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1.
以黄粉虫为材料,采用盐析、亲和柱层析、Sephadex G-100分子筛及DE-52离子交换柱层析等制得纯化倍数约33倍,回收率为38%,比活力为294.7U/mg的几丁质酶制剂.在此基础上,以胶体几丁质为底物,考察黄粉虫几丁质酶的性质.结果表明：该酶催化水解几丁质的Km值为71.4mg/L;酶的最适pH值是6.0;最适温度为45℃左右;酶在pH 5.0～7.0,45℃以下酶活力稳定性较好.Na＋和K＋对酶活无影响;Ca2＋、Cu2＋对酶活起先扬后抑作用;Mn2＋、Mg2＋、Fe3＋、Al3＋对该酶活力均具有不同程度的抑制作用. 相似文献
2.
Hydantoinase and N-carbamoylase play important roles in the production of optically pure amino acids from racemic 5-monosubstituted hydantoins. In this report, hydantoinase and the N-carbamoylase from Burkholderia cepecia, njut01 were purified to homogeneity by chromatography (Pharmacia Explorer 100 system). The substrate specificity, enantioselectivity, pH dependence of activity and temperature stability of the activity were characterized. The results show that the hydantoinase and N-carbamoylase induced from Burkholderia cepecia, njut01 are both strict D-stereo selective enzymes. They both hydrolyze substrates with side chains containing aliphatic and aromatic residues with higher activity and affinity toward aromatic than aliphatic substituted substrates. The hydantoinase is a homotetramer with subtmit molecular weight near 52,000 and is active between pH 6.5 and 10 with an optimum near pH 9.0. The enzyme is active at temperatures up to 60~C, however, it appears instable at higher temperatures. The subunit molecular weight of N-carbamoylase is about 35KD. The N-carbamoylase is active in the pH range from 6.0 to 9.5. The optira-pH is 7.2 and the optinfizing bioconversion temperature of the N-carbamyolase is 52℃. 相似文献
3.
The production of elastase by Bacillus sp. EL31410 at various temperatures was investigated. In order to study the effect of temperature on elastase fermentation,
different cultivation temperatures, ranging from 39 °C to 28 °C, were evaluated in shake flask. The result indicated that
37 °C was best for cell growth at earlier stage; while maximum elastase activity was obtained when the cells were cultivated
at 30 °C. This result was verified by batch fermentation in 5-L bioreactor under 37 °C and 30 °C temperature, respectively.
The specific cell growth rate at 37 °C was higher than that at 30 °C during earlier stage of cultivation. The maximum value
[5.5 U/(h·g DCW)] of elastase formation rate occurred at 24 h at 30 °C compared to 4.6 U/(h·g DCW) at 30 h at 37 °C. Based
on these results, two-stage temperature shift strategy and oscillatory temperature cultivation mode were evaluated in the
next study. When compared to single temperature of 37 °C or 30 °C, both two-stage temperature shift strategy and oscillatory
temperature strategy improved biomass but did not yield the same result as expected for elastase production. The maximum biomass
(both 8.6 g/L) was achieved at 30 h at 37 °C, but at 42 h using two-stage temperature cultivation strategy. The highest elastase
production (652 U/ml) was observed at 30 °C in batch process. It was concluded that cultivation at constant temperature of
30 °C was appropriate for elastase production by Bacillus sp. EL31410.
Project (No. 20276064) supported by the National Natural Science Foundation of China 相似文献
4.
5.
比较了虾几丁质酶和木瓜溶菌酶对再生几丁质与溶壁微球菌作底物时的水解速度 ,证明各有其最适底物 .两者对再生几丁质底物有不同的水解产物 ,证明一为内切酶一为外切酶 相似文献
6.
ZHANG Xiu-yan RUAN Hui MU Lin HE Guo-qing TANG Xing-jun CHEN Qi-he 《浙江大学学报(A卷英文版)》2006,7(11):1948-1955
INTRODUCTION Enzymes are efficient and specific biocatalysts widely used in food industries, but their application in industrial process often involves special properties not found in natural source enzymes. In order to ob- tain desirable enzymes, in the past ten years, scientists have developed rational (Kurth et al., 1998; Mouratou et al., 1999; DeSantis et al., 1999) and irrational de- sign methods (Babbitt and Gerlt, 1997; O’Brien and Herschlag, 1999) to improve the enzyme propert… 相似文献
7.
