Studies on bioflocculant production by a mixed culture of Methylobacterium sp. Obi and Actinobacterium sp. Mayor

BACKGROUND: Bioflocculants effect the aggregation of suspended solutes in solutions thus, a viable alternative to inorganic poly-ionic and synthetic organic flocculants which are associated with deleterious health problems. Consequently, a consortium of two bacteria species were evaluated for optimized bioflocculant yield following the inadequacies of axenic cultures. RESULTS: 16S rDNA nucleotide sequencing and BLAST analysis of nucleotide sequences were used to identify the bacterial species, carbon and nitrogen sources optimally supporting bioflocculant production were assessed and the purified bioflocculant characterized. Nucleotide sequences showed 97% and 96% similarity to Methylobacterium sp. AKB-2008-KU9 and Methylobacterium sp. strain 440. The second isolate, likewise, showed 98% similarity to Actinobacterium OR-221. The sequences were deposited in GenBank as Methylobacterium sp. Obi [accession number HQ537130] and Actinobacterium sp. Mayor [accession number JF799090]. Flocculating activity of 95% was obtained in the presence of Ca(2+) and heat-stability was exhibited with retention of above 70% activity at 100°C in 30 min. In addition, bioflocculant yield was about 8.203 g/l. A dose of 1 mg/ml of purified bioflocculant was optimal for the clarification of Kaolin suspension (100 ml) following Jar test. FTIR spectrum revealed the presence of carboxyl and hydroxyl functional groups amongst others. CONCLUSIONS: The mixed culture produced bioflocculant with high flocculating activity and an improved yield. The efficiency observed with jar test may imply industrial applicability.