Abstract
We evaluated bioflocculant production by a freshwater actinobacteria whose 16S rDNA nucleotide sequence was deposited in GenBank as Streptomyces sp. Gansen (accession number HQ537129). Optimum culture conditions for bioflocculant production were an initial medium pH of 6.8, incubation temperature of 30 °C, agitation speed of 160 rpm and an inoculum size of 2% (v/v) of cell density 1.5 × 108 cfu/mL. The carbon, nitrogen and cation sources for optimum bioflocculant production were glucose (89% flocculating activity), ammonium sulfate (76% flocculating activity) and MgCl2. Bioflocculant pyrolysis showed three step decomposition indicative of three components while chemical analyses showed 78% carbohydrate and 22% protein (wt/wt). The mass ratio of neutral sugar, amino sugar and uronic acids was 4.6:2.4:3. FTIR spectrometry indicated the presence of carboxyl, hydroxyl and amino groups, typical for heteropolysaccharide. The bioflocculant showed a lattice structure as seen by SEM imaging. Its high flocculation activity suggests its suitability for industrial applicability.
Highlights
Flocculants have diverse properties which inform their uses in flocculation technology
We evaluate the bioflocculant production by a freshwater Streptomyces isolated from Tyume river in South Africa
The polymerase chain reaction (PCR) amplification of the 16S rRNA gene of the gram positive bacteria resulted in a PCR product of the expected size (1.5 kb)
Summary
Flocculants have diverse properties which inform their uses in flocculation technology. Flocculants are categorized into three groups, namely the inorganic flocculants which includes salts of aluminum (aluminum sulfate and poly-aluminum chloride); the organic synthetic polymeric flocculants (polyacrylamide derivatives and polyethylene imines), and the natural occurring flocculants of microbial origin, termed bioflocculant, which includes chitosan and sodium alginate [5,6,7]. The inorganic and organic synthetic polymeric flocculants are widely used in industrial processes as they possess high efficiency of flocculation and are inexpensive [6,8]; associated demerits have been colossal and it includes deleterious health problems such as cancer and neuro-toxicity in the case of polyacrylamide derivatives and polyethylene imines and Alzheimer’s disease with respect to salts of aluminum [9,10,11]. Culture conditions were manipulated to optimize bioflocculant yield and the bioflocculant characterized for novelty
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