Acid Hydrolysis Of Hemicellulose Research Articles

The use of hemicellulose acid hydrolysate for hydrolysis of sugarcane trash and its fermentation for producing xylitol

The use of hemicellulose acid hydrolysate for hydrolysis of sugarcane trash and its fermentation for producing xylitol

Mechanism study on Betula wood dowel rotation welding into larch and enhanced mechanism of treating with CuCl2

Mechanical properties and chemical changes of wood dowel welding were studied using untreated and copper chloride (CuCl2)-treated Betula wood dowels. The effects of the welding times (3 s, 5 s, and 7 s) and the highest temperatures in the welding interface were also studied. The treated wood dowels with a welding time of 3 s and the highest temperature of 265.6 °C had the best pullout resistance. Wood constituents were pyrolyzed by the frictional heat generated from rotational welding to form oxygen-containing materials, most of which were C-O materials. With the extension of welding time, welding interface materials were pyrolyzed deeper, but the rate of pyrolysis decreased, which indicated that the pyrolysis of hemicellulose and cellulose might have occurred in the prior period of the welding process. Acid hydrolysis of hemicellulose and cellulose of the wood dowel treated with CuCl2 might have occurred during immersion, which promoted the formation of molten materials by the depolymerization and pyrolysis of wood constituents. With the same welding time, the content of oxygen-containing materials with treated samples was higher than with untreated samples, which might indicate that more pyrolysis and molten reactions occurred in the treated welding interface.

Xylitol production from non-detoxified corncob hemicellulose acid hydrolysate by Candida tropicalis

The interest on use of lignocellulose for producing chemicals is increasing as these feedstocks are low cost, renewable and widespread sources of sugars. Corncob is an attractive raw material for xylitol production due to its high content of xylan. In this study, hemicellulose hydrolysate from corncobs without detoxification was used for xylitol production by Candida tropicalis CCTCC M2012462. Compared with prepared xylose medium, xylitol production with dilute acid hydrolysate medium does not seem to influence specific xylose reductase activity. The decrease in xylitol productivity with dilute acid hydrolysate medium is a result of a lower biomass concentration and lag-phase time. It appears that biomass growth rate is essential for xylitol production. In xylitol fermentation with a low initial inhibitors concentration and substrate feeding strategy, a maximal xylitol concentration of 38.8gl−1 was obtained after 84h of fermentation, giving a yield of 0.7gg−1 xylose and a productivity of 0.46gl−1h−1.

Bioconversion of Hemicellulosic Fraction of Perennial Kans Grass (Saccharum spontaneum) Biomass to Ethanol by Pichia stipitis: A Kinetic Study

Ethanol is a promising alternative energy source for the limited crude oil and can be produced from abundantly available lignocellulosic biomass. Utilization of acid hydrolysate of Kans grass (Saccharum spontaneum), a perennial grass native to South Asia, has been investigated for ethanol production. The dilute acid treatment was applied to hydrolyze the Kans grass biomass for releasing maximum hemicellulosic sugars. The aim of this work was to develop a fermentative system utilizing Kans grass hemicellulose acid hydrolysate as a substrate for ethanol production by Pichia stipitis. It was found that 74% of xylose was converted to ethanol with a yield of 0.429 gp gs −1 and productivity of 0.231 gp l−1 h−1. The appropriate mathematical models for cell and ethanol production rate have been developed to explain theoretically the bioconversion of Kans grass hemicellulose acid hydrolysate to ethanol and validated statistically with the experimental results carried out in the laboratory. The present study revealed that the degradation of sugar, activation and inhibition of cells, and ethanol production were strictly coupled during the bioconversion process of hemicellulosic fraction of Kans grass to ethanol.

