Characterization of Extracellular Polymeric Substances (EPS) Producing Bacteria Isolated from Biofilms Developed on Different Support Materials in Attached Growth Batch Reactors

Dewatering/sludge settling is the major problem that is being tackled by wastewater treatment plant. To overcome this problem, synthetic coagulants (environmental/health hazards) are used. In this contest, 50 bacteria (EPS producing capability) were selected, isolated from biofilms (different support materials). Congo red agar assay indicated 15 (slime producers), 24 (intermediate results) and 11 (non-slime) formers. Whereas tube method indicated 15 (strong), 15 (moderate), 12 (weak) slime and 8 (non-slime) producers. Microtiter plate assay showed 15 (strong) while 35 (moderate) biofilm formers. Dry weight analyses showed the greater concentration of broth (5.33-24.7 g/L) and slime EPS (1.33-13.33 g/L) in individual bacteria as compared to consortia broth (5.66-8.86 g/L) and slime EPS (3.22-6.57 g/L). EPS production was confirmed when an increase in viscosity (16,950-43,450 mPas) was measured. Over all carbohydrate content was higher in consortia (1.233-1.887 mg/ml) as compared to individual bacteria (0.504-0.610 mg/ml). Protein content varied in individual bacteria (0.227-0.52 mg/ml) as well as in consortia (0.178-0.974 mg/ml). FTIR spectra of EPS extract (bacteria and consortia) revealed the presence of functional groups of carbohydrates, proteins, lipids and nucleic acids. Great deal of EPS production was observed by consortia of six bacteria through SEM.