Research Articles

The performance of cellulase in the enzymatic saccharification of lignocellulose depends on the characteristics of lignocellulosic biomass feedstocks and the pretreatment method used. Efficient hydrolysis of specifically pretreated lignocellulose necessitates the knowledge of the characteristics of the optimal commercial cellulases. In this study, commercial cellulase preparations (Accellerase™ 1000, Accellerase® 1500, and Spezyme® CP from DuPont and Cellic® CTec2 from Novozymes) were evaluated for their hydrolysis efficiency of hydrothermally pretreated empty fruit bunches (EFBs). The highest glucose yields of 91.3% and 84.7% were achieved for 30 FPU of Cellic® CTec2/g glucan with and without Cellic® HTec2, respectively. Of the four cellulases tested, Cellic® CTec2, which showed the highest cellobiohydrolase, xylanase, and β-glucosidase activities, showed the highest glucose yield in the enzymatic hydrolysis of hydrothermally pretreated EFBs. The results of this study are valuable for those who plan to enzymatically hydrolyze hydrothermally pretreated EFBs.

Current methods of reducing giant Moso bamboo (Phyllostachys pubescens Mazel) to elements for composite manufacture are often inefficient and waste valuable biomass. This study employed geometric modelling to analyze and optimize the recovery of strands for oriented strand board manufacture. Three geometric models for calculating the numbers of strands, their widths, and their distribution based on culm diameter, wall thickness, target strand thickness, and flitch size were developed to determine an optimum slicing configuration. Real strands were produced by a disk flaker at the model strand thickness of 0.65 mm. Optimum configuration for the maximum number of usable strands per culm was from splitting culms into quarters, tight stacking, and radial slicing through the culm wall, which produced 37% more ‘usable’ strands 10 mm to 30 mm in width, fewer fines, and fewer excessively wide strands. Proportions of real strands fell into three size classes: < 10 mm, 10 mm to 30 mm, and > 30 mm, and closely matched modelled predictions. A slightly bimodal strand width frequency distribution observed from stranding full rounds was reflected in the distribution of the model strands calculated from slicing a full round into 0.65 mm increments.

High-productivity lactic acid bacteria (LAB) strains were screened and their capability to ferment lignocellulose-derived sugars into lactic acid were evaluated. Fifteen LAB strains were successfully isolated from cow dung, haystack, and sheep manure, respectively. Four relatively good strains were selected based on Gram stain, colony morphology, and catalase activity tests. The four strains and commercial inoculants (Lactobacillus pentosus and Enterococcus faecalis) were used to ferment cellobiose/ glucose/xylose to produce high-purity L-lactic acid. One of the strains (N4) presented the highest production of L-lactic acid after fermentation for 12 h and showed a L-lactic acid production of 15.1 g/L, 18.5 g/L, and 2.8 g/L and a productivity of 1.01 g∙L−1∙h−1, 3.68 g∙L−1∙h−1, and 0.47 g∙L−1∙h−1 by metabolizing cellobiose, glucose, and xylose, respectively. Through a phylogenetic tree analysis, strain N4 was identified as Enterococcus faecium and named Enterococcus faecium N4. Enterococcus faecium N4 has a great potential to ferment lignocellulose-derived sugars into L-lactic acid.

There is a strong need to manage low-value forest residues generated from the management practices associated with wildfire, pest, and disease control strategies to improve both the environmental and economic sustainability of forestlands. The conversion of this woody biomass into value-added products provides a great opportunity to benefit both the environment and economy. This study aimed to assess the environmental impacts of converting forest residues into two renewable fuels, cellulosic ethanol and biomethane, by different biochemical conversion pathways. The energy balances and environmental impacts, including acidification, eutrophication, global warming, and photochemical ozone formation, of the two biorefinery approaches were addressed. This work illustrated the advantages of converting forest residues into biomethane from energy and environmental perspectives. The tradeoff between the economic benefits and potential environmental issues need to be carefully considered.

This paper presents the possibility of creating motivational programs for employees working in small and medium-sized enterprises (SMEs). The applicability of the proposed option is verified and presented to a medium-sized enterprise operating in the wood-processing industry in Slovakia. Using cluster analysis, three motivational-oriented groups were defined in the category of managers and three similar motivational-oriented groups in the category of workers. Subsequently, the sampling units were tested by the Tukey’s honest significant difference (HSD) test. In this way, the significance of the differences in arithmetic mean and the standard deviation of the individual motivational factors of the monitored sets at the significance level α = 0.05 were defined. The result of the analysis is a plan to create a group motivational program. The content of this program is a common motivational factor for groups, supplemented by employee-specific factors. Currently, businesses apply unified motivational programs based on two, three, or four main motivators. However, improperly designed and applied motivational programs have a negative impact on employees and do not motivate them to maximize performance. By implementing this method in wood-processing SMEs, the company’s performance can be increased, as the needs of most employees would be met.

