Abstract Description

Bacteria are promising sources of bioflocculants, yet their diversity and regulatory machinery for bioflocculant synthesis remain underexplored. This study focused on evaluating the biosynthetic genes, optimisation and assessment of bioflocculation efficiency in wastewater. The isolated bioflocculant producers were identified by 16S rRNA analysis. Polymerase chain reaction was used to assess the presence of polyketide synthase I (PKS–1), polyketide synthase II (PKS–II), non-ribosomal peptide synthetase (NRPS), epsH and epsJ. The one-factor-at-a-time technique was utilised for optimisation of culture conditions. The total protein and neutral carbohydrate contents of the bioflocculants were determined using Bradford and phenol-sulfuric acid assays, respectively, and their functional groups were characterised using Fourier-transform infrared (FTIR) spectroscopy. The bioflocculants` efficiencies were evaluated in wastewater using the Jar test method. Among the 31 isolates, Klebsiella michiganensis and Klebsiella pasteurii were the potent bioflocculant producers. They both revealed the presence of PKS–II. K. pasteurii possessed the epsH gene. The optimal conditions for maximum bioflocculant production (95% activity) by K. michiganensis were: temperature of 35 oC, pH 5, galactose, tryptophan and 84 hours of incubation. K. pasteurii`s maximum bioflocculant production of 83%.73% was obtained at the temperature of 35 oC, pH 7, galactose, mixture of urea, yeast extract and (NH4)2SO4, and 96 hours of fermentation. The bioflocculant produced by K. michiganensis consisted of 8.10% total proteins and 52.48% neutral carbohydrates. K. michiganensis produced a bioflocculant encompassing 4.92% total proteins and 53.60% of total neutral carbohydrates. FTIR spectra revealed the bioflocculants to share similar functional groups, namely, hydroxyl, carbonyl and amino groups. Their bioflocculants reduced chemical oxygen demand and turbidity of wastewater by more than 70%. The bacteria had promising bioflocculant production with potential applicability in wastewater treatment.