厌氧条件下希瓦氏菌腐殖质还原对偶氮还原的影响

The effects of the humic substances on Azoreduction by Shewanella spp.

以希瓦氏菌属的3个代表种为研究对象，研究了在厌氧条件下腐殖质的存在对偶氮还原的影响。实验结果表明：3个代表菌株在厌氧条件下都有高效的偶氮还原和腐殖质还原功能，1mmol／L偶氮染料在24h内完全脱色，并且偶氮还原与电子供体氧化存在着紧密的偶联关系。腐殖质物质模式物2-磺酸蒽醌AQS在小于1。2mmol／L条件下能显著加速偶氮还原，12h就完全脱色，3mmol／L时18h完全脱色。但当浓度大于3mmol／L时则对偶氮还原产生明显抑制作用。另一腐殖质模式物2，6-双磺酸蒽醌AQDS其浓度在1—3mmol／L以内亦使脱色在12h内完成，4—6mmol／L时15h左右完成脱色。7—12mmol／L仍有一定的脱色促进作用，但随着浓度的提高，其促进作用也逐渐减弱。这说明腐殖质的确可以作为氧化还原中间体穿梭于电子供体与染料的偶氮双键之间促进偶氮还原。但当其浓度达到某一阈值时它就显出与偶氮键竞争电子的本质，从而使偶氮还原速率下降。原因在于他们的氧化还原电势的差异，导致细菌呼吸链的电子递体对腐殖质物质和偶氮键的亲和力不同，从而使不同腐殖质浓度对偶氮键还原产生了不同的影响。

Under anaerobic conditions, Shewanella cinicaD14^T, Shewanella baltica and Shewane-lla putrefaciens are capable of highrate azoreduction and humus reduction. The results indicated that at low concentration （ 〈 2mmol/L） AQS was a accelerator for bacterial azoreduction. However, when the concentration of AQS was more than 5 mmol/L a strong inhibition was occurred. On the other hand, the concentration of AQDS as high as 12 mmol/L the inhibition of azoreduction was still not exhibited, but the effect of acceleration was gradually decreased with the concentration of AQDS increasing （lmmol/L to 12mmol/L）. 6 azo dyes （Table 1） were tested, all of which had a similar results. These results indicated that the humic substances were not only as a redox mediator during the azoreduction, but also as the competitor for electron from respiration chain. Because the humic substances could be act as the terminal electron acceptor for bacterial anaerobic respiration. AQS and AQDS exhibiting different behaviour on the azoreduction were determined by their standard redox potentials.