Hydrolysis Of Wood Research Articles

Characterization ofArxula adeninivorans strains from different habitats

Some Arxula adeninivorans strains selected from wood hydrolysates in Siberia, from soil in South Africa and from maize silage and soil in The Netherlands were compared. DNA-fingerprinting, pulse field gel electrophoresis as well as analysis of secretory proteins have been chosen to describe the similarities among the strains. Combination of the three methods allowed identification of each strain. Strains from the same origin show extensive similarities. The results of the DNA-fingerprints indicate that the strain isolated in Siberia belongs to the group of strains originated from South Africa. However, it differed in the molecular weight of the third chromosome and in the pattern of secretory proteins from the South African isolates.

Effect of surfactants on cellulose hydrolysis

The effect of surfactants on the heterogeneous enzymatic hydrolysis of Sigmacell 100 cellulose and of steam-exploded wood was studied. Certain biosurfactants (sophorolipid, rhamnolipid, bacitracin) and Tween 80 increased the rate of hydrolysis of Sigmacell 100, as measured by the amount of reducing sugar produced, by as much as seven times. The hydrolysis of steam-exploded wood was increased by 67% in the presence of sophorolipid. At the same time, sophorolipid was found to decrease the amount of enzyme adsorbed onto the cellulose at equilibrium. Sophorolipid had the greatest effect on cellulose hydrolysis when it was present from the beginning of the experiment and when the enzyme/cellulose ratio was low.

Evaluation of gel permeation chromatographic techniques and diode-array UV detection for the characterization of biotechnological fermentation substrates and broths

Gel permeation chromatography (GPC) was used for the analysis and characterization of fermentation substrates and broths. Chemical or enzymatic hydrolysis of wood and waste waters from the pulp industry were used as the substrate in ethanol fermentation. Sample pretreatment was carried out by liquid-liquid extraction with dichloromethane and water. The two phases were subjected to analysis by organic and aqueous GPC using a polymer-based GPC column, a silica support and a GPC column with dichloromethane, water and water-miscible tetrahydrofuran as the mobile phases. respectively. Diode-array UV spectrophotometric detection (DAD) of substrates and broths was utilized for characterization complementary to the GPC separations. The DAD method will give UV absorption spectra for different samples providing unique fingerprints for the specific compounds present.

Pretreatment of wood by UCT-solvent for the enzymatic hydrolysis

UCT-solvent pretreatment was carried out on woods (beech and akamatsu (pine)) for the enzymatic hydrolysis, in which pretreatment the ground woods were autoclaved with a mixture of water and cyclo-hexanol (37.5% vol% cyclohexanol) having upper critical temperature (UCT: 184°C) on the mutual solubility curve (named as UCT-solvent). Ninety-five and 92% of Klason lignin were removed from beech and akamatsu, respectively, whereas when the woods were autoclaved with water instead of UCT-solvent, only 43 and 18% of Klason lignin was removed from them, respectively. The excellent ability of UCT-solvent for the removal of Klason lignin is owing to that the solvent disturbs re-coupling between the degradation products. The enzymatic hydrolysis of wood was much improved by UCT-solvent pretreatment: the hydrolytic reactivity of akamatsu was enhanced by 2.8 times comparing with when akamatsu was pretreated with water instead of UCT-solvent.

Effects of cell-wall acetate, xylan backbone, and lignin on enzymatic hydrolysis of aspen wood

Aspen wood substrates with varying degrees of deacetylation, xylan, and lignin removal have been prepared and submitted to enzymatic hydrolysis with a cellulase/hemicellulase preparation for an extended constant period of hydrolysis. Controlled deacetylation has been achieved by treating wood with various alkali metal hydroxide solutions, at various alkali/wood ratios. It has been found that samples with the same extent of deacetylation produce the same sugar yields upon enzymatic hydrolysis. Increased degree of deacetylation increases the yield of sugars obtained from enzymatic hydrolysis, all other compositional parameters held constant. The acetyl group removal is proportional to the stoichiometric relation between added base and wood acetyl content, i.e., the same number of milliequivalents of base/weight of wood remove the same extent of acetyl groups, regardless of the concentration of the base solution. No cation effects are found among Li, Na, and K alkali hydroxide solutions, suggesting that swelling is not as important a parameter as is the removal of the acetyl groups from the xylan backbone in determining the extent of hydrolyzability of the resulting sample.

