Dept. of Chemical Engineering, Indian Institute of Science, Bangalore, India.
Biotechnol Prog. 2009 Sep-Oct;25(5):1328-42. doi: 10.1002/btpr.200.
Ferrous iron bio-oxidation by Acidithiobacillus ferrooxidans immobilized on polyurethane foam was investigated. Cells were immobilized on foams by placing them in a growth environment and fully bacterially activated polyurethane foams (BAPUFs) were prepared by serial subculturing in batches with partially bacterially activated foam (pBAPUFs). The dependence of foam density on cell immobilization process, the effect of pH and BAPUF loading on ferrous oxidation were studied to choose operating parameters for continuous operations. With an objective to have high cell densities both in foam and the liquid phase, pretreated foams of density 50 kg/m(3) as cell support and ferrous oxidation at pH 1.5 to moderate the ferric precipitation were preferred. A novel basket-type bioreactor for continuous ferrous iron oxidation, which features a multiple effect of stirred tank in combination with recirculation, was designed and operated. The results were compared with that of a free cell and a sheet-type foam immobilized reactors. A fivefold increase in ferric iron productivity at 33.02 g/h/L of free volume in foam was achieved using basket-type bioreactor when compared to a free cell continuous system. A mathematical model for ferrous iron oxidation by Acidithiobacillus ferrooxidans cells immobilized on polyurethane foam was developed with cell growth in foam accounted by an effectiveness factor. The basic parameters of simulation were estimated using the experimental data on free cell growth as well as from cell attachment to foam under nongrowing conditions. The model predicted the phase of both oxidation of ferrous in shake flasks by pBAPUFs as well as by fully activated BAPUFs for different cell loadings in foam. Model for stirred tank basket bioreactor predicted within 5% both transient and steady state of the experiments closely for the simulated dilution rates. Bio-oxidation at high Fe(2+) concentrations were simulated with experiments when substrate and product inhibition coefficients were factored into cell growth kinetics.
研究了固定在聚氨酯泡沫上的嗜酸氧化亚铁硫杆菌对二价铁的生物氧化作用。通过将细胞置于生长环境中，将细胞固定在泡沫上，并通过分批传代培养部分细菌激活的泡沫（pBAPUFs）来制备完全细菌激活的泡沫（BAPUFs）。研究了泡沫密度对细胞固定化过程的依赖性、pH 值和 BAPUF 负载对二价铁氧化的影响，以选择连续操作的运行参数。为了在泡沫和液相中都获得高细胞密度，优选预处理密度为 50kg/m3 的泡沫作为细胞支撑物，并在 pH1.5 下进行二价铁氧化以适度控制铁的沉淀。设计并运行了一种用于连续二价铁氧化的新型篮式生物反应器，其特点是结合循环具有搅拌罐的多重效果。将其结果与游离细胞和片状泡沫固定化反应器进行了比较。与游离细胞连续系统相比，使用篮式生物反应器在泡沫的自由体积为 33.02g/h/L 时，铁的产量提高了五倍。建立了固定在聚氨酯泡沫上的嗜酸氧化亚铁硫杆菌细胞氧化二价铁的数学模型，该模型通过有效因子来描述泡沫中的细胞生长。使用游离细胞生长的实验数据以及在非生长条件下细胞附着到泡沫的实验数据来估计模拟的基本参数。该模型预测了在不同泡沫中细胞负载下，pBAPUFs 和完全激活的 BAPUFs 在摇瓶中氧化二价铁的阶段。搅拌罐篮式生物反应器模型预测的模拟稀释率的瞬态和稳态与实验值相差在 5%以内。当将基质和产物抑制系数纳入细胞生长动力学中时，模拟了高 Fe(2+)浓度下的生物氧化。
