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1.
F. Amarita F. Alkorta M. Lescan du Plessix T. Cantabrana C. Rodriguez-Fernandez 《Journal of applied microbiology》1995,78(6):630-635
A study of the β-galactosidase produced by the psychrotrophic bacterium Buttiauxella agrestis has been carried out. This micro-organism was isolated from raw milk and the enzyme isolated using standard methods. Molecular mass was estimated to be 515 kDa. The isoelectric point was close to 4·45. Optimum pH was 7·25. Maximal activity was observed at 50°C and activation energy was estimated to be 39·1 kJ mol-1 . Lactose enhanced thermal stability. Using α-nitrophenyl-β-D-galactopyranoside as the substrate, the K m was 11 μmol 1-1 and V max was 85 U mg-1 protein. β-Mercaptoethanol and ethanol were inhibitors; glycerol acted as a complex effector. The enzyme required divalent cations for activity while it was inhibited by EDTA. When the enzyme was immobilized in diethyl aminoethylcellulose the optimum pH of activity was 8. K m was 47 μmol 1-1 and V max was 96 U mg-1 protein. 相似文献
2.
M. Petruccioli L. Brimer A. R. Cicalini F. Federici 《Journal of applied microbiology》1999,86(2):302-310
Mucor circinelloides LU M40 produced 12·2 mU ml−1 of linamarase activity when grown in a 3 l fermenter in the following optimized medium (g l−1 deionized water): pectin, 10·0; (NH4 )2 SO4 ,
1·0; KH2 PO4 , 2·0; Na2 HPO4 , 0·7; MgSO4 .7H2 O, 0·5; yeast extract, 1·0; Tween-80,
1·0, added after 48 h of fermentation. The purified linamarase was a dimeric protein with a molecular mass of 210 kDa; the enzyme showed optimum catalytic activity at pH 5·5 and 40 °C and had a wide range (3·0–7·0) of pH stability. The enzyme substrate specificity on plant cyanogenic glycosides was wide; the Km value for linamarin was 2·93 mmol l−1 . The addition, before processing, of the fungal crude enzyme to cassava roots facilitated and shortened detoxification; after 24 h of fermentation, all cyanogenic glycosides were hydrolysed. 相似文献
1·0; KH
1·0, added after 48 h of fermentation. The purified linamarase was a dimeric protein with a molecular mass of 210 kDa; the enzyme showed optimum catalytic activity at pH 5·5 and 40 °C and had a wide range (3·0–7·0) of pH stability. The enzyme substrate specificity on plant cyanogenic glycosides was wide; the K
3.
Enhanced degradation of petrol (Slovene diesel) in an aqueous system by immobilized Pseudomonas fluorescens 总被引:1,自引:1,他引:0
The rate of degradation of n -alkanes C12 -C18 , in petrol (Slovene diesel) in an aqueous system, by free and immobilized Pseudomonas fluorescens in shaking flasks was investigated. Cells were immobilized to a biosupport, Biofix, and a biosorbant, Drizit. Analysis of cellular growth of the free and immobilized bacteria over 8 d of incubation with diesel as the sole carbon source, showed a reduction in the lag phase in the immobilized cultures in comparison to the free system. The free system degraded 52·3% of C12 and 11·6% of C13 , but C14 -C18 were not degraded. In comparison to the free system and diesel which had not been exposed to experimental conditions (unexposed), the immobilized systems degraded significantly more of C13 -C18 . Biofix-immobilized cells degraded 14·8% of C12 and an average of 53·5% of C13 -C18 . Drizit-immobilized cells degraded 24·5% of C12 , 52·4% of C13 and an average of 91·2% of C14 -C18 . This study shows the successful use of immobilized bacteria technology to enhance the degradation of diesel in an aqueous system. 相似文献
4.
Of various commercial enzyme preparations examined, Cytolase M102 was found to contain the highest glucosyltransferase activity (55 U ml−1 ). It rapidly converted maltose to panose (Glcα1 → 6Glcα1 → 4Glc) with a V max value of 5·8 mmol l−1 min−1 at 50°C in 0·05 mol l−1 sodium acetate buffer (pH 4·4). The K m value of the enzyme for maltose was 750 mmol l−1 . Yields of panose and glucose after 45 min of reaction, for example, were 47·2% and 52·8%, respectively, on the basis of the amount of maltose consumed. 相似文献
5.
