Biosorption in brewer's spent yeast followed by freeze-drying: A promising strategy to protect vitamin C

Abstract

This study aimed to evaluate the use of a new strategy to protect and preserve vitamin C, considering its instability. The biosorption was applied using alkaline-modified (AY) and 'in natura' (Y) brewer's spent yeast (BSY) followed by freeze-drying. For this purpose, vitamin C was incorporated into the biomass, and an optimization study of biosorption was conducted to achieve the maximum sorption capacity and elucidate the interactions between them. The sorbent dosage, pH, kinetics, and initial concentration were varied, and isotherm models, including the Langmuir, Freundlich, Dubinin–Radushkevich, Sips, and Temkin models, were applied to the experimental data. A favorable sorption process was observed for both materials, and the Sips model presented the best fit, indicating that both chemical and physical interactions occur between vitamin C and BSY. The experimental and theoretical sorption capacities obtained were similar (SC_exp = 19.11 ± 0.97 mg/g and q_m = 17.84 ± 1.11 mg/g for Y and SC_exp = 18.11 ± 2.77 mg/g and q_m = 17.84 ± 0.96 mg/g for AY). The particles before and after incorporation were characterized by confocal laser scanning microscopy, FT-IR, zeta potential, moisture, and water activity, which provided evidence of the presence of vitamin C in BSY and helped elucidate the differences observed between the Y and AY results. The stability of the particles was also evaluated, which revealed that the concentration of vitamin C after 35 days decreased by 38.83 ± 1.21% for Y and 35.29 ± 0.29% for AY. These results indicate that both materials have advantages in biosorption tests; therefore, this innovative and sustainable study uses byproducts to incorporate nutrients and reduce their degradation.