RESUMO
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 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 degrees 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 energy-dispersive X-ray analysis 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.