Formation and Reactions of Leucochromophoric Structures in High Yield Pulping

ABSTRACT Low molecular weight lignols with intact side chains were produced by mild hydrolysis of spruce wood, of unbleached and hydrogen peroxide bleached spruce groundwood and of chemithermomechanical pulp (CTMP). The major monomeric, dimeric and trimeric lignin products derived were isolated by HPLC and characterized by GC-MS and NMR. The behaviour of these products towards photo-oxidation in the solid state on filter paper was studied. Coniferaldehyde structures, the major leucochromophores originally present in spruce wood lignin, were reduced during the CTMP process and eliminated after bleaching with hydrogen peroxide. Diguaiacyl stilbene originating from diarylpropane structures and produced during hydrogen peroxide bleaching were found to be the predominant leucochromophoric structure present in the hydrogen peroxide bleached pulps and these were found to be responsible for the fast photoyellowing of these pulps.

Anaerobic Treatment of Pulp Mill Effluents

A laboratory-scale study on the anaerobic treatment of selected pulp mill streams was carried out in a collaboration between the Research Institute for Environmental Protection and Designing Office of Water and Waste Disposal. Anaerobic treatment of effluents from acid hydrolysis of wood from sulfate cellulose production, and effluents from the sulfite cellulose fibers washing was investigated. The results indicated 80% COD removal and the average methane generation was found to be 340 Ncm3/gCOD removed in case of highly polluted (COD = 63 kgO2/m3) acid hydrolysis effluents. The waste from cellulose washing contained, beside sugars, alsorefractory compounds, such as high-molecular-mass lignin derivatives, resins and tannins. According to that, only 20-30% COD removal was obtained and the methane generation was 270-360 Ncm3/g COD removed.

Growth, death, and oxygen uptake kinetics of Pichia stipitis on xylose

Pichia stipitis NRRL Y-7124 has potential application in the fermentation of xylose-rich waste streams, produced by wood hydrolysis. Kinetic models of cell growth, death, and oxygen uptake were investigated in batch and oxygen-limited continuous cultures fed a rich synthetic medium. Variables included rates of dilution (D) and oxygen transfer (K(1)a) and concentrations of xylose (X), ethanol (E), and dissolved oxygen (C(ox)). Sustained cell growth required the presence of oxygen. Given excess xylose, specific growth rate (micro) was a Monod function of C(ox). Specific oxygen uptake rate was proportional to mu by a yield coefficient relating biomass production to oxygen consumption; but oxygen uptake for maintenance was negligible. Thus steady-state C(OX) depended only on D, while steady-state biomass concentration was controlled by both D and K(1)a. Given excess oxygen, cells grew subject to Monod limitation by xylose, which became inhibitory above 40 g/L. Ethanol inhibition was consistent with Luong's model, and 64. 3 g/L was the maximum ethanol concentration allowing growth. Actively growing cells died at a rate that was 20% of micro. The dying portion increased with E and X.

Effect of pretreatment on simultaneous saccharification and fermentation of hardwood into Acetone/Butanol

The effectiveness of pretreatments on hardwood substrate was investigated in connection with its subsequent conversion by simultaneous saccharification and fermentation (SSF), using Clostridium acetobutylicum. The main objectives of the pretreatment were to achieve efficient separation of lignin from carbohydrates, and to obtain maximum sugar yield on enzymatic hydrolysis of pretreated wood. Two methods have given promising results: (1) supercritical CO2-SO2 treatment, and (2) monoethanolamine (MEA) treatment. The MEA pretreatment removed above 90% of hardwood lignin while retaining 83% of carbohydrates. With CO2-SO2 pretreatment, the degree of lignin separation was lower. Under the scheme of SSF, the pretreated hardwood was converted to acetone, butanol, and ethanol (ABE) via single stage processing by cellulase enzyme system and C. acetobutylicum cells. The product yield in the process was such that 15 g of ABE/100 g of dry aspen wood was produced. In the overall process of SSF, the enzymatic hydrolysis was found to be the rate-limiting step. The ability of C. acetobutylicum to metabolize various 6-carbon and 5-carbon sugars resulted in efficient utilization of all available sugars from hardwood.

