Volume 15 Issue 2

Protective effects of five surfactants were investigated relative to the saccharification of lignocellulose using the impeded Michaelis-Menten model (IMM). The yield of total reducing sugar (Ytrs) and cellulase activity were indexed as the effect of surfactant. The IMM was used to fit the correlation between Ytrs and reaction time to obtain the index (Kobs,0) reflecting the accessibility between cellulose and lignocellulose and the comprehensive index (Ki) reflecting cellulase inactivation and non-specific site adsorption. Results showed that the strongest protective effect was found from polyoxyethylene (80) sorbitan monooleate, followed by rhamnolipid. The surfactants protected cellulase from inactivation and nonspecific site adsorption of lignocellulose in the saccharification, leading to enhanced cellulase activity, especially with respect to carboxymethyl cellulase (CMCase) and filter paper enzyme (FPase) activities. The maximum Ytrs was obtained when the CMCase activity was 136.2 U/mL, while the FPase and β-glucosidase activities should be as high and low as possible, respectively, under the optimized condition. These findings lay the foundation for improving the saccharification efficiency of cellulase and reducing the cost of saccharification of biomass cellulose.

A nonionic surfactant based on chitosan and rosin, i.e. dehydroabietyl glycidyl ether grafted hydroxypropyl chitosan (DAGE-g-HPCS), was synthesized for the first time through reaction between hydroxypropyl chitosan (HPCS) and dehydroabietyl glycidyl ether (DAGE). The surface activities of DAGE-g-HPCS in aqueous solution were investigated via determination of surface tension, and its emulsifying ability was evaluated according to the stability time of emulsion composed of benzene-water with DAGE-g-HPCS as emulsifier; the foam stability was evaluated using the oscillation method. Through modulating the molecular weight of HPCS and the grafting degree (DG) of DAGE-g-HPCS, the emulsion stability and foam stability were surprisingly controllable. Compared to HPCS and specific emulsifier, the stability time of emulsion composed of benzene-water with DAGE-g-HPCS showed a remarkable performance with DG of 16.5% as the emulsifier was 7320 s, and the foam retention of DAGE-g-HPCS with 2.0 g·L-1 was 91.5%. Simultaneously, the critical micelle concentration (CMC) of DAGE-g-HPCS decreased with increased DG, while the emulsifying ability and foam stability exhibited opposite trend. The CMC, emulsifying ability, and foam stability of DAGE-g-HPCS increased with decreased HPCS molecular weight. These results demonstrated that the DAGE-g-HPCS was an excellent surfactant that should be considered as a promising substitute for petrochemical nonionic surfactant.

A new method of paper hydrophobization was evaluated based on a coating agent containing a water emulsion of triethoxymethylsilane with standard starch solutions. The effects of different concentrations on the hydrophobic properties of the resulting silicone-coated materials were investigated using a penetration dynamics analyzer (PDA) and water contact angle measurements. This study also examined the effects of the applied coatings on the paper’s tensile strength, tear index, roughness, air permeance, and ISO brightness. Preliminary studies were conducted on the molecular interaction mechanisms between the silicone agent and starch modifiers, based on solid state nuclear magnetic resonance (NMR) and scanning electron microscope (SEM) images.

Various plant parts of Rhizophora species have been used in the treatment of a variety of diseases and illnesses. However, they have not been tested for antifungal properties related to wood decay fungi, especially the bark extractives. This study examined the methanol (MeOH) crude extracts of R. apiculata and R. mucronata barks in terms of the amount of extracts obtained and their antifungal properties. The antifungal activities of the crude MeOH extracts of both species were determined using the agar dilution method. Methanol crude extract from R. apiculata and R. mucronata were 10.8% and 15.7%, respectively and were toxic to Chaetomium globosum and Gloeophyllum trabeum at the concentration of 50 mg/mL.

Thermally modified birch (Betula pendula Roth) veneers that had been subjected to wood treatment technology (WTT) or thermo vacuum (TV) processes were compared in this study. After modification of veneers in the range of temperatures from 160 °C to 218 °C and times from 0.5 h to 3 h, the color, mass loss, density, tensile strength, hygroscopicity, and decay resistance against brown rot fungus Coniophora puteana were determined. Treatment regimes with the greatest mass loss were at 217 °C for 3.0 h in TV (7.8%) and 160 °C for 0.8 h in the WTT (6.7%). As expected, wood mass loss correlated well with moisture exclusion efficiency (MEE) in all relative humidity (RH) environments (r = 0.95 to 0.99). Strength loss in the WTT was considerable compared to the TV process (57% and 40%, respectively). The resistance against brown rot fungus was moderate with a mass loss of 12% to 33%. Among the investigated samples, the regime 217/3.0/TV showed the best resistance against brown rot fungus and acceptable other properties.