Of 22 commercial juice-processing enzyme preparations investigated, Clarex ML was found to exhibit the highest xylanase activity. The xylanase from Clarex ML was most active at 50–60°C and pH 5·0–5·5. The K m and V max values of the enzyme with oat-spelt xylan as the substrate were 8·6 mg ml−1 and 42 μmol xylose l−1 min−1 , respectively. Xylobiose was the main product of enzymatic hydrolysis of xylan. 相似文献
6.
Abstract. Cyperus longus L. , which has a widespread but disjunct distribution throughout Europe and extends northwards into Britain, was found to be a C4 species based upon its Kranz leaf anatomy, low CO2 compensation point and the labelling of malate as an early product of 14 CO2 fixation. The photosynthetic characteristics of C. longus are similar to many other C4 species with a high maximum rate of photosynthesis (> 1.5 mg CO2 m −2 s −1 ) and a relatively high temperature optimum (30–35°C), but unlike many C4 species the rate of photosynthesis does not decline rapidly below the optimum temperature and a substantial rate (0.6 mgCO2 m−2 s−1 )occursat 15°C. Leaf extension is very slow at 15°C and shows a curvilinear response to temperatures between 15 and 25°C. Leaves extend at a rate of almost 4 cm d−1 at 25°C. 相似文献
7.
Bifidobacterium adolescentis Int-57 isolated from human faeces produced extracellular amylase. The enzyme was purified from the culture supernatant fluids by ammonium sulphate precipitation, gel-filtration chromatography (Sephadex-G-75), ion-exchange chromatography (CM-cellulose) and FPLC. SDS-PAGE of the purified enzyme revealed a major band with an apparent molecular weight of 66 kDa. The pI was 5·2. Enzyme activity was optimal at 50°C, and at pH 5·5. The enzyme was stable at 20–40°C, and at pH 5–6 with a K m value of 2·4 g l−1 soluble starch. The activation energy was 42·3 kJ mol−1 . The enzyme was significantly inhibited by maltose (10%), glucose (10%), Cu2 + (5 mmol l−1 ), Zn2 + (5 mmol l−1 ), N- bromosuccinimide (5 mmol l−1 ), EDTA (5 mmol l−1 ), I2 (1 mmol l−1 ) and activated by β-mercaptoethanol (10 mmol l−1 ). 相似文献
8.
An extracellular β-glucosidase enzyme was purified from the fungus Aspergillus niger strain 322 . The molecular mass of the enzyme was estimated to be 64 kDa by SDS gel electrophoresis. Optimal pH and temperature for β-glucosidase were 5·5 and 50 °C, respectively. Purified enzyme was stable up to 50 °C and pH between 2·0 and 5·5. The Km was 0·1 mmol l−1 for cellobiose. Enzyme activity was inhibited by several divalent metal ions. 相似文献
9.
A novel endocellulase, designated as endoglucanase S, was purified to homogeneity from culture supernatant fluids of the newly isolated Streptomyces sp. LX, and shown not to be identical with previously described endo-β-1,4-glucanases. Both endo- and exo-cellulase activities were found to reside on a monomeric protein of 48 kDa. Its temperature optimum is 50 °C, and it was stable at 60 °C. The optimum pH is 5·5, and it has a broad pH stability from pH 3·0–7·0. The action of the enzyme on carboxymethylcellulose (CMC) suggested that the enzyme behaved as endoglucanase, whereas it was also active on crystalline cellulose with cellodextrin as end-product. Fragmentation of filter paper revealed that the degree of polymerization of residual cellulose decreased with time but only 5·2% of filter paper was converted into soluble carbohydrate. 相似文献
10.
C4 photosynthesis at low temperatures 总被引:12,自引:8,他引:4
S. P. LONG 《Plant, cell & environment》1983,6(4):345-363
Abstract. C4 plants grown in optimum conditions are, by comparison to C3 , capable of higher maximum dry-matter yields and greater efficiencies of water and nitrogen use, yet they are rare outside the subtropics. Both latitudinal and altitudinal limits of C4 distributions correlate most closely with a mean minimum temperature of 8-10°C during the period of active growth. The possibility that the C4 process is inherently incapable of functioning at low temperatures is examined. The reversible effects of chilling on the quantum efficiency of C4 photosynthesis and the functioning of the individual steps in the C4 cycle are examined. Chilling also produces an irreversible loss of capacity to assimilate CO2 which is directly proportional to the light received during chilling. It is suggested that the reversible reduction in capacity to assimilate CO2 and the lack of an alternative pathway for the utilization of lightgenerated reducing power may make C4 species more prone to chilling-dependent photoinhibition. Laboratory studies and limited field observations suggest that this damage would be most likely to occur during photosynthetic induction at the temperatures and light levels encountered on clear, cool mornings during the spring and early summer in cool climates. Even those C4 species occurring naturally in cool climates do not appear fully capable of tolerating these conditions; indeed their growth patterns suggest that they may be adapted by avoiding 'rather than enduring' such conditions. 相似文献
11.
