Continuous Primary Beer Fermentation with Yeast Immobilized in Alginate–Chitosan Microcapsules with a Liquid Core

Abstract

The application of continuous fermentation with immobilized cells in brewing is a challenge because of problems with carrier selection and reactor design, which have economic impacts on the beer produced. Moreover, immobilization alters yeast physiology, which significantly affects beer flavor and aroma. Therefore, the aim of this study was to investigate the feasibility of a continuous fermentation system, consisting of a packed bed column bioreactor, containing lager brewing yeast, immobilized in alginate–chitosan microcapsules with a liquid core, in the primary beer fermentation. The results showed that the system entered in a stationary mode on the 3rd day and worked stably in this mode for 6 days. The “green” beer was taken at every 24 h at the output of the reactor and used for secondary fermentation with the yeast cells leaked from the capsules during the primary fermentation. The extract consumption, ethanol production, and pH change during primary and secondary fermentation were investigated. Some of the secondary yeast metabolites such as vicinal diketones, higher alcohols, esters, and aldehydes in “green” and final beers were determined and it was found that the flavor profile of the final beer was comparable to two industrially produced Bulgarian beers.

Keywords

• continuous fermentation
• packed bed bioreactor
• alginate–chitosan capsules
• secondary metabolites