Development of a rapid startup technology applicable to autotrophic nitrogen removal

氨氧化菌和厌氧氨氧化菌由于其自身的自养特性，生长缓慢，一直是工程上的难题。为了缩短完全自养脱氮工艺的启动时间，对载体表面进行化学修饰，以吸引细菌粘附并形成生物膜。由于已经报道这些细菌生物膜的形成可能是由群体感应（quorum sensing，QS）机制作为细胞-细胞通讯介导的，因此本研究的另一个目的是阐明AOB和厌氧氨氧化细菌生物膜的形成机制。采用辐射接枝聚合法在聚乙烯非织造布上化学接枝甲基丙烯酸缩水甘油酯（GMA）。GMA的环氧基被转化为二乙胺（DEA片），以形成吸引细菌粘附的带正电荷的表面。DEA膜对AOB的固定化速度较快，固定化率是无纺布膜的104倍。氨氧化菌培养9d后，DEA膜的氨氧化速率比未处理膜高4.4倍。DEA膜强化了厌氧氨氧化菌污泥的固定化，使厌氧氨氧化速率提高了2.4倍。将能够降解QS介导的信号化合物，即N-酰基-L-高丝氨酸内酯（AHL）的酰化酶I固定在DEA片上。该片材上的AOB生物膜比原始非织造片材上的生物膜更不坚固并且更稀疏。这表明没有细胞-细胞通讯的AOB生物膜在片材上受到抑制，因为生物膜中的AHLs被破坏。另一方面，对于厌氧氨氧化生物膜没有观察到这种趋势。另一种机制涉及形成生物膜。

Ammonia-oxidizing bacteria (AOB) and anaerobic ammonium-oxidizing (anammox) bacteria have slow growth rates due to their autotrophic nature, which is always an engineering challenge. In order to shorten the startup time of a process for completely autotrophic nitrogen removal, surface of a bacterial carrier was chemically modified to attract bacterial adhesion and biofilm formation. Since it has been reported that these bacterial biofilm formations are potentially mediated by quorum sensing (QS) mechanism as cell-cell communication, another objective of the study was to elucidate biofilm formation mechanisms of AOB and anammox bacteria. Radiation-induced graft polymerization (RIGP) was applied to chemically graft glycidyl methacrylate (GMA) on a non-woven sheet made of polyethylene. The epoxy-group of GMA was converted into diethylamine (DEA sheet) to form a positively-charged surface attractive to bacterial adhesion. The DEA sheet immobilized AOB rapidly, the rate of which was 104-fold as high as a pristine non-woven sheet. After 9 day of AOB incubation, ammonia oxidation rate of DEA sheet was higher than that of the pristine sheet by a factor of 4.4. The DEA sheet enhanced immobilization of anammox bacterial sludge, resulting in 2.4 times higher anammox rate than that on a pristine non-woven sheet.An enzyme-immobilized sheet was fabricated to interrupt cell-cell communication among bacterial cells, which is a trigger to form biofilm. Acylase I, capable of degradingQS-mediated signaling compounds, i.e. N-acyl-L-homoserine lactones (AHLs), was immobilized onto a DEA sheet. AOB biofilm on this sheet was less robust and rather more sparse than that on a pristine non-woven sheet. This suggests that AOB biofilm without cell-cell communication was suppressed on the sheet because of breaking down AHLs in the biofilm. On the other hand, this trend was not observed regarding anammox biofilm. Another mechanism was involved to form the biofilm.