Enhanced Saccharification of Purple Alfalfa via Sequential Pretreatment with Acidified Ethylene Glycol and Urea/NaOH

Purple Alfalfa is an inexpensive, abundant, readily available lignocellulosic material. This work was attempted to develop an efficient combination pretreatment by sequential HClO4–ethyl glycol–H2O (1.2:88.8:10, w/w/w) extraction at 130 °C in 0.5 h and urea/NaOH (urea 12 wt%, NaOH 7 wt%) soaking at −20 °C for 0.5 h for the pretreatment of purple alfalfa. The porosity, morphology, and crystallinity of pretreated purple alfalfa were characterized with SEM, FM, XRD, and FTIR. This combination pretreatment had a significant influence on hemicellulose removal and delignification. The above changes could enhance cellulose accessibility to enzymes and improve the enzymatic digestibility of cellulose. High yields of reducing sugars from pretreated purple alfalfa were obtained at 93.4%. In summary, this combination pretreatment has high potential application in the future.

Techno-economic analysis of recombinant Endo-β-1,4-Glucanase production from Escherichia coli Eg-RK2 culture using oil palm empty fruit bunch

A techno-economic analysis of recombinant cellulase production from E. coli Eg-RK2 was conducted to support the fulfilling of Indonesia’s energy roadmap for ethanol production. The plant utilizes OPEFB as a primary substrate in cellulase production, with an expected lifetime of 12 years. The plant is assumed to be built in Indonesia and it will fulfill 1% of the total market demand. The effect of different pretreatment processes (alkaline, steam explosion, and sequential acid-alkaline) on the profitability parameter was also studied. A simulation using SuperPro Designer was used to calculate the mass and energy balance based on the kinetic parameters of E. coli EgRK2. A technology evaluation showed that alkaline pretreatment provides the highest yield with no known inhibitors formed. The steam explosion pretreatment offers the lowest rate of lignin and hemicellulose removal, and it is understood to form known fermentation inhibitors. The NPVs of the alkaline, steam explosion and sequential acid-alkaline pretreatments are USD 32,121,000, USD -36,841,000, and USD 384,000, respectively, which means the alkaline pretreatment is economically very feasible for the production of cellulase.

Characterization of Microstructure, Chemical, and Physical Properties of Delignified and Densified Poplar Wood

Wood is an attractive and inherently sustainable alternative to many conventional materials. Recent research on improving wood mechanical strength emphasizes wood densification through the partial removal of lignin and hemicelluloses, therefore the chemical and physical properties of delignified and densified wood require further investigation. In this study, poplar wood samples were subjected to alkali and maleic acid hydrotropic delignification with varying degrees of lignin and hemicellulose removal followed by hot pressing, and the microstructure, chemical properties, and dimensional stability of densified wood through delignification were evaluated. The results showed that the complete wood cell collapse was observed near the surface of all the delignified wood blocks, as well as some micro-cracks in the cell walls. The chemical analysis indicated that delignification occurred mainly near the surface of the wood blocks and enhanced hydrogen bonding among the aligned cellulose fibers. For dimensional stability, the set recovery decreased with the increase in alkali dosage, and the considerable fixation of compressive deformation was obtained by a post-densification hydrothermal treatment at 180 °C. These results have demonstrated that the densified wood with delignification can be easily fabricated using the proposed method, and the densified wood exhibited great potential to be used as a sustainable material.

Biological pretreatment of corn stover for enhancing enzymatic hydrolysis using Bacillus sp. P3

The biological pretreatment for the enzymatic hydrolysis of lignocellulosic biomasses depends exclusively on the effective pretreatment process. Herein, we report a significant enhancement of enzymatic saccharification obtained with corn stover using a bacterial strain Bacillus sp. P3. The hemicellulose removal from corn stover by the strain Bacillus sp. P3 was evaluated for enhancing subsequent enzymatic hydrolysis. Therefore, our study revealed that an alkaline-resistant xylanase as well as other enzymes produced by Bacillus sp. P3 in fermentation broth led to a substantially enhanced hemicellulose removal rate from corn stover within pH 9.36–9.68. However, after a 20-day pretreatment of corn stover by the strain P3, the glucan content was increased by 51% and the xylan content was decreased by 35%. After 72 h of saccharification using 20 U/g of commercial cellulase, the yield of reducing sugar released from 20-day pretreated corn stover was increased by 56% in comparison to the untreated corn stover. Therefore, the use of the strain P3 could be a promising approach to pretreat corn stover for enhancing the enzymatic hydrolysis process of industrial bioenergy productions.

