Interaction Between Cobalt Ferrite Nanoparticles and Aspergillus niger Spores

The immobilization of microorganisms has been reported as an alternative to improve the efficiency of processes such as fermentation, anaerobic digestion, bioadsorption, and many others. Since the kinetics of bioprocesses are governed by the adsorbent/adsorbate interaction, it is important to know the mechanisms of interaction between biological materials and supports. This could help to define optimal operating conditions. In this research, the fungus that produces the cellulases, was selected, and the characterization of the interaction between fungal spores and cobalt ferrite magnetic nanoparticles, was performed. In order to select a fungal strain produces cellulase enzymes, a qualitative Congo Red test was carried out with a culture medium rich in carboxymethylcellulose. From five strains, Aspergillus niger was selected. Chitosan coated cobalt ferrite magnetic nanoparticles (CoMNP-C) were synthesized by single-step co-precipitation. The nano-size of CoMNP-C was demonstrated by XRD. The presence of a high content of amino groups (0.144 mM g^-1) was observed, that could have an important role in the interaction between nanoparticles and spores. Adsorption kinetic studies were carried out. The pseudo-equilibrium time was estimated as 90 min. Spores adsorption isotherm was obtained with 3.45 mg of synthesized material at 30 °C. It was found that the adsorption of spores may be described by both models (Langmuir and Freundlich), suggesting a homogeneous surface of the nanoparticles and a multilayer adsorption phenomenon. These results can have transcendence in multiple applications based on the studied process.