共查询到20条相似文献,搜索用时 31 毫秒
1.
Elin Säwén Eine Huttunen Xue Zhang Zhennai Yang Göran Widmalm 《Journal of biomolecular NMR》2010,47(2):125-134
The use of lactic acid bacteria in fermentation of milk results in favorable physical and rheological properties due to in
situ exopolysaccharide (EPS) production. The EPS from S. thermophilus ST1 produces highly viscous aqueous solutions and its structure has been investigated by NMR spectroscopy. Notably, all aspects
of the elucidation of its primary structure including component analysis and absolute configuration of the constituent monosaccharides
were carried out by NMR spectroscopy. An array of techniques was utilized including, inter alia, PANSY and NOESY-HSQC TILT
experiments. The EPS is composed of hexasaccharide repeating units with the following structure: → 3)[α-d-Glcp-(1 → 4)]-β-d-Galp-(1 → 4)-β-d-Glcp-(1 → 4)[β-d-Galf-(1 → 6)]-β-d-Glcp-(1 → 6)-β-d-Glcp-(1 →, in which the residues in square brackets are terminal groups substituting backbone sugar residues that consequently
are branch-points in the repeating unit of the polymer. Thus, the EPS consists of a backbone of four sugar residues with two
terminal sugar residues making up two side-chains of the repeating unit. The molecular mass of the polymer was determined
using translational diffusion experiments which resulted in Mw = 62 kDa, corresponding to 64 repeating units in the EPS. 相似文献
2.
Sushma Deepthi Arli U. B. Trivedi K. C. Patel 《World journal of microbiology & biotechnology》2011,27(6):1415-1422
Cellulomonas flavigena UNP3, a natural isolate from vegetable oil contaminated soil sample has been studied for growth associated exopolysaccharide
(EPS) production during growth on glucose, groundnut oil and naphthalene. The EPS showed matrix formation surrounding the
cells during scanning electron microscopy. Cell surface hydrophobicity and emulsifying activity studies confirmed the role
of EPS as bioemulsifier. Emulsifying activity was found to increase with time (0.2 U/mg for 10 min to 0.27 U/mg for 30 min).
Emulsification index, E24 value increased with the increase in EPS concentration. Degradation of polyaromatic hydrocarbons was confirmed using gas
chromatography analysis. FTIR analysis showed presence of characteristic absorbance at 895.10 cm−1 for β-configuration of glucan. NMR studies also revealed EPS produced by C. flavigena UNP3 as a linear β-1, 3-d-glucan, and a curdlan like polysaccharide. 相似文献
3.
A recombinant putative β-galactosidase from Thermoplasma acidophilum was purified as a single 57 kDa band of 82 U mg−1. The molecular mass of the native enzyme was 114 kDa as a dimer. Maximum activity was observed at pH 6.0 and 90°C. The enzyme
was unstable below pH 6.0: at pH 6 its half-life at 75°C was 28 days but at pH 4.5 was only 13 h. Catalytic efficiencies decreased
as p-nitrophenyl(pNP)-β-d-fucopyranoside (1067) > pNP-β-d-glucopyranoside (381) > pNP-β-d-galactopyranoside (18) > pNP-β-d-mannopyranoside (11 s−1 mM−1), indicating that the enzyme was a β-glycosidase. 相似文献
4.
Prabhu P Tiwari MK Jeya M Gunasekaran P Kim IW Lee JK 《Applied microbiology and biotechnology》2008,81(2):283-290
Based on analysis of the genome sequence of Bacillus licheniformis ATCC 14580, an isomerase-encoding gene (araA) was proposed as an l-arabinose isomerase (L-AI). The identified araA gene was cloned from B. licheniformis and overexpressed in Escherichia coli. DNA sequence analysis revealed an open reading frame of 1,422 bp, capable of encoding a polypeptide of 474 amino acid residues
with a calculated isoelectric point of pH 4.8 and a molecular mass of 53,500 Da. The gene was overexpressed in E. coli, and the protein was purified as an active soluble form using Ni–NTA chromatography. The molecular mass of the purified enzyme
was estimated to be ~53 kDa by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and 113 kDa by gel filtration chromatography,
suggesting that the enzyme is a homodimer. The enzyme required a divalent metal ion, either Mn2+or Co2+, for enzymatic activity. The enzyme had an optimal pH and temperature of 7.5 and 50°C, respectively, with a k
cat of 12,455 min−1 and a k
cat/K
m of 34 min−1 mM−1 for l-arabinose, respectively. Although L-AIs have been characterized from several other sources, B. licheniformis L-AI is distinguished from other L-AIs by its wide pH range, high substrate specificity, and catalytic efficiency for l-arabinose, making B. licheniformis L-AI the ideal choice for industrial applications, including enzymatic synthesis of l-ribulose. This work describes one of the most catalytically efficient L-AIs characterized thus far. 相似文献
5.
