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1.
The hydrolysis of purified celluloses (cotton, Avicel, Cellulose-123, Solka Floc SW40) and cellulosic wastes (rice straw, sugarcane bagasse, wood powders, paper factory effluents) by Sclerotium rolfsii CPC 142 culture filtrate was studied. Factors which effect saccharification such as pH, temperature, enzyme concentration, substrate concentration, produce inhibition, adsorption, and inactivation of enzyme and particle size were studied. Virtually no inhibition (less than 3%) of cellulose hydrolysis by the culture filtrate was observed by cellobiose and glucose up to 100 mg/mL. Filter paper degrading enzyme(s) (but neither carboxymethylcellulase nor beta-glucosidase) was adsorbed on cellulose. The n value in the S. rolfsii system was calculated to be 0.32 for Avicel P.H. 101 and 0.53 for alkali-treated (AT) rice straw indicating penetration of cellulase into AT rice straw. In batch experiments at 10% substrate level, solutions containing 6 to 7%, 3.8 to 4.7%, 4.0 to 5.1%, and 4.2 to 4.9% reducing sugars were produced in 24 to 48 from AT rice straw. AT bagasse, alkali - peracetic acid treated mesta wood and paper factory sedimented sludge effluent, respectively. The main constituent in the hydrolysate from cellulose was glucose with little or no cellobiose, probably due to the high cellobiase content in the culture filtrate.  相似文献   

2.
A complete cellulase from Penicillium pinophilum was evaluated for the hydrolysis of α-cellulose derived from steam exploded sugarcane bagasse and other cellulosic substrates. α-Cellulose at 1% substrate concentration was completely hydrolyzed by Penicillium cellulase within 3 h wherein at 10% the hydrolysis was 100% within 24 h with an enzyme loading of 10 FPU/g. The hydrolysate yielded glucose as major end product as analyzed by HPLC. Under similar conditions, hydrolysis of Sigmacell (microcrystalline cellulose), CP-123 (pulverized cellulose powder) and ball milled Solka Floc were 42%, 56% and 52%, respectively. Further the hydrolysis performance of Penicillium sp. cellulase is compared with Trichoderma reesei cellulase (AccelleraseTM 1000) from Genencore. The kinetics of hydrolysis with respect to enzyme and substrate concentration will be presented.  相似文献   

3.
Cellulases and hemicellulases are key enzymes in the production of alternative fuels and chemicals from lignocellulosic biomass-an abundant renewable resource. Carbon source selection is an important factor in the production of cellulases and hemicellulases. Rice straw--a potential ethanol source--has recently gained considerable interest in Asian countries. Here, we investigated the production of cellulases by using rice straw subjected to various pretreatments as substrates in order to produce cellulases at low costs; we also identified the enzymes' characteristics. Rice straw cutter milled to <3mm was pretreated by wet disk milling, dry ball milling, or hot-compressed water treatment (HCWT). Pretreated rice straw and commercial cellulose, Solka Floc (SF), were used as carbon sources for cellulase production by the fungus Acremonium cellulolyticus. Filter paper cellulase, β-xylanase, and β-xylosidase production from ball- and disk-milled samples were higher than those from SF. Enzymatic activity was absent in cultures where HCWT rice straw was used as carbon source. Wet disk-milled rice straw cultures were more suitable for enzymatic hydrolysis of pretreated rice straw than SF cultures. Thus, wet disk milling may be a suitable pretreatment for producing substrates for enzymatic hydrolysis and generating inexpensive carbon sources for cellulase production.  相似文献   

4.
Cellulose hydrolysis by Celluclast 1.5L (Novozymes A/S, Denmark) enzyme preparation was studied in a special tubular membrane reactor, where a porous stainless steel filter was covered by a non-woven technical textile layer providing a fine, hairy surface for simultaneous adsorption of both the cellulose particles and the biocatalyst. Solka Floc BW 200 powder and Mavicell pellets were used as substrates in the process. Beyond the adsorption studies, the composite membrane was characterized, having 30 l/m2 bar h hydraulic permeability and an ability to retain both cellulose and enzyme, while glucose (product) permeated easily across the membrane. Using Solka Floc substrate experiments were carried out in both the hairy tubular and a “normal” flat sheet membrane bioreactor. It was found that 10% higher average conversion was possible to achieve in the special layered tubular unit compared to the “traditional” ultrafiltration membrane reactors. Finally, milled and sieved Mavicell pellets were applied as substrates, and 70% conversion was reached with the pretreated fraction.  相似文献   

