Research Articles

The paper production process is significantly affected by direct and indirect effects of microorganism proliferation. Microorganisms can be introduced in different steps. Some microorganisms find optimum growth conditions and proliferate along the production process, affecting both the end product quality and the production efficiency. The increasing need to reduce water consumption for economic and environmental reasons has led most paper mills to reuse water through increasingly closed cycles, thus exacerbating the bacterial proliferation problem. In this work, microbial communities in a paper mill located in Italy were characterized using both culture-dependent and independent methods. Fingerprinting molecular analysis and 16S rRNA library construction coupled with bacterial isolation were performed. Results highlighted that the bacterial community composition was spatially homogeneous along the whole process, while it was slightly variable over time. The culture-independent approach confirmed the presence of the main bacterial phyla detected with plate counting, coherently with earlier cultivation studies (Proteobacteria, Bacteroidetes, and Firmicutes), but with a higher genus diversification than previously observed. Some minor bacterial groups, not detectable by cultivation, were also detected in the aqueous phase. Overall, the population dynamics observed with the double approach led us to hypothesize a possible role of suspended bacteria in the re-formation mechanisms of resistant biofilms.

Cinnamomum camphora (L.) Presl. is one of the most important hardwood species indigenous to China that possesses significant antifungal activity. The chemical composition of the extracts from the xylem parts of C. camphora was examined by various solvent extractions. Thirty different components accounting for 79.8% of the total methanol extracts from the xylem of C. camphora were identified by gas chromatography-mass (GC/MS) spectrometry. The major chemical components of methanol extracts are camphor (14.3%), α-terpineol (9.9%), and trans-linalool oxide (furanoid) (7.7%). The chemical composition of chloroform extracts are mainly camphor (17.6%), α-terpineol (11.8%), tetradecanal (5.6%), and (-)-g-cadinene (7.4%). The extracts of C. camphora were tested for resistance to two wood-decaying fungus with hyphal growth. All the C. camphora extracts showed some antifungal activity against the test fungus. The 50% effective concentration of chloroform extracts for Coriolus versicolor(C. versicolor) was 7.8 mg/mL, which was highly toxic, followed by acetone extracts. The methanol extracts with 8 mg/mL concentration had the best suppression effect for Gloeophyllum trabeum (G. trabeum) with an EC50 of 0.3 mg/mL. The results indicated that the major components of the extracts had antifungal activities; thus C. camphora could provide a renewable source for wood preservatives.

Dense silicon carbide (SiC) matrix composites with SiC whiskers and particles as reinforcement were prepared by infiltrating molten Si at 1550 °C into porous preforms composed of pyrolysed rice husks (RHs) and extra added SiC powder in different ratios. The Vickers hardness of the composites showed an increase from 18.6 to 21.3 GPa when the amount of SiC added in the preforms was 20% (w/w), and then decreased to 17.3 GPa with the increase of SiC added in the preforms up to 80% (w/w). The values of flexural strength of the composites initially decreased when 20% (w/w) SiC was added in the preform and then increased to 587 MPa when the SiC concentration reached 80% (w/w). The refinement of SiC particle sizes and the improvement of the microstructure in particle distribution of the composites due to the addition of external SiC played an effective role in improving the mechanical properties of the composites.

To explore the collapse of eucalyptus wood cells during the drying process, continuous and intermittent drying were carried out on Eucalyptus urophylla. The shrinkage throughout the intermittent drying process was less than that of continuous drying. According to observations of cells made using scanning electron microscopy (SEM), there was a large difference in the degree of cell collapse between continuous and intermittent drying. Severe cell collapse was observed after freeze-drying at high moisture content, even after an intermittent drying process. It is clear that collapse recovery via intermittent drying was more extensive than in continuous drying. In particular, ray parenchyma and axial parenchyma recovered from collapse more than did wood fibers.

In this study, the fiber morphology and chemical constituents of a 4-year-old rubber tree (Hevea brasiliensis Muell. Arg.) from the RRIM 2000 clone series were evaluated. The effects of planting density on the fiber morphology and chemical compositions of the clone of rubber wood were also considered. It is clear that the fibers of the rubber wood samples grown under higher planting density were thicker, with a wider lumen diameter than those grown under lower planting density. There were significant interactions between planting density and the height of the tree from which the samples were taken for all measured fiber properties studied. The chemical composition of the clone of rubber wood was determined as per TAPPI standards. Each of the chemical constituents of the rubber wood displayed statistically significant (at the 95% confidence level) interactions with tree section (low, middle, or high) and planting density. Fiber morphology and chemical composition results showed that juvenile rubber trees could supply fiber to produce particleboard and medium density fiberboard. Compared to mature rubber trees (those more than 25 years old), the studied RRIM 2000 clone rubberwood trees were found to be as compatible for use in the wood industry.