Méndez A Pérez C Montañéz JC Martínez G Aguilar CN 《Journal of Zhejiang University. Science. B》2011,12(12):961-968
The combined effects of pH and temperature on red pigment production and fungal morphology were evaluated in a submerged culture
of Penicillium purpurogenum GH2, using Czapek-Dox media with d-xylose as a carbon source. An experimental design with a factorial fix was used: three pH values (5, 7, and 9) and two temperature
levels (24 and 34 °C) were evaluated. The highest production of red pigment (2.46 g/L) was reached with a pH value of 5 and
a temperature of 24 °C. Biomass and red pigment production were not directly associated. This study demonstrates that P. purpurogenum GH2 produces a pigment of potential interest to the food industry. It also shows the feasibility of producing and obtaining
natural water-soluble pigments for potential use in food industries. A strong combined effect (p<0.05) of pH and temperature was associated with maximal red pigment production (2.46 g/L). 相似文献
8.
WEI Pei-lian XU Zhi-nan CEN Pei-lin 《浙江大学学报(A卷英文版)》2007,8(9):1521-1526
Lovastatin production by Aspergillus terreus ATCC 20542 in solid-state fermentation (SSF) was studied. Various substrates were used to evaluate the ability of A. terreus to produce lovastatin. The results showed that either rice or wheat bran was suitable substrate for lovastatin production in SSF. The maximum yield of lovastatin (2.9 mg/g dry substrate) using rice as substrate was achieved after incubating for 11 d at the following optimized process parameters: 50%～60% initial moisture content,pH 5.5,incubation temperature 28 °C. 相似文献
9.
The performance of Al-alloy anode in 4 mol/L KOH with and without stannate and o-aminophenol at 25℃ and 55℃ was studied by hydrogen collection, potentiodynamic polarization and electrochemical impedance spectrum, o-aminophenol acts as a perfect inhibitor because of its adsorbability and forming chelate complex at its optimum concentration of 0.4 mol/L. Stannate enhances the inhibition of o-aminophenol and improves the activity of Al-alloy because of its reduction to tin. There is synergetic effect of stannate with o-aminophenol on the behavior of Al-alloy, and the inhibitive efficiency at 55℃ is better than that at 25 ℃. 相似文献
10.
Wang Xingqing 《上海大学学报(英文版)》1998,2(4):305-310
Ａｌｕｍｉｎｕｍ ＡｌｌｏｙｓTX１ＩｎｔｒｏｄｕｃｔｉｏｎＦｅ－Ａｌｉｎｔｅｒｍｅｔａｌｉｃｓｈａｖｅｇｒｅａｔｐｏｔｅｎｔｉａｌｉｔｉｅｓｆｏｒｓｔｒｕｃｔｕｒａｌａｐｐｌｉｃａｔｉｏｎｓｏｗｉｎｇｔｏｔｈｅｉｒｇｏｏｄｍｅｃｈａｎｉｃａｌｐｒｏｐ... 相似文献
11.
The yeast strain （Y18） was isolated from a soil sample collected from Fildes Peninsula, Antarctica. The strain is a psychrophilic yeast with optimum and maximum growth temperatures of 10 ℃ and 18 ℃, respectively. Teliospores were formed after 7 d on malt agar, when the germination of teliospores was observed. Both inositol and D-glucuronate were assimilated. Positive results of the DBB （diazonium blue B） color reaction, urease test, and starch formation were observed. The major CoQ is Qs. All results indicated that Y18 belongs to the genes of Mrakia. The 18S rDNA sequence analyses showed that Y18 is closely related to Mrakiafrigida. DNA-DNA relatedness study, and some biochemistry characteristics indicated that Y18 represents a new species for which Mrakia psychrophila sp. nov. is proposed. 相似文献
12.
INTRODUCTION The physics of plastic deformation and crack propagation at atomic level is complex but is essential for the development of new materials. This requires an understanding of the atomic level phenomena associated with the plastic deformation. In this con- text, emission of electromagnetic radiation (EMR) during plastic deformation and crack propagation in metals and alloys, and generation of transient mag- netic fields during crack initiation in ferromagnetic materials are rep… 相似文献
13.
