Abstract

We evaluated the bioflocculant production by Virgibacillus species isolated from a marine environment in the Eastern Cape Province of South Africa. Culture conditions for optimal production of the bioflocculant included: glucose as sole carbon source (flocculating activity 91.8%); complex nitrogen source (urea + yeast extract + (NH₄)₂SO₄); inoculum size of 2% (v/v); initial pH 10; and calcium as mediating factor. Optimum dose of the purified bioflocculant for the clarification of 4 g/l kaolin clay suspension at neutral pH was 0.3 mg/ml. Chemical analysis of the purified bioflocculant revealed it to be mainly composed of uronic acids (87% w/w). Scanning electron microscopic observations were indicative of a porous bioflocculant structure. Fourier transform infrared (FTIR) spectrum revealed the presence of carboxyl and hydroxyl groups whilst the themogravimetric analysis (TGA) showed degradation temperature (Td) of 150°C. The bioflocculant appears to hold promise in vast biotechnological applications in a more environmentally friendly and economical manner.

Key words: Virgibacillus sp., bioflocculant, thermostable, polysaccharide.