Hydrolysis Of Wood Research Articles

A biotechnology for the production of new biodiesel fuel

A new biotechnology for the production of biodiesel fuel on the basis of the lipids of filamentous fungi has been developed. The oleaginous mucoralean fungus, which produces up to 47.0–50.0% of lipids similar to rapeseed oil in their composition, are used as a producer. The duration of the fermentation process at 27–28°C is 4–5 days. The main characteristics of the biodiesel fuel based on fungal lipids satisfy the requirements of the basic standards, in particular, EN14214. The possibilities for creating a wasteless closedcycle technology based on the production of biodiesel and chitin in a single fermentation, applying stimulators for the germination of fungal conidia to reduce the duration of fermentations, and using glycerin formed in the synthesis of methyl esters as a source of carbon in a fermentation medium, along with wood hydrolyzates and the wastes of certain food plants in the fermentation process, are shown.

Renewable gasoline from aqueous phase hydrodeoxygenation of aqueous sugar solutions prepared by hydrolysis of maple wood

In this paper we demonstrate an integrated process for the production of high octane gasoline from maple wood by hydrolysis of maple wood into aqueous carbohydrate solutions followed by aqueous phase hydrodeoxygenation of the sugar solutions. The aqueous carbohydrate solutions were prepared by both hydrolysis in hot water and hydrolysis with dilute acids (H2SO4, oxalic acid). The aqueous carbohydrate solutions were a mixture of xylose, water soluble hemicellulose oligomers, acetic acid, glucose, glucose oligomers, and probably some lignin polymers. Hydrolysis with hot water produced primarily hemicellulose oligomers whereas hydrolysis with acids produced mainly xylose and acetic acid. The hydrolysis co-product was a solid enriched in cellulose and lignin. The aqueous streams were hydrodeoxygenated by a two step catalytic process in which the first catalyst bed contained a Ru/C catalyst at 393 K and the second catalyst bed contained a Pt/zirconium phosphate (Pt/ZrP) catalyst at 518 K. The Ru/C catalyst was able to selectively hydrogenate xylose into xylitol but could not selectively hydrogenate the xylose oligomers. The two stage process was able to convert the aqueous carbohydrate streams derived from maple wood into gasoline range products with carbon yields of up to 57% and an estimated octane number of 96.5. No significant catalyst deactivation was observed indicating that the catalysts are very stable. The highest gasoline yield from this two stage process was obtained from the stream produced by acid hydrolysis of maple wood with 0.5 wt% oxalic acid at 433 K for 0.5 h. These results suggest that aqueous phase processing of sugars obtained by hydrolysis is a promising option for the production of fuels and chemicals from lignocellulosic biomass.

Noncatalytic fast hydrolysis of wood

Willow without any pretreatment, and water were studied in an optical micro-reactor, diamond anvil cell by rapid heating (7-10°C/s) to high temperatures and high pressures (up to 403°C and 416 MPa), most of willow (89-99%) dissolved and hydrolyzed in water at 330-403°C within 22 s. It was found that low-density water (e.g., 571 kg/m(3)) solubilized almost all willow with particle size less than 200 μm, and subsequently hydrolyzed to hydrolysates in subcritical water at 354°C and 19 MPa within 9 s. These results were further used to propose a flow process to fast hydrolyze wood in seconds to valuable sugars.

Barrier Films from Renewable Forestry Waste

Biobased free-standing films and coatings with low oxygen permeability were designed from a wood hydrolysate according to a recovery and formulation procedure that provides added value to wood converting industrial processes. Wood components released to the wastewater in the hydrothermal treatment of spruce wood were recovered and converted to an oligo- and polysaccharide-rich, noncellulosic fraction that was utilized in film formulations in a range of concentrations and compositions. Free-standing smooth and transparent films as well as coatings on thin PET were prepared and characterized with respect to oxygen permeability, tensile properties, structure, and water vapor transmission. With oxygen permeabilities as low as below 1 cm(3) μm m(-2) day(-1) kPa(-1) and with adequate mechanical properties, the films and coatings show promising property profiles for renewable packaging applications.