Evaluation of ethanol production by a new isolate of yeast during fermentation in synthetic medium and sugarcane bagasse hemicellulosic hydrolysate

A new xylose fermenting yeast was isolated from over-ripe banana by enrichment in xylose-containing medium. The phylogenetic analysis of ITS1-5.8S-ITS2 region sequences of ribosomal RNA of isolate BY2 revealed that it shows affiliation to genus Pichia and clades with Pichia caribbica. In batch fermentation, Pichia strain BY2 fermented xylose, producing 15 g l−1 ethanol from 30 g l−1 xylose under shaking conditions at 28°C, with ethanol yield of 0.5 g g−1 and volumetric productivity of 0.31 g l−1 h−1. The optimum pH range for ethanol production from xylose by Pichia strain BY2 was 5–7. Pichia strain BY2 also produced 6.08 g l−1 ethanol from 30 g l−1 arabinose. Pichia strain BY2 can utilize sugarcane bagasse hemicellulose acid hydrolysate for alcohol production, efficiency of fermentation was improved by neutralization, and sequential use of activated charcoal adsorption method. Percent total sugar utilized and ethanol yield for the untreated hydrolysate was 17.14% w/v and 0.33 g g−1, respectively, compared with 66.79% w/v and 0.45 g g−1, respectively, for treated hemicellulose acid hydrolysate. This new yeast isolate showed ethanol yield of 0.45 g g−1 and volumetric productivity of 0.33 g l−1 h−1 from sugarcane bagasse hemicellulose hydrolysate detoxified by neutralization and activated charcoal treatment, and has potential application in practical process of ethanol production from lignocellulosic hydrolysate.

Evaluation of a Minimal Energy-Dependent Technique for Preparation ofAilanthus excelsaHemicellulose Acid Hydrolysate Fermentable bySchefferomyces stipitis

A low-energy-dependent sustainable technique for the preparation of hemicellulose hydrolysate from the wood chip of low input and less care-demanding tree, Ailanthus excelsa Roxb., involving two-stage dilute acid hydrolysis technique followed by fermentation by pentose (PS)-fermenting yeast, Schefferomyces stipitis (NCIM 3507), was standardised. The main parameters optimised were acid concentration and heating period. The maximum sugar yield was obtained by hydrolysis with 10% (v/v) sulphuric acid applying pressure at 120°C for 4 min. The hydrolysate thus obtained and treated (treated hemicellulose acid pre-hydrolysate (THAP) with lime and sodium sulphite, however, could not be fermented with S. stipitis, indicating the presence of inhibitors in intolerable concentration. Though it contained lesser sugars, the hydrolysate obtained with 1% acid and treated as above (THAP) could be easily fermented by yeast. Ethanol yield as a result of fermentation of hydrolysate medium containing 40, 50 and 70% of THAP was 8.47, 6.28 and 5.09 g/l, respectively, after 120 h. This paper highlights the use of woody material, A. excelsa, a fast-growing tree adapted for marginal land, as a source of hemicellulose acid hydrolysate fermentable by S. stipitis by applying modified two-stage dilute acid hydrolysis technique with minimal energy input.

Bioconversion of Saccharum spontaneum (wild sugarcane) hemicellulosic hydrolysate into ethanol by mono and co-cultures of Pichia stipitis NCIM3498 and thermotolerant Saccharomyces cerevisiae-VS 3

The lignocellulosic biomass is a low-cost renewable resource for eco-benign liquid fuel 'ethanol'. To resolve the hydrolysis of mixed sugars in lignocellulosic substrate Saccharum spontaneum, the microbial co-cultures of Pichia stipitis NCIM 3498 and thermotolerant Saccharomyces cerevisiae-VS(3) were analyzed for efficient bioconversion of mixed sugars into ethanol. Among the hydrolysis conditions, the acid hydrolysis released maximum sugars along with furans, phenolics and acetic acid. The acidic hydrolysate was detoxified and fermented by monocultures of P. stipitis NCIM3498 (P.S.) and thermotolerant S. cerevisiae VS(3) (S.C.), and co-culture of P.S. (7.5 mL) and S.C. (2.5 mL). Before the fermentation of hemicellulose acid hydrolysate, both the monocultures (P.S. and S.C.), and varying ratios of P.S. and S.C. microorganisms in co-cultures #1, #2 and #3 were grown on simulated synthetic medium. The ethanol yield from monocultures of P.S. (0.44 ± 0.021 g/g), S.C. (0.22 ± 0.01 g/g) and co-culture #3 (0.49 ± 0.02 g/g) revealed unique characteristics of each mono and co-culture technology. The fermentation of hemicellulose acid hydrolysate with monocultures of P.S., S.C. and co-culture #3 produced 12.08 ± 0.72 g/L, 1.40 ± 0.07 g/L, and 15.0 ± -0.92 g/L ethanol, respectively.

