Flocculating Properties of a Bioflocculant Purified from Bacillus Subtilis Isolated from the Stream Sediments of Onyearugbulem Market, Akure, Nigeria

Abstract

Soil samples (sediments of stream, its bank and abattoir soil) were collected from Onyearugbulem market abattoir, Akure, Ondo State, Nigeria. Bacteria were isolated from the above soil samples by dilution and pour plate methods. Screening for best bioflocculating bacteria was also performed. Effects of metal ions (such as Mg2+, Ca2+ and Al3+), temperature and pH on flocculating activities of the bioflocculant were also determined. Six bacterial isolates producing flocculating substances were isolated and the isolate with the best flocculating property was selected. The identified bioflocculant producing bacteria are Bacillus anthracis, B. subtilis, B. thuringiensis, B. cereus, Streptomyces griseus and S. somaliensis. The best bioflocculant producing bacterium was Bacillus subtilis and the flocculating activity of its bioflocculant was stimulated in the presence of Mg2+, Ca2+and Al3+. This bioflocculant was thermostable and retained more than 80% of its flocculating activity after being heated at 100ºC for 25 minutes. It had the highest flocculating activity of 85% at pH 6 with optimum bioflocculant dosage of 0.8 mL. This study suggests soil samples from Onyearugbulem market abattoir as a potential source of bioflocculant-producing bacteria with good bioflocculating properties.