5.
Reducing cellulase cost remains a major challenge for lignocellulose to fuel and chemical industries. In this study, mutants of a novel wild-type cellulolytic fungal strain Talaromyces pinophilus OPC4-1 were developed by consecutive UV irradiation, N-methyl-N`-nitro-N-nitrosoguanidine (NTG) and ethylmethane sulfonate (EMS) treatment. A potential mutant EMM was obtained and displayed enhanced cellulase production. Using Solka Floc cellulose as the substrate, through fed-batch fermentation, mutant strain T. pinophilus EMM generated crude enzymes with an FPase activity of 27.0 IU/mL and yield of 900 IU/g substrate. When corncob powder was used, strain EMM produced crude enzymes with an FPase activity of 7.3 IU/mL and yield of 243.3 IU/g substrate. In addition, EMM crude enzymes contained 29.2 and 16.3 IU/mL β-glucosidase on Solka Floc cellulose and corncob power, respectively. The crude enzymes consequently displayed strong biomass hydrolysis performance. For corncob hydrolysis, without supplement of any commercial enzymes, glucose yields of 591.7 and 548.6 mg/g biomass were obtained using enzymes produced from Solka Floc cellulose and corncob powder, respectively. It was 553.9 mg/g biomass using the commercial enzyme mixture of Celluclast 1.5 L and Novozyme 188. Strain T. pinophilus EMM was therefore a potential fungus for on-site enzyme production in biorefinery processes.  相似文献   

6.
The enzymatic saccharification of three different feedstocks, rice straw, bagasse and silvergrass, which had been pretreated with different dilute acid concentrations, was studied to verify how enzymatic saccharification was affected by the lignin composition of the raw materials. There was a quantitatively inverse correlation between lignin content and enzymatic digestibility after pretreatment with 1%, 2% and 4% sulfuric acid. The lignin accounted for about 18.8–21.8% of pretreated rice straw, which was less than the 23.1–26.5% of pretreated bagasse and the 21.5–24.1% of pretreated silvergrass. The maximum glucose yield achieved, under an enzyme loading 6.5 FPU g?1 DM for 72 h, was close to 0.8 g glucose/g glucan from the enzymatic hydrolysis of the pretreated rice straw; this was twice that from bagasse and silvergrass. A decrease in initial rate of glucose production was observed in all cases when the raw materials underwent enzymatic saccharification with 4% sulfuric acid pretreatment. It is suggested that the higher acid concentration led to an inhibition of β-glucosidase activity. Fourier transform infrared (FTIR) spectroscopy further indicated the chemical properties of the rice straw and silvergrass become more hydrophilic after pretreatment using 2% of sulfuric acid, but the pretreated bagasse tended to become more hydrophobic. The hydrophilic nature of the pretreated solid residues may increase the inhibitive effects of lignin on the cellulase and this could become very important for raw materials such as silvergrass that contain more lignin.  相似文献   

7.
The saccharification of the polysaccharides of barley, oat, and wheat straws and Solka Floc was studied using the extracellular enzyme system synthesized by mutant strain NTG III/6 of the fungus Penicillium pinophilum 87160iii. The enzymes obtained in cultures containing Solka Floc or barley straw as the carbon source were compared. Solka Floc at 10% (w/v) concentration was hydrolyzed to the extent of 70% in 72 h at 50 degrees C using a reaction mixture containing 7 filter paper units/mL of cellulase induced on Solka Floc, but hydrolysis was increased to 90% when the enzyme induced on barley straw was used. Under the same conditions, the polysaccharides in barley, oat, and wheat straws were hydrolyzed, respectively, in 72 h, to the extent of 42-48%, 62%, and 52%, but hydrolysis was increased to 93%, 100%, and 92%, respectively, after treatment of the substrates with alkaline-H(2)O(2) reagent at room temperature.  相似文献   

