Leenen E J, Boogert A A, van Lammeren A A, Tramper J, Wijffels R H
Department of Food Science, Food and Bioprocess Engineering Group, Wageningen Agricultural University, P.O. Box 8129, 6700 EV Wageningen, The Netherlands.
Biotechnol Bioeng. 1997 Aug 20;55(4):630-41. doi: 10.1002/(SICI)1097-0290(19970820)55:4<630::AID-BIT5>3.0.CO;2-I.
The dynamics of growth and death of immobilized Nitrosomonas europaea were studied. For this, the death rate of suspended cells was determined in the absence of ammonium or oxygen by following the loss of respiration activity and by fluorescein-diacetate (FDA)/lissamine-green staining techniques. The death rates obtained (1.06 x 10(-6) s(-1) or 4.97 x 10(-6) s(-1) in the absence of oxygen or ammonium, respectively) were incorporated in a dynamic growth model and the effects on the performance of the immobilized-cell process illustrated by model simulations.These model simulations and experimental validation show that if decay of biomass occurs the biomass concentration in the center of the bead decreases. As a result, the systems react slower to changes in substrate concentrations than if all cells remain viable.To show that cells in the center of the bead died, the FDA and lissamine-green staining techniques were adapted for immobilized cells. It was shown that biomass decay occurred, especially in the center of the bead; the amount of cells decreased there, and the remaining cells were all stained with lissamine green indicating cell death. After the substrate availability was decreased, also cells near the surface of the bead lost their viability. The number of viable cells increased again after increasing the substrate concentration as the result of cell multiplication. At low substrate concentrations and low hydraulic retention times, as for example in the treatment of domestic wastewater, the death rate of cells is thus an important parameter for the performance of the immobilized-cell system. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 630-641, 1997.
研究了固定化欧洲亚硝化单胞菌的生长和死亡动力学。为此，通过跟踪呼吸活性的丧失以及利用荧光素二乙酸酯（FDA）/丽丝胺绿染色技术，在无铵或无氧条件下测定悬浮细胞的死亡率。将得到的死亡率（分别在无氧或无铵条件下为1.06×10⁻⁶ s⁻¹或4.97×10⁻⁶ s⁻¹）纳入动态生长模型，并通过模型模拟来说明其对固定化细胞过程性能的影响。这些模型模拟和实验验证表明，如果生物量发生衰减，珠子中心的生物量浓度会降低。结果，与所有细胞都保持存活的情况相比，该系统对底物浓度变化的反应更慢。为了证明珠子中心的细胞死亡，对FDA和丽丝胺绿染色技术进行了调整以用于固定化细胞。结果表明生物量发生了衰减，尤其是在珠子中心；那里的细胞数量减少，剩余的细胞都被丽丝胺绿染色，表明细胞死亡。底物可用性降低后，珠子表面附近的细胞也失去了活力。由于细胞增殖，底物浓度增加后，活细胞数量再次增加。在低底物浓度和低水力停留时间下，例如在生活污水处理中，细胞死亡率因此是固定化细胞系统性能的一个重要参数。（c）1997约翰威立父子公司。生物技术与生物工程55:630 - 641，1997。
