Strain-dependent protein recovery from yeast by pulsed electric fields: influence of morphological features.

Pulsed electric fields (PEF) enable permeabilization of yeast, facilitating the recovery of nitrogen-rich fractions. However, strain-dependent responses challenge the transferability of conditions. Four yeasts (Saccharomyces cerevisiae SafAle S-23, SafLager S-04 and SafBrew HA-18, and Kluyveromyces lactis CECT 1931) were characterized for cell size, cell wall thickness and composition and treated by PEF at 10-20 kV/cm (19.1-105.7 kJ/kg). Electroporation was quantified by propidium iodide uptake at 1 and 24 h. These measurements were used to define strain-specific conditions achieving ≥90% electroporation at 1 h (T1) and 24 h (T2) post-treatment and maximum-intensity condition (T3). Release of free amino acids, <3 kDa peptides and ≥3 kDa proteins was quantified and effect of PEF treatments on protein solubility was measured. Cell size spanned 8.3-13.9 µm and wall thickness 118.3-233.4 nm, yielding different susceptibility and resealing behaviors across strains. The larger, thin-walled S-23 and S-04 reached at 10 kV/cm and 19.1 kJ/kg, whereas HA-18 and K. lactis required higher PEF intensities, reaching up to 20 kV/cm and 83.7 kJ/kg. Across strains, 50-70% of the free amino-acid pool was recovered after 1 h, while macromolecule recovery increased at 24 h. Protein recovery depended on maintaining persistent permeabilization while avoiding solubility losses (up to ∼37% in S-04). K. lactis showed limited ≥3 kDa release despite preserved solubility, consistent with diffusion constraints imposed by its envelope. Overall, envelope traits modulated electroporation persistence and protein recoverability, enabling strain-tailored PEF settings that balance yield, protein integrity, and energy demand at industrial scale.