Soluble Extracellular Polymeric Substances Produced by Parachlorella kessleri and Chlorella vulgaris: Biochemical Characterization and Assessment of Their Cadmium and Lead Sorption Abilities

In the present study, the potential of lead and cadmium removal by the extracellular polymeric substances (EPS) produced from Parachlorella kessleri and Chlorella vulgaris were investigated. Carbohydrates were the dominant components of EPS from both analyzed species. The contents of reducing sugars, uronic acids, and amino acids were higher in EPS synthesized by C. vulgaris than in EPS from P. kessleri. The analysis of the monosaccharide composition showed the presence of rhamnose, mannose and galactose in the EPS obtained from both species. The ICP-OES (inductively coupled plasma optical emission spectrometry) analyses demonstrated that C. vulgaris EPS showed higher sorption capacity in comparison to P. kessleri EPS. The sorption capacity of C. vulgaris EPS increased with the increase in the amount of metal ions. P. kessleri EPS had a maximum sorption capacity in the presence of 100 mg/L of metal ions. The FTIR analysis demonstrated that the carboxyl, hydroxyl, and carbonyl groups of EPS play a key role in the interactions with metal ions. The present study showed C. vulgaris EPS can be used as a biosorbent in bioremediation processes due to its biochemical composition, the presence of significant amounts of negatively charged uronic acids, and higher sorption capacity.

Automated summary

This study investigated the potential of extracellular polymeric substances (EPS) produced by Parachlorella kessleri and Chlorella vulgaris in removing lead and cadmium. EPS from both species contained carbohydrates as the dominant components. C. vulgaris EPS had higher contents of reducing sugars, uronic acids, and amino acids compared to P. kessleri EPS. Monosaccharide composition analysis showed the presence of rhamnose, mannose, and galactose in the EPS from both species. ICP-OES analyses demonstrated that C. vulgaris EPS had higher sorption capacity than P. kessleri EPS. The study also found that carboxyl, hydroxyl, and carbonyl groups of EPS played a key role in interacting with metal ions. Overall, C. vulgaris EPS showed promising potential as a biosorbent in bioremediation processes.