Assessment of bioflocculant production by actinomycetes from rivers and dams of the Eastern Free State Province of South Africa and their potential in wastewater treatment
Agunbiade, Mayowa Oladele
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Bioflocculation is a process whereby stable aggregates are formed as a result of extracellular polymers produced by certain bacteria and algae. The health related issues associated with the use of chemical synthesized flocculants have necessitated for the use of microbial flocculants which are biodegradable and harmless to the environment in the treatment of water and wastewaters. Actinomycetes are Gram-positive microorganism with high guanine cytosine ratio. These organisms have been implicated in antibiotic production and also has flocculating potential. Their application in the treatment of water and wastewater is yet to be validated. Hence, this study evaluated the isolation of actinomycetes from rivers and dams of the Eastern Cape province of South Africa and validated their potential in wastewater treatment. The optimum medium culture conditions for enhancing bioflocculant production were validated to ascertain optimum flocculating activity. Furthermore, this study confirmed that metal ions supported flocculating activity and showed that the bioflocculants were cation dependent. The selected actinomycetes producing bioflocculant exhibited a flocculating activity exceeding 80% and their identitities were confirmed using 16S rRNA gene sequencing. Basic Local Alignment Search Tool (BLAST) analysis of the nucleotide sequence of the 16S rRNA revealed the bacteria isolated from Sterkfontein dam to have 99% similarity to Streptomyces platensis strain HBUM174787; 98% similarity to Terrabacter sp. MUSC78T and their sequence were deposited in the Genbank as Streptomyces platensis with accession number FJ 486385.1 and Terrabacter sp. with accession number KF682157.1 respectively. Similarly, the BLAST analysis of the nucleotide sequence of 16S rRNA confirmed the isolated strain from Monotsha river to have 99% similarity to Arthrobacter humicola strain R1 and the sequence was deposited in the GenBank as Arthrobacter humicola with accession number KC816574.1. The partial purified bioflocculants were able to flocculate dairy, meat processing, sewage wastewaters and river water. Interestingly, there was a significant removal of chemical oxygen demand, biological oxygen demand, nitrate, turbidity and suspended solids after treating the river and wastewaters with the partial purified bioflocculants. Fourier analysis suggested the presence of carboxyl and hydroxyl functional groups in the purified bioflocculants which serves as the adsorption positions for suspended particles and has been opined to be the best choice of functional groups for flocculation process. In addition, pyrolysis profile and thermal stability analysis of the bioflocculants suggested that the main backbone is a polysaccharide. Interestingly, the partial purified bioflocculant exhibited better flocculating efficiency when compared with the chemical synthesized flocculants in river and wastewaters treatment. Thus, confirming the bioflocculants as an important tool in biotechnology.