Solid state fermentation of rice straw using Penicillium citrinum for chitosan production and application as nanobiosorbent

Chitosan production by Penicillium citrinum using rice straw was investigated by varying the moisture content (50–80%) and particle size of rice straw, and their optimum levels were found to be 70% and 4–5 mm, respectively. A lab scale tray fermenter was later employed to carry out the solid-state fermentation which yielded a maximum chitosan production of 9 g/kg of rice straw. Nanobiosorbents based on the fungal chitosan produced in this study was further prepared and evaluated for heavy metal removal. Magnetic iron (Fe3O4) nanoparticles coated with chitosan and carboxymethyl chitosan (CMC) were used as the nano-biosorbents to remove Cr(VI) and Pb(II) from corresponding aqueous solutions. Maximum removal of Cr (VI) and Pb (II) were 42.43 and 178.2 mg/g with CMCNPs. Heavy metal removal kinetics by the nanobiosorbents followed the pseudo-second order kinetics. Furthermore, the nanobiosorbents were found suitable for reuse for up to three cycles of sorption-desorption.