Immobilization of saccharomyces cerevisiae in novel hydrogels based on hybrid networks of poly(ethylene oxide), alginate and chitosan for ethanol production

Abstract

Hydrogel matrices were designed as hybrid networks of poly(ethylene oxide) (PEO) with natural polymers, alginate or chitosan by UV irradiation. The networks were formulated in the single-stage procedure in which the alginate or chitosan were added to the crosslinking reaction solution of PEO, and two-stage procedure, with additional chemical crosslinking of alginate or chitosan. Double-layer hydrogels composed of PEO hydrogel core with entrapped cells and outer natural hydrogel layer were also synthesized. The hydrogels were characterized by gel fraction yield and degree of equilibrium swelling as well as by rheological measurements. The production of ethanol by immobilized Saccharomyces cerevisiae was used to test the suitability of the synthesized hybrid hydrogels to serve as carriers for cell immobilization. The presence of cells affected the mechanical properties and the structure of the polymer networks. The best system for immobilization was found to be the PEO/alginate/Ca, which exhibited high mechanical strength (G′, 830; GF, 93; ESH2O, 15) without affecting the metabolic functions of the cells. The maximum ethanol yield was 0.42 g/g corresponding to 82 % of the theoretical yield.

Keywords

• hybrid networks
• poly(ethylene oxide)
• alginate
• chitosan
• cell immobilization
• ethanol production