There are several non-utilized or under-utilized hardwood trees common to the Midwestern states. Wood flour (WF) derived from fast-growing Midwest trees (Osage orange, black locust, and red mulberry) were evaluated as a source of bio-based fiber reinforcement. Wood-plastic composites (WPCs) of high-density polyethylene (HDPE), 25 wt.% of WF, and either 0% or 5% by weight of maleated polyethylene (MAPE) were produced via twin screw compounding and injection molding. Specimen bars were evaluated for their mechanical and flexural properties. Composite blends that employed the coupling agent MAPE were superior to composites without MAPE or neat HDPE in terms of their mechanical and flexural properties. The Osage orange WPC composed of juvenile WF had mechanical and flexural properties that were the same as the WPC composed of mature WF. The WPC composed of WF from Midwestern trees were comparable with the WPC composed of pine WF in terms of their mechanical and flexural properties. Soaking the bars of the various WPC blends in distilled water for 28 days altered their weights, mechanical properties, and color. Thermal properties of neat HDPE and WPCs were evaluated using differential scanning colorimetry and thermogravimetric analysis.

The quality of logs entering the production line is important because it controls the quality and yield of veneer. In Romania, Quercus species represent 18% of the total forests, and of which 2% is exclusively the pedunculate oak. The wood of pedunculate oak is hard and elastic, and it has a good natural durability. Due to such features it also has multiple uses in the furniture industry, construction, joinery, and cooperage works. The present work highlights the influence of some characteristics of the raw material on the cutting yield of veneer in the case of pedunculate oak logs purchased from different regions. Defects in the raw material had a certain negative influence on the veneer quality. The defects were identified and prioritized using the Pareto diagram.

The objective of this study was to understand arabinose effects on butyric acid fermentation by Clostridium tyrobutyricum in sugar-supplemented media and biomass hydrolysate. Compared to glucose and xylose, the conversion of arabinose to butyric acid was less efficient with a longer lag phase (4 d) and fermentation period (6 d), and a lower butyric acid yield of 0.26 g/g and 0.15 g/g in 5 g/L and 10 g/L of arabinose media, respectively. However, the addition of 2 g/L or 5 g/L of arabinose to the baseline medium that contained glucose (15 g/L) and xylose (15 g/L) enhanced butyric acid synthesis, resulting in 16.1 g/L and 20.3 g/L of butyric acid, respectively. Further increase in arabinose to 10 g/L in the medium of 10 g/L of glucose and 10 g/L of xylose showed inhibitory effects on C. tyrobutyricum, which suggested that high concentrations of arabinose (> 10 g/L) were not desirable. Dilute-acid pretreated corncobs that contained xylose (19 g/L) and a small amount of arabinose (2 g/L) were a feasible substrate for butyric acid production by C. tyrobutyricum, and resulted in 10.6 g/L butyric acid, which was slightly lower than in the mimic medium (11.3 g/L).

This study presents the results of tool wear and surface roughness of wood processed by plain milling. The tests were done on wood samples of pine and black alder grown in Lithuania in order to clarify time-related tool blunting and the aspects of surface formation. The samples were milled along the fiber in the experimental wood cutting stand at two different cutting and feed speeds. The roughness parameter (Rz) of the processed samples was measured in five sectors along and across the fiber using a contact profilometer. Registered values were analyzed by a Gaussian digital filter and evaluated according to relevant statistics seeking to minimize influence of wood anatomy. The obtained results helped to determine distinctions and variations of surface roughness, which strongly depend on the cutting path, rounding radius of the tool’s cutting edge, cutting, and feed speeds while milling pine and black alder.

Corn pericarp (CP) is an inexpensive agroindustrial by-product that is available in large quantity in Mexico. This work aimed to optimize the use of a dilute sulfuric acid pretreatment for CP hydrolysis to maximize the reducing sugars yield. A 2-step experimental design was used, first a full factorial followed by a central composite design (CCD). The CCD involved sulfuric acid (1.5% to 5%, v/v), a treatment at 121 ºC (15 min to 40 min), and varying CP content (10% to 20%, w/v). The response variables were the reducing sugars, glucose, and solubilized solids. Maximal responses were achieved at 3.4% (v/v) sulfuric acid, 20% (w/v) CP, and 22.3 min. A significant (R² = 0.99) second-order model predicted maximal operational conditions that were experimentally validated: 80.1 g/L reducing sugars, 12.8 g/L glucose, and 69.2% solubilization of CP solids. The dilute sulfuric acid pretreatment solubilized all hemicellulose in CP.