Cheng-long Hou Yu-song Wu You-zhou Jiao Jie Huang Tao Wang Meng-xiang Fang Hui Zhou 《浙江大学学报(A卷英文版)》2017,18(10):819-830
A new concept of low-cost direct air capture technology integrated with a fertilization system is proposed, as an alternative to the application of air derived CO2. A moisture swing sorbent can elevate the CO2 concentration from 400 parts per million (ppm) to several thousand ppm, and this can be used to cultivate plants. Desorption isotherms were determined and are described well by a Langmuir model. The adsorption rate constant and the desorption rate constant were gained at 25 °C, 35 °C, and 45 °C under 1000 ppm concentration of CO2. In accelerated cultivation experiments, the effects of CO2 concentration, light intensity, and spectrum on the CO2 uptake rate of the plants were investigated. A multi-bed desorption system which is capable of providing a continuous and stable CO2 supply for a greenhouse is demonstrated based on the desorption characteristic and CO2 uptake feature of plants. An energy and cost assessment for the integrated system was performed and the results indicated that minimum energy requirements and cost estimate of CO2 are 35.67 kJ/mol and 34.68 USD/t, respectively. This makes direct air capture a competitive and sustainable carbon source for agriculture. 相似文献
14.
INTRODUCTION The use of anaerobic process to treat municipal organic solid waste (MOSW) has dramatically in-creased recently. Anaerobic digestion can be carried out under ambient (<25 °C), mesophilic (25~45 °C) and thermophilic (>45 °C) conditions (El-Mashad et al., 2004). Thermophilic digestion has many advan-tages such as higher metabolic rate and higher con-sequent specific growth rate compared with meso-philic digestion, although the thermophilic bacteria death rate is higher (… 相似文献
15.
Response to temperature stress of reactive oxygen species scavenging enzymes in the cross-tolerance of barley seed germination 总被引：1，自引：0，他引：1
A number of studies have shown the existence of cross-tolerance in plants, but the physiological mechanism is poorly understood.
In this study, we used the germination of barley seeds as a system to investigate the cross-tolerance of low-temperature pretreatment
to high-temperature stress and the possible involvement of reactive oxygen species (ROS) scavenging enzymes in the cross-tolerance.
After pretreatment at 0 °C for different periods of time, barley seeds were germinated at 35 °C, and the content of malondialdehyde
(MDA) and the activities of ROS scavenging enzymes were measured by a spectrophotometer analysis. The results showed that
barley seed germinated very poorly at 35 °C, and this inhibitive effect could be overcome by pretreatment at 0 °C. The MDA
content varied, depending on the temperature at which seeds germinated, while barley seeds pretreated at 0 °C did not change
the MDA content. Compared with seeds germinated directly at 35 °C, the seeds pretreated first at 0 °C and then germinated
at 35 °C had markedly increased activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and
glutathione reductase (GR). The SOD and APX activities of seeds germinated at 35 °C after 0 °C-pretreatment were even substantially
higher than those at 25 °C, and GR activity was similar to that at 25 °C, at which the highest germination performance of
barley seeds was achieved. These results indicate that low-temperature pretreatment can markedly increase the tolerance of
barley seed to high temperature during germination, this being related to the increase in ROS scavenging enzyme activity.
This may provide a new method for increasing seed germination under stress environments, and may be an excellent model system
for the study of cross-tolerance. 相似文献
16.
The optimization of cultural conditions for β-glucanase production byBacillus subtilis ZJF-1A5 was investigated in flask trials. Temperature had great effect on β-glucanase production which maximized at optimal
temperature of 37°C and decreased significantly when temperature was over 37°C. Charge quantity affected β-glucanase production
significantly. Adding oxygen vector N-dodecane or acetic ether benefited β-glucanase production, but it depended on the concentration
and charge quantity. The results of fractional factorial design showed that age and size of inoculum and shaking speed were
the key factors affecting β-glucanase production and the cultivation time span to reach the highest β-glucanase activity.
The optimal cultural conditions for β-glucanase production obtained with CCD were as follows: inoculum age and size (16 h,
3.82% (v/v)), shaking speed 210 r/min, charge quantity of 30 mL in 250 mL flask and initial pH 7.0, cultured at 37°C for 50
h. Repeated experimental results accorded with those predicted by a second-order polynomial model. The amount of β-glucanase,
α-amylase and neutral protease produced byB subtilis ZJF-1A5 was associated partially with cell growth. Those three enzymes' activities increased following the cell growth and
increased significantly when cells entered the stationary phase.
