Cell immobilization by Gel Entrapment in Ca-alginate Beads for Balsamic-styled Vinegar Production

Abstract

The production of a high concentration of acetic acid during vinegar fermentation is a desirable occurrence for Balsamic vinegar. However, acetic acid, high osmotic pressure and low water activity resulting from the cooked grape must, can negatively affect microbial growth during fermentation. To counteract these effects, cell immobilization can improve microbial activity by protecting the cells against harsh environmental conditions. The immobilization of the microbial consortia (non-Saccharomyces yeast and acetic acid bacteria) was carried out using the calcium alginate gel beads entrapment technique. A comparative analysis of the freely suspended and gel entrapped cells was done to further evaluate the effects of surface area or bead size on acetification rates under agitated and non-agitated fermentations. Gel entrapped cell fermentations showed higher acetification rates compared to freely suspended cell fermentations. Static fermentations achieved the anticipated acetic acid production levels (60 g.L -1 ). Under these conditions, smaller beads resulted in higher acetification rates. Surface area of the beads had a significant impact on the acetification rates. Agitation promoted cell shear stress and insufficient acetification during fermentations. Gel entrapped cells using small beads under non-agitated fermentation conditions were effective for balsamic-styled vinegar production.