Volume 9 Issue 4

In this study, banana waste was used to investigate its elicitation potential for induced production of α-amylase from Bacillus licheniformis DSM-1969. Initially, six different media were investigated to select the composition with optimal yield. A comparison of the fermentations in the stirred fermenter or shake flasks revealed that B. licheniformis DSM-1969 was more active to synthesize α-amylase in the fermenter as compared to the shake flask. In the shake flask during the exponential phase, the specific growth rate, generation time, and number of generations were 0.19 h^-1 , 3.48 h^-1, and 5.16 h^-1, respectively, whereas in the stirred fermenter the above values were 0.3 h^-1, 2.31 h^-1 and 5.21 h^-1, respectively. A significant difference was recorded in the specific substrate uptake rate and biomass growth yield during the exponential phase in the stirred fermenter in comparison to the shake flask. The enzyme was purified by ion-exchange chromatography using fast protein liquid chromatography (FPLC). α-amylase was purified 3.9 fold with a specific activity of 38.8 U/mg and molecular weight of 62 kDa. Characterization revealed that purified α-amylase remained stable over a broad pH and temperature range as compared to the crude enzyme. Activity of this novel extra thermo-stable α-amylase was stimulated to variable extents by Zn2+, Co2+, and Mn2+, whereas EDTA and Hg2+ showed inhibitory effects.

Three-layer cross-oriented strand boards, OSB type 3 of 10 mm thick, were industrially manufactured from a mixture of wood species including 50% softwoods, 25% beech, and 25% low hardwoods, using a continuous press line. The effects of line speed and press factor on physical and mechanical properties of OSB/3 (exterior grade) were evaluated, keeping nearly constant the face-core adhesive ratio. The manufactured boards were classified into five groups depending on the pressing parameters. The experimental results showed that all mechanical properties increased, with increasing press factor and decreasing line speed. The ratios of bending strength (MOR) and the modulus of elasticity (MOE) parallel to perpendicular were 1.73 to 1.89 and 2.18 to 2.24, respectively. No significant differences in thickness swell and water absorption were observed. The lowest density was achieved at higher speed, although there was no large variation in densities between groups. Thickness swelling and internal bond after boil test exceeded the EN 300 standard requirements for OSB/3 moisture resistance, excepting a few boards. The results revealed that a correlation between speed and press factor is necessary in order to improve mechanical properties and to keep the physical performance of boards within a limited range of values.

Kraft pulping is one possible pretreatment for softwood to economically produce bioethanol. This work evaluates the techno-economic potential of using the kraft process for producing bioethanol from softwoods in a repurposed or co-located kraft mill. Pretreated loblolly pine was enzymatically hydrolyzed at low enzyme dosages of 5 and 10 FPU/g of substrate. Pretreated residue with 13% lignin content had the highest sugar recovery, 32.7% and 47.7% at 5 and 10 FPU/g, respectively. The pretreated residues were oxygen delignified and refined. In all cases, oxygen delignification improved sugar recovery, while refining was mostly effective for pulps with high lignin content. At 5 FPU/g, the sugar recovery for all kraft pulps was 51 to 53% with oxygen delignification and refining. Increasing the enzyme dosage to 10 FPU/g increased the sugar recovery for these pulps to greater than 60%. Economic analysis for the pulps with different initial lignin content showed that kraft pulps with an initial lignin content of 6.7% with oxygen delignification had an ethanol yield of 285 L/ODt wood and the lowest total production cost of $0.55/L. Pulps with initial lignin content of 18.6% had a total production cost of $0.64/L with an ethanol yield of 264 L/ODt wood.

To acquire activated carbon fiber from phenol-liquefied wood (PLWACF) with better developed pore structure and a high proportion of mesoporosity, the porosity evolution of PLWACF activated at temperatures from 850 to 950 °C by water steam was detected by the physical adsorption of N2 at -196 °C. Results showed that the pore structure was well developed by prolonging the activation time at 850 to 910 °C, and it was easy to obtain PLWACF having exceptionally high surface area (larger than 2560 m2 g-1). However, PLWACF with a specific surface area larger than 3000 m2 g-1 could only be obtained in the late activation stages from 850 to 880 °C. Using this activation process, the mesoporosity was remarkably developed. The mesopore proportion drastically increased with an increase in activation temperature or time, reaching a maximum of 49.5%. The pore size distribution widened as the activation time increased and appeared to accelerate with the use of a higher activation temperature. The mesopore size distribution was enlarged from 2.8 to 5.8 nm.

