Bioflocculant production and heavy metal sorption by metal resistant bacterial isolates from gold mining soil

Two bioflocculant producing bacterial isolates from mining soil samples were investigated for their application in heavy metal removal. The bacterial isolates were identified as Pseudomonas koreensis and Pantoea sp. using 16S rRNA gene. Cadmium resistant genes cadA and CzcD were detected in Pantoea sp. while P. koreensis harbor CzcD and chrA responsible for Cd and Cr resistance respectively. The isolates showed maximum flocculating activity of 71.3% and 51.7% with glucose and yield of 2.98 g L−1 and 3.26 g L−1 for Pantoea sp. and P. koreensis respectively. The optimum flocculating activity was achieved at pH 7.5 and temperature of 30 °C. Fourier transform infrared analysis of the bioflocculants produced by the two isolates showed the presence of carboxyl, hydroxyl and amino groups characteristic of polysaccharide and protein. Heavy metal sorption by bioflocculant of Pantoea sp. removed 51.2% Cd, 52.5% Cr and 80.5% Pb while that of P. koreensis removed 48.5% Cd, 42.5% Cr and 73.7% Pb. The bioflocculants produced have potential in metal removal from industrial wastes. •Pseudomonas koreensis and Pantoea sp. were isolated from a gold mining soil and assessed for bioflocculant production.•71% and 51% flocculation were obtained at optimum conditions (pH 7.5 and 30 °C) for Pantoea sp. and P. koreensis respectively.•Glucose gave the highest yield of 2.98 g L−1 and 3.26 g L−1 for Pantoea sp. and P. koreensis respectively at optimum conditions.•The bioflocculant produced showed significant sorption of Cd, Cr and Pb from solution.•FTIR analysis revealed the bioflocculants produced are glycoproteins.