共查询到20条相似文献,搜索用时 15 毫秒
1.
M. M. Berrocal J. Rodríguez A. S. Ball M. I. Pérez-Leblic M. E. Arias 《Applied microbiology and biotechnology》1997,48(3):379-384
Nine Streptomyces strains were screened for their ability to solubilise and mineralise 14C-labelled lignin during growth in solid-state fermentation. Streptomyces viridosporus was confirmed as an active lignin-degrading organism along with a new isolate, Streptomyces sp. UAH 15, further classified as Streptomyces cyaneus CECT 3335. This organism was able to solubilise and mineralise the [14C]lignin fraction of lignocellulose (44.96 ± 1.77% and 3.41 ± 0.48% respectively) after 21 days of incubation. Cell-free filtrates
from Streptomyces sp. grown in solid-state fermentation were capable of solubilising up to 20% of the [14C]lignin after 2 days incubation, with most of the product detected in the acid-soluble rather than in the water-soluble fraction.
Identification of the extracellular enzymes produced during growth of S. cyaneus CECT 3335 revealed that extracellular peroxidase and phenol oxidase activities were present, with the activity of phenol
oxidase being 100 times greater than peroxidase activity. The activity of these two enzymes was found to correlate with both
solubilisation and mineralisation rates. This is the first report of phenol oxidase activity produced by a Streptomyces strain during growth in solid-state fermentation. A role for the enzyme in the solubilisation and mineralisation of lignocellulose
by S. cyaneus is suggested.
Received: 12 May 1997 / Accepted: 19 May 1997 相似文献
2.
Mineralisation of 14C-labelled synthetic lignin and ligninolytic enzyme activities of litter-decomposing basidiomycetous fungi 总被引:4,自引:0,他引:4
Within a screening program, 27 soil litter-decomposing basidiomycetes were tested for ligninolytic enzyme activities using
agar-media containing 2,2′-azinobis(3-ethylbenzthiazoline-6-sulphonate), a humic acid or Mn2+ ions as indicator substrates. Most active species were found within the family Strophariaceae (Agrocybe praecox, Stropharia coronilla, S. rugosoannulata) and used for mineralisation experiments with a 14C-ring-labelled synthetic lignin (14C-DHP). The fungi mineralised around 25% of the lignin to 14CO2 within 12 weeks of incubation in a straw environment; about 20% of the lignin was converted to water-soluble fragments. Mn-peroxidase
was found to be the predominant ligninolytic enzyme of all three fungi in liquid culture and its production was strongly enhanced
in the presence of Mn2+ ions. The results of this study demonstrate that certain ubiquitous litter-decomposing basidiomycetes possess ligninolytic
activities similar to the wood-decaying white-rot fungi, the most efficient lignin degraders in nature.
Received: 20 April 2000 / Received revision: 12 July 2000 / Accepted: 16 July 2000 相似文献
3.
A. Blanco P. Díaz J. Martínez T. Vidal A. L. Torres F. I. J. Pastor 《Applied microbiology and biotechnology》1998,50(1):48-54
The gene celA, encoding an endoglucanase from the strain Bacillus sp. BP-23, was cloned and expressed in Escherichia coli. The nucleotide sequence of a 1867-bp DNA fragment containing the celA gene was determined, revealing an open reading frame of 1200 nucleotides that encodes a protein of 44 803 Da. The deduced
amino acid sequence of the encoded enzyme shows high homology to those of enzymes belonging to subtype 4 of the family-A cellulases.
The celA gene product synthesized in E. coli showed activity on carboxymethylcellulose and lichenan but no activity was found on Avicel. Activity was enhanced in the
presence of 10 mM Mg2+ and Ca2+ and showed its maximum at 40 °C and pH 4.0. Study of the performance of CelA on paper manufacture from agricultural fibres
showed that treatment with the enzyme improved the properties of the pulp and the quality of paper. CelA treatment enhanced
the physical properties (stretch and tensile index) of paper from wheat straw, while dewatering properties were slightly diminished.
Electron-microscope analysis showed that the surface of straw fibres was modified by CelA.
Received: 11 February 1998 / Received revision: 20 March 1998 / Accepted: 20 March 1998 相似文献
4.
5.
