Volume 14 Issue 1

The presence of lignin sheaths and the crystalline structure of cellulose are two key barriers in the development of corn stover (CS). To remove these two barriers and improve the digestibility of carbohydrates in CS, CS (pretreated by H2O2, H2SO4, NaOH, an enzyme, steam explosion [SE], and SE combined with NaOH [SE-NaOH]) was hydrolyzed. The total reducing sugar yield (Ytrs), accessibility of the enzyme to the substrate (Kobs,0), and gradual loss of the enzyme activity (Ki) were compared by regression analysis of the kinetic model, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. The pretreatment dramatically increased the Ytrs and Kobs,0, and remarkably decreased the Ki. The maximum increase in the Ytrs (106.57%) was obtained after the saccharification reaction of the CS pretreated by SE-NaOH. Physicochemical characterizations of the CS pretreated by SE-NaOH showed that the SE-NaOH pretreatment effectively reduced the lignin sheath, decreased cellulose crystallization, and created favorable conditions for enzymatic diffusion and penetration.

High-intensity microwave radiation was applied to treat and modify larch wood. Using scanning electron microscopy, changes in the microstructure of larch wood due to microwave irradiation were analyzed. After the microwave treatment, the microstructure of the larch wood was varied in its weakest section. The changes of the microstructure, in the pits of the tracheid wall, the plane of the tracheid wall, and the wood ray tissue of the radial section, were notable. The cracks were located among the latewood tracheid, and some of them were throughout the wood ray section, so wood rays were broken along the vertical cell arrangement. The results showed that high-intensity microwave treatment effectively penetrates the narrow channels of larch wood.

Fast pyrolysis is an important technology in biological waste disposal. It can produce fuels (bio-gas and bio-oil) and high-value chemicals. In this paper, camphor wood powder was subjected to fast pyrolysis, and the influence of the pyrolysis and torrefaction pretreatment temperature on the pyrolysis product distribution was investigated. The results showed that camphor wood powder produced higher phenol, 2-methoxy, 2-methoxy-4-vinyl-phenol, and 1, 2, 4-trimethoxybenzene compared with corn straw, rice husk, and wheat straw. The temperature of torrefaction pretreatment and fast pyrolysis simultaneously affected the yield of bio-oil and the composition of the pyrolysis product. The yield of bio-oil was the highest at 500 °C. Additionally, the yield of different high-value chemicals was the highest at 500 °C. When the camphor wood powder was pretreated under conditions of torrefaction, the yield of 3-furfural decreased and that of phenol, 2-methoxy, 2-methoxy-4-vinyl-phenol, 2-furancarboxaldehyde, 5-hydroxymethylfurfural, and 1, 2, 4-trimethoxybenzene increased, especially phenol, 2-methoxy, and 1, 2, 4-trimethoxybenzene. The yields of bio-oil and high-value chemicals were the highest at 500 °C of catalytic pyrolysis and at 300 °C of torrefaction treatment during the fast pyrolysis of camphor wood powder.

Diverse renewable resources, especially those obtained from residual agricultural wastes, are being exploited to reduce the impact of environmental damage. This study presents a method to produce purified cellulose extracted from locally planted pineapple leaves (Ananas comosus). The cellulose was extracted by maceration pretreatment. The heating times were varied. This method is a simpler and more effective approach to delignify the pineapple leaf fibers compared with conventional chemical pulping and bleaching processes. The chemical composition of the cellulose was investigated according to TAPPI standards and by structural analyses, namely Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). The results indicated that the hemicellulose and lignin were partially removed from the cellulose. Chemical analysis confirmed that the cellulose content increased from 25.8% (pineapple leaf fibers) to 70.9% (macerated cellulose). The optimum heating time was 3 h. However, XRD showed that the extracted cellulose had a higher crystallinity index than the initial pineapple leaf fibers. These results indicated that pretreatment via maceration has good potential applications in the production of macerated cellulose.

To realize resource technology from fruit and vegetable waste, a Plackett-Burman (P-B) experiment combined with an orthogonal experimental design were adopted for the optimization of ethanol fermentation from this waste. By using the 12-factor P-B design, it was determined that the significant factors were KH2PO4, cellulase, and yeast extract. The orthogonal experimental design with the ethanol fermentation and reducing sugar as indices showed that the optimum conditions were KH2PO4, cellulase, and yeast extract concentrations of 0.3 g/L, 90 U/mL, and 10 g/L, respectively. Ethanol fermentation from fruit and vegetable waste has provided a feasible application for this waste.