Acid Hydrolysis of Hemicellulose in Green Liquor Pre-Pulping Extract of Mixed Northern Hardwoods

Forest biomass is a promising resource for future biofuels and bioproducts. Pre-pulping extraction of hemicellulose by alkaline (Green Liquor) pretreatment produces a neutral-pH extract containing hemicellulose-derived oligomers. A near-term option for use of this extract is to hydrolyze the oligomers to fermentable monomer sugars. Chips of mixed northern hardwoods were cooked in a rocking digester at 160 degrees C for 110 min in Green Liquor at a concentration of 3% Na2O equivalent salts on dry wood. The mass of wood extracted into the Green Liquor extract was approximately 11.4% of the debarked wood mass, which resulted in a dilute solution of oligomeric hemicelluloses sugars. The concentration of the extract was increased through partial evaporation prior to hydrolysis. Dilute sulfuric acid hydrolysis was applied at conditions ranging from 100 to 160 degrees C, 2% to 6% (w/v) H2SO4, and 2- to 258-min residence time. The maximum fermentable sugar concentration achieved from evaporated extract was 10.7 g/L, representing 90.7% of the maximum possible yield. Application of the biomass pretreatment severity function to the hydrolysis results proved to offer a relatively poor prediction of temperature and reaction time interaction. The combined severity function, which incorporates reaction time, temperature, and acid concentration, did prove to provide a useful means of trading off the combined effects of these three variables on total sugar yields.

Bioconversion of lignocellulosic fraction of water-hyacinth ( Eichhornia crassipes) hemicellulose acid hydrolysate to ethanol by Pichia stipitis

Fermentation of acid hydrolysate of water-hyacinth ( Eichhornia crassipes), a free floating aquatic plant has been investigated for ethanol production. The dilute acid treatment has been applied to utilize the maximum hemicellulosic content of the water-hyacinth. The goal of this work was to investigate, both experimentally and theoretically using mathematical tools, a fermentative system utilizing water-hyacinth ( Eichhornia crassipes) hemicellulose acid hydrolysate as a substrate for ethanol production using Pichia stipitis. It was found that 72.83% of xylose was converted to ethanol with a yield of 0.425 g p/g s and productivity of 0.176 g p/L/h. An appropriate mathematical model was developed to explain theoretically the bioconversion of this hemicellulose acid hydrolysate to ethanol and the model was tested statistically to check the validity of the model.

Sugarcane bagasse hemicellulose hydrolysate for ethanol production by acid recovery process

In order to increase the reducing sugar concentration in the sugarcane bagasse hemicellulose acid hydrolysate and recover the acid, the acid hydrolysis was carried out in an acid recycle process and detoxification of hydrolysate was performed by electrodialysis. Two cycles of acidic treatments increased the reducing sugar concentration from 28 to 63.5 g l −1 and sulphuric acid consumption decreased to 0.056 g g −1 bagasse. After treatment by electrodialysis, 90% of acetic acid in hydrolysate was removed and the recovery ratio of sulphuric acid was 88%. The pretreated hydrolysates, supplemented with nutrient materials, were fermented to ethanol using Pachysolen tannophilus DW06. A batch culture with pretreated hydrolysate as substrate was developed giving 19 g ethanol l −1 with a yield of 0.34 g g −1 sugar and productivity of 0.57 g l −1 h −1.