A net purification of 9·46-, 18·6- and 16·7-fold for filter paper (FP) hydrolytic activity, carboxymethyl (CM) cellulase and β-glucosidase, respectively was achieved through ion exchange and gel chromatographies. The purified enzyme preparation showed an optimal pH of 5·0 for CM cellulase and 5·5 for the other two components. The enzyme activities increased up to 60°–65°C for the three enzyme components and they were stable at 30° or 40°C and pH 4·5 to 5·0 after 20–30 min treatment. The four enzyme components, that is, two FP activities (unadsorbed and adsorbed), a CM cellulase and a β-glucosidase, had Km values of 47·6 mg, 33·3 mg, 4·0 mg and 0·18 mmol/l with V max of 4, 1·28, 66·5 and 1·28 units per mg protein. The molecular weights as determined with SDS-PAGE were found to be 44000, 38000, 55000 and 63000 for the above four enzyme components in the same sequence. A distinct type of synergistic action was observed between these components by their action on dewaxed cotton. Glycerol at 1% strongly repressed the formation of all the cellulolytic enzymes. The role of proteolytic enzymes in in vitro inactivation of cellulases was not apparent. 相似文献
12.
A.M. Strasser de Saad S.E. Pasteris María C. Manca de Nadra 《Journal of applied microbiology》1995,78(5):473-476
The production and stability of pediocin N5p from Pediococcus pentosaceus , isolated from wine, were examined in grape juice medium. Maximum growth and higher titre (4000 U ml-1 ) were observed at a initial pH of 7·5 and 30°C. The activity of the inhibitory substance was stable between pH values from 2·0 to 5·0 at 4° and 30°C. At pH 10·0 it was completely inactivated. When submitted to 30 min at 80°, 100° and 115°C, maximal stability was observed at pH 2·0. Ethanol up to 10% did not affect pediocin activity at acid pH, nor did 40–80 mg 1-1 SO2 , independently or combined with different ethanol concentrations, affect inhibitory activity. 相似文献
13.
A.F. Mohedano J. Fernández P. Gaya M. Medina M. Nuñez 《Journal of applied microbiology》1997,82(1):81-86
Growth and proteinase production by Micrococcus sp. INIA 528 in a batch-operated laboratory fermentor were investigated, with trypticase soy broth as the basal medium for studies on optimum temperature, pH and medium composition. Maximum growth was recorded at 34°C and pH 715, whereas optimum temperature and pH for proteinase production were 31°C and pH 6.25. Maximum rate of enzyme production occurred during the late log and early stationary phases of growth. Addition of 5.0 g 1-1 yeast extract, 1.0 g 1-1 glucose, 1.0 g 1-1 MgSO4 or 1.0 g 1-1 K2 HPO4 to basal medium resulted in a lower enzyme yield, but supplementation of basal medium with 2.5 g 1-1 (NH4 )2 SO4 increased enzyme production by 45%. A high initial biomass added to fresh broth supplemented with 2.5 g 1-1 (NH4 )2 SO4 only increased enzyme activity by 19%, compared to the maximum enzyme activity achieved with the standard inoculum. 相似文献
14.