8.
Summary Fed-batch fermentations of Acidothermus cellulolyticus utilizing mixtures of cellulose and sugars were investigated for potential improvements in cellulase enzyme production. In these fermentations, we combined cellulose from several sources with various simple sugars at selected concentrations. The best source of cellulose for cellulase production was found to be ball-milled Solka Floc at 15 g/l. Fed-batch fermentations with cellobiose and Solka Floc increased cell mass only slightly, but succeeded in significantly enhancing cellulase synthesis compared to batch conditions. Maximum cellulase activities obtained from fermentations initiated with 2.5 g cellobiose/l and 15 g Solka Floc/l were 0.187 units (U)/ml, achieved by continuous feeding to maintain <0.1 g cellobiose/l, and 0.215 U/ml using the same initial medium when 2.5 g cellobiose/l was step-fed after the sugar was nearly consumed. In batch, dual-substrate systems consisting of simple sugars with Solka Floc, substrate inhibition was evident in terms of specific growth rates, specific productivity values, and maximum enzyme yields. Limiting concentrations of glucose or sucrose at 5 g/l, and cellobiose at 2.5 g/l, in the presence of Solka Floc, yielded cellulase activities of 0.134, 0.159, and 0.164 U/ml, respectively. Offprint requests to: M. E. Himmel  相似文献   

9.
Partial acid hydrolysis was studied as a per treatment to enhance enzymatic hydrolysis, such a pretreatment was carried out in a continuous flow reactor on oak corn Stover, newsprint, and Solka Floc at temperatures ranging from 160 to 220°C, acid concentration ranging from 0 to 1.2%, and a fixed treatment time of 0.22 min. The resulting slurries and solids were than hydrolyzed with Trichoderma ressei QM 9414 cellulase at 50°C for 48 hr. For all substrates except Solka Floc, increased glucose yields were achieved during enzymatic hydrolysis of the pretreated materials as compared to hydrolysis of the original substrate. In several cases, after pretreatment, 100° of the potential glucose content of the substrate was converted to glucose after 24hr of enzymatic hydrolysis. It is felt that the increased glucose yields achieved after this pretreatment are due to acid's removal of hemicellulose, reduced degree of polymerization, and possibly due to a change in the crystal structure of the cellulose.  相似文献   

10.
The fermentation of various saccharides derived from cellulosic biomass to ethanol was examined in mono- and cocultures of Clostridium thermocellum strain LQRI and C. thermohydrosulfuricum strain 39E. C. thermohydrosulfuricum fermented glucose, cellobiose, and xylose, but not cellulose or xylan, and yielded ethanol/acetate ratios of >7.0. C. thermocellum fermented a variety of cellulosic substrates, glucose, and cellobiose, but not xylan or xylose, and yielded ethanol/acetate ratios of ~1.0. At nonlimiting cellulosic substrate concentrations (~1%), C. thermocellum cellulase hydrolysis products accumulated during monoculture fermentation of Solka Floc cellulose and included glucose, cellobiose, xylose, and xylobiose. A stable coculture that contained nearly equal numbers of C. thermocellum and C. thermohydrosulfuricum was established that fermented a variety of cellulosic substrates, and the ethanol yield observed was twofold higher than in C. thermocellum monoculture fermentations. The metabolic basis for the enhanced fermentation effectiveness of the coculture on Solka Floc cellulose included: the ability of C. thermocellum cellulase to hydrolyze α-cellulose and hemicellulose; the enhanced utilization of mono- and disaccharides by C. thermohydrosulfuricum; increased cellulose consumption; threefold increase in the ethanol production rate; and twofold decrease in the acetate production rate. The coculture actively fermented MN300 cellulose, Avicel, Solka Floc, SO2-treated wood, and steam-exploded wood. The highest ethanol yield obtained was 1.8 mol of ethanol per mol of anhydroglucose unit in MN300 cellulose.  相似文献   