Polymer induced flocculation and separation of particulates from extracts of lignocellulosic materials

Biofuels from lignocellulosic materials like wood are renewable and sustainable alternatives to petroleum and other fossil fuels. Wood can be grown and harvested without adding to the carbon load of the atmosphere and thus can be part of the solution to the problem posed by global climate changes. Recently much interest has developed on the concept of the forest product biorefinery, where wood is hydrolyzed prior to conventional pulping and papermaking processes and the hydrolyzate consisting of hemicellulose sugars are to be used as a feedstock for biofuels or bioplastics. The purification of the hydrolyzate stream and the separation of fermentable sugars from it thus constitutes an important step in biorefinery processes. The separation of particulate material from wood hydrolyzates is considered in this paper. Sugar maple hardwood was extracted with hot water at 160 degrees C. The extracts contain hemicelluloses (primarily xylooligomers, xylose and xylan), acetic acid and smaller amounts of lignin. The colloidal stability of the extracts plays a critical role in the separation and purification of the wood extracts. Here, we report the size and charge of the particles in the extract measured using standard instruments based on light scattering and microelectrophoresis. Particles were found to be in the size range from approximately 220nm to 270nm. Zeta potential measurements showed them to be negatively charged. By treating the extracts with a cationic flocculating agent poly-DADMAC, it was possible to preferentially precipitate out the colloidal fraction containing lignin and lignin derived compounds. Upon the addition of poly-DADMAC the turbidity of the suspension reduced from 920 NTU to 4 NTU in a 24 h period and particulates sedimented from the extract. The lignin concentration was reduced in the supernatant, while the sugar content remained unchanged. The addition of an indifferent electrolyte hindered the effectiveness of the polyelectrolyte. The optimum pH for the effectiveness of the polymer was found to be around 4.5. In order to accelerate the sedimentation of the particles, Kaolin was added to attach to the flocs after adding the polyelectrolyte. Kaolin helped accelerate the separation of the particulates by almost an order of magnitude. This work shows that flocculation with a cationic polyelectrolyte followed by separation by sedimentation, centrifugation or microfiltration can be an effective technique to purify biorefinery wood extracts.

