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1.
H. Rodríguez R. Alvarez A. Enríquez 《World journal of microbiology & biotechnology》1993,9(2):213-215
Biomass production of Cellulomonas was optimal with 1% (w/v) bagasse pith pre-treated with either 0.2 M NaOH for 1 h at 80°C or 0.4 M NaOH for 40 h at 28 to 30°C. Growth was similar to that obtained with a more severe treatment used as control and compared well with other reports for cellulolytic bacteria cultivated on pre-treated bagasse pith. 相似文献
2.
Abstract: The combined effect of hydrostatic pressure and heat shock on thermotolerance was examined in the deep-sea hyperthermophilic archaeon Pyrococcus strain ES4. Pressure equivalent to the depth of isolation (22 MPa) enhanced ES4's survival at super-optimal temperatures (101–108°C) relative to low pressure (3 MPa). Pressure also raised the temperature at which a putative heat-shock protein (98 kDa) accumulated. ES4 grown at 95°C and 3 MPa displayed immediate enhanced thermotolerance to 105°C after being shifted to 22 MPa. Cultures grown at 95°C and 22 MPa and then heat shocked at 105°C and 3 MPa retained enhanced thermotolerance after decompression. These results suggest that this deep-sea hyperthermophile has developed pressure-induced responses that include increased survival to hyperthermal conditions. 相似文献
3.
Approximately half of the 80 billion tons of crop produced annually around the world remains as residue that could serve as a renewable resource to produce valuable products such as ethanol and butanol. Ethanol produced from lignocellulosic biomass is a promising renewable alternative to diminishing oil and gas liquid fuels. Sugarcane is an important industry in Louisiana. The recently released variety of “energy cane” has great potential to sustain a competitive sugarcane industry. It has been demonstrated that fuel-grade ethanol can be produced from post harvest sugarcane residue in the past, but optimized ethanol production was not achieved. Optimization of the fermentation process requires efficient pretreatment to release cellulose and hemicellulose from lignocellulosic complex of plant fiber. Determining optimal pretreatment techniques for fermentation is essential for the success of lignocellulosic ethanol production process. The purpose of this study was to evaluate three pretreatment methods for the energy cane variety L 79-1002 for maximum lignocellulosic ethanol production. The pretreatments include alkaline pretreatment, dilute acid hydrolysis, and solid-state fungal pretreatment process using brown rot and white rot fungi. Pretreated biomass was enzymatically saccharified and subjected to fermentation using a recombinant Escherichia coli FBR5. The results revealed that all pretreatment processes produced ethanol. However, the best result was observed in dilute acid hydrolysis followed by alkaline pretreatment and solid-state fungal pretreatment. 相似文献
4.
Bismuto E Nucci R Febbraio F Tanfani F Gentile F Briante R Scirè A Bertoli E Amodeo P 《European biophysics journal : EBJ》2004,33(1):38-49
The perturbation induced by mono- and divalent cations on the thermophilicity and thermostability of Solfolobus solfataricus -glycosidase, a hyperthermophilic tetrameric enzyme, has been investigated by spectroscopic and computational simulation methods to ascertain the Hofmeister effects on two strategic protein regions identified previously. Specifically, (1) an extra segment (83–124), present only in the sequence of hyperthermophilic glycosidases and recognized as an important thermostability determinant for the enzyme structure; and (2) a restricted area of the subunit interface responsible for the quaternary structure maintenance. Mono- and divalent cations inhibit to a different extent the -glycosidase activity, whose kinetic constants show an apparent competitive inhibition of the catalytic process that reflects the Hofmeister order. The thermostability is also affected by the nature and charge of the cations, reaching maximal effects for the case of Mg2+. Fourier transform infrared spectroscopy has revealed very small changes in the protein secondary structure in the presence of the investigated cations at 20 °C, while large effects on the protein melting temperatures are observed. Computational analysis of the enzyme structure has identified negative patches on the accessible surface of the two identified regions. Following the Hofmeister series, cations weaken the existing electrostatic network that links the extra segment to the remaining protein matrix. In particular, the perturbing action of cations could involve the ionic pair interactions E107–R245 and E109–R185, thus leading to a local destructuring of the extra segment as a possible starting event for thermal destabilization. A detailed investigation of the electrostatic network at the A–C intermolecular interface of Sgly after energy minimization suggests that cations could cause a strong attenuation of the ion pair interactions E474–K72 and D473–R402, with consequent partial dissociation of the tetrameric structure.Abbreviations Amide I
amide I band in a 2H2O medium
- EM
energy minimization
- ONPG
o-nitrophenyl--d-galactopyranoside
- Sgly
Escherichia coli expressed Sulfolobus solfataricus -glycosidase 相似文献
5.
ORF PAE1610 from the hyperthermophilic crenarchaeon Pyrobaculum aerophilum was first annotated as the conjectural pgi gene coding for hypothetical phosphoglucose isomerase (PGI). However, we have recently identified this ORF as the putative pgi/pmi gene coding for hypothetical bifunctional phosphoglucose/phosphomannose isomerase (PGI/PMI). To prove its coding function, ORF PAE1610 was overexpressed in Escherichia coli, and the recombinant enzyme was characterized. The 65-kDa homodimeric protein catalyzed the isomerization of both glucose-6-phosphate and mannose-6-phosphate to fructose-6-phosphate at similar catalytic rates, thus characterizing the enzyme as bifunctional PGI/PMI. The enzyme was extremely thermoactive; it had a temperature optimum for catalytic activity of about 100°C and a melting temperature for thermal unfolding above 100°C. 相似文献
6.
