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1.
The influence of lignin content and temperature on the biodegradation of lignocellulose in composting conditions 总被引:1,自引:0,他引:1
Vikman M Karjomaa S Kapanen A Wallenius K Itävaara M 《Applied microbiology and biotechnology》2002,59(4-5):591-598
The aim of this research was to study the influence of lignin content and composting temperature on the biodegradation of
lignin-containing pulp and paper products in a controlled composting test (European standard prEN 14046). Lignin reduced the
biodegradation of the samples, and there was a linear correlation between the lignin content and the biodegradation of pulp
and paper products at 58°C. The influence of incubation temperature (35, 50 and 58°C) on biodegradation was studied using
bleached kraft paper containing 0.2 wt% lignin and mechanical pulp (stone-ground wood) containing 24–27 wt% lignin. Mechanical
pulp biodegraded better at lower temperatures, while kraft paper biodegraded well at all three temperatures. Microbial activity
was evaluated by measuring CO2 evolution and the change in ATP content, and fungal biomass by measuring the ergosterol content during the composting experiments.
Kraft paper strongly increased microbial activity during the controlled composting test, but the activity returned to the
background level at the end of the composting test. The proportion of sample carbon converted to microbial biomass carbon
was considerably higher at lower incubation temperatures. Changes in microbial community structure during biodegradation of
mechanical pulp and kraft paper at 50°C were studied by the PCR-based technique denaturing gradient gel electrophoresis. Changes
in the microbial community were observed during the intensive degradation phase of kraft paper.
Electronic Publication 相似文献
2.
The composition of the most abundant facultative anaerobic bacteria populations [faecal coliforms (FC) and enterococci (ENT)]
in sludge can be modified after different treatments. These involve the disposal or reuse of sludge and include: anaerobic
digesters, incineration, composting, pasteurization and lime treatments. In this study, three treatment types (mesophilic
anaerobic digestion, composting and pasteurization) were compared in terms of their ability to reduce both bacterial populations.
The diversity and any changes in composition of main phenotypic groups for both populations were also analyzed. Mesophilic
anaerobic digestion (MAD) was carried out at 35°C for 20 days. Digested sludge was then dehydrated by centrifugation at 2,500 rpm.
Composting (COM) was performed at 55°C with windrow phases. Pasteurization was assayed at 60°C for 90 min (P60), at 80°C for
60 min (P80). A 1–1.5 log unit reduction was observed for FC, and 1 log unit reduction was noted for ENT by MAD treatment.
In composting, this reduction proved higher for FC than for ENT (6 log and 3–4 log units, respectively). Optimal pasteurization
was obtained at 80°C for 60 min, resulting in a 5 log unit reduction for FC and a 2 log unit reduction for ENT. High diversity
indices (Di) for both bacterial populations were detected both before and after implementation of the different treatments. Analyses
of the population’s similarity provided that FC were diverse both before and after COM, P60 and P80 treatments. However, no
differences were observed on the composition of ENT populations after the different treatments assayed. 相似文献
3.
