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51.
52.
L. A. Harrison J. B. Parry J. M. Lynch J. H. Slater 《Applied biochemistry and biotechnology》1984,9(4):361-362
A microbial community capable of degrading pure cellulose has been isolated from soil using a continuous flow chemostat. The
component organisms have been identified as Penicillium nigricans, Paecilomyces liliacinus, Fusarium oxysporum (3 strains),
Aspergillus fumigatus, Gliocladium roseum, and Penicillium simplicissimum.
Extracellular enzyme production (exoglucanase, endoglucanase, and (Β-glucosidase) and cellulose breakdown by the whole community
and the component organisms in pure culture was measured during growth on pure cellulose in batch culture.
After 30 d, 50–60% degradation was achieved by Penicillium simplicissimum, Aspergillus fumigatus, and the mixed culture. These
cultures also produced the highest levels of extracellular endo- and exoglucanase and were able to produce the full enzyme
complex necessary for the degradation of crystalline cellulose. The other isolates were capable of 0–20% degradation and produced
lower levels of enzyme activity. Most were unable to produce the full enzyme complex.
The results indicated that the whole community was no better at degrading pure cellulose than two members in pure culture.
Since the full potential of the community may not be expressed on pure cellulose, breakdown and enzyme production was investigated
during growth on lignocellulose. A large proportion of lignocellulosic material consists of xylan and enzymes capable of degrading
this component were investigated.
The highest percentage degradation and enzyme production (with the exception of Β-glucosidase) after 15 d growth on straw
was achieved by the same three cultures. Studies of their growth on hay and straw were extended over a 60-d period. The rate
and extent of degradation of hay by P. simplicissimum and A. fumigatus was similar to that of the mixed culture, more than
40% degradation occurring in 40 d. However, differences in levels of enzyme activity were observed. The mixed culture produced
lower levels of enzyme activity (with the exception of Β-glucosidase) particularly during the initial states of degradation.
Differences in enzyme production by A. fumigatus and P. simplicissimum were also observed. A. fumigatus produced high levels
of xylanase and endoglucanase while P. simplicissimum produced high levels of exoglucanase. Similar results were observed
on straw.
The composition of the lignocellulosic material was measured by sequential chemical extraction of the solubles, hemicellulose,
cellulose, and lignin. Changes in the composition during degradation were investigated. During the growth of all three cultures
on hay, the total percentage of hemicellulose and cellulose decreased from 84% to less than 45% in 40 d.
Despite significant differences in the enzyme activity, P. simplicissimum, A. fumigatus and the mixed culture were capable
of degrading lignocellulosic material at the same rate. The production of a full cellulase complex appears to be more important
than the production of high levels of individual enzymes. 相似文献
53.
G.P. Parry 《Journal of the mechanics and physics of solids》1984,32(2):133-148
Phase changes involving bifurcation of an internal variable are discussed. It is shown that one particular type of such bifurcation is likely to be preferred above the others, and we present an analysis of the effect of applied stress on that type of bifurcation. Connections are made between the internal (microscopic) picture and the thermoelastic (macroscopic) picture of the phenomenon. 相似文献
54.
The signal-to-noise ratio in steliar speckle interferometry is estimated by direct application of photon counting formulae. This treatment demonstrates that the limiting observable magnitudes are dependent on object size. 相似文献
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59.
Bohlen H Parry AO Díaz-Herrera E Schoen M 《The European physical journal. E, Soft matter》2008,25(1):103-115
We study the shape of gas-liquid interfaces forming inside rectangular nanogrooves (i.e., slit-pores capped on one end). On account of purely repulsive fluid-substrate interactions the confining walls are dry (i.e., wet by vapor) and a liquid-vapor interface intrudes into the nanogrooves to a distance determined by the pressure (i.e., chemical potential). By means of Monte Carlo simulations in the grand-canonical ensemble (GCEMC) we obtain the density ρ(z) along the midline (x = 0 of the nanogroove for various geometries (i.e., depths D and widths L of the nanogroove. We analyze the density profiles with the aid of an analytic expression which we obtain through a transfer-matrix
treatment of a one-dimensional effective interface Hamiltonian. Besides geometrical parameters such as D and L , the resulting analytic expression depends on temperature T , densities of coexisting gas and liquid phases in the bulk ρg,l
x and the interfacial tension γ . The latter three quantities are determined in independent molecular dynamics simulations
of planar gas-liquid interfaces. Our results indicate that the analytic formula provides an excellent representation of ρ(z) as long as L is sufficiently small. At larger L the meniscus of the intruding liquid flattens. Under these conditions the transfer-matrix analysis is no longer adequate
and the agreement between GCEMC data and the analytic treatment is less satisfactory. 相似文献
60.