Xylem parenchyma cells (XPCs) in trees adapt to subzero temperatures by deep supercooling. Our previous study indicated the
possibility of the presence of diverse kinds of supercooling-facilitating (SCF; anti-ice nucleation) substances in XPCs of
katsura tree (Cercidiphyllum japonicum), all of which might have an important role in deep supercooling of XPCs. In the previous study, a few kinds of SCF flavonol
glycosides were identified. Thus, in the present study, we tried to identify other kinds of SCF substances in XPCs of katsura
tree. SCF substances were purified from xylem extracts by silica gel column chromatography and Sephadex LH-20 column chromatography.
Then, four SCF substances isolated were identified by UV, mass and nuclear magnetic resonance analyses. The results showed
that the four kinds of hydrolyzable gallotannins, 2,2′,5-tri-O-galloyl-α,β-d-hamamelose (trigalloyl Ham or kurigalin), 1,2,6-tri-O-galloyl-β-d-glucopyranoside (trigalloyl Glc), 1,2,3,6-tetra-O-galloyl-β-d-glucopyranoside (tetragalloyl Glc) and 1,2,3,4,6-penta-O-galloyl-β-d-glucopyranoside (pentagalloyl Glc), in XPCs exhibited supercooling capabilities in the range of 1.5–4.5°C, at a concentration
of 1 mg mL−1. These SCF substances, including flavonol glycosides and hydrolyzable gallotannins, may contribute to the supercooling in
XPCs of katsura tree. 相似文献
6.
Theodoros Goulas Athanasios Goulas George Tzortzis Glenn R. Gibson 《Applied microbiology and biotechnology》2009,82(6):1079-1088
Four different β-galactosidases (previously named BbgI, BbgII, BbgIII and BbgIV) from Bifidobacterium bifidum NCIMB41171 were overexpressed in Escherichia coli, purified to homogeneity and their biochemical properties and substrate preferences comparatively analysed. BbgI was forming
a hexameric protein complex of 875 kDa, whereas BbgII, BbgIII and BbgIV were dimers with native molecular masses of 178, 351
and 248 kDa, respectively. BbgII was the only enzyme that preferred acidic conditions for optimal activity (pH 5.4–5.8), whereas
the other three exhibited optima in more neutral pH ranges (pH 6.4–6.8). Na+ and/or K+ ions were prerequisite for BbgI and BbgIV activity in Bis–Tris-buffered solutions, whereas Mg++ was strongly activating them in phosphate-buffered solutions. BbgII and BbgIII were slightly influenced from the presence
or absence of cations, with Mg++, Mn++ and Ca++ ions exerting the most positive effect. Determination of the specificity constants (k
cat/K
m) clearly indicated that BbgI (6.11 × 104 s−1 M−1), BbgIII (2.36 × 104 s−1 M−1) and especially BbgIV (4.01 × 105 s−1 M−1) are highly specialised in the hydrolysis of lactose, whereas BbgII is more specific for β-d-(1→6) galactobiose (5.59 × 104 s−1 M−1) than lactose (1.48 × 103 s−1 M−1). Activity measurements towards other substrates (e.g. β-d-(1→6) galactobiose, β-d-(1→4) galactobiose, β-d-(1→4) galactosyllactose, N-acetyllactosamine, etc.) indicated that the β-galactosidases were complementary to each other by hydrolysing different substrates and thus contributing in a different
way to the bacterial physiology. 相似文献
7.
The kinetics of phase separation and microstructure of oat β-glucan/whey protein binary mixtures varying in concentration (4–16% w/v protein, 0.3–1.2% w/v β-glucan) and β-glucan molecular weight (1.3 × 106, 640 × 103, 180 × 103, and 120 × 103 g/mol) was investigated by turbidimetry and fluorescent microscopy. The phase separation of the mixed systems was followed
at pH 7.0 and at room temperature under quiescent conditions. Application of first principles revealed that phase separation
of the systems follows first-order kinetics. Acceleration of the phase-separation process was observed with increase of β-glucan concentration for the three lowest-MW samples but the highest molecular weight (1.3 × 106 g/mol) exhibited the opposite trend. Changes in the polysaccharide molecular weight resulted in considerable differences
in β-glucan aggregate morphology in the mixed systems. The change in the continuity of the mixed system from polysaccharide-,
to bi-, to protein-continuous was confirmed for a wide range of mixed systems differing in biopolymer concentration, and β-glucan molecular weight. 相似文献
8.