Eric Mandrou Paulo Ricardo Gherardi Hein Emilie Villar Philippe Vigneron Christophe Plomion Jean-Marc Gion 《Tree Genetics & Genomes》2012,8(2):353-364
Lignin content and composition are considered as mandatory traits of eucalyptus breeding programs, especially for pulp, paper,
and bioenergy production. In this article, we used 33 Eucalyptus urophylla full-sib families of an 8 × 8 factorial design to provide estimates of genetic parameters for lignin- and growth-related
traits. Secondly, from the sequencing of the 16 unrelated founders, we described the nucleotide and haplotype variability
of cinnamoyl-CoA reductase (CCR), a candidate gene for lignin-related traits encoding the cinnamoyl-CoA reductase. Finally, we tested the association between
CCR polymorphisms and trait variation using a mixed linear model. A high value of narrow sense heritability was obtained for
lignin content (h2 = 0.85) and S/G ratio (h2 = 0.62) indicating that these traits are under strong genetic control. High levels of nucleotide (θπ = 0.0131) and haplotype (Hd = 0.958) diversity were detected for CCR. From an initial set of 152 biallelic single nucleotide polymorphisms (SNPs), a subset of 65 nonredundant loci was selected.
Three intronic SNPs were found to be associated to the variation of S/G ratio after multiple testing correction. In the line
of what has been obtained in forest trees, these SNPs explained between 2.45% and 2.87% of the genetic variance of the trait.
This study demonstrates the interest of the candidate gene approach for quantitative trait nucleotide detection in Eucalyptus and paves the way to gene assisted selection of lignin composition in E. urophylla. 相似文献
6.
Oxidase activity in the developing xylem of branches of Sitka spruce [Picea sitchensis] (Bong) Carr. was expressed in synchrony with the deposition of lignin. The activity was closely associated with the cell
wall but it could be extracted by elution with salt solutions such as 1 M NaCl or CaCl2. A number of different oxidase isoforms with isoelectric points in the range 8–5 were present in these cell wall extracts.
These enzymes displayed a marked preference for the oxidation of coniferyl alcohol and efficiently initiated polymerization
of coniferyl alcohol into insoluble, lignin-like polymers. They also had a substrate preference and profile of sensitivity
to inhibitors that was dissimilar to those reported for classical catechol oxidase or laccase-type polyphenol oxidases. A
novel procedure that combines extraction and affinity chromatography on Concanavalin-A to select high-mannose-type glycoproteins
provided oxidase activity at higher purity and yield than previously used methods. A single band of oxidase activity (apparent
Mr approx. 84 kDa) which was capable of oxidizing α-naphthol/N,N,N′N′-tetramethyl p-phenylene diamine in the absence of added hydrogen peroxide was detected in these cell wall extracts using non-denaturing
sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The addition of hydrogen peroxide did not intensify the staining
of this band but it confirmed the presence of a true peroxidase band of apparent Mr approx. 40 kDa. The properties of this coniferyl alcohol oxidase are different from those of laccase-type polyphenol oxidases
(EC 1.10.3.2) previously implicated in lignin deposition in tree species, and their possible roles in this process are discussed.
Received: 9 January 1997 / Accepted: 14 March 1997 相似文献
7.
Evaluation of solid substrates for enzyme production by Coriolus versicolor, for use in bioremediation of chlorophenols in aqueous effluents 总被引:1,自引:0,他引:1
In the development of a system for the removal of chlorophenols from aqueous effluents, a range of solid substrates for the
growth of Coriolus versicolor were investigated. Substrates included wood chips, cereal grain, wheat husk and wheat bran. Suitability for transformation
of chlorophenols depended on laccase production by the fungus. The greatest amount of laccase (<25 Units g−1 substrate) was produced on wheat husk and wheat bran over 30 days colonisation. Aqueous extracts of laccase from wheat husk
and wheat bran cultures removed 100% of 2,4-dichlorophenol (50 ppm) from solution within 5 h and 75–80% of pentachlorophenol
(50 ppm) within 24 h. Wheat bran was formulated into pellets with biscuit flour to provide a compact substrate for fungal
immobilisation. Addition of 8–12% yeast extract to the pellets increased laccase production five-fold. Colonised pellets were
added to chlorophenol solutions in 200–4000-ml bioreactors, resulting in >90% removal of chlorophenols within 100 min.
Received: 10 April 2000 / Received revision: 4 July 2000 / Accepted: 10 July 2000 相似文献
8.
