Behavior of yeast cells in aqueous suspension affected by pulsed electric field

• Published in: Journal of colloid and interface science 2006-08, Vol.300 (2), p.553-563
• Main Authors: El Zakhem, H., Lanoisellé, J.-L., Lebovka, N.I., Nonus, M., Vorobiev, E.
• Format: Article
• Language: English
• Subjects: Aqueous suspensions; Chemistry; Chemistry, Physical - methods; Culture Media - metabolism; Detergents - pharmacology; Electric Conductivity; Electric fields; Electric Stimulation; Electrical conductivity; Electricity; Electrochemistry - methods; Exact sciences and technology; Fungal Proteins - chemistry; General and physical chemistry; Ions; Non-ionic surfactant; Octoxynol - pharmacology; Osmosis; Percolation; Saccharomyces cerevisiae; Saccharomyces cerevisiae - metabolism; Temperature; Triton X-100; Water - chemistry; Yeast
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2006.04.055

This work discusses pulsed electric fields (PEF) induced effects in treatment of aqueous suspensions of concentrated yeast cells ( S. cerevisiae). The PEF treatment was done using pulses of near-rectangular shape, electric field strength was within E = 2 – 5   kV / cm and the total time of treatment was t PEF = 10 −4 – 0.1   s . The concentration of aqueous yeast suspensions was in the interval of C Y = 0 – 22 (wt%), where 1% concentration corresponds to the cellular density of 2 × 10 8   cells / mL . Triton X-100 was used for studying non-ionic surfactant additive effects. The electric current peak value I was measured during each pulse application, and from these data the electrical conductivity σ was estimated. The PEF-induced damage results in increase of σ with t PEF increasing and attains its saturation level σ ≈ σ max at long time of PEF treatment. The value of σ max reflects the efficiency of damage. The reduced efficiency of damage at suspension volume concentration higher than φ Y ≈ 32   vol% is explained by the percolation phenomenon in the randomly packed suspension of near-spherical cells. The higher cytoplasmic ions leakage was observed in presence of surfactant. Experiments were carried out in the static and continuous flow treatment chambers in order to reveal the effects of mixing in PEF-treatment efficiency. A noticeable aggregation of the yeast cells was observed in the static flow chamber during the PEF treatment, while aggregation was not so pronounced in the continuous flow chamber. The nature of the enhanced aggregation under the PEF treatment was revealed by the ζ-potential measurements: these data demonstrate different ζ-potential signs for alive and dead cells. The effect of the electric field strength on the PEF-induced extraction of the intracellular components of S. cerevisiae is discussed. This work discusses the PEF induced effects in treatments of concentrated yeast cells ( S. cerevisiae) aqueous suspensions. The nature of enhanced aggregation under the PEF treatment was revealed by the measurements of ζ-potentials: the data evidence the difference of ζ-potential signs between alive and dead cells.