Jin Zhou Ju Chu Yong-Hong Wang Si-Liang Zhang Ying-Ping Zhuang Zhong-Yi Yuan 《World journal of microbiology & biotechnology》2008,24(6):789-796
An intracellular S-adenosylmethionine synthetase (SAM-s) was purified from the fermentation broth of Pichia pastoris GS115 by a sequence chromatography column. It was purified to apparent homogeneity by (NH4)2SO4 fractionation (30–60%), anion exchange, hydrophobic interaction, anion exchange and gel filtration chromatography. HPLC showed
the purity of purified SAM-s was 91.2%. The enzyme was purified up to 49.5-fold with a final yield of 20.3%. The molecular
weight of the homogeneous enzyme was 43.6 KDa, as determined by electro-spray ionization mass spectrometry (ESI-MS). Its isoelectric
point was approximately 4.7, indicating an acidic character. The optimum pH and temperature for the enzyme reaction were 8.5
and 35 °C, respectively. The enzyme was stable at pH 7.0–9.0 and was easy to inactivate in acid solution (pH ≤ 5.0). The temperature
stability was up to 45 °C. Metal ions, such as, Mn2+ and K+ at the concentration of 5 mM had a slight activation effect on the enzyme activity and the Mg2+ activated the enzyme significantly. The enzyme activity was strongly inhibited by heavy metal ions (Cu2+ and Ag2+) and EDTA. The purified enzyme from the transformed Pichia pastoris synthesized S-adenosylmethionine (SAM) from ATP and l-methionine in vitro with a K
m of 120 and 330 μM and V
max of 8.1 and 23.2 μmol/mg/min for l-methionine and ATP, respectively. 相似文献
9.
Xiao-Qiang Qi Qing-Li Sun Li-Ping Bai Jun-Jie Shan Yang Zhang Ren Zhang Yuan Li 《Applied microbiology and biotechnology》2009,83(2):361-368
Ebosin, a novel exopolysaccharide produced by Streptomyces sp. 139 has antagonist activity for IL-1R in vitro and remarkable anti-rheumatic arthritis activity in vivo. Its biosynthesis
gene cluster (ste) has been identified. In this study, gene ste17 was expressed in Escherichia coli BL21 and the recombinant protein was purified. With CTP and α-d-glucose-1-phosphate as substrates, the recombinant Ste17 protein was found capable of catalyzing the production of CDP-d-glucose and pyrophosphate, demonstrating its identity as an α-d-glucose-1-phosphate–cytidylyltransferase (CDP-d-glucose synthase). To investigate the function of ste17 in Ebosin biosynthesis, the gene was disrupted with a double crossover via homologous recombination. The monosaccharide composition
of exopolysaccharide (EPS) produced by the mutant Streptomyces sp. 139 (ste17
−) was found significantly altered from that of Ebosin, with glucose becoming undetectable. This gene knockout also negatively
affected the antagonist activity for IL-1R of EPS. These results indicate that the CDP-d-glucose synthase encoded by ste17 gene is involved in the formation of nucleotide sugar (CDP-d-glucose) as glucose precursor in Ebosin biosynthesis.
Xiao-Qiang Qi and Qing-Li Sun contributed equally to this work. 相似文献
10.
Asiya Nazir Rohit Soni H. S. Saini R. K. Manhas B. S. Chadha 《World journal of microbiology & biotechnology》2009,25(7):1189-1197
An endoglucanase (1, 4-β-d glucan glucanohydrolase, EC 3.2.1.4) which was catalytically more active and exhibited higher affinity towards barley β-glucan,
xyloglucan and lichenin as compared to carboxymethylcellulose (CMC) was purified from Aspergillus terreus strain AN1 following ion-exchange and hydrophobic interaction chromatography and gel filtration. The purified enzyme (40-fold) that
apparently lacked a cellulose-binding domain showed a specific activity of 60 μmol mg−1 protein−1 against CMC. The purified enzyme had a molecular weight of 78 and 80 KDa as indicated by sodium dodecyl sulphate–polyacrylamide
gel electrophoresis and gel filtration, respectively, and a pI of 3.5. The enzyme was optimally active at temperature 60°C
and pH 4.0, and was stable over a broad range of pH (3.0–5.0) at 50°C. The endoglucanase activity was positively modulated
in the presence of Cu2+, Mg2+, Ca2+, Na+, DTT and mercaptoethanol. Endoglucanase exhibited maximal turn over number (K
cat) and catalytic efficiency (K
cat/km) of 19.11 × 105 min−1 and 29.7 × 105 mM−1 min−1 against barley β-glucan as substrate, respectively. Hydrolysis of CMC and barley β-glucan liberated cellobiose, cellotriose,
cellotetraose and detectable amount of glucose. The hydrolysis of xyloglucan, however, apparently yielded positional isomers
of cellobiose, cellotriose and cellotetraose as well as larger oligosaccharides. 相似文献
11.