In this study we determined oil degradation rates in the North Sea under most natural conditions. We used the heavy fuel oil,
Bunker C, the major oil pollutant of the North Sea, as the model oil. Experiments were conducted in closed systems with water
sampled during winter and repeated under identical conditions with water collected during summer. No nitrogen or phosphorous
was added and conditions were chosen such that neither oxygen nor nutrients, present in the water, would become limiting during
the experiments. We detected a fourfold increased degradation rate for water samples taken in summer (18°C water temperature)
as compared to water sampled in winter (4°C water temperature). Under the assumption that biodegradation of oil can be regarded
as a Michaelis-Menten type kinetic reaction, the kinectic constants Vmax and KM were determined for oil biodegradation at 4°C and 18°C. At both temperatures KM was about 40 ppm, whereas Vmax was 3–4 times higher at 18°C. From both Vmax and the results of fermentation studies, we determined the maximum rates of Bunker C oil degradation in the North Sea as
∼20 g m−3a−1 at 4°C in winter and 60–80 g m−3a−1 at 18°C in summer. Furthermore, while over 25% of the oil was degraded within 6 weeks in summer, only 6.6% of the oil was
degraded in winter. A higher incubation temperature in winter (18°C) increased both the rate and the percentage of oil degraded,
but degradation did not reach the level obtained during the summer. While these data reflect the oxidation only of the hydrocarbons,
we conducted experiments directly in the open sea to determine the contribution of abiotic factors to oil removal. Approximately
42% of the oil was lost within 6 weeks under these conditions in summer and 65% in winter. However, GC-MS analysis of the
recovered oil showed no significant change in the alkane pattern that would indicate enhanced degradation. Thus, mainly abiotic
factors such as erosion and dispersion rather than degradation were responsible for enhanced oil removal. Especially the high
loss during winter can be attributed to frequent storms resulting in greater dispersion. In conclusion, the higher oil degrading
potential of the microbial population in the North Sea was represented by a four times faster oil degradation during the summer.
In-situ experiments showed that abiotic factors can have an equal (summer) or even higher (winter) impact on oil removal. 相似文献
4.
Identification and characterization of fermentation inhibitors formed during hydrothermal treatment and following SSF of wheat straw 总被引:1,自引:0,他引:1
Mette Hedegaard Thomsen Anders Thygesen Anne Belinda Thomsen 《Applied microbiology and biotechnology》2009,83(3):447-455
A pilot plant for hydrothermal treatment of wheat straw was compared in reactor systems of two steps (first, 80°C; second,
190–205°C) and of three steps (first, 80°C; second, 170–180°C; third, 195°C). Fermentation (SSF) with Sacharomyces cerevisiae of the pretreated fibers and hydrolysate from the two-step system gave higher ethanol yield (64–75%) than that obtained from
the three-step system (61–65%), due to higher enzymatic cellulose convertibility. At the optimal conditions (two steps, 195°C
for 6 min), 69% of available C6-sugar could be fermented into ethanol with a high hemicellulose recovery (65%). The concentration
of furfural obtained during the pretreatment process increased versus temperature from 50 mg/l at 190°C to 1,200 mg/l at 205°C
as a result of xylose degradation. S. cerevisiae detoxified the hydrolysates by degradation of several toxic compounds such as 90–99% furfural and 80–100% phenolic aldehydes,
which extended the lag phase to 5 h. Acetic acid concentration increased by 0.2–1 g/l during enzymatic hydrolysis and 0–3.4 g/l
during fermentation due to hydrolysis of acetyl groups and minor xylose degradation. Formic acid concentration increased by
0.5–1.5 g/l probably due to degradation of furfural. Phenolic aldehydes were oxidized to the corresponding acids during fermentation
reducing the inhibition level. 相似文献
5.
The autolysis of yeast cells has practical implications in the production of fermented foods and beverages and flavourants
for food processing. Protein and RNA degradation during yeast autolysis are well described but the fate of DNA is unclear.
Yeast cells (Saccharomyces cerevisiae) were autolysed by incubating suspensions at 30–60°C (pH 7.0), and at pH 4.0–7.0 (40°C) for 10–14 days. Up to 55% of total
DNA was degraded, with consequent leakage into the extracellular environment of mainly 3′- and 5′-deoxyribonucleotides, and
lesser amounts of polynucleotides. The rate and extent of DNA degradation, composition of the DNA degradation products and
DNase activity were affected by temperature and pH. The highest amount of DNA degradation occurred at 40°C and pH 7.0, where
the highest DNase activity was recorded. DNase activity was lowest at 60°C and pH 4.0, where the proportion of polynucleotides
in the degradation products was higher.
Electronic Publication 相似文献
6.
