Enhancing Se(IV) bioremediation efficiency via immobilization of filamentous fungi and yeasts in eco-friendly alginate bead hydrogels

Abstract

The immobilization of microorganisms in polymeric hydrogel has gained attention as a potential method for applications in various fields, offering several advantages over traditional cell free-living technologies. The present study aims to compare the efficiency of selenium (Se) bioremediation and biorecovery by two different fungal types, both in their free and immobilized forms using alginate hydrogels. Our results demonstrated an improvement in the amount of Se(IV) removed from the hydrogels of Aspergillus ochraceus (∼97%) and Rhodotorula mucilaginosa (∼43%) compared to that of the planktonic cultures (∼57% and ∼9–17%). In both cases, most of the Se(IV) is enzymatically reduced by the cells to amorphous Se(0) nanospheres, which are retained throughout the alginate hydrogels. The extensive growth, colonization and distribution of the cells throughout the highly porous hydrogel, along with their ability to maintain viability over long periods and the preservation of the structural integrity of the hydrogel, demonstrated the enormous biotechnological potential of the studied system for practical applications. The results reported show that the immobilization of fungi in alginate hydrogels is an efficient and environmentally friendly alternative for bioremediation and biorecovery of Se nanoparticles, which are of significant industrial and medical interest within the framework of a circular economy.