共查询到20条相似文献,搜索用时 0 毫秒
1.
John D. Wright Charles E. Wyman Karel Grohmann 《Applied biochemistry and biotechnology》1988,18(1):75-90
Simultaneous saccharification and fermentation (SSF) processes for producing ethanol from lignocellulose are capable of improved
hydrolysis rates, yields, and product concentrations compared to separate hydrolysis and fermentation (SHF) systems, because
the continuous removal of the sugars by the yeasts reduces the end-product inhibition of the enzyme complex. Recent experiments
using Genencor 150L cellulase and mixed yeast cultures have produced yields and concentrations of ethanol from cellulose of
80% and 4.5%, respectively. The mixed culture was employed because B.clausenii has the ability to ferment cellobiose (further reducing end-product inhibition), while the brewing yeastS. cerevisiae provides a robust ability to ferment the monomeric sugars. These experimental results are combined with a process model to
evaluate the economics of the process and to investigate the effect of alternative processes, conditions, and organisms. 相似文献
2.
Pretreatment and enzymatic saccharification of corn fiber 总被引:14,自引:0,他引:14
Corn fiber consists of about 20% starch, 14% cellulose, and 35% hemicellulose, and has the potential to serve as a low-cost
feedstock for production of fuel ethanol. Several pretreatments (hot water, alkali, and dilute, acid) and enzymatic saccharification
procedures were evaluated for the conversion of corn fiber starch, cellulose, and hemicellulose to monomeric sugars. Hot water
pretreatment (121°C, 1 h) facilitated the enzymatic sacch arification of starch and cellulose but not hemicellulose. Hydrolysis
of corn fiber pretreated with alkali un dersimilar conditions by enzymatic means gave similar results. Hemicellulose and starch
components were converted to monomeric sugars by dilute H2SO4 pretreatment (0.5–1.0%, v/v) at 121°C. Based on these findings, a method for pretreatment and enzymatic saccharification
of corn fiber is presented. It in volves the pretreatment of corn fiber (15% solid, w/v) with dilute acid (0.5% H2SO4, v/v) at 121°C for 1 h, neutralization to pH 5.0, then saccharification of the pretreated corn fiber material with commercial
cellulase and β-glucosidase preparations The yield of monomeric sugars from corn fiber was typically 85–100% of the theoretical
yield.
Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard
of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also
be suitable. 相似文献
3.
Douglas de França Passos Nei Pereira Aline Machado de Castro 《Current Opinion in Green and Sustainable Chemistry》2018
- Download : Download high-res image (110KB)
- Download : Download full-size image
4.
A. I. Hatakka 《Applied biochemistry and biotechnology》1984,9(4):363-364
Pretreatment of lignocellulosic materials is considered as the rate-limiting step in an economically feasible process for
enzymatic hydrolysis of cellulose. Biological delignification techniques have not been developed as intensively as physical
and chemical methods. However, white-rot fungi are effective degraders of lignin, and some of them even preferentially remove
lignin from wood compared with carbohydrates, and therefore might be suitable for biological pretreatment of lignocellulose.
White-rot fungi were cultivated on wheat straw and the residue was hydrolyzed withTrichoderma reesei cellulase. Of nineteen fungi examined,Pleurotus ostreatus, Pleurotus sp. 535,Pycnoporus cinnabarinus 115,Ischnoderma benzoinum 108,Phanerochaete sordida 37,Phlebia radiata 79, and two unidentified fungi were found suitable for pretreatment of straw: the yields of reducing sugars and glucose based
on original straw were markedly better compared with uninoculated straw, and these fungi also gave better results thanPolyporus versicolor, a nonselective reference fungus (Cowling, 1961).
In the best cases the efficiency of the biological pretreatment was comparable with that of alkali treatment (2% NaOH, 0.4
g NaOH/g straw, 10 min at 115‡C), but the fungal treatment resulted in a higher proportion of glucose in the hydrolyzates.
Combined fungal and (strong) alkali treatment did not give better results than alkali or fungal treatment alone.
When culture flasks were periodically flushed with oxygen the treatment time could be reduced by about 1 wk with the two fungi,P. sordida 37 andP. cinnabarinus 115, tested. The effect of oxygen in pretreatment reflected the effect of oxygen in the degradation of14C-lignin of poplar wood to14CO2 by these fungi (Hatakka and Uusi-Rauva, 1983).
The economic feasibility of the biological pretreatment process is poor due to the long cultivation times needed. The best
results were obtained with the longest treatment time studied, which was 5 wk. However, the rapid progress in the field of
biological lignin degradation may help to accelerate the delignification process, and also find factors that favor lignin
degradation, but suppress the utilization of carbohydrates. 相似文献
5.