Autolytic degradation of yeast RNA occurs in many foods and beverages and can impact on the sensory quality of the product,
but the resulting complex mixture of nucleotides, nucleosides and nucleobases has not been properly characterised. In this
study, yeast autolysis was induced by incubating cell suspensions of Saccharomyces cerevisiae at 30–60 °C (pH 7.0), and at pH 4.0–7.0 (40 °C) for 10–14 days, and the RNA degradation products formed during the process
were determined by reversed-phase HPLC. Up to 95% of cell RNA was degraded, with consequent leakage into the extracellular
environment of mainly 3′-, 5′- and 2′-ribonucleotides, and lesser amounts of polynucleotides, ribonucleosides and nucleobases.
The rate of RNA degradation and the composition of the breakdown products varied with temperature and pH. RNA degradation
was fastest at 50 °C (pH 7.0). Autolysis at lower temperatures (30 °C and 40 °C) and at pH 5.0 and 6.0 favoured the formation
of 3′-nucleotides, whereas autolysis at 40 °C and 50 °C (pH 7.0) favoured 5′- and 2′-nucleotides. The best conditions for
the formation of the two flavour-enhancing nucleotides, 5′-AMP and 5′-GMP, were 50 °C (pH 7.0) and pH 4.0 (40 °C), respectively. 相似文献
7.
Xylanase, β-glucosidase, β-xylosidase, endoglucanase and polygalacturonase production fromCurvularia inaequalis was carried out by means of solid-state and submerged fermentation using different carbon sources. β-Glucosidase. β-xylosidase,
polygalacturonase and xylanase produced by the microorganisms were characterized. β-Glucosidase presented optimum activity
at pH 5.5 whereas xylanase, poly-galacturonase and β-xylosidase activities were optimal at pH 5.0. Maximal activity of β-glucosidase
was determined at 60°C, β-xylosidase at 70°C, and polygalacturonase and xylanase at 55°C. These enzymes were stable at acidic
to neutral pH and at 40–45 °C. The crude enzyme solution was studied for the hydrolysis of agricultural residues. 相似文献
8.
S. P. Makarenko L. V. Dudareva A. I. Katyshev T. A. Konenkina A. V. Nazarova E. G. Rudikovskaya N. A. Sokolova V. V. Chernikova Yu. M. Konstantinov 《Biochemistry (Moscow) Supplemental Series A: Membrane and Cell Biology》2011,5(1):64-69
The study was focused on fatty acid (FA) composition of lipids from the seedlings and roots of crops having different cold
resistance and grown at 27°C or 4°C. Biosynthesis of FA in the lipids of seedlings and roots of cold-susceptible maize (Zea mays L.) at both growth temperatures was controlled by chloroplast ω6 desaturase and microsomal ω6 desaturase, respectively. The
content of linoleic acid was 56.2% and 43.3% in the coleoptiles of maize seedlings grown at 4 and 27°C, respectively, and
in the roots it was 52.2% and 38.5%, respectively. The content of α-linolenoic acid in the coleoptiles was 6.7–6.8% at both
temperatures, while in the root lipids it was higher at low temperature (3.15% at 27°C vs. 4.7% at 4°C). FA biosynthesis in
the seedling coleoptiles of wheat (Triticum aestivum L.) and Siberian wild rye (Elymus sibiricus L.) grown at low temperature was controlled by the chloroplast ω3 desaturase. A minor increase in the content of α-linolenoic
acid was observed at low temperature: 29.7% to 30.2% in wheat and 22.8% to 25.8% in wild rye. In the root tissues of these
species, the biosynthesis of α-linolenoic acid was controlled by the microsomal ω3 desaturase. The content of α-linolenoic
acid was higher at low temperature: in wheat it was 6.1% at 27°C and 17.1%, and 4°C, while in Siberian wild rye, 7.1% and
12.0% at 4 and 27°C, respectively. 相似文献
9.