When Pseudomonas mendocina NK-01 was cultivated in a 200-L fermentor using glucose as carbon source, 0.316 g L−1 medium-chain-length polyhydroxyalkanoate (PHAMCL) and 0.57 g L−1 alginate oligosaccharides (AO) were obtained at the end of the process. GC/MS was used to characterize the PHAMCL, which was found to be a polymer mainly consisting of 3HO (3-hydroxyoctanoate) and 3HD (3-hydroxydecanoate). T
m and T
g values for the PHAMCL were 51.03°C and −41.21°C, respectively, by DSC. Its decomposition temperature was about 300°C. The elongation at break was
700% under 12 MPa stress. MS and GPC were also carried out to characterize the AO which had weight-average molecular weights
of 1,546 and 1,029 Da, respectively, for the two main components at the end of the fermentation process. MS analysis revealed
that the AO were consisted of β-d-mannuronic acid and/or α-l-guluronic acid, and the β-d-mannuronic acid and/or α-l-guluronic acid residues were partially acetylated at position C2 or C3. 相似文献
12.
Chengwei Hua Qiaojuan Yan Zhengqiang Jiang Yinan Li Priti Katrolia 《Applied microbiology and biotechnology》2010,88(2):509-518
In this study, a novel β-1,3-1,4-glucanase gene (designated as PtLic16A) from Paecilomyces thermophila was cloned and sequenced. PtLic16A has an open reading frame of 945 bp, encoding 314 amino acids. The deduced amino acid sequence shares the highest identity
(61%) with the putative endo-1,3(4)-β-glucanase from Neosartorya fischeri NRRL 181. PtLic16A was cloned into a vector pPIC9K and was expressed successfully in Pichia pastoris as active extracellular β-1,3-1,4-glucanase. The recombinant β-1,3-1,4-glucanase (PtLic16A) was secreted predominantly into
the medium which comprised up to 85% of the total extracellular proteins and reached a protein concentration of 9.1 g l−1 with an activity of 55,300 U ml−1 in 5-l fermentor culture. The enzyme was then purified using two steps, ion exchange chromatography, and gel filtration chromatography.
The purified enzyme had a molecular mass of 38.5 kDa on SDS–PAGE. It was optimally active at pH 7.0 and a temperature of 70°C.
Furthermore, the enzyme exhibited strict specificity for β-1,3-1,4-d-glucans. This is the first report on the cloning and expression of a β-1,3-1,4-glucanase gene from Paecilomyces sp. 相似文献
13.
For the first time, a β-glucosidase gene from the edible straw mushroom, Volvariella volvacea V1-1, has been over-expressed in E. coli. The gene product was purified by chromatography showing a single band on SDS-PAGE. The recombinant enzyme had a molecular
mass of 380 kDa with subunits of 97 kDa. The maximum activity was at pH 6.4 and 50 °C over a 5 min assay. The purified enzyme
was stable from pH 5.6–8.0, had a half life of 1 h at 45 °C. The β-glucosidase had a Km of 0.2 mM for p-nitrophenyl-β-D-glucopyranoside. 相似文献
14.
An N-acetyl-d-lactosamine (LacNAc) specific lectin from tubers of Alocasia cucullata was purified by affinity chromatography on asialofetuin-linked amino activated silica. The pure lectin showed a single band
in SDS-PAGE at pH 8.8 and was a homotetramer with a subunit molecular mass of 13.5 kDa and native molecular mass of 53 kDa.
