Support materials for yeast immobilization affect the concentration of metal ions in the fermentation medium

摘要

Hydrogels are potential absorbers of ions present in the medium, but they can also release some cations (e.g. calcium in calcium alginates). Polyelectrolytes such as alginic acid and poly(acrylic acid) strongly bind polyvalent metal ions. In this paper, the impact of some materials used for the immobilization of yeast, in particular the concentration of certain ions, especially those that play a significant role in the process of fermentation such as calcium, magnesium, zinc and manganese, was assessed. The support for the immobilization of yeast (calcium alginate and polyacrylate) significantly affected the concentration of metal ions in a model solution. Calcium alginate decreased the concentration of Mg~(2+), Zn~(2+) and Mn~(2+) in the solution by about 10-25%, and greatly increased the Ca~(2+) concentration. Polyacrylate, while swelling, decreased the concentration of cations present by up to 50%. Based on the results in this work, no supplementation of wort with divalent metal salts is advised, since it may lead to a stronger cross-linking of polyelectrolytes used, and consequently result in a slower fermentation. Similarly, the relatively high concentration of calcium ions, caused by ion exchange, did not appear to affect the fermentation process.