Laurent Hébert Julien Cauchard Pauline Doligez Lola Quitard Claire Laugier Sandrine Petry 《Current microbiology》2010,60(1):38-41
There is great concern about the potential pathogen contamination of horse manure compost spread in the same fields horses
graze in. To ensure that pathogen destruction occurs, temperatures need to be sufficiently high during composting. Here, we
investigated the survival rate of two marker organisms, Rhodococcus equi and Parascaris equorum eggs, exposed to temperatures potentially encountered during horse manure composting. Our results show that the time required
to achieve a 1 log10 reduction in R. equi population (D-value) are 17.1 h (±1.47) at 45°C, 8.6 h (±0.28) at 50°C, 2.9 h (±0.04) at 55°C and 0.7 h (±0.04) at 60°C. For P. equorum eggs we show that at 45 and 50°C, 2 log10 reduction of viability is reached between 8 and 24 h of incubation and that it
takes less than 2 h at 55 and 60°C to achieve a viability reduction of 2 log10. These results are useful for identifying composting
conditions that will reduce the risk of environmental contamination by R. equi and P. equorum eggs. 相似文献
10.
Fourier transform-infrared (FT-IR), Thermogravimetry (TG), Differential thermal analyses (DTA) and Differential Thermogravimetric (DTG) studies of a mixture
of vegetable waste, saw dust, tree leaves and cow dung for microbial activity (feedstock) and their compost were reported
in three different seasons i.e. winter, spring and summer. The correlation between spectral studies and compost composition
provide information regarding their stability and maturity during composting. FT-IR spectra were conferred the functional
groups and their intensity and TG, DTG and DTA for wt. loss, rate of wt. loss and enthalpy change in compost. Weight loss
in feedstock and compost at two different temperatures 250–350 and 350–500°C was found 38.06, 28.15% for inlet and 14.08,
25.67% for outlet zones in summer and 50.59, 29.76% for inlet and 18.08, 25.67% in outlet zones in spring season, higher (5–10%)
than winter. The corresponding temperatures in DTA in the samples from inlet to outlet zone were; endotherm (100–200°C), due
to dehydration, exotherm (300–320°C), due to peptidic structure loss and exotherm (449–474°C) due to the loss of polynuclear
aromatic structures, which were higher by 4°C and 10–20°C and rate of wt. loss was higher by 5–10% in spring and summer season,
respectively than winter season composting, reported regardless of the maturation age of the compost. Relative intensity of
exotherms (300–320/449–474°C) gave the thermally more stable fractions of organic compound. Our results indicated that the
rotary drum composting of organic matters in spring and summer season gave higher molecular complexity and stability than
the winter season. 相似文献
11.
The main objective of this study was to evaluate the stability of astaxanthin after drying and storage at different conditions
during a 9-week period. Recovery of astaxanthin was evaluated by extracting pigments from the dried powders and analysing
extracts by HPLC. The powders obtained were stored under different conditions of temperature and oxygen level and the effects
on the degradation of astaxanthin were examined. Under the experimental conditions conducted in this study, the drying temperature
that yielded the highest content of astaxanthin was 220°C, as the inlet, and 120°C, as the outlet temperature of the drying
chamber. The best results were obtained for biomass dried at 180/110°C and stored at −21°C under nitrogen, with astaxanthin
degradation lower than 10% after 9 weeks of storage. A reasonable preservation of astaxanthin can be achieved by conditions
180/80°C, −21°C nitrogen, 180/110°C, 21°C nitrogen, and 220/80°C, 21°C vacuum: the ratio of astaxanthin degradation is equal
or inferior to 40%. In order to prevent astaxanthin degradation of Haematococcus pluvialis biomass, it is recommended the storage of the spray dried carotenized cells (180/110oC) under nitrogen and −21°C. 相似文献
12.
