Wood is a material that has been used by humankind for a long time. However, wood researchers and industry have always been concerned about the issues during wood drying and the permeability problems of certain species. In this sense, microwave technology has been applied for wood drying and improving permeability. This paper investigates the microwave drying of two Portuguese wood species, Pinus pinaster sap and heartwood, and Eucalyptus globulus heartwood using small clear specimens. The samples were grouped into six during each microwave treatment run according to their similarity of initial moisture content. Once the drying was completed, control and microwave-treated samples were impregnated with desalinated water to analyze their improvement in water absorption, and the compression strength parallel to the grain was analyzed. The results showed that each wood species behaves differently under microwave drying and initial moisture content. The impregnation results demonstrated that pine and Eucalyptus microwave-treated heartwood samples improved their capability to absorb water. Finally, only the microwave-treated specimens of Eucalyptus heartwood presented a decrease in the values of compression strength parallel to the grain compared to the control group. Therefore, MW treatment presents possibilities for further applications for the wood industry with supporting results.
Pre-hydrolysis-kraft of Eucalyptus globulus by autohydrolysis (batch) and with dilute acid hydrolysis (flow-through reactor) were explored in this study, to examine the recovery of xylooligosaccharides (XOs) from the pre-hydrolysis treatment. The results of this work support the potential reuse of the hydrolysate to increase the recovery yield of added value compounds. The pH of the dilute acid hydrolysis was maintained at 3.5 with acetic acid, to mimic the conditions of the batch reactor medium (autohydrolysis). An increase of XOs recovered was evident when the pre-treatment was in the flow-through reactor instead of the batch reactor. In the latter, a high concentration of furfural was recovered, showing the influence of time in XO conversion through hydrolysis. The total yield of pulp was higher in the flow-through reactor (36.4%) in comparison with the batch system (34.5%) after kraft pulping, which was expected, given the increasing time that the hydrolysate was present in the reactor; however, the difference was small and could have been the result of precipitated compounds in the latter, so this needs further analysis. Keywords: cellulose, Eucalyptus globulus, pre-hydrolysis kraft, xylooligosaccharides
BACKGROUND Chlorella vulgaris is being explored for several applications such as biodiesel production, nutrient supplementation, animal feed and pharmaceutical products. In this study, the performance of a batch culture under progressive light intensity and the effect of hydrogen peroxide (H2O2) concentration on lipid accumulation were investigated. RESULTS Under progressive light intensity (60 to 300 μmol m−2 s−1), a 43% biomass increase was achieved in comparison with the control light conditions (60 μmol m−2 s−1), whereas a 300 μmol m−2 s−1 light intensity caused growth inhibition to the culture. In addition, an increase in carotenoid content from 0.102 mg g−1 biomass (control) to 0.460 mg g−1 (progressive light) and lipid accumulation from 31.0 mg g−1 (control) to 36.5 mg g−1 (progressive light) was observed. However, the moderate illumination conditions (60 μmol m−2 s−1) induced a very significant increase of chlorophyll b, regarding the progressive light mode, increasing the photosynthetic efficiency. After the growth phase, the biomass was subjected to stress conditions by adding H2O2 to the culture medium at different concentrations: 0.75 mmol L−1 increased the lipid content of the biomass from 3.6% to 10.3% in a 3‐day test, reaching lipid productivity of 70.4 mg L−1 day−1, an increase of ≈40% compared to the phosphate starvatiod for the same culture time. CONCLUSION The progressive light system allowed an increase in biomass and lipid accumulation. Together with the exposure to H2O2, this work provides a new approach for lipid and pigment production from microalgae. © 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).
Due to cotton’s declining sustainability, more lignocellulosic materials are being used to produce dissolving pulp for textile applications. Pre-hydrolysis kraft is one of the main processes used to produce this material. Pre-hydrolysis under conventional conditions removes most of the hemicelluloses, but the majority end up as xylose and furfural, traditionally burned in a recovery boiler. The xylooligosaccharides (XOS), derived from hemicelluloses are a specialty product and can be recovered but requires adapted operative conditions. Thus, the objective was to recover XOS and evaluate the effect of pre-hydrolysis conditions on the final pulp characteristics. A flow-through reactor (FTR) was used to study the pre-hydrolysis, which allowed for modification of the retention time of the xylan in the free liquor after extraction from wood. The results have shown that by changing the fluid retention time in the pre-hydrolysis, the proportion of XOS/xylose/furfural recovered can be strongly changed. The hemicellulose content of the dissolving pulp decreased from 6.8% to about 2.6% using the FTR pretreatment.
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