Mechanical and Structural Characterization of Pineapple Leaf Fiber

Evidence-based research had shown that elevated alkali treatment of pineapple leaf fiber (PALF) compromised the mechanical properties of the fiber. In this work, PALF was subjected to differential alkali concentrations: 1, 3, 6, and 9% wt/wt to study the influence on the mechanical and crystal properties of the fiber. The crystalline and mechanical properties of untreated and alkali-treated PALF samples were investigated by X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and tensile testing analysis. The XRD results indicated that crystal properties of the fibers were modified with 6% wt/wt alkali-treated PALF recording the highest crystallinity and crystallite size of 76% and 24 nm, respectively. The FTIR spectra suggested that all alkali-treated PALF samples underwent lignin and hemicellulose removal to varying degrees. An increase in the crystalline properties improved the mechanical properties of the PALF treated with alkali at 6% wt/wt, which has the highest tensile strength (1620 MPa). Although the elevated alkali treatment resulted in decreased mechanical properties of PALF, crystallinity generally increased. The findings revealed that the mechanical properties of PALF not only improve with increasing crystallinity and crystallite size, but are also dependent on the intermediate bond between adjacent cellulose chains.

Biological Pretreatment of Corn Stover for Enhancing Enzymatic Hydrolysis Using Thermoalkalotolerant Cellulolytic Enzymes Produced by Bacillus sp. P3

The biological pretreatment for the enzymatic hydrolysis of lignocellulosic biomasses largely depends on an effective pretreatment process. A significant enhancement of enzymatic saccharification was obtained with corn stover using Bacillus sp. P3. The hemicellulose removal from corn stover by the strain Bacillus sp. P3 was evaluated for enhancing subsequent enzymatic hydrolysis. Therefore, our study revealed that an alkaline resistant xylanase produced by Bacillus sp. P3 in fermentation broth led to a substantially enhanced hemicellulose removal rate from corn stover within pH 9.36–9.68. However, after 20 d pretreatment of corn stover by the strain P3, the glucan content was increased by 51% and the xylan content was decreased by 35%. After 72 h of saccharification using 20 U g− 1 of commercial cellulase, the yield of reducing sugar released from 20 d pretreated corn stover was increased by 56% in comparison to the untreated corn stover. Therefore, the use of the strain P3 could be a promising approach to pretreat corn stover for enhancing the enzymatic hydrolysis process of industrial bioenergy productions.

Enhanced Enzymatic Saccharification of Mixed Sawdust Wastes: Comparison of SPORL, Dilute Acid, Formic Acid, and Ethanol Organosolv Pretreatments

Utilization of the huge quantity of sawdust wastes is urgent. In this study, SPORL, dilute acid pretreatment (DA), formic acid pretreatment (FA), ethanol pretreatment (EtOH/H2O), and sulfuric acid catalyzed ethanol pretreatment (EtOH/H2O/H2SO4), on improving enzymatic hydrolysis of mixed sawdust wastes were comprehensively compared. EtOH/H2O/H2SO4 was the most effective pretreatment in lignin removal from sawdust fiber cell wall, while FA was much more effective in hemicellulose removal. After the pretreatments, the crystallinity of cellulose increased because of the removal of amorphous hemicellulose and lignin. Moreover, the fiber surface became coarse and porous, especially after EtOH/H2O/H2SO4, the structure was destroyed into fragments, which enhanced the cellulase accessibility of cellulose. Therefore, the glucose yield of EtOH/H2O/H2SO4 pretreated substrate was highest among these five pretreatments, achieved at 91.4% with a cellulase loading of only 10 FPU/g glucan. Resumen. Es urgente aprovechar la gran cantidad de residuos de aserrín. En este estudio, SPORL, pretratamiento con ácido diluido (DA), pretratamiento con ácido fórmico (FA), pretratamiento con etanol (EtOH/H2O) y pretratamiento con etanol catalizado con ácido sulfúrico (EtOH/H2O/H2SO4), sobre la mejora de la hidrólisis enzimática de residuos de aserrín mezclado fueron comparados de manera integral. EtOH/H2O/H2SO4 fue el pretratamiento más eficaz para eliminar la lignina de la pared celular de la fibra de aserrín, mientras que el FA fue mucho más eficaz para eliminar la hemicelulosa. Después de los pretratamientos, la cristalinidad de la celulosa aumentó debido a la eliminación de hemicelulosa amorfa y lignina. Además, la superficie de la fibra se volvió gruesa y porosa, especialmente después de EtOH/H2O/H2SO4, la estructura se destruyó en fragmentos, lo que mejoró la accesibilidad de celulasa de la celulosa. Por lo tanto, el rendimiento de glucosa del sustrato pretratado con EtOH/H2O/H2SO4 fue el más alto entre estos cinco pretratamientos, alcanzado al 91,4% con una carga de celulasa de solo 10 FPU / g de glucano.

