Volume 8 Issue 3

Pretreatment with white-rot fungi can effectively remove lignin and decompose the structure of biomass to enhance subsequent enzymatic hydrolysis. This study developed a novel fungal pretreatment of biomass, which was operated under non-sterile conditions. The white-rot fungus Irpex lacteus colonized stably on the non-sterile substrates and effectively degraded lignin. After non-sterile fungal pretreatment for 42 days, lignin was degraded by 43.8%. The maximum saccharification efficiency was 7-fold higher after enzymatic hydrolysis compared to that of raw corn stover. Furthermore, the production of ethanol from corn stover improved. During non-sterile biological pretreatment, several microorganisms coexisted with Irpex lacteus, and the microbial community generated abundant by-products that greatly improved the efficiency of enzymatic hydrolysis. Non-sterile fungal pretreatment presents a feasible and promising technology for the production of biofuels by integrating on-farm wet storage systems. Moreover, it provides a low-cost bioconversion process and a stable, secure, and environmentally friendly energy supply.

Six alcohol-soluble hemicellulosic preparations from rice straw were comparatively studied, and their physicochemical characterizations were examined. The treatments of the dewaxed rice straw with 60% methanol, 60% ethanol, 60% n-propanol, 60% n-butanol, 60% ethanol containing 0.01 M HCl, and 60% ethanol containing 0.25 M NaOH at 75 ºC for 3 h were able to solubilize 10.4, 10.4, 6.2, 6.5, 7.4, and 55.0% of the original hemicelluloses, respectively. The results showed that methanol and ethanol had similar solubilization capacity of hemicelluloses and gave slightly higher solubility compared to n-propanol and n-butanol. The major monosaccharide of the four neutral alcohol-soluble hemicellulosic fractions was xylose (31.78-36.80%) followed by glucose (26.35-39.39%), galactose (15.05-17.17%), and arabinose (14.93-15.58%), whereas the alkaline ethanol-soluble hemicellulosic fraction contained the highest amount of xylose (59.62%). By combining 1H, 13C, and 2D-HSQC NMR with FT-IR spectroscopy, the alkaline ethanol-soluble hemicellulosic fraction can be structurally defined as 4-O-methyl-α-D-glucurono-L-arabino-D-xylans.

In the present work, a type of PU film was made from peroxy-acid-derived wheat straw lignin by reacting varying amounts of lignin ranging from 10 to 50 wt% (with respect to PEG), polyethylene glycol (Mn = 1000), and tolylene 2,4-diisocyanate without catalyst. The effects of lignin content on the tensile property and thermostability of the lignin polyurethane films obtained were investigated. The thermal conductivity of lignin polyurethane films was also studied. Results showed that when the lignin content increased, the glass transition temperature (Tg) and tensile strength of the lignin polyurethane film increased, but the onset decomposition temperature and elongation at break decreased. When the lignin content was 40 wt%, the lignin polyurethane film had the best overall properties. In addition, compared with PU films, lignin PU films showed better heat-insulating properties.

Response surface methodology (RSM) was used to optimize the co-production of a mixture of crude cellulosic and hemicellulosic enzymes (endoglucanase, xylanase, and mannanase) by Aspergillus terreus K1 in solid-state fermentation (SSF) using palm kernel expeller (PKE) as the sole carbon source. These enzymes have gained renewed interest due to their efficacy to improve the digestibility of PKE for use in diets of mono-gastric animals (poultry, pigs, and fish). The results showed that temperature, moisture, inoculum concentration, and initial pH had significant (P< 0.05) effects on the enzymes production. Using PKE as a solid substrate, maximum endoglucanase, mannanase, and xylanase (17.37, 41.24, and 265.57 U/g DM, respectively) were obtained at 30.5 °C, 62.7% moisture, 6% inoculum, and pH 5.8. The enzyme activities recorded were close to the predicted values (19.97, 44.12, and 262.01 U/g DM, respectively).

In this study, the in-plane shear modulus of 3-, 5-, and 7-ply lauan wood (Shorea sp.) was measured by conducting an asymmetric four-point bending (AFPB) test with various specimen depth/length ratios and subsequently performing a flexural vibration (FV) test and finite element analysis (FEA). The results obtained from the experiment and the FEA revealed that the in-plane shear modulus was dependent on the depth/length ratio of the specimen. The dependence of the in-plane shear modulus obtained from the AFPB test was more significant than that obtained from the FV test. Additionally, the in-plane shear modulus values obtained from the AFPB test varied more significantly than those obtained from the FV test. In determining the in-plane shear modulus of plywood, the FV test was therefore superior to the AFPB test.