Aqueous, acetone, and ethanol extracts of Coccoloba uvifera L. (Polygonaceae) leaves were assessed for their antibacterial and antifungal activities. The fungal pathogens Fusarium culmorum, Rhizoctonia solani, and Botrytis cinerea were isolated from strawberry plants, and they were molecularly identified through internal transcribed spacers (ITS) sequence analysis. Wood treated with ethanol extract at 3% showed the highest inhibition of R. solani, B. cinerea, and F. culmorum growth, with mycelial growth inhibited by 64.4%, 100%, and 38.5%, respectively. Moderate growth inhibition was found against the plant pathogenic bacteria Agrobacterium tumefaciens, Pectobacterium carotovorum subsp. carotovorum, Erwinia amylovora, Ralstonia solanacearum, Pectobacterium atrosepticum, and Dickeya solani. High-performance liquid chromatography analysis identified the phenolic and flavonoid compounds in the extracts. Regarding phenolic acid compounds, benzoic, ellagic, gallic, and o-coumaric acids were found as the main compounds in ethanol, acetone, and aqueous extracts. Regarding flavonoids, rutin, myricetin, and quercetin were identified in aqueous, acetone, and ethanol extracts. The results suggesting that the extracts can be used as environmentally friendly bioagents.

Biocomposites composed of polypropylene (PP) poplar wood flour (WF) (0% and 20%), microcrystalline cellulose (MCC) (0%, 2%, and 6%), and starch powder (SP) (0%, 5%, and 10%) were examined. The mechanical, physical, biodegradability, and morphological properties were assessed. The mechanical properties, water absorption (WA), thickness swelling (TS), and biodegradability were improved by adding WF to PP. By increasing MCC and SP, the composite modulus of rupture (MOR), modulus of elasticity (MOE), tensile modulus, WA, TS, and biodegradability increased. The tensile strength increased by increasing MCC, while the opposite was true for SP. An increase in WA and TS of composite, would decrease static contact angle. The morphological studies indicated that by adding MCC and SP, the composite stress transfer and distribution ability and structural bonding of the composite improved. By increasing the biodegradability and reducing the sample weights, the extent of surface degradability increased.

Bacterial blight disease due to Xanthomonas campestris pv. translucens results in yield losses in barley, Hordeum vulgare L., especially in warm climates. Bio-based bactericides represent a safe alternative to harmful chemicals for controlling a wide range of phytopathogens. The bacterial strains (Brevibacterium linens, Bacillus subtilis, B. thuringiensis) were tested as antagonistic potential against X. campestris disease in barley seedlings. Antagonists were applied as seed biopriming and soil drench in X. campestris infested soil. Soil-drenching treatment was more efficient than the biopriming application. A significant increase in shoot length with a clear decrease in seed germination was recorded. Fresh and dry weights of shoot and root lengths of the treated plants were markedly improved. The remarkable antagonistic activity of B. linens, B. subtilis, and B. thuringiensis against X. campestris could be attributed to the capability to produce bioactive molecules that can trigger systemic resistance in the infected seedlings.

Effects of the number of layers and the number and typology of finger joints were studied relative to the bending behavior of glulam beam made of Scots pine (Pinus sylvestris) laminates. The investigated parameters of glulam beams with constant overall dimensions (width × depth × length) of 90 mm × 90 mm × 1710 mm were lamination thickness (18 mm or 30 mm), the distance of the finger joints (200, 400, and 600 mm), and finger direction (horizontal and vertical). A total of 14 experimental samples were produced (12 different finger joint beams and two reference beams without finger joints) and tested under four-point bending tests. Taguchi orthogonal experimental design was used to evaluate and optimize test results using the S/N ratio. The effects of main and interactions between producing parameters on strength of glulam beam were determined by variance analysis. According to the results of the analysis, it was determined that the number of layers and the direction of the finger had a significant effect on the flexural strength of the beams, but the finger distance was not significant. Moreover, the highest strength values were obtained in 5-layer finger-jointed beams with vertical finger direction.

Conventional formaldehyde-based wood binders for composites have been reported as hazardous to humans after prolonged exposure to released fumes. Therefore, this research was conducted to evaluate suitability of citric acid-modified corn starch as binder for wood composites. Corn starch was gelatinized before it was reacted with citric acid, mixed with wood particles, pre-pressed, and finally hot-pressed before characterization and evaluation. Through Fourier transform infrared analysis, ester groups were detected at 1736.8 cm-1, which was characteristic for starch modified with citric acid. Bending test results on citric acid modified corn starch wood composites showed 16.8 N/mm2 and 4020 N/mm2 for modulus of rupture and modulus of elasticity, respectively. Addition of 2% urea-formaldehyde increased these numbers to 17.9 N/mm2 and 5190 N/mm2, respectively. Internal bonding additionally increased from 0.88 N/mm2 to 0.95 N/mm2. All test specimens passed mechanical strength requirements by JIS A 5908 (2003). Based on the demand specification for the final usage of the wood composite, it can be concluded that citric acid modified starch is a possible successful choice as the adhesive, with or without additional urea formaldehyde resin.