Pretreatment has been regarded as the most efficient strategy for conversion of lignocellulosic biomass to fermentable sugars. In this work, sulfolane pretreatment was performed to break the intricate structure of shrub willow for inhabitation of the enzymatic accessibility to holocellulose. The effects of varying pretreatment parameters on enzymatic hydrolysis of shrub willow were investigated. It was found that sulfolane was more compatible with lignin instead of carbohydrate, and the loss of carbohydrate could be attributed to water and acid generated from sulfolane. The optimum conditions leading to maximal sugar recovery from enzymatic saccharification were confirmed. After pretreatment of shrub willow powder in sulfolane at 170 °C for 1.5 h with mass ratio of sulfolane to substrate of 5, the sugar release could reach 555 mg/g raw materials (352 mg glucose, 203 mg xylose) when combining 20 FPU cellulase, 20 CBU β-glucosidase, and 1.5 FXU xylanase, representing 78.2 % of glucose and 56.6 % of xylose in shrub willow. This enhanced enzymatic saccharification was due to delignification and removal of a proportion of hemicelluloses, as confirmed by X-ray diffraction analysis, scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, gas chromatography, and ionic chromatography. Thus, these studies prove sulfolane pretreatment to be an effective and promising approach for biomass to biofuel processing. 相似文献
6.
Effects of wet-pressing-induced fiber hornification on enzymatic saccharification of lignocelluloses
This article reports the effect of wet-pressing-induced fiber hornification on enzymatic saccharification of lignocelluloses.
A wet cellulosic substrate of bleached kraft eucalyptus pulp and two wet sulfite-pretreated lignocellulosic substrates of
aspen and lodgepole pine were pressed to various moisture (solids) contents by variation of pressing pressure and pressing
duration. Wet pressing reduced substrate moisture content and produced irreversible reduction in fiber pore volume—fiber hornification—as
reflected in reduced water retention values (WRVs), an easily measurable parameter, of the pressed substrates. Wet pressing
resulted in a reduction in substrate enzymatic digestibility (SED) by approximately 20% for the two sulfite-pretreated substrates
when moisture content was reduced from approximately 75% to 35%. The reduction in SED for the cellulosic substrate was less
than 10% when its moisture content was reduced from approximately 65% to 35%. The results indicated that reduction in SED
is negligible when samples were pressed to solids content of 40% but observable when pressed to solids content of 50%. It
was also found that WRV can correlate to SED of hornified substrates resulting from the same never-dried or pressed sample
independent of the hornification process (e.g., pressing or drying). This correlation can be fitted using a Boltzmann function.
Cellulase adsorption measurements indicated that wet-pressing-induced fiber hornification reduced cellulose accessibility
to cellulase. The results obtained in this study provide guidelines to high-solids enzymatic saccharification of pretreated
biomass. 相似文献
7.
Hongming Lou Huanran Lai Shun Wu Xiuli Li Dongjie Yang Xueqing Qiu Jinhao Huang Conghua Yi 《Cellulose (London, England)》2014,21(5):3361-3369
The effects of long-chain fatty alcohols (LFAs) on the enzymatic hydrolysis of crystalline cellulose by two commercial Trichoderma reesei cellulase cocktails (CTec2 and Celluclast 1.5L) were studied. It was found that n-butanol inhibited the enzymatic hydrolysis, but n-octanol, n-decanol and n-dodecanol had strong enhancement on enzymatic hydrolysis of crystalline cellulose in the buffer pH range from 4.0 to 6.0. LFAs can increase the hydrolysis efficiency of crystalline cellulose from 37 to 57 % at Celluclast 1.5L loading of ten filter paper units (FPU)/g glucan. LFAs have similar enhancement on the enzymatic hydrolysis of crystalline cellulose mixed with lignin or xylan. The enhancement of LFAs increased with the decrease of the crystallinity index. LFAs not only enhanced the high-solid enzymatic hydrolysis of lignocellulose, but also improved the rheological properties of high-solid lignocellulosic slurries by decreasing the yield stress and complex viscosity. Meanwhile, LFAs can improve the enzymatic hydrolysis of cellobiose to glucose, especially at low cellulase loading. 相似文献
8.