The effect of enzyme and substrate levels on the specific hydrolysis rate of pretreated poplar wood

The hydrolysis of pretreated poplar wood was carried out with initial concentrations of 1.26, 2.52, 5.04 mg proteinJmL of GC123Trichoderma reesei. cellulase and substrate concentrations of 2.5% wJv, 5% w/v, and 10% wJv at pH 4.8 and 40°C. The concentration of enzyme protein remaining in solution, the glucose concentration, and the total potential glucose concentrations were measured as a function of time during the hydrolysis. The enzyme rapidly adsorbed initially, reaching a maximum in about 30 min. About 55–75% of the cellulase returned to solution as the remaining cellulose was hydrolyzed. Dilution of the unhydrolyzed residue, largely lignin, did not cause additional desorption of the cellulase. The specific hydrolysis rate (i.e., the rateJamount of adsorbed enzyme) declined significantly with increased conversion, even when corrected for glucose inhibition. At a given initial substrate concentration, the specific rate was found to be largely independent of the total enzyme concentration. However, at a given fractional conversion, the specific rate was found to be reduced by increased substrate concentration.

Ethanol production from sulphuric acid wood hydrolysate ofPinus radiata using free and immobilized cells ofPichia stipitis

Ethanol was produced by a strain ofPichia stipitis adapted to an inhibitory acid wood hydrolysate ofPinus radiata. The best ethanol productivity for batch cultures was 0.21 g/l h at 0.7% ethanol. Varying culture conditions increased ethanol concentration to 0.76%, however the productivity decreased to 0.18 g/l h. A decrease in ethanol concentration in the culture fluid was noted late in the batch which suggested ethanol catabolism. Values of kinetic parameters (Km,Ks,μmax, andVmax) were evaluated for this system. The use of calcium alginate immobilized cells in a continuous-flow stirred tank reactor lead to enhanced fermentative performance, namely a maximum productivity of 0.27 g/l h and 1.13% ethanol yield. The immobilized cells in continuous flow reactors represent an attractive option for fermenting sugars released by sulphuric acid hydrolysis ofP. radiata wood.

A technical and economic analysis of acid-catalyzed steam explosion and dilute sulfuric acid pretreatments using wheat straw or aspen wood chips

Lignocellulosic biomass is one of the most plentiful and potentially cheapest feedstocks for ethanol production. The cellulose component can be broken down into glucose by enzymes and then converted to ethanol by yeast. However, hydrolysis of cellulose to glucose is difficult, and some form of pretreatment is necessary to increase the susceptibility of cellulose to enzymatic attack. An analysis has been completed of two pretreatment options, dilute sulfuric acid hydrolysis and sulfur dioxide impregnated steam explosion, for two feedstocks, wheat straw and aspen wood chips. Detailed process flow sheets and material and energy balances were used to generate equipment cost information. A technical and economic analysis compared the two feedstocks for each of the two pretreatments. For the same pretreatment, sugars produced from aspen wood hydrolysis were cheaper because of the higher carbohydrate content of aspen, whereas dilute acid pretreatment is favored over acid-catalyzed steam explosion.

Adsorption and desorption of cellulase components during enzymatic hydrolysis of steamed shirakamba (Betula platyphylla Skatchev) wood

Abstract The adsorption behavior of Trichoderma viride cellulases on steamed shirakamba ( Betula platyphylla Skatchev) wood was studied. Substrate/enzyme (S/E) ratio, hydrolysis time and saccharification extent as well as the presence or absence of lignin in the substrate were taken into consideration as factors affecting the enzyme adsorption. Filter paperase (FPase) components were adsorbed more selectively than other cellulase components on the substrate. The presence of lignin in the steaamed hardwood tended to slow down the enzyme adsorption, but it did not appear to restrict the extent of hydrolysis of the carbohydrate moiety. The changes in the composition of the enzyme preparation during the course of hydrolysis were analyze by fast protein liquid chromatography (FPLC). The irreversible adsorption of specific cellulase components was not observed in the prolonged hydrolysis of steamed shirakamba wood containing abundant lignin. The removal of lignin from steamed hardwood prior to hydrolysis is not always necessary for the recycling of cellulolytic enzymes.

Reactivity Toward Phenol of Lignin from the Hydrolysis of Sweetgum Wood with Concentrated Sulfuric Acid

Abstract Sweetgum wood was hydrolyzed at 20°C and 50°C for different time periods with 68% sulfuric acid. The lignin residues obtained were subjected to a phenolation reaction. For lignin prepared at the lower temperature the maximum phenol uptake was 9.5%, and at the higher temperature only 5–6%. When wood prehydrolyzed with dilute acid was used the phenol uptake rose to 12.5%. However, all the sulfuric acid hydrolysis lignins showed much lower reactivity toward phenol than the 20% phenol uptake exhibited by lignin isolated using concentrated hydrochloric acid.