Novotný C Erbanová P Cajthaml T Rothschild N Dosoretz C Sasek V 《Applied microbiology and biotechnology》2000,54(6):850-853
Growth parameters, ligninolytic enzyme activities and ability to degrade polycyclic aromatic hydrocarbons by the fungus Irpex lacteus were characterized and compared with those of other white rot fungi capable of rapid decolorization of poly R-478 and Remazol
Brilliant Blue R dyes. I. lacteus was able to grow on mineral and complex media and efficiently colonized sterile and non-sterile soil by exploratory mycelium
growing from a wheat straw inoculum. In shallow stationary cultures growing on high nitrogen mineral medium containing 45 mM
ammonium as nitrogen source, the fungus produced lignin peroxidase (LIP), Mn-dependent peroxidase (MnP) and laccase simultaneously,
the respective maximal activities of 70, 970 and 36 U/l being attained around day 18. Growing in nitrogen-limited medium (2.4 mM
ammonium), no LIP was formed and levels of MnP and laccase decreased significantly. During growth in sterile soil, the fungus
synthesized LIP and laccase but not MnP. I. lacteus efficiently removed three- and four-ringed PAHs from liquid media and artificially spiked soil. The variety of ligninolytic
enzymes, robust growth, capability of soil colonization and resistance to inhibitory action of soil bacteria make I. lacteus a suitable fungal organism for use in bioremediation.
Received: 30 March 2000 / Accepted: 19 May 2000 相似文献
9.
J. Clark Mason Michelle Richards Wolfgang Zimmermann Paul Broda 《Applied microbiology and biotechnology》1988,28(3):276-280
Summary We have utilized strains of three actinomycete species, Actinomadura sp, Streptomyces cyaneus and Thermomonospora mesophila, to study the solubilisation of lignocellulose. The production of extracellular proteins, was measured for each of the organisms during 17 days growth using medium containing either glucose or ball-milled straw. Some of the extracellular proteins (as identified by SDS gel electrophoresis) were present under both growth conditions, but others were specific to the type of medium or the period of incubation. The levels of proteins were compared with the abilities of the extracellular protein preparations to solubilise a substrate of 14C-labelled lignocellulose. About 6% of the radioactive material were solubilised when the extracellular proteins from the cultures grown on glucose were incubated with the substrate, compared to 20–30% that were solubilised by the extracellular proteins from the cultures grown on ball-milled straw. Partial characterisation of an enzyme from S. cyaneus responsible for the solubilisation of lignocellulose was achieved by gel filtration of the extracellular proteins, using Superose 12. Material that eluted from the column with an apparent molecular weight of about 20 000 accounted for all of the solubilisation of 14C-labelled (i.e. lignin-derived) moieties. In contrast, when the eluate was tested for the presence of cellulases and xylanases most of the activities were found in fractions containing material with an apparent molecular weight of about 45 000. We conclude that in cultures of S. cyaneus grown on ball-milled straw, a single extracellular enzyme is responsible for the solubilisation of lignin in lignocellulose, and that this enzyme is unlikely to be a cellulase or a xylanase. 相似文献
10.
Detoxification of wood hydrolysates with laccase and peroxidase from the white-rot fungus Trametes versicolor 总被引:1,自引:0,他引:1
L. J. Jönsson E. Palmqvist N.-O. Nilvebrant B. Hahn-Hägerdal 《Applied microbiology and biotechnology》1998,49(6):691-697
Fermentation of wood hydrolysates to desirable products, such as fuel ethanol, is made difficult by the presence of inhibitory
compounds in the hydrolysates. Here we present a novel method to increase the fermentability of lignocellulosic hydrolysates:
enzymatic detoxification. Besides the detoxification effect, treatment with purified enzymes provides a new way to identify
inhibitors by assaying the effect of enzymatic attack on specific compounds in the hydrolysate. Laccase, a phenol oxidase,
and lignin peroxidase purified from the ligninolytic basidiomycete fungus Trametes versicolor were studied using a lignocellulosic hydrolysate from willow pretreated with steam and SO2. Saccharomyces cerevisiae was employed for ethanolic fermentation of the hydrolysates. The results show more rapid consumption of glucose and increased
ethanol productivity for samples treated with laccase. Treatment of the hydrolysate with lignin peroxidase also resulted in
improved fermentability. Analyses by GC-MS indicated that the mechanism of laccase detoxification involves removal of monoaromatic
phenolic compounds present in the hydrolysate. The results support the suggestion that phenolic compounds are important inhibitors
of the fermentation process.
Received: 3 November 1997 / Received revision: 4 February 1998 / Accepted: 6 February 1998 相似文献
11.
