# Regulatory Machinery of Bacterial Bioflocculant Synthesis and Optimisation and Assessment of Bioflocculation Efficiency in Wastewater

## TL;DR

This study explores how bacteria produce bioflocculants and finds optimal conditions for their use in wastewater treatment.

## Contribution

The study identifies key genes and optimal conditions for bioflocculant production in Klebsiella species.

## Key findings

- Klebsiella michiganensis and K. pasteurii are potent bioflocculant producers with high activity under optimized conditions.
- Bioflocculants from these bacteria reduced wastewater chemical oxygen demand and turbidity by over 70%.
- Optimal production conditions varied between the two species, including temperature, pH, and nutrient sources.

## Abstract

Bacteria are promising sources of bioflocculants, yet their regulatory machinery for bioflocculant synthesis remains 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 and rpoB gene 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. A one-factor-at-a-time technique was utilised for optimisation of culture conditions. The bioflocculants’ efficiencies were evaluated in wastewater using the Jar test method. Among 31 isolates, Klebsiella michiganensis and Klebsiella pasteurii were the most 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 a temperature of 35 °C, pH of 5, galactose, tryptophan and 84 h of incubation. K. pasteurii’s maximum bioflocculant production of 83% was obtained at a temperature of 35 °C and pH of 7, with galactose, a mixture of urea, yeast extract, and ammonium sulphate (NH4)2SO4 and 96 h of fermentation. Their bioflocculants reduced the chemical oxygen demand and turbidity of wastewater by more than 70%. The bacteria had promising bioflocculant production with potential applicability in wastewater treatment.