Ryo Hasegawa Akiko Maruyama Minoru Nakaya Sachiko Tsuda Yohji Esashi 《Physiologia plantarum》1995,93(4):713-718
Germinating seeds of many species contain two types of β-cyanoalanine synthase (CAS, EC 4.4.1.9) that convert HCN to β-cyanoalanine. One is cytoplasmic CAS (cyt-CAS), which is precipitated by 50 to 60% (NH4 )2 SO4 and has a pH optimum of 10.5. Cytoplasmic CAS is present at high levels in dry seed and its activity does not increase during imbibition. The activity of cyt-CAS is not affected by exogenously applied ethylene (C2 H4 ), except in rice ( Oryza sativa cv. Sasanishiki). The second type of CAS found in seed is mitochondrial CAS (mit-CAS), which is precipitated by 60 to 70% (NH4 )2 SO4 and has a pH optimum of 9.5. Mitochondrial CAS is present at low levels in dry seed, and its activity increases greatly during imbibition in the seeds of all species tested. Exposure to C2 H4 stimulated mit-CAS activity in seeds of rice, barley ( Hordeum vulgare cv. Hadakamugi). cucumber ( Cucumis sativus cv. Kagafushinari) and cocklebur ( Xanthium pennsylvanicum ). The increase in the mit-CAS activity in cocklebur in response to C2 H4 commenced alter a lag period of 2 to 3 h when the duration of soaking was short (16 h), but commenced without a lag period when the seeds were soaked for three months. Application of both chloramphenicol and cycloheximide to the axial and cotyledonary tissues of cocklebur seeds strongly inhibited growth as well as the increase in mit-CAS activity. It is postulated that the mit-CAS is synthesized de novo during imbibition and that its activity is regulated by C2 H4 , CO2 which also promotes seed germination in some species, was ineffective m stimulating mit-CAS activity in cocklebur seeds. 相似文献
15.
L. Janda T. Pavelka P. Tichý J. Spíek & M. Petíek 《Journal of applied microbiology》1997,83(4):470-476
Thermomonospora curvata contains α-1,4-glucosidase that is induced duringgrowth on maltose and starch. Maltose acts as an inducer of α-glucosidase even in thepresence of glucose. An intracellular thermostable α-glucosidase from T. curvata wasdetected in the crude extract on SDS-PAGE by means of modified colour reaction afterrenaturation of the enzyme. The enzyme was purified 59-fold to homogeneity with a yield of17·7% by a combination of ion-exchange and hydrophobic interaction chromatography andgel filtration. The enzyme has an apparent molecular mass of 60±1 kDa and isoelectric point4·1. The α-glucosidase exhibits optimum activity at pH 7·0–7·5 and54°C. The activity is inhibited by heavy metals and is positively affected by Ca2 + andMg2 +. The enzyme hydrolyses maltose, sucrose, p-nitrophenyl-α- d -glucopyranoside and maltodextrins from maltotriose up to maltoheptaose with a decreasingefficiency. The Km for maltose and p-NPG are 12 and 2·3 mmol l−1 ,respectively. 相似文献
16.
A. Otero M.C. García M.L. García M. Prieto B. Moreno 《Journal of applied microbiology》1988,64(2):117-122
Burgos cheese was manufactured from pasteurized ewes milk inoculated with Staphylococcus aureus strains FRI 137 and FRI 361, at levels of ca 103 and 105 cfu/ml and stored at 4°, 10° and 15°C and at room temperature (10°-15°C). Populations of Staph. aureus and mesophilic aerobes, pH, and production of thermonuclease and enterotoxins C1 and C2 were investigated. Aerobic counts increased during cheese-making and storage. With both test strains, important growth was observed only during the storage period, the larger levels corresponding to the higher temperatures. Although Staph. aureus strains attained populations of over 108 cfu/g, no enterotoxin was detected. Strain FRI 361 reached 107 cfu/g without production of a detectable amount of thermonuclease. With strain FRI 137, the minimal population associated with enzyme activity was influenced by the inoculum size. Staphylococcus aureus counts are better indicators of staphylococcal growth in Burgos cheese than the thermonuclease test. 相似文献
17.
Cassava peels were used as a substrate for the production of cellulolytic enzymes. Under solid substrate fermentation conditions and a Rhizopus sp., thermostable cellulolytic enzymes were produced. Optimal production temperature and pH were 45°C and 5.6 respectively. Kinetic studies of the enzymes showed that the cellulase C1 activity was optimal at pH 5.0 and 50°C, whereas that of cellulase Cx was optimal at pH 7.0 and 60°C. The enzymes degraded ca 44% of sorghum grains in 6 h, thus suggesting a possible use in saccharification processes. The results also showed the possibility of re-cycling cassava peels as a cheap substrate for the enzyme industry. and accepted 6 June 1989 相似文献
18.
