In our previous study we reported on the bioflocculant production by a Bacillus species isolated
from sediment samples of Algoa Bay in the Eastern Cape Province of South Africa. In the current study we
carried out further evaluation on the effect of different culture conditions on the bioflocculant production, as
well as characterised the bioflocculant produced in detail. The bacteria produced bioflocculant optimally
under the following conditions: using sodium carbonate (95.2% flocculating activity) and potassium nitrate
(76.6% flocculating activity) as carbon and nitrogen sources, respectively; inoculum size of 3% (v/v); initial
pH 9.0; and Al3+ as coagulant aid. The crude bioflocculant retained 44.2% residual flocculating activity after
heating at 100°C for 15 min. Chemical analysis of the Bacillus sp. Gilbert purified bioflocculant demonstrated
that it was composed mainly of polysaccharide. Fourier transform infrared spectroscopy analysis revealed the
presence of hydroxyl, carboxyl and methylene groups in the bioflocculant and energydispersive Xray anal
ysis detected the elemental composition in mass proportion (% w/w) of C, N, O, S and P as
4.12:7.40:39.92:3.00:13.91. Scanning electron micrograph image of the bioflocculant revealed an amorphous
compound.
DOI: 10.1134/S0003683814010104