Enhanced mechanical stability and sensitive swelling performance of chitosan/yeast hybrid hydrogel beads

Abstract

Up to the present time, improving the mechanical stability of hydrogel beads is still a challenging task for future applications of chitosan hydrogels. In this work, novel and eco-friendly chitosan/yeast hybrid hydrogel beads were fabricated by facile introduction of yeast cells into the chitosan matrix through alkali gelation. A detailed mechanism of formation of the beads is proposed and the structures and morphologies of the manufactured products were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), respectively. The mechanical stability test showed that impregnation of yeast cells into the chitosan matrix could effectively enhance the mechanical stability of chitosan/yeast hybrid hydrogel beads under the effects of various intensities of ultrasonic waves and centrifugal forces in comparison with pure chitosan hydrogel beads. The resultant product with 40 wt% yeast content achieved a maximum swelling ratio of 31.7 g g⁻¹ in distilled water. The swelling kinetics and diffusion kinetics of chitosan/yeast hybrid hydrogel beads in distilled water were also investigated. Benefiting from the coupling effect of its crosslinked three-dimensional network structure and ample chemical functional groups derived from its own components, chitosan/yeast hybrid hydrogel beads have manifested a rapid and adjustable response to external environmental stimuli including the pH of the external solution, salt concentration, ionic valence and temperature. In particular, the distinct loading and slow-release efficiency of chitosan/yeast hybrid hydrogel beads for humic acid as a fertilizer model is pH-dependent. This makes the chitosan/yeast hybrid hydrogel beads good candidates for controlled-release carrier biomaterials, which is very likely to develop into a patented utilization of chitosan/yeast hybrid hydrogel beads in future applications.