11.
Recombinant xylanase preparations from Nonomuraea flexuosa (Nf Xyn, GH11) and Thermoascus aurantiacus (Ta Xyn, GH10) were evaluated for their abilities to hydrolyze hydrothermally pretreated wheat straw. The GH family 10 enzyme Ta Xyn was clearly more efficient in solubilizing xylan from pretreated wheat straw. Improvement of the hydrolysis of hydrothermally pretreated wheat straw by addition of the thermostable xylanase preparations to thermostable cellulases was evaluated. Clear synergistic enhancement of hydrolysis of cellulose was observed when cellulases were supplemented even with a low amount of pure xylanases. Xylobiose was the main hydrolysis product from xylan. It was found that the hydrolysis of cellulose increased nearly linearly with xylan removal during the enzymatic hydrolysis. The results also showed that the xylanase preparation from T. aurantiacus, belonging to GH family 10 always showed better hydrolytic capacity of solubilizing xylan and acting synergistically with thermostable cellulases in the hydrolysis of hydrothermally pretreated wheat straw.  相似文献   

12.
The cellulase enzyme system of Trichoderma reesei RUT C-30 has been separated by DEAE ion exchange chromatography into four fractions. Their specificity towards substituted cellulose and cellooligosaccharides was revealed by analytical IEF and activity stains. Fraction EGI (26% of the total protein) exhibited mainly endoglucanase activity on carboxymethylcellulose (CMC) whereas endoglucanases EGII and EGIII (15% of the total protein) showed high activity towards CMC as well as xylan, 4-methylumbelliferyl cellobioside [MeUmb(Glc)2] and p-nitrophenyl lactoside (pNPL). A subfraction of EGI (pI 5.9) which has been described in the literature as a cellobiohydrolase (CBHII) was isolated by preparative isoelectric focusing, and was shown to have only 3 U CMCase activity per milligram. Turbidimetric measurements and phase contrast microscopy demonstrated differences between endoglucanase and cellobiohydrolase behaviour during the hydrolysis of purified cellulose (Solka Floc BW-40). Treatment of the purified cellulose with endoglucanases resulted in fibre breakdown into small particles. This was contrasted with no morphological change to the fibres when contacted with the cellobiohydrolase. By this technique it was revealed that the EGI subfraction (pI 5.9) behaves as an endoglucanase and not as a cellobiohydrolase. Incubation of this enzyme with acid-swollen cellulose resulted in cellotriose production, as it did with other endoglucanases which exhibited CMCase activities >; 100 U mg−1. Cellotriose was not present during the hydrolysis of acid-swollen cellulose with the CBHI fraction.  相似文献   

13.
Liquid hot water, steam explosion, and dilute acid pretreatments of lignocellulose generate soluble inhibitors which hamper enzymatic hydrolysis as well as fermentation of sugars to ethanol. Toxic and inhibitory compounds will vary with pretreatment and include soluble sugars, furan derivatives (hydroxymethyl fulfural, furfural), organic acids (acetic, formic and, levulinic acid), and phenolic compounds. Their effect is seen when an increase in the concentration of pretreated biomass in a hydrolysis slurry results in decreased cellulose conversion, even though the ratio of enzyme to cellulose is kept constant. We used lignin-free cellulose, Solka Floc, combined with mixtures of soluble components released during pretreatment of wood, to prove that the decrease in the rate and extent of cellulose hydrolysis is due to a combination of enzyme inhibition and deactivation. The causative agents were extracted from wood pretreatment liquid using PEG surfactant, activated charcoal or ethyl acetate and then desorbed, recovered, and added back to a mixture of enzyme and cellulose. At enzyme loadings of either 1 or 25mg protein/g glucan, the most inhibitory components, later identified as phenolics, decreased the rate and extent of cellulose hydrolysis by half due to both inhibition and precipitation of the enzymes. Full enzyme activity occurred when the phenols were removed. Hence detoxification of pretreated woods through phenol removal is expected to reduce enzyme loadings, and therefore reduce enzyme costs, for a given level of cellulose conversion.  相似文献   

