Research Articles

Lignocellulosic biomass is the most abundant organic raw material in the world. Cellulose and hemicellulose from plants and other biomass can be hydrolyzed to produce sugars. Native lignocellulosic biomass provides limited accessibility to cellulase enzymes due to structural features. The investigations were carried out with waste lignocellulosic raw material, consisting of maize stalks and cobs. Enzyme hydrolysis was performed after acid hydrolysis with a cellulasic product. It was established that the enzyme stage, as a first treatment phase, was inefficient. It was found that cellulase activity was considerably improved after acid hydrolysis of a crushed mass. A two-stage process with acidic and then enzyme hydrolysis method was most efficient and promising for obtaining sugars for ethanol production.

Lignocellulosic fibers have received much more attention than ever before from the research community all over the world during the past few years because of their enormous advantages. A study on the preparation of new series of polymer composites using Pine Needles as a reinforcing material in Urea - Formaldehyde resin has been made. Mechanical properties of intimately mixed particle reinforced (Pine Needles) composites have been studied. Effects of different loading of reinforcement in terms of weight % on static mechanical properties such as tensile, compressive, flexural and wear properties have also been evaluated. The Urea-Formaldehyde resin prepared was subjected to evaluation of its optimum mechanical properties. The reinforcing of the resin with Pine Needles was accomplished in particle size of 200 micron by employing optimized resin. The present work reveals that mechanical properties of the Urea- Formaldehyde resin increases to a considerable extent when reinforced with Pine Needle Particles. Thermal (TGA/ DTA/DTG) and morphological studies (SEM) of the resin and polymer composites thus synthesized have also been studied. The results obtained suggest that Pine Needles can be a premium candidate for the reinforcement of high-performance polymer composites.

With the aim of increasing the sugars concentration in dilute-acid lignocellulosic hydrolyzate to more than 100 g/l for industrial applications, the hydrolyzate from spruce was concentrated about threefold by high-pressure or vacuum evaporations. It was then fermented by repeated fed-batch cultivation using flocculating Saccharomyces cerevisiae with no prior detoxification. The sugars and inhibitors concentrations in the hydrolyzates were compared after the evaporations and also fermenta-tion. The evaporations were carried out either under vacuum (VEH) at 0.5 bar and 80°C or with 1.3 bar pressure (HPEH) at 10 7.5 °C, which resulted in 153.3 and 164.6 g/l total sugars, respectively. No sugar decomposition occurred during either of the evaporations, while more than 96% of furfural and to a lesser extent formic and acetic acids disappeared from the hydrolyzates. However, HMF and levulinic acid remained in the hydrolyzates and were concentrated proportionally. The concentrated hydrolyzates were then fermented in a 4 l bioreactor with 12-22 g/l yeast and 0.14-0.22 h-1 initial dilute rates (ID). More than 84% of the fermentable sugars present in the VEH were fermented by fed-batch cultivation using 12 g/l yeast and initial dilution rate (ID) of 0.22 h-1, and resulted in 0.40±0.01 g/g ethanol from the fermentable sugars in one cycle of fermentation. Fermentation of HPEH was as successful as VEH and resulted in more than 86% of the sugar consumption under the corresponding conditions. By lowering the initial dilution rate to 0.14 h-1, more than 97% of the total fermentable sugars were consumed, and ethanol yield was 0.44±0.01 g/g in one cycle of fermentation. The yeast was able to convert or assimilate HMF, levulinic, acetic, and formic acids by 96, 30, 43, and 74%, respectively.

The effect of adsorbed and soluble carboxymethyl cellulose (CMC) on dispersing, dewaterability, and fines retention of pulp fibre suspensions was investigated. CMC was added to a suspension in the presence of electrolytes, causing its adsorption to the fibre surfaces, or to a suspension without electrolytes, so that it stayed in the liquid phase. Both the CMC adsorbed on fibre surfaces and that in the liquid phase were able to disperse the fibre suspension due to the ability of CMC to reduce fibre-to-fibre friction in both phases. Adsorbed CMC promoted the formation of a water-rich microfibrillar gel on the fibre surfaces through the spreading out of microfibrils, leading to a decrease in friction at the fibre-fibre contact points and to the increased dispersion of fibres. CMC in the liquid phase of the suspension was in turn thought to prevent fibre-to-fibre contacts due to the large physical size of the CMC molecules. CMC in both phases had detrimental effects on dewatering of the pulp suspension, but adsorbed CMC caused more plugging of the filter cake, and this was attributed to its ability to disperse fibre fines, in particular. Thus, adsorbed CMC also reduced fines retention considerably more than did CMC in the liquid phase of a suspension.

