低氧条件下不同电子受体对克雷伯氏菌降解菲的影响

Effects of Different Electron Acceptors on the Biodegradation of Phenanthrene by Klebsiella sp. ZS1 under Low-Oxygen Condition

为考察低氧条件下不同电子受体对于克雷伯氏菌(Klebsiella sp.ZS1,下称ZS1)降解菲的影响,在8%氧分压下,分别添加20 mmol/L Na_2SO_4、20 mmol/L NaNO_3、10 mmol/L FeCl_3为电子受体进行降解菌的培养.通过分光光度法和平皿计数法分别测定电子受体消耗率和菌体生长量,并采用气-质联用法(GC-MS)测定ρ(菲),对不同电子受体影响下的菌体生长量和ρ(菲)进行单因素方差分析.结果表明,在低氧环境下ZS1降解菲过程中,SO_4^(2-)、NO_3^-、Fe^(3+)的消耗率分别为74.7%、0.2%、4.5%;电子转移速率分别为1 899、0.366 3、7.679μmol/d.未接种ZS1时,ρ(菲)只减少了10.1%;接种ZS1后,不添加电子受体和分别添加SO_4^(2-)、NO_3^-、Fe^(3+)下菲的降解率分别为68.9%、86.2%、72.9%和68.5%,一级动力学方程求得的降解速率常数分别为0.181、0.360、0.186、0.183 d-1.添加SO_4^(2-)组ZS1的生长量是不添加电子受体组的2.5倍,而添加NO_3^-或Fe^(3+)时与不添加电子受体组基本相等.研究显示,在低氧条件下,ZS1降解菲过程中可同时利用SO_4^(2-)和O_2为电子受体;添加SO_4^(2-)作为外源电子受体对ZS1的生长及降解能力有很强的促进作用;而添加NO_3^-和添加Fe^(3+)对ZS1降解菲和ZS1的生长没有显著影响.

In order to investigate the effects of different electron acceptors on the degradation of polycyclic aromatic hydrocarbons by Klebsiella sp. ZS1 under low-oxygen condition,the biodegradation ability was tested with the addition of three common electron acceptors,namely,20 mmol/L Na_2SO_4,20 mmol/L NaNO_3,and 10 mmol/L FeCl_3. Low-oxygen condition（ 8% O_2） was controlled in a hypoxia station. The electron acceptor utilization and bacterial growth were measured by the national standard analytical methods; the remaining phenanthrene was determined by gas chromatography-mass spectrometry（ GC-MS）. Changes of the bacterial growth and the remaining phenanthrene were analyzed by one-way ANOVA. The results showed that ZS1 used SO_4^（2-）,NO_3^- and Fe^（3＋） as electron acceptors at the utilization ratio of 74. 7%,0. 2% and 4. 5%,respectively. Meanwhile,the electron transfer rates were 1899、0. 3663、7. 679 μmol/d,respectively. Phenanthrene only decreased by 10. 1% without inoculating ZS1. However,when ZS1 was inoculated,the degradation rates of no addition of electron acceptor and addition of SO_4^（2-）,NO_3^- and Fe^（3＋） were 68. 9%, 86. 2%, 72. 9% and 68. 9%,respectively. The degradation rate constants determined using a first-order kinetic equation were 0. 181,0. 360,0. 186 and 0. 183d- 1. The bacteria growth with SO_4^（2-）addition group was 2. 5times that of the control group,while the groups with addition of NO_3^- and Fe^（3＋）were similar to the control group,respectively.The results indicated that ZS1 can use SO_4^（2-）and O_2 at the same time as its electron acceptor under low-oxygen conditions,while NO_3^- and Fe^（3＋） cannot be used. Furthermore,the addition of SO_4^（2-）as an electron acceptor obviously stimulated the biodegradation of phenanthrene and the growth of the strain when compared to the control. However,the addition of NO_3^- and Fe^（3＋）had no statistically significant effect either on the reduction of phenanthrene or the growth of the bacterium.