the enzyme non-productive binding. A novel combined pretreatment process of poplar sawdust was established in this study based on the sequential acetic acid and alkali treatment with poly (ethylene glycol) diglycidyl ether (PEGDE). Effects of each treatment step on chemical composition, cellulose accessibility, and enzymatic digestibility of poplar sawdust was investigated. Acetic acid pretreatment remarkably increased cellulose accessibility while also producing a relatively high quantity of xylooligosaccharides (XOS) (37.6% of raw xylan). However, enzymatic digestibility remained low (28.3%) despite hemicellulose disruption. Post alkali treatment was next applied, leading to improvement on cellulose accessibility and enzymatic hydrolysis. Enzymatic hydrolysis was improved more significantly by successive alkali treatment with PEGDE. Its potential mechanisms attributable to enzymatic hydrolysis improvement were explored by revealing the changes to lignin properties. This work successfully demonstrated that recalcitrant waste woody biomass can be biorefined into both high-value XOS as well as relatively high yield of fermentable sugars. [ABSTRACT FROM AUTHOR]