El Zakhem H, Lanoisellé J-L, Lebovka N I, Nonus M, Vorobiev E
Laboratoire de Génie des Procédés Industriels, UMR CNRS 6067, BP20529, Département Génie Chimique, University of Technology of Compiégne, 60205 Compiègne, France.
J Colloid Interface Sci. 2006 Aug 15;300(2):553-63. doi: 10.1016/j.jcis.2006.04.055. Epub 2006 Apr 25.
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 2x10(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 sigma was estimated. The PEF-induced damage results in increase of sigma with t(PEF) increasing and attains its saturation level sigma approximately sigma(max) at long time of PEF treatment. The value of sigma(max) reflects the efficiency of damage. The reduced efficiency of damage at suspension volume concentration higher than phi(Y) approximately 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 zeta-potential measurements: these data demonstrate different zeta-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.
本文探讨了脉冲电场（PEF）对浓缩酵母细胞（酿酒酵母）水悬浮液处理的诱导效应。PEF处理采用近似矩形脉冲，电场强度在E = 2 - 5 kV/cm范围内，总处理时间为t(PEF)=10(-4)-0.1 s。酵母水悬浮液的浓度在C(Y)=0 - 22（wt%）区间，其中1%的浓度对应细胞密度为2x10(8)个细胞/mL。使用Triton X - 100研究非离子表面活性剂添加剂的影响。在每次施加脉冲期间测量电流峰值I，并根据这些数据估算电导率σ。PEF诱导的损伤导致σ随着t(PEF)增加而增大，并在长时间PEF处理时达到其饱和水平σ≈σ(max)。σ(max)的值反映了损伤效率。在悬浮液体积浓度高于约32 vol%的φ(Y)时损伤效率降低，这是由近球形细胞随机堆积悬浮液中的渗流现象所解释的。在存在表面活性剂的情况下观察到较高的细胞质离子泄漏。为了揭示混合对PEF处理效率的影响，在静态和连续流动处理室中进行了实验。在PEF处理期间，在静态流动室中观察到酵母细胞有明显聚集，而在连续流动室中聚集不那么明显。通过ζ电位测量揭示了PEF处理下增强聚集的性质：这些数据表明活细胞和死细胞具有不同的ζ电位符号。讨论了电场强度对PEF诱导的酿酒酵母细胞内成分提取的影响。
