Abstract
We evaluated the bioflocculant production potential of an Actinobacteria, which was isolated from a freshwater environment in the Eastern Cape province of South Africa. 16S rDNA nucleotide sequencing analyses revealed that the actinobacteria belongs to the Brachybacterium genus, and the sequences were deposited in the GenBank as Brachybacterium sp. UFH, with accession number HQ537131. Optimum fermentation conditions for bioflocculant production by the bacteria include an initial medium pH of 7.2, incubation temperature of 30 °C, agitation speed of 160 rpm and an inoculum size of 2% (vol/vol) of cell density 3.0 × 108 CFU/mL. The carbon, nitrogen and cation sources for optimum bioflocculant production were maltose (83% flocculating activity), urea (91.17% flocculating activity) and MgCl2 (91.16% flocculating activity). Optimum bioflocculant production coincided with the logarithmic growth phase of the bacteria, and chemical analyses of the bioflocculant showed 39.4% carbohydrate and 43.7% protein (wt/wt). The mass ratio of neutral sugar, amino sugar and uronic acids was 1.3:0.7:2.2. Fourier transform infrared spectroscopy (FTIR) indicated the presence of carboxyl, hydroxyl and amino groups, amongst others, typical for heteropolysaccharide and glycosaminoglycan polysaccharides. Bioflocculant pyrolysis showed thermal stability at over 600 °C, while scanning electron microscope (SEM) imaging revealed a maze-like structure of interlaced flakes. Its high flocculation activity suggests its suitability for industrial applicability.
Highlights
Flocculants are used in various industrial processes to floc out suspended solutes from solvents; these applications includes water treatment, downstream processing in fermentation processes and mineral ore treatment in metallurgical industries [1,2,3,4,5]
An amplicon size of 1.5 kb was obtained from the polymerase chain reaction (PCR)
The use of bioinformatics tool, viz., the Basic Local Alignment Search Tool (BLAST), for the analysis of the nucleotide sequence of the 16S rDNA showed the Actinobacteria to have 99% similarity to that of Brachybacterium sp. b110-100S, and the nucleotide sequence was deposited in GenBank as Brachybacterium sp
Summary
Flocculants are used in various industrial processes to floc out suspended solutes from solvents; these applications includes water treatment (municipal and wastewater), downstream processing in fermentation processes and mineral ore treatment in metallurgical industries [1,2,3,4,5]. They are generally categorized into three: inorganic flocculants, organic synthetic polymeric flocculants and the flocculants of microbial origin, known as a bioflocculant [6,7,8]. Yield optimization was attempted through manipulation of physicochemical parameters and subsequently, the bioflocculant was characterized for novelty through compositional analyses, pyrolysis property determination and morphological and functional group elucidation
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