Volume 12 Issue 4

Chemical modification by attaching functional groups to lignocellulosic pulp fibers might be a strategy for improving the pulp, and thereby, paper properties. Several studies have described positive effects on paper strength properties for handsheets prepared from cationic-modified pulp or pulp fractions. This study addressed whether these effects are related to the cationic groups, e.g., by increasing electrostatic attraction and thus paper strength, or rather side effects of the chemical modification process, e.g., fiber flexibilization. To eliminate or at least minimize these side effects, only the fines fraction, which was already highly flexible, was cationized. While the addition of cationized fines affected various pulp and paper properties, most notably drainage time, no difference in strength properties was observed when comparing the addition of cationic or unmodified fines to different pulps or fractions thereof.

To produce cellulosic ethanol more economically, utilization of whole slurry of pretreated lignocellulose without separating liquid and solid fractions after thermal and/or chemical pretreatment of lignocellulose may be advantageous in terms of process economics. To carry out such processing on mixtures, which contain pretreatment byproducts, quantitative evaluation of the degree of inhibition of enzymatic hydrolysis and yeast fermentation by pretreatment byproducts are important. Therefore, in this study, the inhibitory effect of byproducts, focusing on sugar degradation products including furfural, hydroxymethylfurfural (HMF), acetic acid (AA), formic acid (FA), and levulinic acid (LA), on enzyme and microbial performance was investigated. The experimental conditions for SSF media containing the inhibitors were optimized by response-surface methodology-ridge analysis. The saccharification using commercial cellulase was most remarkably inhibited (approximately 28%) by HMF. The ethanol production by Saccharomyces cerevisiae was nearly completely inhibited (approximately 80%) by furfural. The toxicity was noted as HMF > FA > furfural > AA ≈ LA for enzymatic hydrolysis, and furfural > HMF > FA > AA > LA for yeast ethanol production. The results indicated that the inhibitor accumulation during pretreatment should be controlled for subsequent effective saccharification and fermentation.

In kraft recovery systems, there is a trend toward increasing solids content of the black liquor injected to the furnace. Higher solids contributes to combustion efficiency and stable boiler operations. However, the presence of silica can adversely affect the viscosity of the mixture in such cases. Sodium aluminate, which was used as a desilicating agent during the black liquor combustion, had an excellent effect on the removal of silicon from the bamboo kraft black liquor (BKBL) to solve the problems presented by silicon. The apparent viscosities of thick BKBL with the addition of varied sodium aluminate loading were studied with a rotational rheometer. The thick BKBL behaved as a pseudo-plastic fluid that exhibited shear-thinning. However, shear-thickening appeared when the shear rate exceeded 30 s-1 at 98 °C, which would influence the flow stability of BKBL in pipelines. When the loading was 1.5 wt.%, sodium aluminate promoted the flow and droplet formation of thick BKBL by reducing its structural strength. The Ostwald-de Waele model provided an ideal fit to the apparent viscosity data. Hence, it could be used to accurately predict apparent viscosity changes in thick BKBL.

Physical, mechanical, chemical, and thermal properties of sugar palm (Arenga pinnata) fiber were investigated for specimens obtained from three different locations: Kuala Jempol (Peninsular Malaysia), Tawau (West Malaysia), and Tasik Malaya (Indonesia). The morphology of the fiber were observed through scanning electron microscopy (SEM), the thermal properties by thermogravimetric analysis (TGA), tensile properties according to ASTM D3379, and chemical analysis by using neutral detergent fiber (NDF) and acid detergent fiber (ADF). This study confirmed that in sugar palm fiber, the highest chemical content of cellulose resulted in the highest strength and thermal stability of the fiber. Fiber originating from Kuala Jempol had the highest cellulose content of 44.53%, followed by Indonesia (44.47%) and Tawau (43.75%). Kuala Jempol fiber (233.28 MPa) also had the highest tensile strength, followed by Indonesia (211.03 MPa) and Tawau (201.30 MPa), which was affected by the cellulose content in the fiber. Thus, fiber originating from Kuala Jempol had better quality than the others as a reinforcement material in manufacturing of polymer composites.

Using renewable energy sources provides a promising solution to minimize the overuse of conventional energy sources as well as to reduce pollution. Biogas technology is one solution that offers the conversion of waste streams to a renewable source of higher value. Anaerobic digestion of organic waste from industrial processes produces energy in the form of biogas, which has an advantage of preventing odor release, and has minimal pathogens. In this study, two different sources of bio-waste were investigated for their biogas potential, namely palm date waste and olive pomace. All of the samples produced biogas; however, the amount produced was only 20% to 40% of what conventional substrates typically produced. Producing biogas that uses only olive biomass offers a solution to the waste disposal problem, but it is not efficient for biogas production. For optimal heat utilization and maximizing biogas production, mixing of different feedstock was identified as a valid solution. Hence, a model of mixing other sources of bio-waste, such as chicken manure, can activate sludge and is proposed to boost the biogas production.