Carex meyeriana Kunth was subjected to biological pretreatment with the white-rot fungus Trametes hirsuta C7784, and the structural changes of the lignin were investigated. Results showed that there was a slight decrease in carbohydrate content after pretreatment for 3 weeks, but a noticeable decrease in lignin and carbohydrate contents after 6 weeks. Detail structural analysis of the isolated lignin from the samples revealed that Carex meyeriana Kunthlignin consisted mainly of p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) units with minor p-coumarate and ferulate units. The predominant lignin interunits were β–O-4´ ether linkages, followed by phenylcoumaran, together with a lower portion of resinol and tricin substructures. After pretreatment for 6 weeks, the contents of β–β´ and β-5´ linkages notably decreased, suggesting that the fungus preferentially attacked these linkages. The pretreatment led to an increase of S/G ratio from 0.64 in the control to 0.83 in the sample pretreated for 6 weeks. The comprehensive understanding of the structural changes of lignin offers new insights into the biological degradation of Carex meyeriana Kunth by white-rot fungus.

The interactions between colloidal wood pitch and various commercially available mineral particles were assessed. The experiments were conducted by adding PCC, GCC, kaolin, and bentonite particles to laboratory-made pitch emulsions, and the mixtures were analyzed using flow cytometry. The results showed that most of the tested minerals were quite hydrophilic. The hydrophobicity of the mineral particles increased significantly in the presence of colloidal pitch, which showed that interactions between the pitch and the mineral surfaces occurred. The charge of the mineral particles was very important; the pitch–mineral populations formed with cationic minerals were more hydrophobic than those formed with anionic minerals. Water-soluble galactoglucomannans from spruce diminished the adsorption of pitch onto cationic minerals, while they had no significant effect on the adsorption of pitch onto anionic minerals.

Maleic anhydride-acylated chitosan (MAAC) was prepared and employed to improve the wet strength of handsheets. UV-Vis spectroscopy, elemental analysis, and chemical titration methods were used to analyze the resultant MAAC. Pretreatment and curing conditions were investigated when MAAC was used to improve the wet strength of handsheets. The results revealed that the wet strength performance was highest at a pretreatment pH of 6 and that the wet strength index and the ratio of wet to dry strength increased with increasing pretreatment temperature and MAAC dose. A higher curing temperature was beneficial and improved the wet strength performance of paper. Polyamideamine-epichlorohydrin (PAE) resin performed better than MAAC with varied soaking durations. However, MAAC also reached about 80% of the wet strength of PAE and showed its potential as an alternative to PAE.

The objective of this study was to develop an effective method for the removal of inhibitory compounds without decreasing oligosaccharides in spent sulfite liquor (SSL). The oligosaccharide fermentation was subsequently conducted by using Pichia stipitis, which is one of the feasible strains that can produce ethanol from oligosaccharides. The effect of inhibitory compounds on ethanol fermentation from cellobiose by P. stipitis was investigated. No ethanol was produced from cellobiose in the presence of more than 5 g/L of acetic acid. At 1 g/L of acetic acid, 2.6 g/L of ethanol was obtained after 40 h of fermentation. The removal of acetic acid in the SSL by the combined CaO and ion exchange resin treatments was also studied. The acetic acid concentration of softwood SSL was decreased from 5.2 to 0.9 g/L without decreasing oligosaccharides concentration by the combined method. Finally, the improvement of ethanol fermentation from oligosaccharides in the SSL by using the combined CaO and ion exchange resin treatments was studied. 1.3 g/L of ethanol was obtained from the SSL treated by the combined methods, while 6.5 g/L of total oligosaccharides were consumed. No ethanol was obtained from the untreated SSL.

In this work, fresh poplar logs were chemically impregnated with a pulse-dipping machine. The impregnated timbers were compressed and dried by use of a multilayer hot-press drying kiln. With a compression rate of 28.67%, such an approach not only enhanced the density and mechanical properties of the treated wood, but also influenced the set recovery from the compressive deformation. Extra urea was added into the modifier to optimize the effect of the set recovery; however the result was a slight decrease in the mechanical properties. The positions of the X-ray diffraction (XRD) peaks did not change, which indicated that the structure of the cellulose was not noticeably affected by this treatment. The Fourier transform infrared spectroscopy (FT-IR) analysis showed that the intensity amide (N–C=O) absorption peak increased significantly due to the chemical impregnation. Scanning electron microscopy (SEM) showed that the high strain in the hot-press process drastically reduced the volume of void spaces in the specimens and deformed the cell lumens.