Insights into the polysaccharides and proteins production from Penicillium citrinum during bioleaching of spent coin cells

Abstract

The essential role of polysaccharides and proteins of extracellular polymeric substances (EPS) has been well known in the bioleaching process. However, there is no information on the role of these compositions in the bioleaching of spent coin cells (SCCs). This study investigated protein and polysaccharide production as biological macromolecules during the bioleaching of SCCs at various pulp densities using adapted Penicillium citrinum. The adaptation improved the tolerance index of fungi for the bioleaching up to a pulp density of 30 g/L. The EPS analysis indicated that loosely bound EPS (LB-EPS) contained a high concentration of polysaccharides. Instead, the most protein content was concentrated at tightly bound EPS (TB-EPS). Both protein and polysaccharide keep growing up to 20 g/L of pulp density during the entire period of bioleaching, and the maximum binding rate of Mn and Li to EPS was 43% and 15%, respectively. Pearson correlation indicated the positive correlation of the protein and the polysaccharides content on bioleaching efficiencies. From the FTIR spectroscopy, the principal functional groups on Mn and Li binding were OH and carboxyl. The FE-SEM analysis revealed the deformation of EPS at 30 g/L of pulp density, which suggested the toxic effect of this pulp density.