Bioconversion of water-hyacinth ( Eichhornia crassipes) hemicellulose acid hydrolysate to motor fuel ethanol by xylose–fermenting yeast

Water-hyacinth ( Eichhornia crassipes) hemicellulose acid hydrolysate has been utilized as a substrate for ethanol production using Pichia stipitis NRRL Y-7124. Hydrolysate fermentability was considerable improved by boiling, and overliming up to pH 10.0 with solid Ca(OH) 2 in combination with sodium sulfite. The percent total sugar utilized and ethanol yield ( Y p/ s ) for the untreated hydrolysate were 20.15±0.17% and 0.19±0.003 g p g s −1, respectively, compared with 76.0±0.32% and 0.35 g p g s −1, respectively for the treated material. The fermentation was very effective at an aeration rate of 0.02 v/v/m, temperature 30±0.2 °C and pH 6.0±0.2. However, the volumetric productivity ( Q p ) was still considerably less than observed in a simulated synthetic hydrolysate medium with a sugar composition similar to the hemicellulose acid hydrolysate. l-Arabinose was not fermented but assimilated. The presence of acetic acid in the hydrolysate decreased the ethanol yield and productivity considerably.

Ethanol production from wheat straw hemicellulose hydrolysate by Pichia stipitis

Ethanol production was evaluated from wheat straw (WS) hemicellulose acid hydrolysate using an adapted and parent strain of Pichia stipitis. NRRL Y-7124. The treatment by boiling and overliming with Ca(OH) 2 significantly improved the fermentability of the hydrolysate. Ethanol yield ( Y p/ s ) and productivity ( Q p av) were increased 2.4±0.10 and 5.7±0.24 folds, respectively, compared to neutralized hydrolysate. Adaptation of the yeast to the hydrolysate resulted further improvement in yield and productivity. The maximum yield was 0.41±0.01 g p g s −1, equivalent to 80.4±0.55% theoretical conversion efficiency. Acetic acid, furfurals and lignins present in the hydrolysate were inhibitory to microbial growth and ethanol production. The addition of these inhibitory components individually or in various combinations at a concentrations similar to that found in hydrolysate to simulated medium resulted a reduction in ethanol yield ( Y p/ s ) and productivity ( Q p av). The hydrolysate used had the following composition (expressed in g l −1): xylose 12.8±0.25; glucose 1.7±0.3; arabinose 2.6±0.21 and acetic acid 2.7±0.33.

Inhibition of the fermentation of oak hemicellulose acid-hydrolysate by minor sugars

Synthetic xylose media and detoxified oak hemicellulose acid-hydrolysates with different starting xylose contents were fermented batchwise by two strains of Pachysolen tannophilus. Maximum productivities were calculated from the experimental data of ethanol concentration using a graphical procedure. The kinetic parameters calculated for the fermentations of both carbon sources indicate that a competitive inhibition is exerted by the minor sugars (arabinose, rhamnose, and galactose) that are metabolised only slowly or not at all.

Ethanol production from eucalyptus wood hemicellulose hydrolysate by Pichia stipitis

Ethanol production was evaluated from eucalyptus wood hemicellulose acid hydrolysate using Pichia stipitis NRRL Y-7124. An initial lag phase characterized by flocculation and viability loss of the yeast inoculated was observed. Subsequently, cell regrowth occurred with sequential consumption of sugars and production of ethanol. Polyol formation was detected. Acetic acid present in the hydrolysate was an important inhibitor of the fermentation, reducing the rate and the yield. Its toxic effect was due essentially to its undissociated form. The fermentation was more effective at an oxygen transfer rate between 1.2 and 2.4 mmol/L h and an initial pH of 6.5. The hydrolysate used in the experiences had the following composition (expressed in grams per liter): xylose 30, arabinose 2.8, glucose 1.5, galactose 3.7, mannose 1.0, cellobiose 0.5, acetic acid 10, glucuronic acid 1.5, and galacturonic acid 1.0. The best values obtained were maximum ethanol concentration 12.6 g/L, fermentation time 75 h, fermentable sugar consumption 99% ethanol yield 0.35 g/g sugars consumed, and volumetric ethanol productivity 4 g/L day. (