Chitwadee Phithakrotchanakoon Yosita Rudeekit Sutipa Tanapongpipat Thanawadee Leejakpai Sei-ishi Aiba Isao Noda Verawat Champreda 《Biologia》2009,64(2):246-251
A thermophilic Streptomyces sp. capable of degrading various aliphatic polyesters was isolated from a landfill site. The isolate, Streptomyces sp. BCC23167, demonstrated rapid aerobic degradation of several polyesters, including polyhydroxyalkanoate copolymers, poly(ɛ-caprolactone) and polybutylene succinate at 50°C and neutral pH. The degrading activity was repressed by glucose and cellobiose,
but tolerant to repression by other carbon substrates. Degradation of a commercial poly[(R)-3-hydroxybutyrate-co-3-hydroxyhexanoate] (PHBHx) by Streptomyces sp. BCC23167 progressed from surface to bulk as suggested by the slight decrease in polymer molecular weight. Differential
scanning calorimetry analysis of PHBHx film degradation by Streptomyces sp. BCC23167 showed that relative crystallinity of the film increased slightly in the early stage of degradation, followed
by a marked decrease later on. The surface morphology of degraded films was analyzed by scanning electron microscopy, which
showed altered surface structure consistent with the changes in crystallinity. The isolate is thus of potential for application
in composting technology for bio-plastic degradation. 相似文献
13.
Towards a reduction in excess sludge production in activated sludge processes: biomass physicochemical treatment and biodegradation 总被引:15,自引:0,他引:15
M. Rocher G. Goma A. Pilas Begue L. Louvel J. L. Rols 《Applied microbiology and biotechnology》1999,51(6):883-890
To decrease activated sludge production, microbial cell lysis can be amplified to enhance cryptic growth (biomass growth
on lysates). Cell breakage techniques (thermal, alkaline, acid) were studied to generate Alcaligenes eutrophus and sludge lysates and to evaluate their biodegradability. Gentle treatment conditions produced the best results. Complete
cell deactivation was obtained for temperatures higher than 55 °C. The release kinetics were similar for temperatures varying
from 60 °C to 100 °C. A 20-min incubation was suitable for reaching 80% of the maximum releasable carbon. In thermal-chemical
hydrolysis, NaOH was the most efficient for inducing cell lysis. Carbon release was a two-step process. First an immediate
release occurred, which was of the same order of magnitude for A. eutrophus and sludge [100–200 mg dissolved organic C (DOC) g total suspended solids (TSS)−1], followed by a post-treatment release. The second step was virtually equivalent to the first for sludge, and weaker for
A. eutrophus (<50 mg DOC g TSS−1). The biodegradability of the soluble fraction, both the immediate and the post-treatment carbon release, was investigated.
The optimal degradation yield, obtained with sludge cells, reached 55% after 48 h of incubation and 80% after 350 h. The most
consistent lysis and biodegradation results occurred at pH 10 and 60 °C after a 20-min incubation.
Received: 30 October 1998 / Received revision: 16 February 1999 / Accepted: 20 February 1999 相似文献
14.
A variety of autotrophic, sulfur- and hydrogen-oxidizing thermophilic bacteria were isolated from thermogenic composts at
temperatures of 60–80° C. All were penicillin G sensitive, which proves that they belong to the Bacteria domain. The obligately
autotrophic, non-spore-forming strains were gram-negative rods growing at 60–80°C, with an optimum at 70–75°C, but only under
microaerophilic conditions (5 kPa oxygen). These strains had similar DNA G+C content (34.7–37.6 mol%) and showed a high DNA:DNA
homology (70–87%) with Hydrogenobacter strains isolated from geothermal areas. The facultatively autotrophic strains isolated from hot composts were gram-variable
rods that formed spherical and terminal endospores, except for one strain. The strains grew at 55–75° C, with an optimum at
65–70° C. These bacteria were able to grow heterotrophically, or autotrophically with hydrogen; however, they oxidized thiosulfate
under mixotrophic growth conditions (e.g. pyruvate or hydrogen plus thiosulfate). These strains had similar DNA G+C content
(60–64 mol%) to and high DNA:DNA homology (> 75%) with the reference strain of Bacillus schlegelii. This is the first report of thermogenic composts as habitats of thermophilic sulfur- and hydrogen-oxidizing bacteria, which
to date have been known only from geothermal manifestations. This contrasts with the generally held belief that thermogenic
composts at temperatures above 60° C support only a very low diversity of obligatory heterotrophic thermophiles related to
Bacillus stearothermophilus.
