纤铁矿微生物异化还原过程的动力学特征及其影响因素

The kinetic characteristics of the microbial dissimilatory reduction of lepidocrocite

基于脱色希瓦氏菌(Shewanella decolorationis S12)和纤铁矿相互作用的现象,探讨了电子供体、纤铁矿浓度及氧化还原中介体2-磺酸钠蒽醌(AQS)对其相互作用的影响.结果表明,AQS的加入使纤铁矿的微生物还原程度得到加强.反应末期,乳酸钠浓度为20mmol.L-1时,在添加AQS的10.0mmol.L-1的纤铁矿体系中,被还原解离出的Fe(Ⅱ)浓度是无AQS体系中的180.2%.纤铁矿的归一化还原速率表明,当电子供体浓度一定时,随着纤铁矿浓度的增加,纤铁矿的还原酶促反应显著减弱.米氏拟合方程表明,以不同浓度的纤铁矿为底物时,S12菌-纤铁矿相互作用过程的拟合校正R2系数分别为0.8285(添加AQS)和0.9348(未添加AQS),电子转移载体的存在及底物类型的不同均对底物饱和时的反应速度(Vmax)和米氏常数(Km)值均有一定程度的影响.在微生物还原纤铁矿过程中,氧化还原中介体AQS使得其还原程度加剧,用于ATP合成所需能量ΔE值也随之升高,S12菌和纤铁矿的还原反应达到平衡时,Gibbs自由能变化(ΔGr)达最大值.

Dissimilatory Fe（Ⅲ） and Mn（Ⅳ） oxide reduction by microorganisms has an important influence on the geochemistry and fate of organic or metal contaminants in the environment. Identification of the kinetic characteristics of the microbial reduction of Fe（ Ⅲ ） and Mn（Ⅳ ） oxide is the key to understand the mechanism of the interaction of ＂ microbial-oxide-contaminants＂. The current study mainly discussed the influence of anthraquinone-2- sulfonate （AQS）, the concentration of the electron donor and lepidocrocite on the reduction of lepidoerocite by S12. The results showed that the electron shuttle, AQS, can enhance the degree of lepidocroeite reduction. In the system containing 20 mmol· L^-1 lactate and 10 mmol· L^-1 lepidocrocite, the reductively produced Fe（ Ⅱ ） concentration was as much as 1.80 times that in the non-AQS addition cell-lepidocroeite reaction system. The Michaelis- Meuten kinetic model fit calculations showed significant correlation between the initial reduction rate and the substrate concentration with a correlation coefficient, Adj. R-Square,R2, as high as 0. 9348. The electron shuttle, AQS, had considerable influence on Vmax and Km values and enhanced the degree of the bioreduction of lepidocrocite, leading to more energy （△E） driving ATP synthesis. When the microbial redox reaction almost kept in balance, the △Gr values reached the maximum.