The Biotechnological Potential of Bacterial Extracellular Polymeric Substances in Lead Biosorption

PFARISO MAUMELA^*Mahloro Hope Serepa-Dlamini

• University of Johannesburg, Johannesburg, South Africa

Abstract Overview: Extracellular polymeric substances are composed of a diverse range of functional groups, thereby making a strong case for their consideration as biosorbents in heavy metal bioremediation. Objective: This study assessed strategies to enhance the biotechnological potential of extracellular polymeric substances produced by an endophytic bacterium, Bacillus MHSD_36. Methods: Design of experiments were used to optimise the yield of extracellular polymeric substances from Bacillus MHSD_36. A mixture design was subsequently used to develop a cocktail of EPS and hydrophobicity components for the optimal biosorption of lead. Results: The production of the EPS, from MHSD_36, was optimized through lead induction at a concentration and time of 5.23 mg/L and 10.75 h, respectively. The optimum yield was 1.65 g/L EPS. The use garden compost, as an alternative growth medium, was sufficient to give an EPS yield (1.15 g/L) comparable to sucrose based medium (1.25 g/L) under optimal induction conditions. The EPS from the Bacillus MHSD_36 had a Pb biosorption of 14.24%. However, a mixture of EPS with the hydrophobicity components significantly enhanced the Pb biosorption. The optimal proportion for the mixture was estimated to be 0.25 and 0.75, respectively with a maximum Pb biosorption of 95.8%. The acid recovery of EPS after the biosorption was effective to recover and recycle EPS in heavy metal biosorption. Conclusion: The production of EPS using garden compost and the subsequent recovery after biosorption of heavy metal offers a sustainable approach for the biotechnological application of bacterial EPS in environmental bioremediation.