A biocomposite film from bacterial polyester, poly(3- hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), and natural cellulose was developed by the solution casting method. The structure, the mechanical, thermal, and barrier properties (oxygen and water vapor), and the biodegradation of the PHBH/cellulose biocomposite films were studied. With an increase in cellulose content, the tensile strength of biocomposite films increased from 28.5 MPa to 45.9 MPa, an improvement of 351% compared with neat PHBH. The PHBH/cellulose biocomposite films exhibited improved thermal stability, with the maximum thermal decomposition temperature increased from 264 °C to 330 °C. More importantly, PHBH/cellulose biocomposite films possessed better barrier properties against oxygen, up to approximately 10 times more than neat PHBH. With cellulose content increased from 50 wt% to 90 wt%, the mass loss of composite films increased gradually and then decreased. This high performance biocomposite has potential to expand the use of cellulose from renewable bioresources and the practical application of PHBH-based biodegradable plastics instead of traditional petrochemical materials in the packaging field.

Wood-plastic composites (WPCs) have been widely used as exterior construction materials. The effect of alkali-treated (with NaOH concentrations of 1%, 3%, 5%, and 7%) eucalyptus fiber on the three-body abrasion behaviors of eucalyptus/polyvinyl chloride (PVC) composites was investigated. The results showed that the eucalyptus fiber treated with NaOH had a higher crystallinity and improved hardness and impact strength. The wear loss and rate of alkali-treated eucalyptus/PVC composites was noticeably decreased compared to the natural eucalyptus fiber. The scanning electron microscopy (SEM) examination on the worn surfaces revealed that the main wear mechanism of the eucalyptus/PVC composites was a combination of microcutting and microindentations.

The pore structure of the coating layer is one of the most important factors in determining the printability of coated papers. The coating pigment and binder are two principal components in paper coating, and their characteristics have a critical influence on the coating structure. The glass transition temperature (Tg) of latex binders affects the mechanical strength and pore structure of the pigment coating layer because the latex Tg influences the binding ability of latex and the shrinkage of the coating layer during the drying process. In this study, styrene-acrylate (S/A) core-shell structure latexes with different monomer compositions in the core and shell layers were designed, and their properties were compared with those of a conventional latex. These core-shell latexes were prepared using the same monomers in the same proportion and were used to investigate the effect of the core-shell structure on the structural and mechanical properties of the coating layer. The hard-shell latex with a high styrene content in the shell part yielded paper that was glossier and less rough and formed finer pores, resulting in an increased ink absorption rate into the coated paper compared to the other types of latex. The hard-shell structure showed better performance in printing uniformity and had less mottling.

This study aimed to develop a facile synthesis process of porous starch wall materials from purple sweet potato (PSP) for microencapsulation via enzymatic treatment. The optimum extraction conditions of purple sweet potato starch (PSP-S) were first attained by an orthogonal experiment. Response surface methodology was performed through the enzymatic hydrolysis of PSP-S using an α-amylase and glucoamylase complex to optimize the process parameters for the production of porous starch. Optimal reaction conditions were: the mass ratio (w/w) of glucoamylase to α-amylase of 6.39, amount of substrate of 19.5 g, and amount of enzymes of 0.53%. The surface morphology, microstructure, and thermal stability of the obtained samples were characterized with scanning electron microscopy, Fourier-transform infrared, and thermogravimetric analyses, respectively. The purple sweet potato porous starch (PSP-PS) had a stable oil adsorption capacity, and the molecular structure and thermal stability of porous starch were not substantially different from those of native starch. This study offers a simple yet efficient approach to produce fully biodegradable food-based porous materials for potential applications in oil microencapsulation.

Enzymatic/mild acidolysis lignin was extracted from both unbleached and bleached eucalyptus pulp, and the difference in lignin structures was analyzed by nuclear magnetic resonance spectroscopy. The unbleached pulp lignin was chlorinated with chlorine dioxide, and the mechanism of adsorbable organic halide (AOX) formation was investigated. Chlorinated reaction products were detected by gas chromatography-mass spectrometry. There is a possibility of producing three different chlorobenzene or chlorophenol products from S/S lignin dimers that are connected with β-O-4 bonds. Based on quantum chemistry theory, three reaction pathways were investigated using molecular simulation techniques. The results showed that pathway 1 possessed the lowest reaction activation energy, which made it the most favored thermodynamically. The β-O-4 bond of the lignin dimer was cleaved. Following that scission, 2-chloro-3,5-dimethoxy-methyl benzene was the most likely product to be generated from the chlorination reaction of the syringyl unit. These results provide theoretical guidance for further reduction of AOX in chlorine dioxide bleaching.