Research Articles

Aspergillus sojae has been previously shown to produce exo-polygalacturonase (exo-PG) in synthetic media, where the potential of the organism to utilize agricultural substrates was not considered so far. In this study, the utilization of agro-based products was taken into account in the enhanced production of exo-PG using an A. sojae mutant by applying statistical design methods. Complex sources (orange peel, wheat bran, and corn meal), simple sugar sources (glucose, maltrin, and sugar beet syrup), and two phosphate salts were screened using D-optimal design method. Orange peel yielded the highest exo-PG activity with all simple sugars and phosphate sources. According to the results of response surface methodology (RSM), the optimum concentrations of orange peel, sugar beet syrup, and (NH4)2SO4 were found to be 10, 60, and 8 g L-1, respectively. The exo-PG activity under these conditions was 145.4 U m L-1 in shake flask cultures. In bioreactor studies enzyme production was induced at low pH values; thus highest production was obtained under uncontrolled pH conditions, in which the pH dropped to 2.0 in 72 h. As a result high exo-PG could be produced by an A. sojae mutant using a cost-effective medium containing agro-industrial substrates. Another important advantageous outcome was the low optimal pH, which is especially desired in industrial fermentations prone to contamination problems. In fact this highlights the easy adaptation of this fermentation to industrial scales.

Although biological pretreatment has the advantages of being environmentally friendly and having low-energy consumption, it usually requires a relatively long incubation time. In this study, a novel combined pretreatment with white-rot fungus and alkali at near room-temperature for saccharification of corn stalks was investigated to speed up the biological process. Biological pretreatment with Irpex lacteus or Echinodontium taxodii can improve enzymatic hydrolysis of corn stalk greatly, but the process requires a long time (60 days) to achieve a satisfactory sugar yield. The combination processes with the fungi were compared with the sole pretreatments. The results showed that the time of the biological process could be shortened to 15 days when the bio-treatment with I. lacteus was combined with alkali pretreatment. The efficiency of alkali pretreatment can be also enhanced significantly by biological treatment. 271.1mg/g of final glucose yield was obtained for the combination pretreatment, which was an improvement of 50.4% and 28.3% in comparison with the sole alkali pretreatment at the same and optimum reaction time, respectively. In conclusion, the combination of biological pretreatment with alkali processes not only speeded up the biological process, but also improved the sugar yield in comparison to the sole pretreatment and is favorable for the development of biological pretreatment.

chips prior to mechanical pulping, which would offer new feedstocks for the production of chemicals and fuels. The aim of this study was to evaluate pre-extraction to maximize pre-extraction yield, while minimizing negative impacts on wood chips. The effects of three independent process variables (NaOH charge, pre-extraction temperature, and time) on three dependent variables (pre-extraction yield, xylan extraction yield, and cellulose content based on original wood) were studied using a Box-Behnken experimental design. The mathematical models were obtained and validated well. It was found that NaOH charge, time, interaction between NaOH charge and time, and interaction between temperature and time have significant effects on xylan extraction yield. The xylan extraction yield was 22.55%; i.e., about 37.3 kg of xylan could be extracted from one ton of oven-dried aspen chips under the conditions of 5.68% NaOH charge, 100 °C, and 35 min.

This study investigated the effects of different treatments of coir fibers (Cocos nucifera L.), and cement:coir ratio on physical and mechanical properties of cement-bonded composites. Three treatments: adding 4% of CaCl2, immersion in hot water at 80°C for 90 minutes, and immersion in NaOH aqueous solution at 5% for 72 hours and two cement:fiber ratios (3:1 and 4:1) were chosen for manufacturing 24 panels. After 28 days of setting, characterization was made through static bending (MOE, MOR), parallel compression (COMP), internal bonding (IB), thickness swelling (TS), and water absorption (WA) (2 and 24 hours of water immersion) tests. Treating coir fibers with hot water provided an improvement in the panel’s properties. This treatment had better results in MOE and COMP. Panels produced with CaCl2 addition were resistant as well; however coir fibers treated with NaOH produced cement/coir composites with unsatisfactory physical and mechanical properties.

Copper coating was deposited on Fraxinus mandshurica veneers for preparing EMI shielding composite by electroless plating using glyoxylic acid as reducing agent in the solution. XPS and SEM were used to analyze the activation process. It was found that a continuous chitosan membrane was loaded on the wood surface. XPS results showed that Pd(II) ions were ed on a chitosan membrane on the wood surface through an N-Pd σ coordination bond. After reduction, part of Pd(II) absorbed formed very little Pd(0) particles on the chitosan-treated wood surface. The activated wood veneers were immersed into a plating bath in which copper film was successfully initiated. The coatings were characterized by SEM-EDS, XPS, and XRD. The metal deposition, surface , and electromagnetic shielding effectiveness were measured. The morphology of the coating was uniform, compact, and continuous. The wood grains were preserved on the plated wood veneer, which had a copper-like color and sheen. EDS, XPS, and XRD results indicated that the coating consisted of Cu0 with crystalline structure. The surface resistivity and copper deposition reached 175.14 mΩ·cm-2 and 21.66 g/m2 when the veneer was pretreated with 0.8 % chitosan for 8 min and plated for 30 min at 55 oC. The plated veneers exhibited good electromagnetic shielding effectiveness of over 60 dB in frequency ranging from10 MHz to 1.5 GHz.

