Research Articles

It is well known that enzymatic hydrolysis is hampered by soluble inhibitors, while lignosulfonate (LS) generated from the sulfite pretreatment could enhance saccharification under certain conditions. To explain the roles of the LS during the hydrolyzing process, two types of LS were tested on selected lignocellulosic substrates and investigated through surface activity analysis and designed hydrolyzing experiments. The results showed that the LS with higher surface activity bound to and saturated the enzyme at a lower dosage and more effectively influenced the enzymatic hydrolysis. Both lignosulfonates, irrespective of their molecular weight and sulfonation degree, inhibited or enhanced the enzymatic saccharification related to two opposing mechanisms, i.e., competitive inhibition by the LS and its beneficial role on the enzyme activity. According to the Michaelis-Menten equation, the rate of cellulase-substrate complex conversion into product did not change with the introduction of the LS, whereas the specific binding affinity of the enzyme to the substrate was noticeably altered. With the introduction of LS, the stability of the enzyme increased, which increased the final hydrolysis yield. The hypothesis that the inhibition effects of LS could be effectively overcome by increasing the substrate content and the buffer concentration of the hydrolysates was confirmed through additional experiments.

A long-acting and slow-release material for chlorine dioxide, based on bagasse pulp (BP) was prepared with a superabsorbent resin as the slow-release substrate and agar as the cross-linking agent. The stable ClO2 solution and the acidic activator were locked into the network structure of the superabsorbent resin, which was prepared with a carboxymethyl cellulose made from bagasse pulp. Because of the network structure of the resin, the diffusion resistance was greatly increased, and the effective release time was up to 2 months. The mechanism for the release process of the ClO2 was explored, and a kinetic model was established based on modified Fick’s diffusion law. The results showed that the release process was a diffusion-controlled process. When compared with a zero-order kinetic model and a Higuchi model, the new established model had better fitting results, and it more fully reflected the release patterns and characteristics of the ClO2.

Corncob, a renewable biomass waste, has been successfully explored as a low-cost crude carbon source to prepare controlled morphology, and result in higher value-added carbons through a ZnCl2/NaCl treatment and direct pyrolysis process. The synthesis route is simple, green, and results in carbons with different morphology and porous structures by varying the ratio of the eutectic salt ZnCl2/NaCl. Moreover, the adsorption capacities of different carbon materials for formaldehyde and butyraldehyde were tested further. It was demonstrated that NaCl and ZnCl2 could be utilized as a mesopore template, and as a micropore activation agent for carbon materials, respectively. Although the mesopores can provide a fast diffusion channel, and the micropores can enhance adsorption ability, the specific surface area originating from the mesopores was proportional to the amount of butyraldehyde adsorption, and the specific surface area of the micropores was beneficial to the amount of formaldehyde adsorption taking place. The adsorption isotherms follow Langmuir and pseudo first-order kinetic modeling. Additionally, the whole process belongs to physical adsorption.

Foam-filled two-dimensional lattice structures were designed, and their compression performance was studied relative to corresponding structures without the foam. The experimental results showed that the compressive load of foam-filled lattice structures improved greatly compared with foam-unfilled specimens. The specific energy absorption (SEA) of foam-unfilled specimens exceeded that of the corresponding foam-filled lattice structure. The maximum energy absorption efficiency of the foam-unfilled lattice structure exceeded 1.5, while that of the foam-filled lattice structure was less than 1. The theoretically predicted compression performance was close to the experimental results. The wood-based lattice structure exhibited excellent specific strength and stiffness compared with other structures.

The unregulated release of titanium dioxide nanoparticles into the environment has raised concern, in particular due to the impact of the nanoparticles on indigenous micro-biome in our ecosystem. This paper reports a study on antifungal activity of titanium dioxide nanoparticles on a healthy growing fungi species, Candida albicans, a known opportunistic pathogen. A quantification of the total cell death was performed using a direct staining method, Trypan blue exclusion assay. Exposure to nanoparticles not only altered the growth rate, but also affected the onset and length of Candida albicans growth phases. The log and the onset of the death phase were shortened and accelerated, respectively. Up to 65% of the Candida albicans were killed after exposure to 100 μg/mL of the anatase titanium dioxide nanoparticles, while only 33% were killed with rutile. A higher dosage and incubation time of the nanoparticles increased their toxicity. Cells suffered from morphological changes upon the nanoparticle exposure, which correlates well with the results showing an altered growth phase culture.

