Volume 11 Issue 4

Sequential solid-state and submerged cultivation with various lignocellulosic biomasses as a substrate for lignocellulolytic enzyme production by Pleurotus ostreatus were assessed by measuring endoglucanase, xylanase, and laccase activities. An unconventional pre-culture method was established by cultivating the P. ostreatus mycelia in a solid substrate medium for an initial fungal growth phase, followed by a transition to submerged fermentation through adding a liquid culture medium. The lignocellulolytic enzymes of P. ostreatus in different fermentation methods revealed wide differences. The higher yields of endoglucanase (3152 ± 139 U/L), xylanase (3064 ± 40 U/L), and laccase (543 ± 21 U/L) were achieved by using the sequential solid-state submerged method compared to conventional solid-state and submerged cultivation. Generally speaking, sequential solid-state and submerged fermentation of cottonseed hull is favorable for laccase secretion, whereas sequential solid-state and submerged fermentation of corncob provides better production of hydrolytic enzymes. These results revealed that the nature of the lignocellulosic biomass and the fermentation method play an important role in the expression of lignocellulolytic enzymes. This indication would be helpful in optimizing the production of integrated industrial lignocellulolytic enzymes.

This study investigated the thermo-chemical degradation and fast pyrolysis of watermelon seed shells (WSS), pumpkin seed shells (PSS), and sunflower seed shells (SSS). The raw materials and pyrolysis products were analyzed. The results showed that the carbon content (52.96%), hydrogen content (7.38%) and higher heating value (HHV) (23.88 MJ/kg) of PSS were highest, and the bio-oil from the PSS pyrolysis had high amounts of phenolic compounds. For SSS, the content of holocellulose (83.47 wt.%) was the highest, but the lignin content (13.62 wt.%) was lower than the other samples. The gas yield from the SSS pyrolysis was the largest and the bio-oil content of acids (acetic acid 36.53%) and ketones (1-hydroxy-2-propanone 9.90%) were higher. For WSS, the yield of the biochar was 39.14 wt.%. Additionally, the raw materials’ structures were similar. The thermal decomposition process of all seed shells had three stages, i.e. dehydration, active pyrolysis, and passive pyrolysis. In all three kinds of bio-oil, the components were mainly guaiacol-type and phenol-type. The guaiacol-type in the bio-oils from PSS (43.78%) and WSS (32.33%) were higher than in the bio-oil from SSS.

The emission standard for adsorbable organic halogen (AOX) has been adjusted as a mandatory assessment indicator in the papermaking industrial pollutants emission standards of China. To provide a theoretical basis to reduce AOX formation, a kinetic model of the first chlorine dioxide bleaching stage (D0) is presented for elemental chlorine-free (ECF) bleaching of eucalyptus kraft pulp. The kinetics of the D0 stage can be expressed as dW/dt = 314.6e-20.53/RT[H+]0.21[ClO2]0.41K0.98, where the reaction series for lignin, chlorine dioxide dosage, and H+ concentration are 0.98, 0.41, and 0.21, respectively. The reaction activation energy was 20.53 kJ.mol-1. R2 was greater than 0.9, which means that the model was shown to have high prognostic ability and feasibility. In the D0 stage, mostly lignin was removed and the reaction was fast. Much AOX was formed at the beginning of bleaching, and the reaction rate was primarily determined by the lignin content and chlorine dioxide dosage. H+ existed primarily as a catalyst and had little influence on AOX formation. The AOX formation occurs easily, as the reaction activation energy is less than 30 kJ.mol-1.