Martin Vaupel Julia A. Vorholt R. K. Thauer 《Extremophiles : life under extreme conditions》1998,2(1):15-22
N
5,N
10-Methenyltetrahydromethanopterin cyclohydrolase (Mch) is an enzyme involved in methanogenesis from CO2 and H2 which represents the energy metabolism of Methanopyrus kandleri, a methanogenic Archaeon growing at a temperature optimum of 98°C. The gene mch from M. kandleri was cloned, sequenced, and expressed in Escherichia coli. The overproduced enzyme could be purified in yields above 90% in one step by chromatography on phenyl Sepharose in 80% ammonium
sulfate. From 3.5 g cells (250 mg protein), approximately 18 mg cyclohydrolase was obtained. The purified enzyme showed essentially
the same catalytic properties as the enzyme purified from M. kandleri cells. The primary structure and properties of the cyclohydrolase are compared with those of the enzyme from Methanococcus jannaschii (growth temperature optimum 85°C), from Methanobacterium thermoautotrophicum (65°C), and from Methanosarcina barkeri (37°C). Of the four enzymes, that from M. kandleri has the lowest isoelectric point (3.8) and the lowest hydrophobicity of amino acid composition. Besides, it has the highest
relative content of glutamate, leucine, and valine and the lowest relative content of isoleucine, serine, and lysine. Some
of these properties are unusual for enzymes from hyperthermophilic organisms. They may reflect the observation that the cyclohydrolase
from M. kandleri is not only adapted to hyperthermophilic conditions but also to the high intracellular concentrations of lyotrophic salts
prevailing in this organism.
Received: July 14, 1997 / Accepted: August 28, 1997 相似文献
7.
Christian Baumann Martin Judex Harald Huber R. Wirth 《Extremophiles : life under extreme conditions》1998,2(2):101-108
Genomes of various hyperthermophilic and extremely thermophilic prokaryotes were analyzed with respect to size, physical
organization, and 16S rDNA copy number. Our results show that all the genomes are circular, and they are in the size range
of 1.6–1.8 Mb for Pyrodictium abyssi, Methanococcus igneus, Pyrobaculum aerophilum, Archaeoglobus fulgidus, Archaeoglobus lithotrophicus, and Archaeoglobus profundus (the two bacteria Fervidobacterium islandicum and Thermosipho africanus possess genomes of 1.5-Mb size). A systematic study of all validly described species of the order Sulfolobales revealed the existence of two classes of genome size for these archaea, correlating with phylogenetic analyses. The Metallosphaera–Acidianus group, plus Sulfolobus metallicus, have genomes of ca. 1.9 Mb; the other members of the order Sulfolobales group possess genomes >2.7 Mb. The special case of Stygiolobus azoricus is discussed.
Received: August 10, 1997 / Accepted: January 1, 1998 相似文献
8.
Yoshihisa Tomonaga Ryosuke Kaneko Masaru Goto Toshihisa Ohshima Kazuaki Yoshimune 《Biochemistry and Biophysics Reports》2015
Homoserine dehydrogenase (HSD; 305 amino acid residues) catalyzes an NAD(P)-dependent reversible reaction between l-homoserine and aspartate 4-semialdehyde and is involved in the aspartate pathway. HSD from the hyperthermophilic archaeon Sulfolobus tokodaii was markedly activated (2.5-fold) by the addition of 0.8 mM dithiothreitol. The crystal structure of the homodimer indicated that the activation was caused by cleavage of the disulfide bond formed between two cysteine residues (C303) in the C-terminal regions of the two subunits. 相似文献
9.
This paper reports the characterization of an alkaline phosphatase (AP) from an aerobic hyperthermophilic Archaeon Aeropyrum pernix K1. The native AP was purified into homogeneity. The enzyme is predicted as a homodimeric structure with a native molecular
mass of about 75 kDa and monomer of about 40 kDa. Apparent optimum pH and temperature were estimated at 10.0 and above 95°C,
respectively. Magnesium ion increased both the stability and the activity of the enzyme. A. pernix AP has been demonstrated as a very thermostable AP, retaining about 76% of its activity after being incubated at 90°C for
5.5 h and 67% of its activity after being incubated at 100°C for 2.5 h, respectively, under the presence of Mg(II). Enzyme
activity was increased in addition of exogenous Mg(II), Ca(II), Zn(II), and Co(II). 相似文献
10.
Hansen T Arnfors L Ladenstein R Schönheit P 《Extremophiles : life under extreme conditions》2007,11(1):105-114
Recently, unusual non-regulated ATP-dependent 6-phosphofructokinases (PFK) that belong to the PFK-B family have been described
for the hyperthermophilic archaea Desulfurococcus amylolyticus and Aeropyrum pernix. Putative homologues were found in genomes of several archaea including the hyperthermophilic archaeon Methanocaldococcus jannaschii. In this organism, open reading frame MJ0406 had been annotated as a PFK-B sugar kinase. The gene encoding MJ0406 was cloned
and functionally expressed in Escherichia coli. The purified recombinant enzyme is a homodimer with an apparent molecular mass of 68 kDa composed of 34 kDa subunits. With
a temperature optimum of 85°C and a melting temperature of 90°C, the M. jannaschii nucleotide kinase represents one of the most thermoactive and thermostable members of the PFK-B family described so far.
The recombinant enzyme was characterized as a functional nucleoside kinase rather than a 6-PFK. Inosine, guanosine, and cytidine
were the most effective phosphoryl acceptors. Besides, adenosine, thymidine, uridin and xanthosine were less efficient. Extremely
low activity was found with fructose-6-phosphate. Further, the substrate specificity of closely related PFK-Bs from D. amylolyticus and A. pernix were reanalysed. 相似文献