Effect of drying on the hydroxyl accessibility and sorption properties of pressurized hot water extracted wood

Hot water extraction (HWE) treatment changes the physicochemical properties of the wood, including hygroscopic properties. HWE treatment decreases the hydroxyl accessibility of the wood, but the relevance of other mechanisms that change hygroscopic properties are not fully understood. This study investigates the effect of drying on the hydroxyl accessibility and sorption properties of wood. Pressurized hot water extraction (HWE) treatment was applied at 140 °C for 1–5 h to Scots pine (Pinus sylvestris L.) sapwood samples in order to remove increasingly more hemicellulose from the cell wall matrix. Following HWE treatment, half of the wood samples were oven-dried and then re-soaked, while the other half was kept in a fully saturated state. The samples were investigated by applying a new approach that was based on the deuteration of accessible hydroxyl groups, which was followed by the measurement of mass loss due to re-protonation. Sorption properties of the wood samples were studied by measuring moisture content, sorption isotherms and dimensional changes. The present results showed that accessible hydroxyl group content decreased only due to hemicellulose removal during the HWE treatment and was unaffected by oven-drying. However, oven-drying enhanced the effect of HWE treatments in reducing the water-saturated dimensions and the moisture content of wood. Therefore, the additional reductions in hygroscopicity and water-saturated dimensions were not related to changes in sorption site density.

Performance Evaluation of Cellulose Nanofiber with Residual Hemicellulose as a Nanofiller in Polypropylene-Based Nanocomposite

Residual hemicellulose could enhance cellulose nanofiber (CNF) processing as it impedes the agglomeration of the nanocellulose fibrils and contributes to complete nanofibrillation within a shorter period of time. Its effect on CNF performance as a reinforcement material is unclear, and hence this study seeks to evaluate the performance of CNF in the presence of amorphous hemicellulose as a reinforcement material in a polypropylene (PP) nanocomposite. Two types of CNF were prepared: SHS-CNF, which contained about 11% hemicellulose, and KOH-CNF, with complete hemicellulose removal. Mechanical properties of the PP/SHS-CNF and PP/KOH-CNF showed an almost similar increment in tensile strength (31% and 32%) and flexural strength (28% and 29%) when 3 wt.% of CNF was incorporated in PP, indicating that hemicellulose in SHS-CNF did not affect the mechanical properties of the PP nanocomposite. The crystallinity of both PP/SHS-CNF and PP/KOH-CNF nanocomposites showed an almost similar value at 55–56%. A slight decrement in thermal stability was seen, whereby the decomposition temperature at 10% weight loss (Td10%) of PP/SHS-CNF was 6 °C lower at 381 °C compared to 387 °C for PP/KOH-CNF, which can be explained by the degradation of thermally unstable hemicellulose. The results from this study showed that the presence of some portion of hemicellulose in CNF did not affect the CNF properties, suggesting that complete hemicellulose removal may not be necessary for the preparation of CNF to be used as a reinforcement material in nanocomposites. This will lead to less harsh pretreatment for CNF preparation and, hence, a more sustainable nanocomposite can be produced.

Rendering Banana Plant Residues into a Potentially Commercial Byproduct by Doping Cellulose Films with Phenolic Compounds

This study seeks to render residues from banana plants into a useful byproduct with possible applications in wound dressings and food packaging. Films based on cellulose extracted from banana plant pseudostem and doped with phenolic compounds extracted from banana plant leaves were developed. The phenolic compounds were extracted using batch solid-liquid and Soxhlet methods, with different drying temperatures and periods of time. The total phenolic content and antioxidant activity were quantified. The optimum values were obtained using a three-day period batch-solid extraction at 40 °C (791.74 ± 43.75 mg/L). SEM analysis indicates that the pseudostem (PS) films have a porous structure, as opposed to hydroxyethyl cellulose (HEC) films which presented a homogeneous and dense surface. Mechanical properties confirmed the poor robustness of PS films. By contrast HEC films manifested improved tensile strength at low levels of water activity. FTIR spectroscopy reinforced the need to improve the cellulose extraction process, the success of lignin and hemicellulose removal, and the presence of phenolic compounds. XRD, TGA and contact angle analysis showed similar results for both films, with an amorphous structure, thermal stability and hydrophilic behavior.