José-Henrique Pinto Donatien Pascal Kamden 《Applied biochemistry and biotechnology》1997,61(3):289-297
Five different chemical pretreatments, using dilute sulfuric acid, sodium hydroxide, hydrogen peroxide and sodium hydroxide,
peroxymonosulfate, and acetic acid, were applied to aspen thermomechanical fibers. The pretreated fibers were submitted to
enzymatic hydrolysis and the liberated glucose was monitored. High glucose concentrations were observed for the peroxymonosulfate
and the acetic acid pretreated samples. Glucose concentrations greater than 25 g/L were obtained in these cases. This corresponds
to conversions on the order of 90% of the pretreated substrate glucose content. 相似文献
9.
Hongming Lou Haifeng Zhou Xiuli Li Mengxia Wang J. Y. Zhu Xueqing Qiu 《Cellulose (London, England)》2014,21(3):1351-1359
The effects of lignosulfonate (LS) on enzymatic saccharification of pure cellulose were studied. Four fractions of LS with different molecular weight (MW) prepared by ultrafiltration of a commercial LS were applied at different loadings to enzymatic hydrolysis of Whatman paper under different pH. Using LS fractions with low MW and high degree of sulfonation can enhance enzymatic cellulose saccharification despite LS can bind to cellulase nonproductively. The enhancing effect varies with LS properties, its loading, and hydrolysis pH. Inhibitive effect on cellulose saccharification was also observed using LS with large MW and low degree of sulfonation. The concept of “LS-cellulase aggregate stabilized and enhanced cellulase binding” was proposed to explain the observed enhancement of cellulose saccharification. The concept was demonstrated by the linear correlation between the measured amount of bound cellulase and saccharification efficiency with and without LS of different MW in a range of pH. 相似文献
10.
Mais Ursula Esteghlalian Ali R. Saddler John N. 《Applied biochemistry and biotechnology》2002,98(1-9):463-472
In an attempt to elucidate the effect of reduced mixing on the enzymatic hydrolysis of lignocellulosic feedstocks, a pretreated
softwood substrate was hydrolyzed under various mixing regimes using a commercial cellulase mixture. The substrate was generated
by SO2-catalyzed steam explosion of Douglas fir wood chips followed by alkali-peroxide treatment to remove lignin. Three mixing
regimes were tested; continuous mixing at low (25 rpm) and high (150 rpm) speeds, and mixing at low-speed interspersed with
5-min intervals of high-speed agitation at 150 rpm. At both substrate concentrations (7.5 and 10% [w/w]), the mixed-speed
mixing was able to produce sufficiently high conversion rates and yields (93% after 96 h), close or slightly better than those
obtained under vigorous mixing (150 rpm). The low-speed shaking produced appreciably lower conversion yields at both levels
of substrate concentration. Therefore, the mixed-speed regime may be a viable process option, because it does not seem to
have an adverse impact on the cellulose conversion yield and can be an effective means of reducing the mixing energy requirements
of an enzymatic hydrolysis process. 相似文献
11.
Effect of pretreatment severity on the enzymatic hydrolysis of bamboo in hydrothermal deconstruction
Bamboo was subjected to hydrothermal deconstruction to release xylans for the enhancement of enzymatic hydrolysis. The de-waxed and de-starched bamboo culm was non-isothermally pretreated in a batch reactor at a solid to liquid ratio of 1:10 g/mL at 120–240 °C. With the increase of the maximum heating temperature from 120 to 240 °C, the pH value of the liquor decreased from 5.98 to 2.71. A maximum yield of the non-volatile components in the liquid was achieved at a pretreatment severity of 4.20. With the increase of the pretreatment severity from 1.18 to 4.82, the yield of the solid residue decreased from 99.52 to 59.91 %, accompanying a decrease of xylan content from 28.86 to 0 %, an increase of glucan content from 42.80 to 59.14 % and an increase of lignin content from 28.10 to 40.57 %. The solid residues after the hydrothermal pretreatment were comprehensively characterized by FT IR, XRD, and element analysis. Enzymatic hydrolysis of the solid residues was assayed by commercial cellulase. Under enzymatic hydrolysis for 96 h, the enzymatic hydrolysis of the pretreated bamboo at the pretreatment severity of 4.82 was 81.16 %, which equaled to 4.7 times of that of the untreated bamboo. This study provided an environmentally friendly process to pretreat biomass for the production of energy. 相似文献
12.