아세톤에 의한 목재 조성분의 분리

본 연구는 산염이 첨가된 아세톤 용액으로 목질바이오매스를 가수분해하여 효과적으로 화학적 조성분을 분리할 수 있는 최적조건을 확립하는데 있다. 아세톤에 의한 목질바이오매스의 가수분해에서 <TEX>$Al_2(SO_4)_3$</TEX>은 우수한 촉매로 작용하였으며, 최적 농도는 0.01 M (6.3 wt%)였다. 본 실험에서는 아세톤과 물의 비율을 9 : 1로 맞추고 <TEX>$Al_2(SO_4)_3$</TEX>의 최적 농도조건에서 신갈나무재와 소나무재를 <TEX>$200^{\circ}C$</TEX>에서 45분 동안 가수분해하여 각각 92.7%와 92.4% 분해율을 나타냈다. 아세톤과 물의 비율이 8 : 2에서는 반응시간을 60분으로 연장하였을 경우 신갈나무재의 가수분해율은 92.7%였으나, 소나무재는 반응온도를 <TEX>$210^{\circ}C$</TEX>로 상승시켜야 신갈나무재에 버금가는 가수분해율을 얻을 수 있었다. 가수분해 온도와 시간을 증가시키면 가수분해산물로부터 분리, 회수되는 리그닌은 증가하였으나, 탄수화물 함량은 급격히 감소하는 경향을 보였다. 리그닌과 당의 회수량을 고려해 보면, 목질바이오매스의 최적 가수분해 조건은 아세톤과 물의 비율 8 : 2, 아세톤 용액에 대한 <TEX>$Al_2(SO_4)_3$</TEX> 농도는 6.3 wt%, 가수분해 온도와 시간은 각각 <TEX>$190^{\circ}C$</TEX>와 60분으로 나타났고, 이 조건에서 당의 회수율은 목질바이오매스 전건중량 기준으로 신갈 나무재와 소나무재에서 각각 47.6%와 51.4%로 나타났고, 리그닌 회수율은 각각 18.2%와 13.7%로 측정되었다. The purpose of this study was to seek the optimum condition for effective separation of the chemical constituents of wood biomass by means of hydrolysis of acetone solution in presence of acid salt as a catalyst. Out of diverse acid salts the catalytic effect of aluminum sulfate (<TEX>$Al_2(SO_4)_3$</TEX>) was the most excellent during the hydrolysis of wood biomass in the acetone solution and the optimum concentration was 0.01 M (6.3 wt%). In the condition of mixture ratio of acetone and water to 9 : 1 as well as optimum concentration of aluminum sulfate two wood biomass species, oak wood (Quercus mongolica Fischer) and Pine wood (Pinus densiflora Sieb. et Zucc.), was hydrolyzed for 45 minutes at <TEX>$200^{\circ}C$</TEX> and the degree of hydrolysis was determined to 92.7% and 92.4%, respectively. Extending the reaction time to 60 minutes in the mixture ratio of acetone and water to 8 : 2 the degree of hydrolysis of oak wood was also ca. 92.7%. In the case of Pinus, however, the similar hydrolysis ratio was obtained at <TEX>$210^{\circ}C$</TEX>. As the temperature and hydrolysis time increased, the quantitative amount of lignin recovered from the hydrolysate clearly increased, whereas the total amount of carbohydrates in the hydrolysate decreased rapidly. Considering the recoverable amount of lignin and carbohydrate in the hydrolysate, the best condition for the hydrolysis of wood biomasses were confirmed to the mixture ratio of acetone and water to 8 : 2, the concentration of aluminum sulfate of 6.3 wt%, hydrolysis temperature of <TEX>$190^{\circ}C$</TEX> for 60 minutes. In this condition the total amounts of carbohydrate in the hydrolysates of oak wood and pine wood were estimated to 47.6% and 51.4%, respectively. The amount of lignin recovered from the hydrolysates were ca. 18.2% for oak wood and 13.7% for pine wood.

Effects of organosolv pretreatment and enzymatic hydrolysis on cellulose structure and crystallinity in Loblolly pine

Ethanol organosolv pretreatment was performed on Loblolly pine to enhance the efficiency of enzymatic hydrolysis of cellulose to glucose. Solid-state 13C NMR spectroscopy coupled with line shape analysis was used to determine the structure and crystallinity of cellulose isolated from pretreated and enzyme-hydrolyzed Loblolly pine. The results indicate reduced crystallinity of the cellulose following the organosolv pretreatment, which renders the substrate easily hydrolyzable by cellulase. The degree of crystallinity increases and the relative proportion of para-crystalline and amorphous cellulose decreases after enzymatic hydrolysis, indicating preferential hydrolysis of these regions by cellulase. The structural and compositional changes in this material resulting from the organosolv pretreatment and cellulase enzyme hydrolysis of the pretreated wood were studied with solid-state CP/MAS 13C NMR spectroscopy. NMR spectra of the solid material before and after the treatments show that hemicelluloses and lignin are degraded during the organosolv pretreatment.

Humin-like substances formed under the conditions of industrial hydrolysis of wood

Pathways of formation of humin-like substances from carbohydrates and furan compounds under the conditions of acid hydrolysis of wood were studied.

Depolymerization of lignocellulosic biomass to fuel precursors: maximizing carbon efficiency by combining hydrolysis with pyrolysis

