Faculty of Science, Agriculture and Engineering

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Browsing Faculty of Science, Agriculture and Engineering by Author "Akapo, Charles Sewanu Oluwaseun"

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    Production and characterisation of bioflocculant produced by bacterial isolates from Richards Bay harbour, Kwazulu Natal
    (University of Zululand, 2019) Akapo, Charles Sewanu Oluwaseun; Basson, A.K.; Ntombela, Z.G.
    Bioflocculants are safe and biodegradable extracellular polymers produced by microorganisms during their growth. In comparison with conventionally used flocculants, bioflocculants have the advantage of being safe (no known toxic effects), biodegradable and harmless to the environment. In this study, halophile novel bacteria was isolated from Richards Bay Harbour, Kwazulu-Natal, Republic of South Africa and screened for bioflocculant producing potential using a production medium at 30 oC for 72 hours with a shaking speed of 160 rpm. Kaolin clay suspension was used as test material. Microorganisms with bioflocculant-producing potential were further identified using 16S rRNA molecular sequencing method. Among the identified isolates, one with flocculating activity above 70% was used for bioflocculant production. Bacillus atrophaeus culture conditions were optimised for improved flocculating activity as well as the production yield. To obtain an optimum culture medium condition, the parameters such as carbon and nitrogen (energy) sources, inoculum size, metal ions, cultivation time, initial pH of the medium, incubation temperature, shaking speed and fermentation time were investigated. The bioflocculant was extracted using ice-cold ethanol and purified with the mixture of chloroform and butanol (5:7 v/v). The purified bioflocculant was characterized using FTIR, scanning electron microscopy (SEM) equipped with element analyser and TG analyser. The bioflocculant was further analysed for its chemical composition. The purified bioflocculant BA-CGB was also assessed for antimicrobial activity properties and further applied on Vulindlela domestic wastewater and Mzingazi river water. Among the screened isolates, three of them with more than 70% flocculating activities were identified through 16S rRNA as Bacillus safensis, Bacillus pumilus xxi and Bacillus atrophaeus. A bioflocculant yield of 3.165 g was recovered for B. atrophaeus after 96 hours of incubation from 1 liter of fermentation broth in the presence of 4% inoculum size, glucose, ammonium chloride, at pH 9 and temperature of 35 oC as well as shaking speed of 110 rpm stimulated by Ba2+ . The bioflocculant BA-CGB produced, showed a strong thermal stability character as managed to attain more than 60% flocculating activity at 121 °C for 15 min, with 0.4 mg/ml dosage size and Ca2+ as a stimulating agent. The flocculating activity of purified BA-CGB was greatly influenced by a wide pH range (3-12). BA-CGB is amorphous in structure, composed of carbohydrates (65%), uronic acid (25%) and trace proteins (10%). Functional groups include hydroxyl, carboxyl, amine, amide and elements such as carbon and oxygen among others, were present in the molecular chain of bioflocculant BA-CGB. No antimicrobial activity was observed with bioflocculant BA-CGB. 0.4 mg/ml dosage size of a bioflocculant was more effective in flocculating wastewater, improving COD, BOD and removing nitrates, phosphates as well as sulphate from Mzingazi riverwater and Vulindlela domestic wastewater. This bioflocculant holds a promising future to replace in-use chemical flocculants in wastewater treatment
University of Zululand