Iva Jovanovic Jon K. Magnuson Frank Collart Barbara Robbertse William S. Adney Michael E. Himmel Scott E. Baker 《Cellulose (London, England)》2009,16(4):687-697
Genome sequencing of a variety of fungi is a major initiative currently supported by the Department of Energy’s Joint Genome
Institute. Encoded within the genomes of many fungi are upwards of 200+ enzymes called glycoside hydrolases (GHs). GHs are
known for their ability to hydrolyze the polysaccharide components of lignocellulosic biomass. Production of ethanol and “next
generation” biofuels from lignocellulosic biomass represents a sustainable route to biofuels production. However, this process
has to become more economical before large scale operations are put into place. Identifying and characterizing GHs with improved
properties for biomass degradation is a key factor for the development of cost effective processes to convert biomass to fuels
and chemicals. With the recent explosion in the number of GH encoding genes discovered by fungal genome sequencing projects,
it has become apparent that improvements in GH gene annotation processes have to be developed. This will enable more informed
and efficient decision making with regard to selection and utilization of these important enzymes in bioprocess that produce
fuels and chemicals from lignocellulosic feedstocks. 相似文献
13.
Bioconversion of secondary fiber fines to ethanol using counter-current enzymatic saccharification and Co-fermentation 总被引:7,自引:0,他引:7
This research examined several enzymatic and microbial process for the conversion of waste cellulosic fibers into ethanol.
The first was a one-stage process in which pulp fines were contacted with commercial enzyme solutions. The second process
used sequential, multistage saccharification. The third used sequential enzyme addition in a countercurrent mode. Experiments
compared the results with various feed stocks, different commercial enzymes, supplementation with β-glucosidase, and saccharification
combined with fermentation. The highest saccharification (65%) from a 4% consistency pulp and the highest sugar concentration
(5.4%) from an 8% consistency pulp were attained when 5 FPU/g plus 10 IU/g of β-glucosidase were used. Sequential addition
of enzyme to the pulp in small aliquots produced a higher overall sugar yield/U enzyme than the addition of the same total
amount of enzyme in a singledose. In the saccharification and fermentation experiments, we produced 2.12% ethanol from a 5.4%
sugar solution. This represents 78% of the theoretical maximum. This yield could probably be increased through optimization
of the fermentation step. Even when little saccharification occurred, the enzyme facilitated separation of water, fiber, and
ash, so cellulase treatment could be an effective means for dewatering pulp sludges. 相似文献
14.
Applied Biochemistry and Biotechnology - The effects of steam explosion pretreatment on the physical and chemical properties of rice straw and on the enzymatic saccharification of the straw were... 相似文献
15.
Yoko Yamamoto Ningning Cheng Keiichi Koda Kiyohiko Igarashi Yutaka Tamai Yasumitsu Uraki 《Cellulose (London, England)》2017,24(4):1849-1862
Amphipathic lignin derivatives (ALDs), prepared from hardwood acetic acid lignin and softwood soda lignin via coupling with a mono-epoxylated polyethylene glycol, have been reported to improve the enzymatic saccharification efficiency of lignocellulose while maintaining significant residual cellulase activity after saccharification. We previously demonstrated that the effect of ALDs was caused by a direct interaction between ALDs and Cel6A (or CBH II). In this study, a different ALD was prepared from softwood kraft lignin in addition to aforementioned ALDs. The interactions between all the ALDs and the enzymes other than Cel6A, such as Cel7A and Cel7B, in a cellulase cocktail were investigated using surface plasmon resonance. The kraft lignin-based ALD showed the highest residual cellulase activity among all ALDs and an improved cellulolytic enzyme efficiency similar to those of the other ALDs. All ALDs were found to directly associate with major enzymes in the cellulase cocktail, Cel6A and Cel7A (or CBH I), but not with Cel7B (or EG I). In addition, the ALDs showed a much higher affinity to amino groups than to hydroxy and carboxy groups. In contrast, polyethylene glycol (molecular mass 4000 Da), one part of the ALD and a previously reported enzymatic saccharification enhancer, did not adsorb onto any enzymes in the cellulase cocktail or the amino group. Size exclusion chromatography demonstrated that the ALDs formed self-aggregates in both water and chloroform; the formation process in the latter was especially unique. Therefore, we conclude that the high residual cellulase activity is attributed to the direct association of ALD aggregates with the CBH group. 相似文献
16.
Chao Zhang Xinshu Zhuang Zhao Jiang Wang Fred Matt Franz St. John J. Y. Zhu 《Cellulose (London, England)》2013,20(4):1937-1946
Three pairs of solid substrates from dilute acid pretreatment of two poplar wood samples were enzymatically hydrolyzed by cellulase preparations supplemented with xylanase. Supplementation of xylanase improved cellulose saccharification perhaps due to improved cellulose accessibility by xylan hydrolysis. Total xylan removal directly affected enzymatic cellulose saccharification. Furthermore, xylan removal by pretreatment and xylanase are indifferent to enzymatic cellulose saccharification. However, more enzymatic xylose and glucose yields were obtained for a substrate with lower xylan content after a severer pretreatment at the same xylanase dosage. The effectiveness of xylanase at increased dosages depended on the substrates structure or accessibility. High xylanase dosages were more effective on well pretreated substrates than on under-pretreated substrates with high xylan content. The application sequence of xylanase and cellulase affected cellulose saccharification. This effect varied with substrate accessibility, perhaps due to competition between xylanase and cellulase binding to the substrate. 相似文献
17.
