Yeast biomass biorefinery assisted by Pulsed Electric Fields (PEF) for obtaining oenological compounds Biorrefinería de biomasa de levadura utilizandoPulsos eléctricos de alto voltaje (PEF) para obtener compuestos enológicos
Year: 2026
Type: dissertation
Abstract: Global food systems must feed a growing population while operating within finite planetary resources. Sustainable and circular food systems seek to valorize by-products as renewable sources of nutrients, bioactive compounds and functional ingredients. Fermentation industries generate large amounts of yeast biomass that is often downgraded to low-value uses, despite its richness in compounds with potential applications in the pharmaceutical, cosmetic and food sectors, including winemaking. Unlocking this potential requires extraction technologies that access intracellular and structural yeast components while preserving functionality and meeting industrial constraints on energy use and cost. Conventional mechanical, thermal, chemical and enzymatic methods can disrupt yeast cells, but they usually favor the recovery of a single main product and often rely on harsh conditions. In contrast, biorefinery concepts aim to generate several marketable products from a single biomass stream. Pulsed Electric Fields (PEF) represent a promising enabling technology for such a yeast biorefinery. In PEF processing, short, high-intensity electric pulses are applied to a cell suspension, inducing extensive electroporation of cytoplasmic membranes in continuous flow, enhancing mass transfer and triggering enzyme-driven reactions while avoiding complete cell disruption in a single step. The overarching objective of this thesis was to evaluate PEF as a processing tool to implement a cascade yeast biorefinery under conditions compatible with industrial practice. First, the impact of PEF treatments on Saccharomyces cerevisiae cells and on their subsequent extraction behavior during incubation was characterized. Treatment conditions were defined that achieved extensive electroporation while preserving overall cell structure. Under these conditions, PEF coupled membrane permeabilization with the onset of autolytic processes, leading to a time-dependent release of compounds. Cytoplasmic solutes were recovered on a much shorter time scale than cell wall-associated components, and low molecular weight solutes were extracted more extensively than larger proteins, indicating a degree of selectivity linked to molecular size and localization. Building on these observations, post-PEF incubation conditions were adjusted to steer extraction kinetics and the composition of the resulting extracts. Amino acids and peptides such as glutathione were released rapidly, whereas proteins were recovered more slowly, mainly through PEF-induced autolysis and associated proteolysis with distinct kinetics and product profiles compared with conventional heat-mediated autolysis. When these principles were transferred to spent brewer's yeast, they supported the design of a sequential extraction cascade in which antioxidant-rich, nitrogen-rich and cell wall-derived fractions were recovered in a controlled order from the same industrial by-product. Finally, the functional performance of PEF-derived fractions was evaluated in oenological applications. A glutathione-rich extract obtained by PEF-assisted extraction acted as an effective antioxidant in white grape must, providing protection comparable to commercial preparations while enabling a reduction in SO2 addition and browning. Nitrogen-rich extracts from spent brewer’s yeast functioned as microbial nutrients that sustained yeast growth and enhanced wine fermentation performance to levels similar to those achieved with commercial yeast extracts and oenological nutrients. Overall, this thesis establishes a PEF-enabled yeast biorefinery in which continuous-flow electroporation and mild post-treatment incubation enable sequential fractionation of yeast biomass into functional ingredients for circular food systems.
Source: Zaguan (Universidad de Zaragoza)
Language: English
Subfield: Biotechnology
Domain: Life Sciences
Open Access status: green
Funder: Ministerio de Universidades
Awards: G1788098107, G6166841516
OpenAlex ID: W7225437803