Abstract Cellulolytic actinomycetes were isolated from the hindgut of four different termites: Macrotermes, Armitermes, Odontotermes and Microcerotermes spp.
The isolated actinomycetes ( Streptomyces sp. and Micromonospora sp.) were grown on cellulosic substrates and their extracellular cellulase (Cl , Cx and cellobiase) activity evaluated; using filter paper as a substrate for Cl , carboxymethylcellulose (CMC) for Cx and d -cellobiose for cellobiase, all strains were shown to degrade soluble and insoluble cellulose; optimum pH for growth was 6.2–6.7 at 28°C; three strains could grow at 48°C on cellulosic substrates.
Some strains exhibited high cellulase activity, constant for 5–7 days, but inhibition by glucose was a common feature for almost all isolates. 相似文献
The isolated actinomycetes ( Streptomyces sp. and Micromonospora sp.) were grown on cellulosic substrates and their extracellular cellulase (C
Some strains exhibited high cellulase activity, constant for 5–7 days, but inhibition by glucose was a common feature for almost all isolates. 相似文献
19.
Ki-Seok Yoon Yukiko Sakai Natsuki Tsukada Kiyoshi Fujisawa & Hirofumi Nishihara 《FEMS microbiology letters》2009,290(1):114-120
Membrane-bound [NiFe]-hydrogenase from Hydrogenophaga sp. AH-24 was purified to homogeneity. The molecular weight was estimated as 100±10 kDa, consisting of two different subunits (62 and 37 kDa). The optimal pH values for H2 oxidation and evolution were 8.0 and 4.0, respectively, and the activity ratio (H2 oxidation/H2 evolution) was 1.61 × 102 at pH 7.0. The optimal temperature was 75 °C. The enzyme was quite stable under air atmosphere (the half-life of activity was c . 48 h at 4 °C), which should be important to function in the aerobic habitat of the strain. The enzyme showed high thermal stability under anaerobic conditions, which retained full activity for over 5 h at 50 °C. The activity increased up to 2.5-fold during incubation at 50 °C under H2 . Using methylene blue as an electron acceptor, the kinetic constants of the purified membrane-bound homogenase (MBH) were V max =336 U mg−1 , k cat =560 s−1 , and k cat / K m =2.24 × 107 M−1 s−1 . The MBH exhibited prominent electron paramagnetic resonance signals originating from [3Fe–4S]+ and [4Fe–4S]+ clusters. On the other hand, signals originating from Ni of the active center were very weak, as observed in other oxygen-stable hydrogenases from aerobic H2 -oxidizing bacteria. This is the first report of catalytic and biochemical characterization of the respiratory MBH from Hydrogenophaga . 相似文献
20.
Respiratory metabolism during cold storage of apple fruit. II. Alternative oxidase is induced at the climacteric 总被引:2,自引:0,他引:2
Rubbing applied to a young tomato internode inhibited the elongation of this internode and increased soluble peroxidase activity. These morphological and biochemical changes were observed both at the site of rubbing (local response) and in the neighbouring internode (systemic response). The cellular, biochemical, and molecular mechanisms leading to inhibition of internode elongation are not fully understood. It was proposed that mechanical stimuli increased the oxidation of IAA, via the induction of specific peroxidases and stimulated the lignification processes. In order to gain more information about the role of these enzymes, analysis of changes in peroxidase activities were performed. Qualitative analysis of isoperoxidases, by means of native cathodic PAGE, showed four induced isoforms termed C1 , C2 , C3 , and C4 . The major isoform (C2 ) was purified to homogeneity and partially characterized. This isoform is probably unglycosylated, with a molecular mass of 36 kDa and a neutral pI of 7.1. The effects of pH and temperature on the activity were determined with guaiacol as electron donor. Optima were obtained at pH 5 and at a temperature of 55°C. The activity of the purified enzyme was not affected by Ca2+ , Mg2+ and Mn2+ as was reported for some basic peroxidases. Analysis of substrate specificity revealed that this isoperoxidase acted on ABTS, o -dianisidine, pyrogallol, guaiacol, coniferyl alcohol (monolignol) and IAA but not on syringaldazine. Activitiy of C2 isoperoxidase on coniferyl alcohol and IAA suggests a possible role of peroxidase C2 in inhibition of internode elongation, observed in rubbed plants, probably via an increase in lignification processes and regulation of IAA levels in internode tissues. 相似文献