Valorization of Brewer’s Yeast Biomass Through the Production of Extracts by Pulsed Electric Fields for Enhancing Microbial Growth and Wine Fermentation

Abstract Spent brewer’s yeast (SBY) is an abundant by-product from beer production, rich in nitrogenous compounds. However, its valorization is hindered by the resistance of the yeast cell wall and the risk of co-extracting undesirable compounds. Pulsed electric fields (PEF) offer a selective and energy-efficient alternative to recover intracellular components. This study aimed to evaluate nitrogen-rich extracts obtained by PEF-assisted extraction of SBY as a sustainable nutrient source for microbial growth and wine fermentation. SBY biomass was treated using continuous-flow PEF (15 kV/cm, 150 µs) and incubated at 37 °C for 48 h to induce endogenous proteolysis. Moreover, a sequential extraction strategy was evaluated, allowing prior recovery of glutathione before proteolytic incubation. The resulting nitrogen-rich extracts were characterized for free α-amino nitrogen (FAN) and soluble protein content and evaluated as the sole nitrogen source in Saccharomyces cerevisiae growth media and white grape must fermentation. All SBY extracts showed FAN concentrations comparable to a commercial yeast extract (250 mg /g extract). Protein content was higher at pH 8, though this did not affect growth performance. The sequential strategy allowed glutathione recovery without altering nitrogen composition or microbial proliferation. Ten grams per liter of SBY extract was identified as optimal concentration for supporting microbial growth, matching the performance of a commercial yeast extract. In fermentation trials, the PEF-derived extract enhanced fermentative kinetics, allowing complete fermentation four days earlier than the unsupplemented control, and reduced residual sugars to levels similar to those achieved with a commercial enological nutrient (< 0.7 g/L). These findings validate the use of PEF to obtain functional nitrogen-rich extracts from SBY, supporting their application in microbial and enological processes within circular bioeconomy strategies.