It was heat stable up to 55 °C for 15 min and showed optimum hemagglutination activity from pH 2 to 11. The lectin was affected
by denaturing agents such as urea (2 m), thiourea (2 m) and guanidine–HCl (0.5 m) and did not require Ca2+ and Mn2+ for its activity. It was a potent mitogen at 10 μg/ml towards human peripheral blood mononuclear cells with 50% growth inhibitory
potential towards SiHa (human cervix ) cancer cell line at 100 μg/ml. 相似文献
15.
The structure of furcellarans obtained from red algae Furcellaria lumbricalis collected in Estonia was determined. Native and alkali-modified furcellarans were examined by gas chromatography/mass spectrometry
(GC/MS), and 13C-nuclear magnetic resonance spectroscopy (NMR) and were compared with commercial furcellaran (FMC Food Ingredients). The
polysaccharide preparation consisted mainly of (1→3) linked β-D-galactopyranose, (1→4) linked 3,6-anhydro-α-D-galactopyranose and (1→3) linked β-D-galactopyranose 4-sulphate. Alkaline treatment removed the sulphate precursor sequences with formation of 3,6-anhydrogalactose
that improved the furcellaran gelling ability. 相似文献
16.
Jin Kang Young-Min Kim Nahyun Kim Du-Woon Kim Seung-Hee Nam Doman Kim 《Applied microbiology and biotechnology》2009,83(6):1009-1016
Hydroquinone (HQ) functions as a skin-whitening agent, but it has the potential to cause dermatitis. We synthesized a HQ fructoside
(HQ-Fru) as a potential skin-whitening agent by reacting levansucrase from Leuconostoc mesenteroides with HQ as an acceptor and sucrose as a fructofuranose donor. The product was purified using 1-butanol partition and silica-gel
column chromatography. The structure of the purified HQ-Fru was determined by 1H and 13C nuclear magnetic resonance, and the molecular ion of the product was observed at m/z 295 (C12 H16 O7 Na)+. The HQ-Fru was identified as 4-hydroxyphenyl-β-d-fructofuranoside. The optimum condition for HQ-Fru synthesis was determined using a response surface method (RSM), and the
final optimum condition was 350 mM HQ, 115 mM sucrose, and 0.70 U/ml levansucrase, and the final HQ-Fru produced was 1.09 g/l.
HQ-Fru showed anti-oxidation activities and inhibition against tyrosinase. The median inhibition concentration (IC50) of 1,1-diphenyl-2-picrylhydrazyl scavenging activity was 5.83 mM, showing higher antioxidant activity compared to β-arbutin
(IC50 = 6.04 mM). The K
i
value of HQ-Fru (1.53 mM) against tyrosinase was smaller than that of β-arbutin (K
i
= 2.8 mM), indicating that it was 1.8-times better as an inhibitor. The inhibition of lipid peroxidation by HQ-Fru was 105.3%
that of HQ (100%) and 118.9 times higher than that of β-arbutin (0.89% of HQ). 相似文献
17.
Tony Marcio da Silva Alexandre Maller André Ricardo de Lima Damásio Michele Michelin Richard John Ward Izaura Yoshico Hirata João Atilio Jorge Héctor Francisco Terenzi Maria Lourdes T. M. de Polizeli 《Journal of industrial microbiology & biotechnology》2009,36(12):1439-1446
A glucoamylase from Aspergillus niveus was produced by submerged fermentation in Khanna medium, initial pH 6.5 for 72 h, at 40°C. The enzyme was purified by DEAE-Fractogel
and Concanavalin A-Sepharose chromatography. The enzyme showed 11% carbohydrate content, an isoelectric point of 3.8 and a
molecular mass of 77 and 76 kDa estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis or Bio-Sil-Sec-400
gel filtration, respectively. The pH optimum was 5.0–5.5, and the enzyme remained stable for at least 2 h in the pH range
of 4.0–9.5. The temperature optimum was 65°C and retained 100% activity after 240 min at 60°C. The glucoamylase remained completely
active in the presence of 10% methanol and acetone. After 120 min hydrolysis of starch, glucose was the unique product formed,
confirming that the enzyme was a glucoamylase (1,4-alpha-d-glucan glucohydrolase). The K
m was calculated as 0.32 mg ml−1. Circular dichroism spectroscopy estimated a secondary structure content of 33% α-helix, 17% β-sheet and 50% random structure,
which is similar to that observed in the crystal structures of glucoamylases from other Aspergillus species. The tryptic peptide sequence analysis showed similarity with glucoamylases from A. niger, A. kawachi,
A. ficcum, A. terreus, A. awamori and A. shirousami. We conclude that the reported properties, such as solvent, pH and temperature stabilities, make A. niveus glucoamylase a potentially attractive enzyme for biotechnological applications. 相似文献
18.
