Production and characterization of biopolymer as bioflocculant from thermotolerant Bacillus subtilis WD161 in palm oil mill effluent

Five bacterial strains were screened for polymer production in five synthetic media (GP, PS, GL, PL and PR). The highest polymer yield was obtained from Bacillus subtilis WD161 in PR medium (8.89 g/L). Cultivation at 30, 45 and 60 °C indicated that they were thermotolerant with the maximum biopolymer yield at 45 °C. Using palm oil mill effluent (POME) as medium, the nitrogen had to be supplemented to 1.28 g/L (equal to that in PR medium) with the initial pH adjusted to 7.0 and cultivation at 30 °C. Characterization based on its composition and functional groups revealed that the biopolymer WD161 was glycoprotein with the molecular weight of 1.54 × 106 Da. FT-IR analysis revealed the presence of amine (NH2), hydroxyl, carboxyl and carbonyl groups. It was also a bioflocculant and its flocculating activity to precipitate the suspended solid in POME increased by 35% under the optimum condition.