Received: 20 July 1995 / Accepted: 25 September 1995 相似文献
15.
Xyloglucanase from an extracellular culture filtrate of alkalothermophilic Thermomonospora sp. was purified to homogeneity with a molecular weight of 144 kDa as determined by SDS-PAGE and exhibited specificity towards
xyloglucan with apparent K
m of 1.67 mg/ml. The enzyme was active at a broad range of pH (5–8) and temperatures (40–80°C). The optimum pH and temperature
were 7 and 70°C, respectively. The enzyme retained 100% activity at 50°C for 60 h with half-lives of 14 h, 6 h and 7 min at
60, 70 and 80°C, respectively. The kinetics of thermal denaturation revealed that the inactivation at 80°C is due to unfolding
of the enzyme as evidenced by the distinct red shift in the wavelength maximum of the fluorescence profile. Xyloglucanase
activity was positively modulated in the presence of Zn2+, K+, cysteine, β-mercaptoethanol and polyols. Thermostability was enhanced in the presence of additives (polyols and glycine)
at 80°C. A hydrolysis of 55% for galactoxyloglucan (GXG) from tamarind kernel powder (TKP) was obtained in 12 h at 60°C and
6 h at 70°C using thermostable xyloglucanases, favouring a reduction in process time and enzyme dosage. The enzyme was stable
in the presence of commercial detergents (Ariel), indicating its potential as an additive to laundry detergents. 相似文献
16.
Comparison of SHF and SSF processes for the bioconversion of steam-exploded wheat straw 总被引:6,自引:0,他引:6
F Alfani A Gallifuoco A Saporosi A Spera M Cantarella 《Journal of industrial microbiology & biotechnology》2000,25(4):184-192
Two processes for ethanol production from wheat straw have been evaluated — separate hydrolysis and fermentation (SHF) and
simultaneous saccharification and fermentation (SSF). The study compares the ethanol yield for biomass subjected to varying
steam explosion pretreatment conditions: temperature and time of pretreatment was 200°C or 217°C and at 3 or 10 min. A rinsing
procedure with water and NaOH solutions was employed for removing lignin residues and the products of hemicellulose degradation
from the biomass, resulting in a final structure that facilitated enzymatic hydrolysis. Biomass loading in the bioreactor
ranged from 25 to 100 g l−1 (dry weight). The enzyme-to-biomass mass ratio was 0.06. Ethanol yields close to 81% of theoretical were achieved in the
two-step process (SHF) at hydrolysis and fermentation temperatures of 45°C and 37°C, respectively. The broth required addition
of nutrients. Sterilisation of the biomass hydrolysate in SHF and of reaction medium in SSF can be avoided as can the use
of different buffers in the two stages. The optimum temperature for the single-step process (SSF) was found to be 37°C and
ethanol yields close to 68% of theoretical were achieved. The SSF process required a much shorter overall process time (≈30
h) than the SHF process (96 h) and resulted in a large increase in ethanol productivity (0.837 g l−1 h−1 for SSF compared to 0.313 g l−1 h−1 for SHF). Journal of Industrial Microbiology & Biotechnology (2000) 25, 184–192.
Received 02 December 1999/ Accepted in revised form 20 July 2000 相似文献
17.