The authors developed a high-throughput method for analyzing softwood lignin using tetra-n-butylphosphonium hydroxide (TBPH). Wood meal, TBPH, and hydrogen peroxide (H2O2) were introduced into a screw-capped glass test tube and allowed to react in a pressure cooker at 121 °C for 3 h to solubilize the wood meal. The solubilized polysaccharide was precipitated by the addition of a poor solvent such as methanol. After removal of the polysaccharide, the lignin concentration was measured via ultra-violet (UV) absorption spectroscopy. The series of operations performed was summarized as the TBPH method. The TBPH method was characterized as a simple and rapid procedure that used common equipment and was suitable for multiple-sample analysis. Softwood sample groups were prepared, and the lignin contents of these samples were measured by the TBPH method, the Klason method, and the acetyl bromide method to determine the accuracy of the proposed method. The TBPH method showed a high coefficient of determination (R2 = 0.94) when compared to the Klason method. By contrast, the acetyl bromide method showed a comparatively low correlation (R2 = 0.71) with the Klason method. This study revealed that the TBPH method presented high-throughput rapid analysis and good accuracy for soft wood lignin analysis.

The degradation of cellulose in wheat straw during aqueous ethanol organosolv (AEO) treatment under different pulping conditions was investigated. For this purpose, molecular weight distribution (MWD) and degree of polymerization (DP) of the resulting cellulose pulp were determined using high performance size exclusion chromatography (HPSEC). The most pronounced effects regarding cellulose degradation were observed when varying the ethanol-to-water ratio. UV detection in HPSEC indicated that residual lignin in wheat straw fibers from organosolv treatments does not occur in free form, but rather is associated with hemicellulose (xylan) and to a minor extent also with cellulose. The established method was suitable for relative comparisons of MWD of variously treated wheat straw fibers and hence for obtaining information regarding the severity of organosolv treatment in terms of cellulose degradation. In summary, AEO treatment at a low ethanol-to-water ratio favours the efficient delignification and removal of xylan from wheat straw, but this occurs at the price of a greatly reduced fiber quality in terms of DP.

In order to utilize finger-jointed rubberwood as raw material for the production of structural wood products, the finger joint efficiencies of rubberwood specimens taken from three factories in Thailand were evaluated. This study investigated the finger profile, modulus of rupture (MOR), and modulus of elasticity (MOE) of finger-jointed rubberwood from all selected factories. The effect of finger orientations (vertical and horizontal) on MOR and MOE values was also examined. The results showed that all selected factories used the same finger profile for manufacturing finger jointing of rubberwood samples. The finger orientations had no noticeable effect on the MOR and MOE values. The MOR values of finger-jointed rubberwood obtained from all selected factories were different. They ranged from 55 to 78 MPa. A primary cause of failure for specimens with lower MOR values was the poor surface bonding of fingers. The MOE values of samples were similar for all selected factories ranging from 9,710 to 12,200 MPa. According to BS EN 338 (2016), finger jointed rubberwood from some factories was inappropriate for production of high strength structural wood products.

Steam explosion (STEX) is an effective method of degumming kenaf and separating kenaf fibers. The residence time has a strong effect on the STEX process, and its mechanism of degumming kenaf was studied in this paper. In this research, five different residence times were chosen to treat kenaf at 1 MPa STEX pressure. The morphological changes were recorded using an optical camera and scanning electron microscopy (SEM). The chemical and physical properties of kenaf fiber were analyzed using wet chemistry analysis and a standard mechanical test. The cellulose content increased with increasing residence time. The breaking strength of kenaf fiber reached the highest level at 5 min residence time. It was also found that four different levels of kenaf fiber exist in the steam explosion process. This finding is very helpful for the degumming method development.

Fungal glycoside hydrolase family GH12 has a single catalytic domain, exhibiting a great diversity of properties and application potentials in biomass biorefinery, feed, and textile industries. To discover new GH12 enzymes from white- and brown-rot basidiomycetes for application in the saccharification of lignocelluloses, two putative genes, VvGH12A and VvGH12B, were identified from the Volvariella volvacea genome and classified into basidiomycetous subfamily GH12-1 and GH12-2, respectively. One enzyme VvGH12A was successfully expressed in Pichia pastoris, and characterized. VvGH12A was the most active on CMC but with broad substrate specificities on polysaccharides with b-1,4 linked and b-1,3-1,4-mixed glucans. Furthermore, VvGH12A was also active on xylan and mannan. Unlike other fungal GH12 endoglucanases, VvGH12A showed a weak processivity independent of the carbohydrate-binding module (CBM) due to both “endo” and “exo” types of enzyme activity. The pH-optimum was significantly affected by the acidity and basicity of amino acid at site 98. The enzyme optimum pH was engineered to a higher neutral or alkaline pH (from pH 6.5 to pH 7.0-8.0) when Asp98 was replaced with nonpolar or neutral or amide residue. VvGH12A exhibited synergistic action with crude cellulase from Trichoderma reesei D-86271 (Rut C-30) in saccharification of delignified wheat straw, suggesting that VvGH12A plays a functional role in efficiently hydrolyzing plant cell wall polysaccharides.