Abstract:
Characterization of bioflocculant-producing bacteria isolated from bioflocs was
prompted to explore marine bacteria that enhanced bioflocculation process in
aquaculture wastewater treatment. Certain bacteria were believed to secrete extracellular
polymeric substances (EPS) which response to the physiological stress encountered in
the natural environment that can act as bioflocculants. The objectives of this study were
identification of bioflocculant-producing bacteria isolated from bioflocs, evaluation on
their flocculating activity and characterization of protein composition in extracellular
polymeric substances (EPS) produced by identified bioflocculant-producing bacteria. In
this study, standard methods on phenotypic and genotypic identification of bacteria
including biochemical test and molecular approaches were employed. Six species
known as Halomonas venusta, Bacillus cereus, Bacillus subtilis, Bacillus pumilus,
Nitratireductor aquimarinus and Pseudoalteromonas sp. were successfully identified as
bioflocculant-producing bacteria. Their flocculating activities were examined using Jar
Test. The highest flocculating activity was exhibited by Bacillus cereus with 93% while
iv
Halomonas venusta showed the lowest record with 59% of flocculating activity.
Extracted EPS that acted as bioflocculants were obtained from culture supernatant by
using cold ethanol precipitation method. Protein content determination using Bradford
assay indicated all six species of bioflocculant-producing bacteria showed different
protein concentration that ranged between 1.377 μg/mL to 1.455 μg/mL. On Sodium
Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE) gel, several protein
bands with different molecular weight that ranged between 12 kDa to 100 kDa were
observed
