Environmental Engineering Reference
In-Depth Information
polyhydroxyalkanoic acid) are cleaved by hydrolysis. Different types of enzymes
are involved in this process depending upon the types of bond to be hydrolysed (for
example, proteases, esterases and glucoside hydrolases). Protease (proteolytic enzyme)
catalyses the hydrolysis of peptide bonds as well as the hydrolysis of ester linkages.
On the basis of their mechanism of action they are classiied into four groups: a)
serine proteases, b) cysteine proteases, c) metal containing proteases, and d) aspartic
proteases. These names indicate the key catalytic groups in the active site.
a
b
c
d
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7:36:01 PM
WD
11.7 mm
Mag
500x
Det
ETO
100.0
µ
m
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HV
20.00 kV
Mag
1.547 x
WD
10.2 mm
det
ETO
mode
SE
bit
0*
30
µ
m
Figure 3.2
Different stages of fouling and degradation of HDPE in the marine
environment. Control and sample immersed in seawater for a) 1 month;
b) 3 months; c) 6 months; and d) SEM images of the control and a 6 month
sample − the latter shows symptoms of degradation
3.3.1.2 Enzymic Oxidation
Hydrophobic polymers initially undergo oxidation. The biological process of oxidation
is catalysed by a large group of enzymes and they are divided into monooxygenases
and dioxygenases (oxidoreductases). The oxidation or reduction of a substrate can
occur in many ways. The difference here is based on the electron acceptor (O
2
,