14.
Enzymic saccharification of gamma ray and alkali pretreated sawdust, rice straw, and sugar cane bagasse showed higher release of reducing sugar from pretreated substrates. By gamma ray treatment alone (500 kGy) reducing sugar release of 2.8, 9.2, and 10 g/l was obtained from 7.5% (w/v) sawdust, rice straw, and bagasse and the same substrates showed reducing sugar release of 4.2, 30, and 20 g/l respectively when treated with alkali (0.1 g/g). Combination of gamma ray with alkali treatment further increased the reducing sugar release to 10.2, 33, and 36 g/l from sawdust, rice straw, and bagasse respectively. The effects of gamma ray and alkali treatment on saccharification varied with the nature of the substrate.  相似文献   

15.
Park EY  Naruse K  Kato T 《Bioresource technology》2011,102(10):6120-6127
Cellulase production in cultures of Acremonium cellulolyticus was significantly improved by using waste milk pack (MP) that had been pretreated with cellulase. When MP cellulose pretreated with cellulase (3 FPU/g MP) for 12 h was used as the sole carbon source for A. cellulolyticus culture in a 3-L fermentor, the cellulase activity was 16 FPU/ml. This was 25-fold higher (0.67 FPU/ml) compared with untreated MP cellulose and was comparable to that achieved with pure cellulose (Solka Floc). As the pretreatment progressed, roughness on the surface of untreated MP cellulose became to be smooth, but development of fissures on the surface of pretreated MP cellulose was observed. Cellulase pretreatment of MP increased both the accessibility of A. cellulolyticus to the surface and number of adsorption sites of cellulase on the surface of MP cellulose, leading to improved cellulase production in the A. cellulolyticus.  相似文献   

16.
Direct anaerobic bioconversion of cellulosic substances into ethanol by Clostridium thermocellum ATCC 27405 has been carried out at 60 degrees C and pH 7.0 (initial for 100 L) under continuous sparging of oxygen free nitrogen in a culture vessel. Raw bagasse, mild alkali-treated bagasse, and solka floc were used as substrates. The extent of conversion of raw bagasse (cellulose, 50%; hemicellulose, 25%; lignin, 19%) was observed as 52% (w/w) and 79% (w/w) in the case of mild alkali and steam-treated bagasse (cellulose, 72%; hemicellulose, 11%; lignin, 12%), respectively. Use of bagasse concentration above 10 g/L showed a decreased rate in ethanol production. An inoculum age between 28-30 h and cell mass content of 0.027-0.036 g/L (dry basis) were used. The results obtained with raw and pretreated bagasse have been compared with those of highly pure Solka Floc (hemicellulose, 10%). Studies on the product inhibition indicated a linear fall of the percent of survivors with time. An Arrhenius type correlation between the cell decay rate constant and the product concentration was predicted. Even at low levels, the inhibitory effects of products on cell viability, the specific growth rate, and extracellular cellulase enzyme were observed.  相似文献   

17.
The commercial production of chemicals and fuels from lignocellulosic residues by enzymatic means still requires considerable research on both the technical and economic aspects. Two technical problems that have been identified as requiring further research are the recycle of the enzymes used in hydrolysis and the reuse of the re calcitrant cellulose remaining after incomplete hydrolysis. Enzyme recycle is required to lower the cost of the enzymes, while the reuse of the spent cellulose will lower the feedstock cost. The conversion process studied was a combined enzymatic hydrolysis and fermentation (CHF) procedure that utilized the cellulolytic enzymes derived from the fungus Trichoderma harzianum E58 and the yeast Saccharomyces cerevisiae. The rate and extent of hydrolysis and ethanol production was monitored as was the activity and hydrolytic potential of the enzymes remaining in the filtrate after the hydrolysis period. When a commercial cellulose was used as the substrate for a routine 2-day CHF process, 60% of the original treated, water-extracted aspenwood was used as the substrate, only 13% of the original filter paper activity was detected after a similar procedure. The combination of 60% spent enzymes with 40% fresh enzymes resulted in the production of 30% less reducing sugars than the original enzyme mixture. Since 100% hydrolysis of the cellulose portion is seldom accomplished in an enzymatic hydrolysis pro cess, the residual cellulose was used as a substrate for the growth of T. harzianum E58 and production of celulolytic enzymes. The residue remaining after the CHF process was used as a substrate for the production of the cellulolytic enzymes. The production of enzymes from the residue of the Solka Floc hydrolysis was greater than the production of enzymes from the original Solka Floc.  相似文献   

