Volume 12 Issue 1

Effects of the addition of spray-dried lignocellulosic material in polylactic acid (PLA) were evaluated in this work. The lignocellulosic material was produced by spray-drying unbleached fibrous material provided by a paper mill. Beforehand, this material was made hydrophobic in the sizing step of the papermaking process. We propose that size present on the lignocellulose powder may act as a potential alternative to commonly-used coupling agents in the compounding of cellulosic filler with PLA. The lignocellulose powder was compounded with PLA in various amounts by extrusion and injection-moulding. Homogeneous dispersion of the lignocellulose powder in PLA was achieved. However, comprehensive mechanical and microscopic characterisation revealed only minor positive effects of the filler on PLA in a limited number of cases. Further investigation by gel permeation chromatography (GPC) showed a reduction of the average molar mass of the PLA matrix with increasing filler content, partly due to the residual inorganic matter in the spray-dried powder. This effect overshadowed the homogeneous dispersion and resulted in composites with weaker mechanical properties in most cases.

Hemicelluloses were separated from poplar wood and exposed to thermal treatment. Changes in chemical content were investigated from 180 °C to 220 °C in a nitrogen atmosphere. Fourier transform infrared spectroscopy, X-ray diffraction, and differential thermal gravimetric analysis were used to characterize the hemicellulose before and after the thermal treatment. The effects of temperature on hygroscopicity and color were measured. The results showed that hemicelluloses were sensitive to temperature. β-glucosidic bonds and side chains in hemicelluloses were cleaved around 180 °C, and the increased temperature promoted the breaking process. Esterification reactions happened during the treatment. When the treatment temperature reached 220 °C, all side chains broke down, and partial carbonization occurred. Therefore, the color became darker, and the hydrophobicity increased. This study could help to explain the changes in wood that occur during thermal treatment.

In order to reduce production costs, heated explosion gases generated from dilute-sulfuric acid catalytic steam explosion (SE) pretreatment in the pilot production were recovered to provide energy for subsequent steps and to supply heated water (gas condensate water) for the washing steps. However, organic compounds in the explosion gases accumulated in the circulating water during continuous production, which affected subsequent enzymatic hydrolysis steps. The aim of this work was to investigate the major organic components in SE pretreatment gaseous products, their formation mechanism, and their inhibitory effects on the subsequent enzymatic hydrolysis of pretreated corn stalk.

Z. mobilis has been widely studied as a potential microbe for consolidated bioprocessing to convert lignocellulosic biomass to fermentable sugars while at the same time producing ethanol. To achieve this goal, Z. mobilis must be evaluated for the production of cellulolytic enzyme. This work reports on the potential of intracellular and extracellular crude extracts from Z. mobilis ZM4 and TISTR 551 to hydrolyze various cellulosic materials including carboxymethylcellulose (CMC), delignified rice bran, microcrystalline cellulose, and filter paper. Crude intracellular extracts from ZM4 and TISTR 551 showed high endoglucanase activity with CMC substrates at an optimal pH of 6 to 7 and temperature range of 30 to 40 °C. The endoglucanase activity from the crude extracts was significantly higher than the exoglucanase activity. Of the high crystalline celluloses substrates tested, the best results were obtained for the hydrolysis of delignified rice bran by crude intracellular enzyme extracts of Z. mobilis TISTR 551.

Traditionally, 5-hydroxymethylfurfural (HMF) is produced by using a water-organic solvent medium, which inevitably increases production costs and adds subsequent separation processes. To minimize cost and/or toxic organic solvent usage, this study presents an effective pathway for producing HMF from cellulose. The process uses a fixed bed reactor with a steam stripping process in which the cellulose is converted into HMF and other products in the presence of acidic inorganic salts. In the process, the cellulose was hydrolyzed to glucose, which was followed by isomerization to fructose and fructose dehydration into HMF. The produced HMF was easily vaporized into the gas phase, which avoided its conversion into undesired byproducts. An acceptable HMF yield of 28.2 mol% was obtained using KH2PO4 as the catalyst at 270 °C. This technology could be used to obtain both HMF and furfural (FF) from different lignocellulosic biomasses. This stripping technology has advantages such as the lack of organic solvents, showing an alternative and green HMF and/or FF production from lignocellulosic biomass.