Lignocellulosic biomass is an economical and renewable feedstock for microbial production of bulk chemicals such as lactic acid. In many cases, simultaneous saccharification and fermentation (SSF) can achieve lower cost and higher productivity than the classical double step fermentation. Thus, in the present study, bagasse sulfite pulp was directly employed to produce lactic acid by SSF, using thermophilic Bacillus coagulans strain CC17. The effects of various factors, including CaCO3 addition time and the initial buffered pH, on lactate production were investigated. It was found that Bacillus coagulans strain CC17 could perform well at conditions that are also optimal for fungal cellulase. The addition of CaCO3 as the buffering reagent is critical for the production of lactic acid and maintaining pH. Maximum production of lactic acid was obtained by adding CaCO3 after 3 h fermentation. When pH 7 was used as the initial pH, strain CC17 produced about 20.68 g/L lactic acid from 20 g/L cellulose content of BSP with 15 FPU of Cellulast 1.5L/g cellulose and 15 CBU of Novozyme 188 /g cellulose. The results showed that this strain has potential to be used for direct lactic acid fermentation from lignocellulosic biomass via SSF.

The raw material requirements for the indirect liquefaction of biomass are strict. In particular, the ratio of H2/CO must be greater than or equal to 1. However, traditional biomass gasification has problems that include a low H2/CO ratio and low carbon conversion rates. This study proposes a three-stage gasification optimization model in which pyrolysis products are separated before being put through a second gasification step. The optimized model simulation used MATLAB software and the experiments were carried out in a biomass, high-temperature entrained-flow bed. The results demonstrate that, compared to traditional mixing gasification, three-stage gasification can effectively increase the H2 content in syngas. The H2 content can reach 42.3%, which is 4.6% higher than in traditional gasification. Additionally, this process can increase the H2/CO ratio to 1.23, which is 43% higher than the ratio 0.86 in traditional gasification. This also could provide raw materials for the indirect liquefaction of syngas. Thus, three-stage gasification can eliminate the need for intermediate steps such as steam reforming and adding external H2. Experiments indicated that the best gasification conditions were a first gasification time of 0.6s and a gasification temperature of 1100 °C, under which the H2/CO ratio reached a maximum of 1.2.

A green and efficient process was developed for the conversion of biomass-derived furfuryl alcohol to ethyl levulinate using eco-friendly solid acid catalysts (zeolites and sulfated oxides) in ethanol. Studies for optimizing the reaction conditions such as the substrate concentration, the reaction time, the temperature, and the catalyst loading dosage were performed. With SO42−/TiO2 as the catalyst, a high ethyl levulinate yield of 74.6 mol% was achieved using a catalyst load of 5 wt% at 398 K for 2.0 h. The catalyst recovered through calcination was found to maintain good catalytic activity (47.8 mol%) after three cycles, and it was easily reactivated by re-soaking in H2SO4 solution. Catalyst characterization was based on BET surface area, NH3-TPD, and elemental analysis techniques.

Hydrolysis is a reaction to produce sugars from lignocellulosic raw materials for biochemical production. The present study elucidates the hydrolysis of cellulose and formation of glucose decomposition products catalyzed by 5% to 20% (w/w) formic acid at 180 to 220 °C with an initial cellulose concentration of 10 to 100 g/L. Microcrystalline cellulose was used as a model compound. The experimental findings indicated that cellulose hydrolysis follows first-order kinetics in formic acid. A side reaction from cellulose to non-glucose products was required to explain the experimental results. A kinetic model was developed for the hydrolysis of microcrystalline cellulose in formic acid, based on a rate constant expression in accordance with the specific acid catalysis. The model showed good agreement with the experimental data. This study demonstrates how kinetic parameters can be fitted in a case-specific manner for the hydrolysis part of the kinetic model, while the well-established glucose decomposition model is utilized directly from literature.

The aim of this study was to evaluate the technical viability of using tannin adhesives derived from Stryphnodendron adstringens (Mart.) Coville barks in the production of plywood. 0, 25, 50, 75, and 100% tannin-based adhesives (TF) derived from barbatimão barks were combined with commercial phenol-formaldehyde (PF) adhesive. The properties of the adhesives were determined, and plywood was produced. The panels were produced with five crossed layers, an adhesive grammage of 360 g/m² (double line), and an assembly time of 10 min. A pressing cycle at a temperature of 150 °C, specific pressure of 12 kgf/cm², and duration of 10 min was used. With the exception of the parallel modulus of elasticity, panels produced with 25, 50, 75, and 100% barbatimão-derived tannin adhesive met NBR 31:000.05-001/2 standards (ABNT 2001). The tannin barbatimão adhesive proved feasible for use in plywood panels destined for both humid and dry environments.