Effect of ozonation on the reactivity of lignocellulose substrates in enzymatic hydrolyses to sugars
E. M. Ben’ko O. R. Manisova V. V. Lunin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(7):1108-1113
The efficiency of pre-treatment of aspen wood with ozone for subsequent enzymatic hydrolysis into sugars is determined by the amount of absorbed ozone. The ozone absorption rate depended on the water content in the sample being ozonized and was maximum at a relative humidity of wood of ~40%. As a result of ozone pre-treatment, the initial rate of the enzymatic hydrolysis of wood under the action of a cellulase complex increased eightfold, and the maximum yield of sugars increased tenfold depending on the ozone dose. The ozonation at ozone doses of more than 3 mol/PPU (phenylpropane structural unit of lignin) led to a decrease in the yield of sugars because of the oxidative destruction of cellulose and hemicellulose. The alkaline ozonation in 2 and 12% NaOH was inefficient because of the accompanying oxidation of carbohydrates and considerably decreased the yield of sugars. 相似文献
18.
Jian Du Yuanyuan Li Hongman Zhang Hongbo Zheng He Huang 《Cellulose (London, England)》2014,21(4):2409-2417
The enzymatic hydrolysis of lignocelluloses is a key step in the production of ethanol. Economic considerations for large-scale implementation of the process require operation at high solid concentrations. However, the decrease in cellulose conversion offsets the advantages of working at high solid concentrations. The conversion showed a linear decrease in the reaction of pretreated corn stover (PCS) from 2 to 20 % (w/w) and filter paper from 1 to 10 % (w/w) initial total solid content. Hydrolysis experiments with PCS at various mixing speeds showed that the mass transfer limitation could not restrict the cellulose conversion except the solid concentrations over 5 % DM(w/w). The lignin, if added separately, does not correspond directly to the decrease. At increased concentrations, furfural and 5-hydroxymethylfurfural played a part in the effect, and 5-hydroxymethylfurfural only affected exoglucanase. Product inhibition caused by glucose accumulation at increased solid concentrations was found to be a significant and perhaps principal factor. The decrease in yield was caused by the synergetic inhibition, which was more serious with increased solid concentrations. 相似文献
19.
20.
Robert F. H. Dekker 《Applied biochemistry and biotechnology》1990,23(1):25-39
Aβ-glucosidase preparation derived fromAspergillus niger was immobilized onto a magnetic support and used in the enzymatic saccharification of a lignocellulosic material. The enzyme was immobilized onto polyethyleneimine-glutaraldehyde activated magnetite (PAM) and also onto titanium (IV) oxide (TiO2)-coated magnetite (TAM). Although > 80% of the protein applied was immobilized, only 15–27% of the enzyme activity was recovered after immobilization. Theβ-glucosidase immobilized onto TiCO2-coated magnetite suffered from enzyme being removed from the matrix under hydrolysis-use conditions, whereas the PAM enzyme remained attached to the matrix. The physicochemical properties of the immobilizedβ-glucosidase preparations are described. Both immobilizedβ-glucosidase preparations were capable of completely hydrolyzing cellobiose. Recycling of the immobilized enzymes (IME) resulted in reduced rates of hydrolysis with each recycling of the enzyme, although cellobiose was still capable of being completely hydrolyzed. The reduced hydrolysis performance was attributable to physical losses of IME during recovery and, in the case of TAM, enzyme loss from the matrix. Supplementing cellulase digests of steam-explosion pretreatedEucalyptus regnons pulps with immobilizedβ-glucosidase resulted in enhanced hydrolysis. Cellulose-to-glucose yields of 80% of theoretical predictions resulted within 24 h. The magnetically immobilizedβ-glucosidase could easily be recovered from the lignocellulose solids suspension in a stirred batch reactor by applying a magnetic field. The recycled immobilized enzyme continued to convert cellobiose into glucose in 80% yields over a 24-h period. This is the first report of a magnetically immobilizedβ-glucosidase preparation used in the enzymatic saccharification of a lignocellulosic material. 相似文献