Project (No. B0608) supported by the National Natural Science Foundation of China and a grant (2001121B25) from Hangzhou Science
and Technology Development Project of Zhejiang Province, China 相似文献
17.
Xue Wang Liang-fei Zhan Qian-gang Pan Zhi-jun Liu Hong Liu Yong-shun Tao 《浙江大学学报(A卷英文版)》2010,11(10):756-760
A 9% Cr ferritic steel weld metal containing 1% Co, partially substituted for nickel, was prepared by submerged arc welding (SAW) processing. The microstructure and creep properties of the weld metal were investigated. The microstructure exhibited a fully tempered martensitic structure free of δ-ferrite. The creep properties of the obtained weld metal were inferior to those of the P92 base metal at 600 and 650 °C. The values of A and n for weld metal in the Norton power law constitution at 650 °C are 1.1×10?21 and 8.1, respectively. 相似文献
18.
Luciferase from firefly lantern extract was immobilized on CNBr-activated Sepharose 4B. The kinetic properties of immobilized
luciferase were extensively studied. TheK
m′ for D-luciferin is 11.9 μmol/L, the optimum pH and temperature for Sepharose-bound enzyme were 7.8 and 25°C respectively.
A luminescence fiber optic biosensor, making use of immobilized crude luciferase, was developed for assay of ATP. The peak
light intensity was linear with respect to ATP concentration in range of 10−9–10−5 mol/L. A biological application was also demonstrated with the determination of serum ATP from rats bred in low versus normal
oxygen environments. 相似文献
19.
This study was undertaken to isolate and characterize the protease activity of human eye lens sample of mature and hyper mature cataract. Samples were collected just after surgery of the cataract lens and were stored at -20°C. The total protein extract was isolated from 5 samples in each case (mature and hyper mature cataract) and clear supernatant obtained after centrifugation was used as an enzyme source. The optimum pH for the proteases of mature cataract was 7.5 while the proteases of hyper mature cataract were recorded for maximum activity at pH 5.5 and 7.5. The optimum temperature for both enzyme sources was 50 °C. Effect of different metal ions such as potassium, lead, silver, zinc and borate was studied. In each case protease activity was increased. Reducing agent e.g. β mercaptoethanol also caused an increase in activity indicating the involvement of sulfhydryl groups. Protease activity was also located on agar plates. 相似文献
20.
In this paper, a new ternary non-azeotropic mixture of HFC-161/125/143a (0.15/0.45/0.40 in mass fraction), as a promising
mixed refrigerant to R404A, is presented. The ozone depletion potential (ODP) of the new refrigerant is zero and its basic
thermodynamic properties are similar to those of R404A, but its global warming potential (GWP) is much smaller than those
of R507A and R404A. Meanwhile, theoretical calculations show that, under the working condition I (the average evaporation
temperature: −23 °C, the average condensing temperature: 43 °C, the superheat temperature: 28 °C, the subcooling temperature:
5 °C), the volumetric refrigerating effect and specific refrigerating effect of the new mixture are 2.33% and 15.48% higher,
respectively, than those of R404A. The coefficient of performance (COP) of the new mixture is 5.19% higher than that of R404A
and the pressure ratio of the new mixture is 0.82% lower than that of R404A. Equally, under the working condition II (the
average evaporation temperature: −40 °C, the average condensing temperature: 35 °C, the superheating temperature: 30 °C, the
subcooling temperature: 5 °C), the volumetric refrigerating effect and specific refrigerating effect of the new mixture are
2.24% and 20.58% higher, respectively, than those of R404A. The COP of the new mixture is 4.60% higher than that of R404A
and the pressure ratio of the new mixture is similar to that of R404A. The performances of the new mixture and R404A are compared
in a vapor compressor refrigeration apparatus originally designed for R404A under several working conditions (condensing temperatures:
35–45 °C, evaporation temperatures: −40–−20 °C). Experimental results show that the new mixture can obtain a higher COP, by
6.3% to 12.1%, and a lower pressure ratio, by 1.8% to 6.6%, compared to R404A; although the discharge temperature of the new
mixture is slightly higher than that of R404A. The advantages of the new mixture will be further verified in the actual system. 相似文献