Separation of solids from liquid swine manure and subsequent thermochemical conversion (TCC) of the solids fraction into oil is one way of reducing the waste strength and odor emission. Such processing also provides a potential means of producing renewable energy from animal wastes. Gravity settling and mechanical separation techniques, by means of a centrifuge and belt press, were used to remove the solids from liquid swine manure. The solid fractions from the above separation processes were used as the feedstock for the TCC process for oil production. Experiments were conducted in a batch reactor with a steady temperature 305 oC, and the corresponding pressure was 10.34 Mpa. Gravity settling was demonstrated to be capable of increasing the total solids content of manure from 1% to 9%. Both of the mechanical separation systems were able to produce solids with dry matter around 18% for manure, with 1% to 2% initial total solids. A significant amount of volatile solid (75.7%) was also obtained from the liquid fraction using the belt press process. The oil yields of shallow pit manure solids and deep pit manure solids with belt press separation were 28.72% and 29.8% of the total volatile solids, respectively. There was no visible oil product obtained from the deep pit manure solids with centrifuge separation. It is believed that it is the volatile solid content and the other components in the manure chemical composition which mainly determine the oil production.

Dhaincha (Sesbania aculeata) is one of the annual plants in Bangladesh that has potential as a fiber source. It is a crop generally cultivated for its nutritive value to soil. This paper describes the effect of harvesting age of dhaincha on chemical, morphological, pulp, and papermaking properties and its bleachability. Dhaincha is a short length fiber that can be used as a substitute to hardwood. Fiber length was found to increase slightly with increasing age of the plant. The alpha-cellulose content in dhaincha increased and pentosan decreased with increasing age. Dhaincha pulp was prepared from 2, 3, 4, 5, and 6 month old plants under identical cooking conditions. Pulp yield (43-45 %) and kappa number (26-30) did not follow direct correlation with plant age. But physical properties of unbleached pulp increased linearly with the increase of age. Bleachability of dhaincha pulp was quite poor. The bleachability of pulp was improved when the age of dhaincha was increased.

Oxidative polymerization of two isolated lignans, secoisolariciresinol, and secoisolariciresinol diglucoside, as well as the lignan macromolecule, by a high redox potential Trametes hirsuta laccase was studied with different analytical methods. The reactivity of laccase with the different compounds was studied by an oxygen consumption measurement. The polymerization of laccase-treated lignans was evidenced by size exclusion chromatography, reversed phase - high performance liquid chromatography, and matrix-assisted laser desorption/ionisation - time of flight mass spectrometry. The data showed that the selected substrates could be oxidised by laccase. Secoisolariciresinol and secoisolariciresinol diglucoside were polymerized by laccase to a similar extent. The lignan macromolecule reacted to a lesser extent. Polymerization of the macromolecule proceeded mainly via its secoisolariciresinol diglucoside moieties. Furthermore, it was shown that ferulic acid can be linked to polymerized secoisolariciresinol via decarboxylation by laccase. This investigation showed that lignans can be enzymatically modified by Trametes hirsuta laccase.

Direct dye with a high affinity for cellulose substrate was utilized as a cellulose anchor to promote retention of paper strengthening additives under various conditions associated with the wet end of a paper machine. Direct Red 28 (DR) was covalently linked to anionic polyacrylamide (A-PAM) via a condensation reaction using water-soluble carbodiimide. The DR-conjugated A-PAM (DR-A-PAM) demonstrated good retention efficiency, resulting in strength enhancement of handsheets. Anionic trash showed no interference with the performance of DR-A-PAM in the wet end, while the additive performance was sensitive to calcium ions. Surface plasmon resonance analysis gave useful information on the cellulose-anchoring ability of DR-A-PAM. Dye molecules were irreversibly adsorbed onto the cellulose substrate under aqueous conditions, while A-PAM possessed no significant affinity for cellulose. These results suggest that anionic DR moieties in DR-A-PAM molecules served as a cellulose-anchor, possibly due to multiple CH-π interaction between hydrophobic face of cellulose substrate and π-conjugated system of dye molecules. Such a unique interaction of direct dye and cellulose provides a new insight into the wet end system, and does not depend on conventional electrostatic attraction.

Municipal wastes have become a severe problem in developed and developing countries during the last century, paper being the main constituent. Not all of the waste paper can be recycled, and therefore alternative procedures for the use of the remaining material should be pursued. The aim of the present work was the application of cellulases for waste paper treatment and the subsequent glucose production and optimization of the conditions for such treatment. Glucose thereafter can be utilized for production of ethanol or other chemicals by specific microbial cultures. The work focused in the stabilization of cellulases by cross-linking or by the addition of specific crown ether based compounds to improve glucose production. The results indicated that enzymatic treatment of waste paper is of particular interest, since it may be an alternative way to carry out municipal wastes treatment and concomitant glucose production. By the application of the proposed procedure, the total amounts of municipal wastes can be greatly reduced and production of bioethanol can be achieved.

This experimental study was conducted to investigate the role of poly-vinyl-alcohol (PVA) treatment in improving the sliding wear behaviour of pure bamboo. The effects of dipping time in PVA solution and applied load on wear behaviour of bamboo samples were determined. The wear volume of bamboo was reduced when it was treated with PVA. The wear volume during sliding was increased with increasing of applied load, whereas the coefficient of friction was reduced on PVA treatment. Worn surfaces were observed by using SEM and discussed to explain the mechanism of wear.