In this paper we study the carbon efficiency of combining hydrolysis and pyrolysis processes using maple wood as a feedstock. A two-step hydrolysis of maple wood in batch reactors, that consisted of a thermochemical pretreatment in water followed by enzymatic hydrolysis, achieved an 88.7 wt% yield of glucose and an 85 wt% yield of xylose as liquid streams. The residue obtained was 80 wt% lignin. A combination of TGA and pyroprobe studies was used for the pyrolysis of pure maple wood, hemicellulose-extracted maple wood, and the lignin residue from the hydrolysis of maple wood. Pyrolysis of raw maple wood produced 67 wt% of condensable liquid products (or bio-oils) that were a mixture of compounds including sugars, water, phenolics, aldehydes, and acids. Pyrolysis of hemicellulose-extracted maple wood (the solid product after pretreatment of maple wood) showed similar bio-oil yields and compositions to raw maple wood while pyrolysis of the lignin residue (the final solid product of enzymatic hydrolysis) produced only 44.8 wt% of bio-oil. The bio-oil from the lignin residue is mostly composed of phenolics such as guaiacol and syringol compounds. Catalytic fast pyrolysis (CFP) of maple wood, hemicellulose-extracted maple wood, and lignin residue produced 18.8, 16.6 and 10.1 wt% aromatic products, respectively. Three possible options for the integration of hydrolysis with pyrolysis processes were evaluated based on their material and carbon balances: Option 1 was the pyrolysis/CFP of raw maple wood, option 2 combined hemicellulose extraction by hydrolysis with pyrolysis/CFP of hemicellulose-extracted maple wood, and option 3 combined the two-step hydrolysis of hemicellulose and cellulose sugar extraction with pyrolysis/CFP of the lignin residue. It was found that options 1, 2, and 3 all have similar overall carbon yields for sugars and bio-oils of between 66 and 67%.

Larkinella arboricola sp. nov., a new spiral-shaped bacterium of the phylum Bacteroidetes isolated from the microbial community of decomposing wood

An aerobic gram-negative bacterial strain Z-0532 with ring-shaped cells forming spirals in the course of growth was isolated from the humified solution produced by spruce wood decomposition. The new isolate was a chemoorganotrophic, mesophilic, moderately acidophilic organism with the temperature range of 6–32°C (optimum at 25–28°C) and pH range from 4.7 to 7.2 (optimum at pH 5.5–6.5). A broad range of substrates was used as carbon and energy sources, including sugars, some organic acids and polyalcohols, and soluble polymeric compounds (gelatin, esculin, starch, xylan, laminarin, dextrin, casein hydrolysate, and Tween-40). According to its physiological and biochemical characteristics, strain Z-0532 is a typical member of the trophic group of oligotrophic bacteria, which utilize the products of wood hydrolysis dissipated by xylotrophic microorganisms. The G+C base content of strain Z-0532 was 52.1 mol %. Sequencing of the 16S rRNA gene of the new isolate revealed 98% similarity to Larkinella insperata LMG 22510T, which is a recently described species of the family Spirosomaceae of the phylum Bacteroidetes. The level of DNA: DNA homology between this species and strain Z-0532 was only 40%. The differences in the phenotypic and genotypic characteristics suggested classification of the isolate obtained from decomposing wood as a new species of the genus Larkinella, Larkinella arboricola sp. nov., with the type strain Z-0532T (=VKM B-2528T = DSM 21851T).

Alcohol-based biofuel production from waste wood hydrolysate

Alcohol-based biofuel production from waste wood hydrolysate

Deactivation of catalysts for fossil coal and biomass conversion

Increasing interest in the use of resources of organic raw materials alternative to petroleum stimulates researchers to study the catalytic intensification of fossil coal and vegetable biomass conversion. The industrial use of the developed technologies is restricted by the problem of enhanced catalyst deactivation. The main reasons for catalyst deactivation in solid organic raw materials conversion are considered in the review. The possible ways of the successful solution of the problem of catalyst deactivation in the processes of coal and biomass liquefaction and gasification and wood delignification and hydrolysis are exemplified by the studies accomplished over the last decade. In the case of technologies using the synthetic catalysts, the methods of their regeneration developed for the catalytic processing of heavy petroleum residues can be applied. The catalyst regeneration is not demanded for the processes accomplished in a fluidized catalytic bed under the conditions of catalyst loss as a result of its attrition and in the case of the application of melted catalysts, cheap iron-containing catalysts, catalytically active slag materials, and natural minerals. The substitution of dissolved catalytic systems for solid catalysts allows for the diminishing of their deactivation in the processes of wood delignification and hydrolysis.