B. C. Okeke A. Paterson J. E. Smith I. A. Watson-Craik 《Applied microbiology and biotechnology》1997,48(4):563-569
Sterilised and non-sterilised soils contaminated with pentachlorophenol (PCP) were inoculated with solid substrate cultures
of Lentinula edodes LE2 (“shiitake” mushroom) to simulate monoculture bioremediation treatments and treatments in which the fungus competes with
natural microflora. With monocultures of L. edodes, rates of PCP depletion were rapid for the initial 4 weeks and, although thereafter the rate decreased, 99% biotransformation
was obtained in 10 weeks. In mixed culture, PCP biotransformation by L.␣edodes was markedly slower and only 42% of the PCP was depleted after 10 weeks. Maximal rates of PCP transformation, biomass (ergosterol)
accumulation and oxidative enzymes (phenol oxidase and manganese-peroxidase) production were observed after 2 weeks of incubation.
In monocultures, phenol oxidase activity was 195.5 U g−1 and Mn-peroxidase 138.4 U g−1. In mixed cultures, fungal enzyme activities were markedly lower: 70.33 U g−1 for phenol oxidase and 85.0 g−1 for Mn-peroxidase. Analyses of soil metabolites after 10 weeks revealed that monocultures of L.edodes had eliminated both PCP and pentachloroanisole. Pentachloroanisole, however, was detected in soils with the mixed microflora.
Both dechlorination and mineralisation of the xenobiotic compound were effected by L. edodes LE2.
Received: 7 April 1997 / Accepted: 14 June 1997 相似文献
12.
M. D. Montiel J. Rodríguez M. I. Pérez-Leblic M. Hernández M. E. Arias J. L. Copa-Patiño 《Applied microbiology and biotechnology》1999,52(2):240-245
Fifty actinomycete strains were screened for the production of mannanase activity during growth in both liquid and solid
media. Streptomyces scabies CECT 3340 and Streptomyces ipomoea CECT 3341 were selected for their ability to produce high levels of mannanase (294.3 U/l and 242.9 U/l, respectively) during
growth in liquid culture. β-Mannosidase (15.3 U/l) and α-galactosidase (7.7 U/l) activities were also detected in culture
filtrate from S. scabies CECT 3340. Highest levels of mannanase activity for S. scabies CECT 3340 were achieved in media containing locust bean gum and asparagine (4.8 U mg−1 protein) whilst in S. ipomoea CECT 3341 greatest activity was detected in media containing locust bean gum and yeast extract (13.2 U mg−1 protein). No carboxymethylcellulase activity was detected. In biobleaching experiments, enzyme treatment, carried out with
mannanase activity produced by S. ipomoea CECT 3341, followed by alkaline extraction of pine kraft pulp resulted in the release of colour (A
465, 0.69) and chromophoric material from the pulp (A
237, 12.9; A
254, 6.9 and A
280, 6.7). The ability of this enzyme complex to improve the bleaching of pine kraft pulps was also shown by a pulp brightness
increase (2.4 units ISO) and a reduction in kappa number (from 21.4 units to 20.1 units) with the absence of variations on
the viscosity values.
Received: 23 February 1999 / Received revision: 1 April 1999 / Accepted: 6 April 1999 相似文献
13.
Previous mechanical studies using algae have concentrated on cell extension and growth using creep-type experiments, but
there appears to be no published study of their failure properties. The mechanical strength of single large internode cell
walls (up to 2 mm diameter and 100 mm in length) of the charophyte (giant alga) Chara corallina was determined by dissecting cells to give sheets of cell wall, which were then notched and fractured under tension. Tensile
tests, using a range of notch sizes, were conducted on cell walls of varying age and maturity to establish their notch sensitivity
and to investigate the propagation of cracks in plant cell walls. The thickness and stiffness of the walls increased with
age whereas their strength was little affected. The strength of unnotched walls was estimated as 47 ± 13 MPa, comparable to
that of some grasses but an order of magnitude higher than that published for model bacterial cellulose composite walls. The
strength was notch-sensitive and the critical stress intensity factor K
1c was estimated to be 0.63 ± 0.19 MNm−3/2, comparable to published values for grasses.
Received: 4 April 2000 / Accepted: 21 July 2000 相似文献
14.
The recombinant laccase from Thermus thermophilus was applied to the biobleaching of wheat straw pulp. The best bleaching effect was when the pulp was treated with 3 U laccase g−1 dry pulp at 90°C, pH 4.5, 8% consistency for 1.5 h. Under these conditions, the pulp brightness was increased by 3.3% ISO,
and the pulp kappa number was decreased by 5.6 U. Enzymatic treatment improved the bleachability of wheat straw pulp but caused
no damage to the pulp fibers. The use of enzyme-treated pulp saved 25% H2O2 consumption in subsequent peroxide bleaching without decreasing the final brightness. Pulp biobleaching in the presence of
5 mM ABTS further increased the pulp brightness by 1.5% ISO. This is the first report on the application of laccase from T. thermophilus in the pulp and paper sector. 相似文献
15.
