Toxicity evaluation test on P. aureus
Seed germination is a complex physiological and biochemical
process in plants that can be affected severely by several
environmental factors. Starch is the major component of
most of the world's crop yield and degradation of starch is
essential for seed germination. In germinating seeds, starch
degradation is initiated by α-amylase producing soluble
oligosaccharides from starch. These are then hydrolyzed by
α-amylase to liberate maltose and finally, glucosidase breaks
down maltose into glucose providing energy to germinating
seeds. Two controls were used, untreated effluent and tap
water. Untreated effluent was used to compare the effectiveness
of treatment in reducing toxicity. Tap water was used to
see the normal process of seed germination test. Results of
seed germination test revealed that the untreated effluent
above 10% (V/V) inhibited amylase activity and thereafter a
continuous decline in α-amylase activity was observed at
higher concentration (>10%) (Fig. 5). However, the seeds
treated with tap water have shown lower amylase activity
(0.3 U) than the seeds treated with 20% and 80% (V/V)
concentration of untreated and treated effluent, respectively.
This revealed that untreated effluent acted as growth promoter
at lower concentration (10%) whereas after treatment it
was found as growth supporter up to 80%. This indicated that
toxicity has been reduced significantly after bacterial degradation.
The growth promoting effects of untreated effluent on
amylase at lower concentration might be due to the presence
of optimumlevel of organic nutrients essential for plant growth
(Kannan and Oblisami, 1990). The reduction in amylase activity
at higher concentration of undegraded effluentmight be due to
the high pollution content affecting various physiological and
biochemical processes during the seed germination.
Further, the denaturing SDS-PAGE of α-amylase enzyme
extracted from germinating seeds treated with same concentration
of untreated and treated effluent has yielded three
bands of different molecular weight and intensity/concentration
(Fig. 5c–d). Results indicated that the concentration of
amylase enzyme (i.e., the intensity of band) decreases
gradually as the concentration of untreated effluent increases
at 10%. Phaseolus seeds treated with more than 40% (V/V)
concentration of untreated effluent have shown reduced
amylase activity compared to control and no amylase activity
or enzyme production was observed in seeds treated with
100% (V/V) concentration of untreated effluent (Fig. 5c–d).