《Journal of Fermentation Technology》1987,65(4):441-447
A new model is proposed to deal with the composting reaction. This model made it possible to calculate the courses of the rate of carbon dioxide evolution, volatile matter conversion, temperature, and moisture content under various aerating operations. The prediction by the model was compared with measurements in laboratory and commercial scale compostings, and was found to agree satisfactorily with the measurements. The model was then used to search for the optimum conditions to obtain sufficiently dry compost.There are two key factors that affect the rate of water vaporization in composting: the aeration rate and the reaction temperature. These two factors are interrelated. The optimum reaction temperature for biological reaction was approximately 60°C regardless of the aeration rate in the parameter range studied. The calculation based on this model suggests that water can be eliminated most effectively when the aeration is so controlled as to keep the reactor at its optimum reaction temperature i.e., 60°C. The drying efficiency was evaluated in terms of the rate of water removal and the total amount of water removed in one batch operation. 相似文献
18.
Construction of a stable microbial community with high cellulose-degradation ability 总被引:42,自引:0,他引:42
Haruta S Cui Z Huang Z Li M Ishii M Igarashi Y 《Applied microbiology and biotechnology》2002,59(4-5):529-534
We bred a microbial community capable of degrading rice straw with high efficiency. The microbial community degraded more
than 60% of rice straw within 4 days at 50 °C. The high stability of the community's degradation ability was demonstrated
by its tolerance of being subcultured several times in medium with/without cellulosic material, being heated to 95 °C, and
freezing at –80 °C. The community degraded both nonsterilized and sterilized substrate; and its degradation ability was not
affected by pH changes in the medium (initial pH 5–9). PCR-denaturing gradient gel electrophoresis (DGGE) analyses based on
16S rDNA fragments showed that the community structure remained constant after multiple subcultures extending over 2 years.
DNA sequence analyses of DGGE bands indicated the coexistence of both aerobic and anaerobic bacteria in the community.
Electronic Publication 相似文献
19.
Properties of the extracellular amylase produced by the psychrotrophic bacterium, Arthrobacter psychrolactophilus, were determined for crude preparations and purified enzyme. The hydrolysis of soluble starch by concentrated crude preparations
was found to be a nonlinear function of time at 30 and 40 °C. Concentrates of supernatant fractions incubated without substrate
exhibited poor stability at 30, 40, or 50 °C, with 87% inactivation after 21 h at 30 °C, 45% inactivation after 40 min at
40 °C and 90% inactivation after 10 min at 50 °C. Proteases known to be present in crude preparations had a temperature optimum
of 50 °C, but accounted for a small fraction of thermal instability. Inactivation at 30, 40, or 50 °C was not slowed by adding
20 mg/ml bovine serum albumin or protease inhibitor cocktail to the preparations or the assays to protect against proteases.
Purified amylase preparations were almost as thermally sensitive in the absence of substrate as crude preparations. The temperature
optimum of the amylase in short incubations with Sigma Infinity Amylase Reagent was about 50 °C, and the amylase required
Ca+2 for activity. The optimal pH for activity was 5.0–9.0 on soluble starch (30 °C), and the amylase exhibited a K
m with 4-nitrophenyl-α-D-maltoheptaoside-4,6-O-ethylidene of 120 μM at 22 °C. The amylase in crude concentrates initially hydrolyzed raw starch at 30 °C at about the same
rate as an equal number of units of barley α-amylase, but lost most of its activity after only a few hours. 相似文献
20.
O. I. Smotrov V. M. Borzenkov V. I. Surovtsev 《Russian Journal of Bioorganic Chemistry》2011,37(5):564-568
The influence of pH within the range 6.9–10.0 on the kinetic parameters of Micrococcus lysodeicticus cell lysis catalyzed by hen egg lysozyme has been studied at 25°C and 37°C. The effective pK
b values have been calculated for the group determining lysozyme catalytic activity. The ΔH
ion value indicates that this group is a carboxyl, although its pK (9.15 at 25°C) is far beyond the range characteristic of carboxylic groups. The cause of this abnormal pK
b value is supposed to be the strong negative charge of the bacterial cell wall. As a result, the enzyme, which catalyzes the
hydrolysis of N-acetylglucosamine-N-acetylmuramic acid copolymer, operates in a highly acidic microenvironment. 相似文献