Indirect evidence has suggested that lignin peroxidase (LiP) of the white-rot fungus Phanerochaete chrysosporium catalyses oxidative decolourisation and depolymerisation of macromolecules from brown coal in vivo. In this study we show
that LiP catalyses these transformations in vitro. Unmethylated (USC45 coal) and methylated (MWSC6 coal) fractions of solubilised
macromolecules (M
r > 30 000) from a brown coal were treated with a semi-purified preparation of LiP isozymes from P. chrysosporium. Both coal fractions were decolourised, losing between 26% and 39% of their absorbance at both 280 nm and 400 nm, in reactions
that had an absolute requirement for H2O2 and veratryl alcohol. Neither coal fraction was transformed when the enzyme was heat-inactivated or in the presence of the
LiP inhibitor metavanadate. Gel-permeation chromatography showed that MWSC6 coal but not USC45 was depolymerised and yielded
low-molecular-mass (M
r < 30 000) fragments. Nine monomeric products were identified by GC-MS.
Received: 20 March 1998 / Received revision: 3 September 1998 / Accepted: 3 September 1998 相似文献
16.
H. Okada T. Sekiya K. Yokoyama H. Tohda H. Kumagai Y. Morikawa 《Applied microbiology and biotechnology》1998,49(3):301-308
A cbh2 cDNA encoding Trichoderma reesei QM9414 cellobiohydrolase II, located on the expression vector whose copy number is controlled by the level of gentamicin,
was successfully expressed under the control of a human cytomegalovirus promoter in the fission yeast, Schizosaccharomyces pombe. The 24-amino-acid leader peptide of the cbh2 gene was recognized by the yeast, enabling the efficient secretion of the heterologous cellobiohydrolase. The transformed
S. pombe strain produced over 115 μg cellobiohydrolase proteins/ml rich medium supplemented with malt extract and 100 μg/ml gentamicin.
The molecular masses of the recombinant cellobiohydrolases, secreted as two molecular species, were estimated to be 70 kDa
and 72 kDa by sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE). Deglycosylation treatments revealed that
the recombinant enzymes were overglycosylated and scarcely susceptible to α-mannosidase. The recombinant enzymes showed no
carboxymethylcellulase activity, but showed similar characteristics to those of a native enzyme purified from T. reesei in their optimum pH and temperature, pH and temperature stabilities, and V
max values toward phosphoric-acid-swollen cellulose as substrate, except that their K
m values were about fourfold higher than that of the native enzyme.
Received: 4 August 1997 / Received revision: 13 October 1997 / Accepted: 31 October 1997 相似文献
17.
Purification and properties of a novel raw starch degrading cyclomaltodextrin glucanotransferase from Bacillus firmus 总被引:3,自引:0,他引:3
B. N. Gawande A. Goel A. Y. Patkar S. N. Nene 《Applied microbiology and biotechnology》1999,51(4):504-509
A novel raw starch degrading cyclomaltodextrin glucanotransferase (CGTase; E.C. 2.4.1.19), produced by Bacillus firmus, was purified to homogeneity by ultrafiltration, affinity and gel filtration chromatography. The molecular weight of the
pure protein was estimated to be 78 000 and 82 000 Da, by SDS-PAGE and gel filtration, respectively. The pure enzyme had a
pH optimum in the range 5.5–8.5. It was stable over the pH range 7–11 at 10 °C, and at pH 7.0 at 60 °C. The optimum temperature
for enzyme activity was 65 °C. In the absence of substrate, the enzyme rapidly lost its activity above 30 °C. K
m and k
cat for the pure enzyme were 1.21 mg/ml and 145.17 μM/mg per minute respectively, with soluble starch as the substrate. For cyclodextrin
production, tapioca starch was the best substrate used when gelatinized, while wheat starch was the best substrate used when
raw. This CGTase could degrade raw wheat starch very efficiently; up to 50% conversion to cyclodextrins was obtained from
150 g/l starch without using any additives. The enzyme produced α-, β- and γ-cyclodextrins in the ratio of 0.2:9.2:0.6 and
0.2:8.6:1.2 from gelatinized tapioca starch and raw wheat starch with 150 g/l concentration respectively, after 18 h incubation.