Enzymatic degradation products of lignin, having potential for added value, were obtained by extraction and subsequent enzymatic treatments of oil palm empty fruit bunch (OPEFB). The objective was to optimize the production of OPEFB lignin degradation products and study the effects of different enzymes and reaction media. Powder of OPEFB lignin was recovered from organsolv black liquor by using methanol, acidified water, and deionized water, respectively. OPEFB lignin was later subjected to enzymatic hydrolysis in an incubator shaker for 24 h using laccase and cutinase in various reaction media, including phenol, water, and acetate buffer. Nine compounds were recovered as OPEFB lignin degradation products, namely hydroxybenzoic acid, hydroxybenzaldehyde, vanillic acid, vanillin, syringic acid, syringaldehyde, coumaric acid, ferulic acid, and guaiacyl alcohol. When laccase was used in water, the product with the highest concentration was syringaldehyde (4061.1 ± 89.9 mg/L), and followed by hydroxybenzoic acid (1029.8 ± 50.2 mg/L). Vanillic acid was the product with the highest concentration (126 ± 97.5 g/L) found when laccase was used in phenol. When cutinase was used in water, products with the highest concentrations in the medium were syringaldehyde (4837.6 ± 156.4 mg/L) and syringic acid (2387.7 ± 105.3 mg/L). High performance liquid chromatography (HPLC) was used to quantify the OPEFB lignin degradation products.

The pulping of birch wood using dilute aqueous nitric acid solution under atmospheric pressure was studied. The pulping conditions, delignification reaction course, and waste-liquid recovery were studied in detail. The optimum cooking conditions were 9.2% nitric acid for 4.3 h at 85 °C. The pulp yield at these conditions was 51.1%, the lignin content was 5.1%, and the brightness was 50%. The delignification course during the pulping involved two phases, namely, bulk and residual phases. The bulk phase was 0 to 1.5 h long, and the delignification level was 92.6% of the total dissolved lignin. The residual phase was 1.5 h to 4.5 h long, and the delignification level reached about 7.4% of the total dissolved lignin. The waste liquid could no longer be used after six rounds of recycling. The contents of nitrogen and organic matter in the organic fertilizer prepared using the final-round of recycled waste liquid were in line with the indicators for the preparation of organic fertilizer.

In order to detect the size and shape of defects inside wood, a propagation velocity model of stress wave in the longitudinal section of trees in different direction angles was proposed and evaluated. The propagation velocity model was established through theoretical analysis. Four representative tree species in the northeast region of China were taken as test samples. The propagation velocity of stress wave in the longitudinal section of trees in different directions was measured using a nondestructive testing instrument. The corresponding regression model was obtained, which was in good agreement with the theoretical mathematical model. For the larch log samples, a healthy multiple regression model (z = 109.2×2 – 182.1y2 + 36.78x2y2 – 34.76x2y4 + 1627) with correlation coefficient R2 = 0.97 and root mean square error RMSE =17.81 was used to conduct two-dimensional imaging of defective logs. Based on the results of two-dimensional imaging, the highest fitness of the images was 94.24%, and the lowest error rates of defect cavities was 6.11%. The imaging results showed that this method accurately detected the internal defects of trees and was not affected by the size of defects.

Sodium carboxymethyl cellulose (CMC) is a major cellulosic derivative that has a wide variety of applications. The solubility of CMC is affected by the degree of substitution (DS) of carboxymethyl groups and their distribution along the CMC molecular chain. In this study, an enzymatic hydrolysis technique was used to determine the distribution of carboxymethyl substituents. Two key parameters, namely the average length of the molecular chain segments not susceptible to enzymatic hydrolysis by cellulases (L ̅Sn, including chains fully substituted or containing single unsubstituted unit) and the average length for the molecular chain segments susceptible to enzymatic hydrolysis (L ̅Gn, unsubstituted chains segments), were obtained. This approach was subsequently applied to characterize four CMC samples having similar DS values (~0.80). The distributions of carboxymethyl substituents along the CMC molecular chain were found to be drastically different. The L ̅Sn varied from 9.6 to 49.5, while the L ̅Gn was almost constant (from 4.5 to 5.4). This information was correlated to the CMC solubility. The swelling ratio and the dynamic contact angle revealed that the CMC samples with higher L ̅Sn exhibited stronger swelling and wettability than those with lower L ̅Sn. The dissolving time of the CMC molecule decreased substantially with the increase in L ̅Sn.

The effect of nanofibrillated cellulose (NFC) was investigated relative to the strength of chemi-mechanical pulp (CMP) and paper. The NFC was added at five levels: 0%, 2%, 4%, 6%, and 8%. Handsheets with a basis weight of 60 g/m2 were prepared, and the physical properties (air resistance and surface roughness), the mechanical properties (tensile strength, burst strength, and tear strength), and the optical properties (brightness, opacity, and yellowness) were measured according to TAPPI standards. By increasing the NFC content, the tensile strength, burst strength, air resistance, brightness, and whiteness increased by 10.9%, 12.5%, 23.6%, 0.6%, 3.5%, and 6.8%, respectively, compared to the control (0% NFC) samples. By increasing the NFC content, the tear strength, roughness, and opacity decreased by 10.4%, 11.1%, and 0.6% compared to the control samples.