Quantitative analysis of sugars in wood hydrolyzates with 1H NMR during the autohydrolysis of hardwoods

The focus of this work was to determine the utility of 1H NMR spectroscopy in the quantification of sugars resulting from the solubilization of hemicelluloses during the autohydrolysis of hardwoods and the use of this technique to evaluate the kinetics of this process over a range of temperatures and times. Yields of residual xylan, xylooligomers, xylose, glucose, and the degraded products of sugars, i.e., furfural and HMF (5-hydroxymethyl furfural), were determined. The monosaccharide and oligomer contents were quantified with a recently developed high resolution 1H NMR spectroscopic analysis. This method provided precise measurement of the residual xylan and cellulose remaining in the extracted wood samples and xylose and glucose in the hydrolyzates. NMR was found to exhibit good repeatability and provided carbohydrate compositional results comparable to published methods for sugar maple and aspen woods.

Increased Saccharification Yields from Aspen Biomass Upon Treatment with Enzymatically Generated Peracetic Acid

The recalcitrance of lignocellulosic biomass to enzymatic release of sugars (saccharification) currently limits its use as feedstock for biofuels. Enzymatic hydrolysis of untreated aspen wood releases only 21.8% of the available sugars due primarily to the lignin barrier. Nature uses oxidative enzymes to selectively degrade lignin in lignocellulosic biomass, but thus far, natural enzymes have been too slow for industrial use. In this study, oxidative pretreatment with commercial peracetic acid (470 mM) removed 40% of the lignin (from 19.9 to 12.0 wt.% lignin) from aspen and enhanced the sugar yields in subsequent enzymatic hydrolysis to about 90%. Increasing the amount of lignin removed correlated with increasing yields of sugar release. Unfortunately, peracetic acid is expensive, and concentrated forms can be hazardous. To reduce costs and hazards associated with using commercial peracetic acid, we used a hydrolase to catalyze the perhydrolysis of ethyl acetate generating 60-70 mM peracetic acid in situ as a pretreatment to remove lignin from aspen wood. A single pretreatment was insufficient, but multiple cycles (up to eight) removed up to 61.7% of the lignin enabling release of >90% of the sugars during saccharification. This value corresponds to a predicted 581 g of fermentable sugars from 1 kg of aspen wood. Improvements in the enzyme stability are needed before the enzymatically generated peracetic acid is a commercially viable alternative.

Quantitative solid state NMR analysis of residues from acid hydrolysis of loblolly pine wood

The composition of solid residues from hydrolysis reactions of loblolly pine wood with dilute mineral acids is analyzed by 13C Cross Polarization Magic Angle Spinning (CP MAS) NMR spectroscopy. Using this method, the carbohydrate and lignin fractions are quantified in less than 3 h as compared to over a day using wet chemical methods. In addition to the quantitative information, 13C CP MAS NMR spectroscopy provides information on the formation of additional extractives and pseudo lignin from the carbohydrates. Being a non-destructive technique, NMR spectroscopy provides unambiguous evidence of the presence of side reactions and products, which is a clear advantage over the wet chemical analytical methods. Quantitative results from NMR spectroscopy and proximate analysis are compared for the residues from hydrolysis of loblolly pine wood under 13 different conditions; samples were treated either at 150 °C or 200 °C in the presence of various acids (HCl, H 2SO 4, H 3PO 4, HNO 3 and TFA) or water. The lignin content determined by both methods differed on averaged by 2.9 wt% resulting in a standard deviation of 3.5 wt%. It is shown that solid degradation products are formed from saccharide precursors under harsh reaction conditions. These degradation reactions limit the total possible yield of monosaccharides from any subsequent reaction.