Production of 2,3-butanediol from wood hydrolysate byKlebsiella pneumoniae

2,3-Butanediol was produced at 12g/l (27% w/w yield) from the reducing sugars in wood hydrolysate byKlebsiella pneumoniae NRRL B-199. Ethanol was present at 4 g/l and acetoin at 0.4 g/l. Optimum conditions for a 48 h fermentation were pH 6.0, 30°C and 50 g reducing sugars/l. Adding 1% (w/v) malt extract to the medium-enhanced butanedlol production to 13.3 g/l (yield 29%) without changing ethanol production.

Adsorption of cellulase from Trichoderma reesei on cellulose and lignacious residue in wood pretreated by dilute sulfuric acid with explosive decompression

The adsorption of cellulase on cellulose and a lignacious residue was examined by using cellulase from Trichoderma reesei, hardwood pretreated by dilute sulfuric acid under high pressure, and a lignacious residue prepared by a complete enzymatic hydrolysis of the pretreated wood. A significant amount of cellulase was found to adsorb on the lignacious residue during the hydrolysis of the pretreated wood. Hence, the adsorption of enzyme on the lignacious residue as well as cellulose must be taken into account in the development of the hydrolysis kinetics. It was found that the adsorption of enzyme on cellulose and on the lignacious residue could be represented by Langmuir type isotherms. The data show that the pretreatment at a higher temperature results in more enzyme adsorption on the cellulose fraction and less on the lignacious residue fraction. The relationship between the hydrolysis rate and the amount of enzyme adsorbed is discussed.

Production of ethanol from sugars in wood hydrolysate byFusarium oxysporum

Wood hydrolysate used for ethanol production by two strains ofFusarium oxysporum contained 2.3% (w/v) reducing sugars (xylose and glucose). Ethanol production at the optimum reducing sugar concentration of 54.8 g/l medium, at pH 5.5, and 30°C was 12.3 g/l and 11.7 g/l byF. oxysporum D-140 and NCIM-1072, respectively in shake flasks during 96 h fermentation. The maximum production of ethanol under optimum cultural conditions, and in the presence of yeast extract plus minerals, was 13.2 g/l medium byF. oxysporum D-140 over 108 h fermentation.

Evaluation of Alkaline Earth and Transition Metals for Use in the Ion Moderated Partition Chromatography of Sugars

Abstract The elution behavior of 28 sugars and related compounds from high performance chromatography columns packed with alkaline earth and transition metals was investigated. As expected from the well-known chromatography of the commercially available calcium, silver, and lead form columns, elution behavior is highly metal-ion form specific. A significant data base of sugar elution versus column cationic-form was generated to permit the selection of new columns to enhance the separation of specific eluting species. Sugars resulting from the hydrolysis of wood were closely examined. Arabinose and galactose, known to be difficult to separate on commercially available lead and silver-form columns, were well separated on custom-packed rubidium and cesium-form columns.

HTST hydrolysis of wood: Modelling of the kinetics and projections on reactor configuration

We present experimental data on hydrolysis of wood in high temperature short residence time (HTST) and low acid concentration conditions. Effects of temperature, acid concentration, particle size and liquid/solid ratio are discussed. A kinetic model is proposed which accounts for effects of temperature and acid concentration. This kinetic model is used to predict performance of a twin-screw extruder as a hydrolyser which consists of ideal mixed flow or plug flow reactor units in series.

Influence of phenolics on biomass production by Candida utilis and Candida albicans

The effect of some lignin degradation products, which can be present in wood hydrolysates, on biomass production by Candida sp. was studied. Suspected inhibitors were used as supplements in growth media for C. utilis and C. albicans containing pure glucose as a carbon energy source. The metabolism of inhibitors by C. utilis and C. albicans is approximately the same and is extremely sensitive to the structure and concentration of the phenolic additive. ID 50 and ID 100 values for a 50% or a 100% growth inhibition for 20 lignin monomer model compounds during Candida sp. cultivation were established. Comparison of ID values has shown that the least toxic compounds for C. utilis and C. albicans biomass growth and yield are vanillyl alcohol, conipheryl alcohol and syringic acid. The most toxic compounds are salicylic acid, cinnamic acid, benzoic acid and o-vanillin.