VACUUM-ASSISTED BIOSORPTION OF ASCORBIC ACID INTO BREWER'S SPENT YEAST

Due to the wide availability and low added value attributed to the brewing yeast Saccharomyces pastorianus, its application in the development of new processes and food ingredients has been explored. The use of yeast cells to protect nutrients, such as ascorbic acid (AA), becomes an alternative to avoid degradation and provide a controlled release, given the importance of this nutrient, which has several biological functions. One of the techniques that can be used with the purpose of incorporating AA into yeast cells consists of vacuum-assisted biosorption, which aims at hydrodynamic transfer through negative pressures for a few seconds, thus being a fast, simple process with the potential to change the permeability of yeast cell membranes, allowing their enrichment to be facilitated. Therefore, the present work proposes the application of brewer's yeast as a vehicle for the incorporation of AA, through vacuum impregnation and quantification by HPLC. Thus, a study was carried out to optimize the mass, vacuum time and concentration of AA. After constant stirring for 10 min and a subsequent 60 s of vacuum, 25.3 % of AA present in solution was incorporated into the yeast cell. Without the vacuum, with just 10 min of biosorption time between yeast and AA, the incorporation was null. The vacuum time was also evaluated, reaching constant incorporation values from 40 s. For the biosorption capacity, the concentrations of AA in solution were varied, reaching 25.15 mg/g when using a concentration of 5000 ug/mL of AA. Isothermal models were applied to the experimental data and Sips was the one that presented the best adjustments, with R2=0.9859 and χ2=1.62. In this way, in addition to already having high nutritional value, yeasts can serve as a vehicle for incorporating AA through vacuum-assisted biosorption, thus being an efficient method to protect and allow its controlled release.