Wheat straw was pretreated by combined mechanical destruction and alkaline pretreatments to enhance enzymatic saccharification. Four strategies were employed to evaluate the potential of wheat straw as a feedstock for fermentable sugar production. The effects of the pretreatments on the substrate morphology, size distribution, chemical composition, and cellulose crystallinity, along with the subsequent enzymatic digestibility, were investigated. Optical microscope images showed that mechanical pretreatment alone resulted in poor fiber defibrillation, wherein samples mostly consisted of rigid fiber bundles, while integrated mechanical destruction and alkaline pretreatment led to relatively good fiber defibrillation. Low temperature NaOH/urea pretreatment can fibrillate the rigid fiber bundles into a relatively loose network and alter the structure of the treated substrate to make cellulose more accessible. The glucan conversion rates were 77% and 95% for integrated mechanical destruction and alkaline pretreatments and mechanical destruction followed by low temperature NaOH/urea and ammonium/urea pretreatments, respectively, after 72 h of enzymatic hydrolysis with enzyme loadings of 10 FPU cellulase per g of oven-dry substrate.

This study investigated the pulping process of cooking rice straw in tris-(2-hydroxyethyl) ammonium acetate ionic liquid under microwave irradiation. The optimal processing conditions were determined via othogonal experimentation based on analyses of the effects of the main factors, namely the mass ratio of ionic liquid to rice straw, cooking time, and microwave power, on the cooking of pulp. Those conditions are as follows: mass ratio of ionic liquid to rice straw 5:1, cooking time 30 min, and microwave power 350 W. When subsequent verification experiments were conducted under the conditions above, the pulp yield was as high as 47.28%, the ionic liquid was able to be recycled, and the recovery was as high as 96.9%. The physical properties of the paper confirmed that paper of satisfactory commercial quality could be produced using this technology.

Hydrolysis of corn leaf utilizing two treatment sequences was carried out in this study. The first treatment was chemical and involved subjecting the corn leaf to an alkaline pre-treatment and then to a smooth acid hydrolysis. The second consisted of biological delignification using the strain Trametes sp. 44 H88, followed by enzymatic hydrolysis using the enzymatic extract produced by Trichoderma sp. H88. The ligninolytic extract produced by Trametes sp. 44 H88 was used to detoxify the hydrolyzate. The results indicate that biological pre-treatment with delignification is more favorable and improves the subsequent hydrolysis, regardless of whether the hydrolysis is chemical or biological. The chemical treatment sequence obtained 80% conversion of monosaccharides, while the biological treatment sequence resulted in a 87% conversion rate. Finally, the use of the ligninolytic extract for the dephenolization of the hydrolyzate reduced the presence of compounds of phenolic origin by 23%.

In this work, α-cellulose was extracted from Phyllostachys nidularia Munro using an acidified sodium chlorite treatment followed by alkali treatments, and cellulose nanofibers (CNFs) were then extracted from α-cellulose via the combination of sulfuric acid (64 wt%) and low-intensity ultrasonication. The results showed that superior CNFs were successfully extracted and their diameters were in the range of 5 to 20 nm. Fourier transform infrared spectroscopy (FTIR) suggested that a majority of the hemicellulose and lignin were removed from the original material and that the chemical constituents of α-cellulose and CNFs were similar. X-ray diffraction (XRD) analysis indicated that the relative crystallinity of CNFs was significantly increased to approximately 69.32% and all specimens presented a typical cellulose I crystal form. Thermogravimetric analysis (TGA) showed that the thermostability of the CNFs was greatly increased.

Bamboo is a natural bio-composite that has outstanding mechanical properties. Fibers are the structural building block of bamboo. Understanding the effect of fiber area on tensile properties of moso bamboo (Phyllostachys pubescens Mazei ex. H. Lebaie) will shed light on natural efficient design of bamboo. In this paper, fiber area and tensile properties of bamboo were tested on four bamboo slices, and a relationship found between fiber area and tensile properties. The results indicated that fiber volume increased exponentially in the radial direction from the inside to the outside of the culm wall. Bamboo tensile strength and MOE were linearly proportional to the fiber area. Fiber area also influenced bamboo fracture modes.

In this study, alkaline pretreatment at a bench scale (15-L capacity) was performed to obtain a higher solid residue for the SSF (simultaneous saccharification and fermentation) of Miscanthus sacchariflorus “Goedae-Uksae 1” (GU) under the following conditions: 1 M NaOH concentration, 150 °C, and 60 min residence time. Compositional analysis and scanning electron microscope analysis revealed the pretreatment to be highly effective for achieving delignification and morphological changes. Spiral impellers were used for the rapid liquefaction of pretreated GU into slurry, and no additional nutrients were added to the fermentation mixture to reduce overall process costs. The SSF was subsequently conducted in a laboratory-scale fermenter (5-L capacity) for 108 to 120 h with 12% and 16% glucan containing pretreated GU. Consequently, 62.8 g/L and 81.1 g/L of ethanol were obtained. Based on these data, the theoretical ethanol yields from 1 kg of GU (dry weight base) were estimated at 164.6 to 171.1 g/L.