Effect of exogenous AHLs on ANAMMOX biofilm process under natural temperature in winter
Maintaining the efficient performance of anaerobic ammonia oxidation(ANAMMOX)biofilm under low-temperature conditions is a great challenge.The effects of two exogenous signaling molecules,hexanoyl homoserine lactone(C6-HSL)and octanoyl homoserine lactone(C8-HSL),on the ANAMMOX biofilm process were examined under the natural temperature in winter.The results showed that the addition of C6-HSL and C8-HSL promoted the nitrogen removal performance of the process under low temperature fluctuation,which increased the total nitrogen removal by 48.09％and 44.36％,respectively,and effectively enhanced the adaptability of ANAMMOX biofilm to the low-temperature environment.Under the low-temperature fluctuation,C6-HSL and C8-HSL regulated the activities of hydrazine dehydrogenase(HDH)(1.77and 1.57times higher than that of the control group,respectively),which significantly enhanced the activities of ANAMMOX;promoted the secretion of PN and PS in the extracellular polymers(EPS),especially in the TB-EPS,and altered the hydrophobicity of the secondary structure of proteins,which led to enhanced biofilm adhesion performance(The OD600values were enhanced by 55.12％and 68.32％,respectively).In addition,based on 16S rRNA sequencing,C6-HSL and C8-HSL effectively promoted the growth of Candidatus Kuenenia at low temperature and up-regulated the abundance of functional genes related to nitrogen metabolism.
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