Characterization of bioflocculant produced by Proteus mirabilis PJC12 isolated from Tendele coal mine wastewater and its application.
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Date
2021
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University of Zululand
Abstract
Flocculation has been widely used as one of the most effective methods for removal of suspended particles in water or wastewater treatment. Synthetic flocculants are conventionally used because of their high flocculating activity, low-cost production and availability. However, synthetic flocculants have been reported to have negative impacts on the environment and have caused some serious health problems including neurotoxicity and cancer-genic to humans. Consequently, bioflocculants appear to be an alternative to synthetic flocculants because bioflocculant are eco-friendly, biodegradable, non-toxic and able to function at a low dosage.
In the current study, the potential for bioflocculant production of bacterial isolates recovered from Tendele coal mine wastewater (Kwa-Somkhele) in the KwaZulu-Natal (KZN) Province of the Republic of South Africa (RSA) was evaluated. The isolates were screened for bioflocculant production using kaolin clay suspension (0.4% w/v). The isolate with the best flocculating activity was selected for the study. In the nutrient ager plate, the colony appeared as round and cream white in colour. The isolate was identified by 16S ribosomal ribonucleic acid (rRNA) as Proteus genus. The analysis of 16S rRNA nucleotide sequence of the bacterium showed 99% similarity to Proteus mirabilis PJC12 with accession number MK 802115.1. The optimisation of nutrients and culture conditions were examined and revealed that optimum inoculum size was 1% (w/v) for maximum bioflocculant production by P. mirabilis PJC12. Fructose as carbon source and organic nitrogen source (yeast extract) was the most favoured for the bioflocculant production. The optimal initial pH of production medium was 6. Optimum temperature was 30oC and the shaking speed of 140 rpm was optimum. At
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72 hrs of incubation period under optimal culture conditions, 2,7 g of pure bioflocculant was recovered from 1 L of bioflocculant production medium of P. mirabilis PJC12.
Chemical characterisation of pure bioflocculant was done. Elemental analysis of pure bioflocculant by scanning electron scanning (SEM) showed the morphological images and the presence of the elements C, O, N, Na, Mg, Al, P, S, Cl, K and Ca in the percentage of 17.61%, 45.27%, 0.44%, 4.62%, 0,47%, 14,99%, 0,77%, 1.10%, 1.46% and 13.24% respectively. Functional groups were examined using Fourier Transform Infrared (FTIR) spectrometry and revealed the presence of hydroxyl group, carbonyl group, carboxyl and amide functional group. Optimization of parameters of pure bioflocculant for application plays a critical role on the maximum performance of the pure bioflocculant and these parameters including dosage size, cations, pH and thermo stability were examined. Upon optimization, the optimum dosage size of the pure bioflocculant was 0.6 g/mL with flocculating activity of 89%. The bioflocculant performed best in the presence of BaCl2 (cation) with flocculating activity of 94%. The bioflocculant was stable at a wide pH range 3 -12 with the highest flocculating activity of 96% at pH 7. The bioflocculant produced by P. mirabilis PJC12 revealed to be thermostable capable of retaining more than of 70% flocculating activity at 100oC after 30 min of exposure.
The bioflocculant showed some good removal efficiency when applied in wastewater for treatment with removal efficiencies of 94% (COD), 97% (BOD), 78%(Ca), 60%(P), and 90%(P) in Vulindlela wastewater.
Description
A dissertation submitted to the Department of Biochemistry and Microbiology in fulfilment of the requirements for the Degree of Master of Science (Microbiology) in the Faculty of Science and Agriculture at the University of Zululand, 2021.
Keywords
Bioflocculant, Proteus mirabilis, Tendele coal mine