Characterization and flocculation properties of biopolymeric flocculant (glycosaminoglycan) produced by Cellulomonas sp. Okoh.

AIMS: Bioflocculant production potential of an actinobacteria isolated from a freshwater environment was evaluated and the bioflocculant characterized. METHODS AND
RESULTS: 16S rDNA nucleotide sequence and BLAST analysis was used to identify the actinobacteria and fermentation conditions, and nutritional requirements were evaluated for optimal bioflocculant production. Chemical analyses, FTIR, 1H NMR spectrometry and SEM imaging of the purified bioflocculant were carried out. The 16S rDNA nucleotide sequences showed 93% similarities to three Cellulomonas species (strain 794, Cellulomonas flavigena DSM 20109 and Cellulomonas flavigena NCIMB 8073), and the sequences was deposited in GenBank as Cellulomonas sp. Okoh (accession number HQ537132). Bioflocculant was optimally produced at an initial pH 7, incubation temperature 30°C, agitation speed of 160 rpm and an inoculum size of 2% (vol/vol) of cell density 1·5 × 10(8) cfu ml(-1). Glucose (88·09% flocculating activity; yield: 4·04 ± 0·33 g l(-1)), (NH(4))2 NO(3) (82·74% flocculating activity; yield: 4·47 ± 0·55 g l(-1)) and MgCl(2) (90·40% flocculating activity; yield: 4·41 g l(-1)) were the preferred nutritional source. Bioflocculant chemical analyses showed carbohydrate, protein and uronic acids in the proportion of 28·9, 19·3 and 18·7% in CPB and 31·4, 18·7 and 32·1% in PPB, respectively. FTIR and 1H NMR indicated the presence of carboxyl, hydroxyl and amino groups amongst others typical of glycosaminoglycan. SEM imaging revealed horizontal pleats of membranous sheets closely packed.
CONCLUSION: Cellulomonas sp. produces bioflocculant predominantly composed of glycosaminoglycan polysaccharides with high flocculation activity. SIGNIFICANCE AND IMPACT OF THE STUDY: High flocculation activity suggests suitability for industrial applications; hence, it may serve to replace the hazardous flocculant used in water treatment.