Densified wood is a promising engineered wood product, especially for heavy-duty applications. This study optimized the temperature and duration of the thermo-hygromechanical (THM) densification process applied to sugar maple (Acer saccharum Marsh.) wood. The response variables studied were compression set recovery and hardness. The THM densification process was performed at three temperatures (180°C, 200 °C, and 220 °C), densification times (450 s, 900 s, and 1350 s), and post-treatment times (900 s, 1350 s, and 1800 s). Response surface methodology was used to analyze the impact of the three parameters. The effect of temperature on the density profile across thickness was also determined. The results suggested that the optimum densification conditions resulting in high hardness and low compression set recovery were obtained at a temperature of 180 °C, a densification time of 1004 s, and a post-treatment time of 1445 s. Additionally, the density of the densified samples was relatively homogeneous across thickness, although it was dramatically increased compared with control samples. However, density did not increase linearly with temperature. A much higher weight loss occurred at 220 °C, resulting in a significant decrease in density and hardness, whereas little compression set recovery was observed for sugar maple densified at this temperature.

A degradable starch/lignin blend film was prepared using corn starch and sodium lignosulfonate via a casting and solvent evaporation method. The effect of sorbitol content on the swelling properties of starch/lignosulfonate blend films was investigated. The effect of lignosulfonate content on the swelling and mechanical properties was also studied. The results showed that when the mass ratio of sorbitol to starch changed over a wide range, from 0:9 to 9:9, the water absorption of the blend films increased at first and then decreased. When the mass ratio of lignosulfonate to starch changed in the same range, the ultimate stress of the blend films decreased markedly, while the water absorption and elongation at break did not show any regular pattern. When the mass ratios of sorbitol to starch and lignosulfonate to starch were both 6:9, the resultant film presented good elasticity and improved hydrophobicity compared to those without lignosulfonate.

A xylanase (Xyn10A) gene from the saline-alkali-tolerant microorganism Bacillus cellulosilyticus DSM 2522 was cloned and expressed in Escherichia coli BL21 (DE3). The open reading frame was composed of 1008 base pairs, and it encoded 335 amino acid residues belonging to glycosyl hydrolase family 10. The optimal temperature and pH of the purified Xyn10A were 40 °C and 8.0, respectively. The Xyn10A was sensitive to heat and showed obvious cold-adapted activity, retaining 38.3%, 55.7%, and 82.9% of the optimal activity at 4, 20, and 30 °C, respectively. Xyn10A also showed a high level of NaCl tolerance. The highest activity was observed with 1.5 M NaCl. The specific enzyme activity of Xyn10A was as much as 163.8 U/mg. Kinetic assays showed that Km, Vmax, and Kcat were 2.56 mg/mL, 202.5 μM/min/mg, and 132.6 /s, respectively. Additionally, the main hydrolysis products using birchwood xylan as substrate were xylobiose, xylotriose, and xylotetraose, as determined by thin layer chromatography analysis. As a cold-adapted and salt-tolerant enzyme, Xyn10A is an ideal candidate for further research and biotechnological applications.

Monitoring displacements and weather impact of complex structures, such as a large cable-stayed footbridge, generates a large amount of data. To extract, visualize, and classify health-monitoring data for better comprehension, multivariate statistical analysis is a powerful tool. This paper describes screening to evaluate if principal component analysis is useful for health monitoring data. Principal component analysis (PCA) and projections to latent structures by means of partial least squares (PLS) modeling were used to achieve a better understanding of the complex interaction between bridge dynamics and weather effects. The results show that PCA gives a good overview of the collected data, and PLS modeling shows that winds from east and west best explain bridge movements.

The effect of steaming treatment on the dynamic modulus of oak wood (Quercus castaneifolia, C. A. Mey.; Fagaceae) containing a water resistant glue-finger joint was investigated. Sample joints were made with two different types of waterproof adhesives, polyurethane (PU) and epoxy, and the samples were tested by a free flexural vibration method according to flexural and longitudinal free vibration modes. Compared with the epoxy joints, the PU finger-joints retained elastic moduli closer to their initial values. In all three vibration tests, finger-jointed oak wood specimens with either glue retained their moduli of elasticity, after the steaming treatments. In the case of longitudinal-tangential (LT) vibration, some increases were observed for the evaluated elastic moduli. After steaming, the obtained dynamic values decreased. For epoxy-bonded specimens, the correlation coefficient in terms of the elastic modulus before and after steaming were weak. There were some acceptable PU-bonded specimens, but there was a considerable decrease after steaming.