18.
The Zymomonas mobilis genes for ethanol production have been integrated into the chromosome of Klebsiella oxytoca M5A1. The best of these constructs, strain P2, produced ethanol efficiently from cellobiose in addition to monomeric sugars. Utilization of cellobiose and cellotriose by this strain eliminated the requirement for external beta-glucosidase and reduced the amount of commercial cellulase needed to ferment Solka Floc SW40 (primarily crystalline cellulose). The addition of plasmids encoding endoglucanases from Clostridium thermocellum resulted in the intracellular accumulation of thermostable enzymes as coproducts with ethanol during fermentation. The best of these, strain P2(pCT603T) containing celD, was used to hydrolyze amorphous cellulose to cellobiose and produce ethanol in a two-stage process. Strain P2(pCT603T) was also tested in combination with commercial cellulases. Pretreatment of Solka Floc SW40 at 60 degrees C with endoglucanase D substantially reduced the amount of commercial cellulase required to ferment Solka Floc. The stimulatory effect of the endoglucanase D pretreatment may result from the hydrolysis of amorphous regions, exposing additional sites for attack by fungal cellulases. Since endoglucanase D functions as part of a complex in C. thermocellum, it is possible that this enzyme may complex with fungal enzymes or bind cellulose to produce a more open structure for hydrolysis.  相似文献   

19.
The Zymomonas mobilis genes for ethanol production have been integrated into the chromosome of Klebsiella oxytoca M5A1. The best of these constructs, strain P2, produced ethanol efficiently from cellobiose in addition to monomeric sugars. Utilization of cellobiose and cellotriose by this strain eliminated the requirement for external beta-glucosidase and reduced the amount of commercial cellulase needed to ferment Solka Floc SW40 (primarily crystalline cellulose). The addition of plasmids encoding endoglucanases from Clostridium thermocellum resulted in the intracellular accumulation of thermostable enzymes as coproducts with ethanol during fermentation. The best of these, strain P2(pCT603T) containing celD, was used to hydrolyze amorphous cellulose to cellobiose and produce ethanol in a two-stage process. Strain P2(pCT603T) was also tested in combination with commercial cellulases. Pretreatment of Solka Floc SW40 at 60 degrees C with endoglucanase D substantially reduced the amount of commercial cellulase required to ferment Solka Floc. The stimulatory effect of the endoglucanase D pretreatment may result from the hydrolysis of amorphous regions, exposing additional sites for attack by fungal cellulases. Since endoglucanase D functions as part of a complex in C. thermocellum, it is possible that this enzyme may complex with fungal enzymes or bind cellulose to produce a more open structure for hydrolysis.  相似文献   

20.
Penicillium echinulatum was evaluated as a cellulolytic enzyme producer in shaking flasks and bioreactor submerged culture using sugarcane bagasse as carbon source. Sodium hydroxide delignified steam-exploded pretreated bagasse (SDB) and hydrothermal pretreated bagasse had a maximum filter paper activity (FPase) of 2.4 and 2.6 FPU/mL, respectively. Delignified acid pretreated bagasse and Celufloc 200TM (CE) carbon sources displayed maximum FPase of 1.3 and 1.6 FPU/mL while in natura bagasse (INB) provided the lowest enzyme activity, ca. 0.4 FPU/mL. Measurement of surface specific area of lignocellulosic material and scanning electron microscopic images showed a possible correlation between fungal mycelia accessibility to lignocellulosic particles and obtained cellulolytic enzyme activity of fermentation broth. Fed-batch experiments performed in a controlled bioreactor attained the highest value of FPase of 3.7 FPU/mL, enzyme productivity of 25.7 FPU/L h, and enzyme yield from cellulose equal to 134 FPU/g with SDB. Enzyme hydrolysis of steam-pretreated bagasse accomplished with the obtained supernatant of fermentation broth (10 FPU/g of biomass and 5 % w/v) performed better than commercial cellulose complex. The results showed that P. echinulatum has potential to be used as an on-site enzyme platform aiming second bioethanol production from sugarcane lignocellulosic residue.  相似文献   

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