Received: 25 September 1998 / Received revision: 15 December 1998 / Accepted: 21 December 1998 相似文献
18.
The biodegradation of phenol by a pure culture of Pseudomonas putida was investigated in a continuously fed stirred-tank reactor, under aerobic conditions. The dilution rate was varied between
0.0174 h−1 and 0.278 h−1, covering a wide range of dissolved oxygen and the inhibition region of phenol. Through non-linear analysis of the data,
a dual-substrate growth kinetics, Haldane kinetics for phenol and Monod kinetics for oxygen, was derived with high correlation
coefficients. Respective biokinetic parameters were evaluated as μm = 0.569 h−1, K
p = 18.539 mg/l, K
i = 99.374 mg/l, K
o = 0.048 mg/l, Y
x/p = 0.521 g microorganism/g phenol and Y
x/o = 0.338 g microorganism/g oxygen, being in good agreement with other studies in the literature. Maintenance factors for both
phenol and oxygen were calculated for the first time for P. putida while the saturation coefficient for oxygen, K
o, was genuinely evaluated from the constructed model, not imported or adapted from other studies as reported in the literature.
All pertinent biokinetic parameters for P. putida have been calculated from continuous system data, which are most appropriate for use in continuous bioprocess applications.
Received: 29 July 1996 / Received revision: 18 November 1996 / Accepted: 23 November 1996 相似文献
19.
Production of transgenic tall fescue and red fescue plants by particle bombardment of mature seed-derived highly regenerative tissues 总被引:29,自引:0,他引:29
Highly regenerative tissues of tall fescue and red fescue produced from mature seed-derived embryogenic callus were induced
and proliferated on medium containing 2,4-dichlorophenoxyacetic acid (4.5 or 9.0 μM), 6-benzylaminopurine (0, 0.044, 0.44
or 2.2 μM) and cupric sulfate (0.1 or 5.0 μM) under dim-light conditions (10 to 30 μE m–2 s–1, 16 h light). Tall fescue tissues were transformed with three plasmids containing the genes for hygromycin phosphotransferase
(hpt), phosphinothricin acetyltransferase (bar) and β-glucuronidase (uidA;gus), and red fescue with three plasmids containing hpt, uidA and a synthetic green fluorescent protein gene [sgfp(S65T)]. DNA from T0 plants of eight independently transformed lines from tall fescue and 11 from red fescue were analyzed by PCR and DNA blot
hybridization. The co-expression frequency of all three transgenes [hpt/bar/uidA or hpt/uidA/sgfp(S65T)] in transgenic tall fescue and red fescue plants was 25–27%; for two transgenes [hpt/bar or hpt/uidA for tall fescue and hpt/uidA or hpt/sgfp(S65T) for red fescue], the co-expression frequency was 50–75%.
Received: 28 September 1999 / Revision received: 13 March 2000 / Accepted: 16 March 2000 相似文献
20.
Pastor FI Pujol X Blanco A Vidal T Torres AL Díaz P 《Applied microbiology and biotechnology》2001,55(1):61-68
The gene celB encoding an endoglucanase from Paenibacillus sp. BP-23 was cloned and expressed in Escherichia coli. The nucleotide sequence of a 4161 bp DNA fragment containing the celB gene was determined, revealing an open reading frame of 2991 nucleotides that encodes a protein of 106,927 Da. Comparison
of the deduced amino acid sequence of endoglucanase B with known β-glycanase sequences showed that the encoded enzyme is a
modular protein and exhibits high homology to enzymes belonging to family 9 cellulases. The celB gene product synthesized in E. coli showed high activity on carboxymethyl cellulose and lichenan while low activity was found on Avicel. Activity was enhanced
in the presence of 10 mM Ca2+ and showed its maximum at 53 °C and pH 5.5. The effect of the cloned enzyme in modifying the physical properties of pulp
and paper from Eucalyptus was tested (CelB treatment). An increase in mechanical strength of paper and a decrease in pulp dewatering properties were
found, indicating that CelB treatment can be considered as a biorefining. Treatment with CelB gave rise to an improvement
in paper strength similar to that obtained with 1,000 revolutions increase in mechanical refining. Comparison with the performances
of recently developed endoglucanase A from the same strain and with a commercial cellulase showed that CelB produced the highest
refining effect.
Received: 25 February 2000 / Received revision: 4 July 2000 / Accepted: 9 July 2000 相似文献