Release of Mannoproteins during Saccharomyces cerevisiae Autolysis Induced by Pulsed Electric Field

Abstract

The potential of the application of pulsed electric fields (PEF) to induce accelerate autolysis of a commercial strain of Saccharomyces cerevisiae for winemaking use was evaluated. The influence of PEF treatments of different intensity (5–25 kV/cm for 30–240 μs) on cell viability, cytoplasmic membrane permeabilization and release of mannoproteins and compounds absorbing at 260 and 280 nm has been investigated. After 8 days of incubation at 25°C the Abs600 of the suspension containing the control cells was kept constant while the Abs600 of the suspension containing the cells treated by PEF decreased. The measurement of the absorbance at 260 and 280 nm revealed no release of UV absorbing material from untreated cells after 8 days of incubation but the amount of UV absorbing material released drastically increased in the samples that contained cells treated by PEF after the same storage period. After 18 days of storage the amount of mannoproteins released from the untreated cell was negligible. Conversely, mannoprotein concentration increased linearly for the samples containing cells of S. cerevisiae treated by PEF. After 18 days of incubation the concentration of mannoproteins in the supernatant increased 4.2 times for the samples containing cells treated by PEF at 15 and 25 kV/cm for 45 and 150 μs. Results obtained in this study indicates that PEF could be used in winemaking to accelerate the sur lie aging or to obtain mannoproteins from yeast cultures.

Microbial lipid extraction from Lipomyces starkeyi using irreversible electroporation

“…Generally, the microbial cells have phospholipids and peptidoglycan which contain polar molecules with ligand groups, giving a net negative charge on the outer surface of the cell that are susceptible to the action of strong electrical fields . Yeast cell wall, with a thickness of 100–200 nm, is an elastic, layered structure that protects the cell from osmotic swelling and physical stress is mainly composed of β (1→3)‐ d ‐glucan, β (1→6)‐ d ‐glucan, chitin, and mannoprotein(s) . The mannoproteins forming the outer wall layer of the yeast cell which determines the permeability of the wall for macromolecules are highly glycosylated, and have numerous phosphate groups in their carbohydrate side chains, confers a net negative charge to the cell surface .…”

Pulsed electric field‐assisted extraction of valuable compounds from microorganisms

“…However, the release of mannoproteins, which form part of the cell wall, progressed gradually and did not reach its maximum until after 25 days of incubation. At this time, the amount of mannoproteins released from PEF‐treated cells was 10 times higher than that of those released from control cells (Martínez et al., ). Mannoprotein release is a result of the degradation of the cell wall by the cytoplasmic enzymes.…”

“…The permeabilization of the cytoplasmic membrane has been widely described as the cause of improved release of certain compounds due to PEF; additionally, it has been newly proven that PEF treatments also activate yeast autolysis, thereby leading to the self‐degradation of the constituents of yeast cells by their own proteases and β‐glucanases. (Martínez et al., ). After PEF treatments that caused permeabilization, the release of intracellular proteins and nucleic acids from S. cerevisiae was observed mainly during the initial hours.…”

“…It can be evidenced by the increment of optical density of the media at 260 and 280 nm, respectively. Likewise, plasmolysis of cells due to the entrance of water into the cytoplasm denotes electroporation and can be observed microscopically (Martínez, Cebrián, Álvarez, & Raso, 2016).…”

Incubation time after pulsed electric field treatment of microalgae enhances the efficiency of extraction processes and enables the reduction of specific treatment energy

“…4) could however be explained by an autolysis-like process accelerated by permeabilisation of the plasma membrane and eventually of intracellular membrane leading to the intracellular release of still functional enzymes. In fact, PEF-treatment was already suggested as an autolysis inducer in the yeast Saccharomyces cerevisiae(Martínez et al, 2016). Future work should focus on elucidating the possible role of an autolysis-like process.…”