Both the energy shortage and pollution tend to slow down economic development and affect our daily lives. Some microorganisms not only can digest pollutants, but also can convert pollutant metabolites to triacylglycerol (TAG) that can be used to produce biodiesel. Here, we present results showing that the bacterium strain LDS5, a mutant of Rhodococcus sp. RHA1 (RHA1) generated in our lab, could grow well in chemithermomechanical pulping (CTMP) effluent, a type of paper mill wastewater, reduce chemical oxygen demand (CODCr) and biochemical oxygen demand (BOD5) significantly, and produce TAG. Our data suggest that this strain has the potential to be used in paper mill wastewater treatment as well as in the development of biodiesel using biomass from paper mills.

In an attempt to explain variations in delignification behaviors among different hardwood species, the kraft pulping delignification rates of Eucalyptus urograndis, E. nitens, E. globulus, sweet gum, maple, red oak, birch, red alder, cottonwood, and acacia were obtained and correlated with their respective lignin chemical structures. Since H-factor for hardwood is calculated based on the softwood activation energy (Ea) value, a comparison between softwood vs. hardwood activation energy was also performed. Lignin was isolated by a modified isolation protocol, using alkaline pretreatment of the wood prior to isolation. The lignin preparations were analyzed via quantitative 13C NMR spectroscopy. Substantial variations were found among the hardwood species studied. A linear correlation between the kraft delignification rate and the amount of syringyl units was found. Activation energy values obtained for kraft pulping of hardwoods were very similar and almost identical to the value obtained for softwood. Birch was the only species with outlier behavior.

1-octadecanol is known to be a highly effective agglomerating agent for nonimpact-printing toners. However, it was found that some xerographic toners did not agglomerate under alkaline conditions. The effect of alkali on the agglomeration was studied with two different toners, one carrying no surface charge and one carrying a negative charge. The effect of the addition of a cationic surfactant on the agglomeration under neutral and alkaline conditions was then studied using two different cationic surfactants. It was found that both toners agglomerated better under neutral conditions than under alkaline conditions. The toner carrying no surface charge agglomerated much better than the toner carrying a negative charge under either alkaline or neutral conditions. The addition of a cationic surfactant greatly improved the agglomeration of the toner carrying a negative charge but had relatively small effect on that of the toner carrying no surface charge. It is recommended that agglomeration of mixed office waste with 1-octadecanol should be carried out under neutral conditions with the addition of a small amount of a cationic surfactant.

The present study deals with the utilization of a cellulosic material, i.e. fungal biomass of Mucor heimalis, for the removal of cadmium from aqueous solution in a batch system. Effects of various parameters such as pH, biomass dosage, contact time, and initial metal concentrations were investigated. The sorption of cadmium followed pseudo-second-order rate kinetics (R2=0.998). Intraparticle diffusion was found not to be the sole rate-controlling step. Thermodynamic studies revealed that the sorption of cadmium was feasible, spontaneous, and exothermic. Various isotherm models viz. Langmuir, Freundlich, Redlich–Peterson, Dubinin-Radushkevich, and Temkin isotherms were applied. The Langmuir and Redlich–Peterson models were found to be in good agreement with experimental data with high R2, low RMSE, and low χ2 values. The Redlich–Peterson isotherm constant g was found to be unity, which implies a good fit to the Langmuir model. The maximum sorption capacity calculated from the Langmuir isotherm was 85.47 mg/g at optimum conditions of pH 6.0, contact time of 35 min, biomass dosage of 1g/L, and temperature of 25 oC.

An inexpensive methodology is proposed to identify and locate a single defect within a wooden beam using free a flexural vibration technique. A similar approach has been introduced in the literature based on free longitudinal vibration, which was selected to be a leading frontier for the present research. The flexural vibration technique was tested for five groups of the absolutely clear specimens while holding a manually drilled hole at 0.1, 0.2, 0.3, 0.4, and 0.5 of their total span. The beams were tested in free flexural vibration with both ends in a free condition before and after drilling, and relative shifts of modal frequencies due to the presence of the defects were measured and compared to their mathematically calculated values in a sinusoidal equation. Using the method of least squares, a coincidence factor was developed based on the differences of the measured and calculated shifts of the four initial resonance frequencies where the minimum district of the coincidence factor curves successfully indicated the defected area. Though the longitudinal vibration approach was promising enough to estimate the position of the defect, its combination with the flexural vibration might increase the degree of confidence in the identifications.