Optimization of bioflocculant production by bacteria isolated from oil-polluted soil and fermented maize effluent

Abstract

This study involved isolation of bioflocculant producing bacteria from soil and waste water. The isolates were tested for flocculation activities and  those deemed fit were identified and the optimal environmental conditions for bioflocculant production were also determined. Samples were collected from oil-contaminated soil in Redeemer's University and fermented maize waste water. Microbial isolation was done using standard
microbiological methods and identification was done using morphology, biochemical and molecular method with universal primer for 16SrRNA gene. Environmental conditions (pH, Temperature and cations) and media composition (nitrogen and carbon sources) were altered to optimize bioflocculant production and activities. Percentage flocculating activities were determined and calculated using standard method. We also adjusted
revolution rate and standing time to determine the optimum conditions for flocculation activities. Two bioflocculant producing isolates (Bacillus cereus and Lysinibacillus fusiformis) from oil-polluted soil and two from fermented maize waste water (Bacillus thuringiensis and Bacillus tropicus) were obtained. Neutral pH, temperature o of 30 C and inclusion of CaCl were the best conditions for bioflocculant production in all isolates except for 2 Lysinibacillus fusiformis which was best with acidic pH condition. Maltose as the carbon source was the best for all isolates except Bacillus  thuringiensis (fructose) and ammonium was the best nitrogen source for all isolates except Bacillus cereus (peptone). Although condition III showed optimum condition for flocculation activities, the percentage activities were generally lower than normal condition. The highest percentage flocculating activities o of 98% were by Bacillus cereus and Bacillus tropicus at 30 C, neutral pH and 1% (w/v) CaCl salt with soluble starch 2 and maltose as their carbon source respectively. These bacteria can be exploited for their use as flocculants in water treatment.

Keywords: Agro-residues; Bio-friendly; Bioflocculant; Contaminated soil; Optimization