Satomura T Zhang XD Hara Y Doi K Sakuraba H Ohshima T 《Applied microbiology and biotechnology》2011,89(4):1075-1082
The activity of a dye-linked l-proline dehydrogenase (dye-l-proDH) was found in the crude extract of an aerobic hyperthermophilic archaeon, Pyrobaculum calidifontis JCM 11548, and was purified 163-fold through four sequential chromatography steps. The enzyme has a molecular mass of about
108 kDa and is a homodimer with a subunit molecular mass of about 46 kDa. The enzyme retained more than 90% of its activity
after incubation at 100 °C for 120 min (pH 7.5) or after incubation at pHs 4.5–9.0 for 30 min at 50 °C. The enzyme catalyzed
l-proline dehydrogenation to Δ1-pyroline-5-carboxylate using 2,6-dichloroindophenol (DCIP) as the electron acceptor and the Michaelis constants for l-proline and DCIP were 1.67 and 0.026 mM, respectively. The prosthetic group on the enzyme was identified as flavin adenine
dinucleotide by high-performance liquid chromatography. The subunit N-terminal amino acid sequence was MYDYVVVGAG. Using that
sequence and previously reported genome information, the gene encoding the enzyme (Pcal_1655) was identified. The gene was
then cloned and expressed in Escherichia coli and found to encode a polypeptide of 415 amino acids with a calculated molecular weight of 46,259. The dye-l-proDH gene cluster in P. calidifontis inherently differs from those in the other hyperthermophiles reported so far. 相似文献
19.
Aneta Monika Białkowska Hubert Cieśliński Karolina Maria Nowakowska Józef Kur Marianna Turkiewicz 《Archives of microbiology》2009,191(11):825-835
A psychrotrophic bacterium producing a cold-adapted β-galactosidase upon growth at low temperatures was classified as Arthrobacter sp. 20B. A genomic DNA library of strain 20B introduced into Escherichia coli TOP10F′ and screening on X-Gal (5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside)-containing agar plates led to the isolation of β-galactosidase gene. The β-galactosidase gene (bgaS) encoding a protein of 1,053 amino acids, with a calculated molecular mass of 113,695 kDa. Analysis of the amino acid sequence
of BgaS protein, deduced from the bgaS ORF, suggested that it is a member of the glycosyl hydrolase family 2. A native cold-adapted β-galactosidase was purified
to homogeneity and characterized. It is a homotetrameric enzyme, each subunit being approximately 116 kDa polypeptide as deduced
from native and SDS–PAGE, respectively. The β-galactosidase was optimally active at pH 6.0–8.0 and 25°C. P-nitrophenyl-β-d-galactopyranoside (PNPG) is its preferred substrate (three times higher activity than for ONPG—o-nitrophenyl-β-d-galactopyranoside). The Arthrobacter sp. 20B β-galactosidase is activated by thiol compounds (53% rise in activity in the presence of 10 mM 2-mercaptoethanol),
some metal ions (activity increased by 50% for Na+, K+ and by 11% for Mn2+) and inactivated by pCMB (4-chloro-mercuribenzoic acid) and heavy metal ions (Pb2+, Zn2+, Cu2+). 相似文献
20.
Filipa M. Lupi Helena M. L Fernandes Isabel Sá-Correia Júlio M. Novais 《Journal of applied phycology》1991,3(1):35-42
Temperature profiles (range 20–33 °C) were obtained for growth and exopolysaccharide (EPS) biosynthesis of the microalga Botryococcus braunii strain UC 58 under photoautotrophic conditions. The maximum temperature for growth was 32 °C and the temperature dependence
of the specific growth rate was described by the Hinshelwood equation based on the Arrhenius relationship. The optimal range
of temperatures for growth and extracellular EPS synthesis (25–30 °C) concurred and production of 4.5–5 g l−1 of EPS was obtained routinely, leading to high broth viscosities. Below 23 °C EPS biosynthesis was negligible, although the
specific growth rate maintained high values. At supraoptimal temperatures EPS biosynthesis decreased, accompanying the increase
in doubling time.
The polymers formed at temperatures within the optimal range for production, when dissolved in water, produced solutions (2
gl−1) with the highest viscosity, suggesting that their molecular weight showed the highest values. The degree of polymerization
of the EPS synthesized at suboptimal and supraoptimal temperatures was significantly below the values within the optimal range. 相似文献