Yeast immobilization on peanut hulls for potential application in beer fermentation

The potential of using peanut hulls as support material for immobilization of yeast cells during beer fermentation was evaluated. After treatment of peanut hulls with 0.5% (w/v) NaOH, FTIR analysis revealed an important change on its chemical composition. For instance, the proportion of lignin decreased and as a result the adsorption of yeast cells onto the support material during fermentation was favoured. Cell adhesion onto the conditioned support in 8° Brix laboratory malt wort as fermentation medium was evaluated, observing a maximal cell adhesion (2.56×108 cells/g of dried support) at 20.5 h of cultivation. Evaluations of the performance of the biocatalyst in fermentations at 15±0.5°C in 14° Brix laboratory malt wort indicated a proper stability in terms of physical integrity (confirmed by SEM observation) and improved fermentation kinetics. The fermentation time was shortened to approximately four days and the rates of reducing sugar consumption and ethanol production were improved when compared to fermentations carried out with free suspended cells. These results show a promising potential of peanut hulls as support material in beer fermentation.