Biomedical Engineering Reference
In-Depth Information
(3) Cellulase is an enzyme system with multiple components. A synergistic effect
exists between each component. The component and proportion of cellulase are
greatly different because of different strains or the same strain under different
culture conditions, leading to a different degradation process for cellulose. The
scientific complexity of cellulase and the degradation process affect the determi-
nation of cellulase activity; it is more difficult to determine the activity of a single
component in a crude enzyme preparation.
(4) Determination of cellulase activity generally refers to the cellulase that are
secreted. Although some bacteria and basidiomycetes have a strong ability to
degrade cellulose, there is less research to determine their activity because its
degradation mechanism is less understood. It does not reflect the actual state to
study enzyme activity with a traditional activity measurement method. Generally, it
is difficult to detect their activities.
(5) If cellulase activity unit is demonstrated according to the international provisions
(the amount of enzyme needed to catalyze 1
mol in 1 min), the value of cellulase
activity is generally low. Some scholars apply values of mg
h
1
,mg
(24 h)
1
,or
(30 min)
1
to represent units, making it difficult to compare units.
In short, the determination method for cellulase activity relates to the structural
complexity of the substrate and is difficult to standardize. In addition, problems
include multicomponent cellulase preparation and different cellulase enzymatic
mechanisms.
mg
2. Method for determination of cellulase activity
Compared with the general enzymes, determination of cellulase activity is complex
and difficult. It is more difficult to measure vitality of each single component of
cellulase preparation. The measurement methods that can comprehensively reflect
the activity of each group are different because of different structural properties of
substrate used. Cellulase solubility activity, cellulase saccharification activity, and
enzyme activity of each component are described next.
(1) Cellulose solubility activity
Such measuring methods generally qualitatively describe cellulase activity, and
some can describe it quantitatively. The choice of measurement method is mainly
based on the nature of the work. For example, such determination methods are
suitable for cellulose microbial screening
①
Turbidimetric method
The turbidimetric method was invented in the 1960s. Li and Nummi took 0.03 %
Avicel and milled cellulose powder as a substrate, respectively, and measured
turbidity or OD change to indicate enzyme activity. For the concentration per
time unit determination, 20 mL appropriately diluted enzyme solution were mixed
with 3 mL substrate with a turbidity of 80 and concentration of 0.04 %; 10-
20 % was used at 50
ı
C within 10 min. The slope was the initial reaction rate;
the decline of turbidity per minute was the unit of enzyme activity. For OD per