A comparison of stress tolerance in YPD and industrial lignocellulose-based medium among industrial and laboratory yeast strains

In general, it is believed that fermentation by yeast under harsh industrial conditions, especially if substrates such as wood hydrolysate or lignocellulosic substrates are used, requires the use of so-called industrial strains. In order to check whether this is always true, a comparison of performance was made using two industrial strains and four commonly used laboratory strains, the haploid and diploid versions of CEN-PK and X2180, under industrially relevant stress conditions. The industrial strains were a Swedish commercial baker's yeast strain and a strain previously isolated from an industrial bioethanol production plant using lignocellulosic substrate. Stress conditions included, apart from growth in the lignocellulosic substrate itself, elevated concentrations of glucose, NaCl, ethanol, and lactate as well as low pH. Results showed that, indeed, the strain adapted to lignocellulosic substrate also possessed the highest growth rate as well as shortest duration of the lag phase in this type of medium. However, the higher the additional stress level, the lower the difference compared to other strains, and X2180 in particular displayed a high resistance to these additional stress conditions. Furthermore, no difference in performance could be detected between the haploid or diploid versions of the laboratory strains. It might be that, at least under some circumstances, a laboratory strain such as X2180 could be an industrially attractive production organism with the advantage of facilitating the possibilities for making controlled genetic manipulations.

Comparison of vacuum and high pressure evaporated wood hydrolyzate for enthanol production by repeated fed-batch using flocculating Saccharomyces cerevisiae

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.

Ethanol production from a membrane purified hemicellulosic hydrolysate derived from sugar maple by Pichia stipitis NRRL Y-7124

In an effort to devise inexpensive and sustainable production of ethanol fuel, experiments were conducted to establish conditions for Pichia stipitis NRRL Y-7124 to ferment a membrane treated wood hydrolysate derived from sugar maple to produce ethanol. The degree of aeration required to effectively utilize xylose, produce ethanol, and minimize xylitol formation as well as the optimal hydrolysate concentration were the conditions examined. P. stipitis produced the highest concentrations of ethanol in shake flasks at 150 rpm (14.3 g/L in 71 h), and 50% hydrolysate maximized ethanol yield (12.4 g/L in 51.5 h). In the 50% hydrolysate cultures, P. stipitis produced ethanol at a rate of 0.24 g/L×h with a yield of 0.41 g ethanol/g wood-derived carbohydrate.

Complete dissolution and hydrolysis of wood in hot water

AbstractWhen willow and water were heated rapidly (7–16°C/s) to high temperatures and high pressures, most of willow (90 vol %) dissolved in water at 341°C in 2.5 s without complete dissolution. Adding 0.8 wt % Na2CO3, complete dissolution of willow (concentration up to 35 vol %) was observed at 329–367°C and water densities of 322–787 kg/m3 (14–106 MPa) in 1.5 s. By cooling the solublized willow immediately, micron particles were obtained via precipitation. If heated further to 400°C, willow was completely hydrolyzed to sugars/sugar oligomers in 14.6 s at homogeneous conditions. A flow reactor was proposed to completely solubilize willow for the production of micron particles, sugars, bio‐fuels and chemicals continuously. © 2008 American Institute of Chemical Engineers AIChE J, 2008

Ethanol production from xylose and wood hydrolyzate by Mucor indicus at different aeration rates

The fungus Mucor indicus is able to produce ethanol from xylose as well as dilute-acid lignocellulosic hydrolyzates. The fungus completely assimilated 10 g/L xylose as the sole carbon and energy source within 32 to 65 h at an aeration rate of 0.1 to 1.0 vvm. The highest ethanol yield was 0.16 g/g at 0.1 vvm. Xylitol was formed intermediately with a maximum yield of 0.22 g/g at 0.5 vvm, but disappeared towards the end of experiments. During cultivation in a mixture of xylose and glucose, the fungus did not assimilate xylose as long as glucose was present in the medium. The anaerobic cultivation of the fungus in the hydrolyzate containing 20% xylose and 80% hexoses resulted in no assimilation of xylose but complete consumption of the hexoses in less than 15 h. The ethanol yield was 0.44 g/g. However, the xylose in the hydrolyzate was consumed when the media was aerated at 0.067 to 0.333 vvm. The best ethanol yield was 0.44 g/g at 0.067 vvm. The results of this study suggest that M. indicus hydrolyzate can be first fermented anaerobically for hexose assimilation and subsequently continued under oxygen-limited conditions for xylose fermentation.