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A Novel Bioreactor for High Density Cultivation of Diverse Microbial Communities
Published on: December 25, 2015
Bioaugmentation with novel direct ammonia-oxidizing bacteria enhances nitrogen removal in microalgal-bacterial
Chengyi Luo1, Qixing Hu1, Long Cheng2
1Green Energy Industry Research Center, Huazhong University of Science and Technology (HUST), Wuhan 430074, China; Hubei Key Laboratory of Multi-media Pollution Cooperative Control in Yangtze Basin, School of Environmental Science & Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074, China.
Abstract:
Nitrate accumulation remains a major constraint for nitrogen removal in microalgal-bacterial granular sludge (MBGS) systems, primarily due to insufficient denitrification within oxygen-rich microenvironments. This study investigated the effects of bioaugmenting MBGS with two direct ammonia-oxidizing (Dirammox) bacteria, Acinetobacter sp. ACI-9 and Alcaligenes ammonioxydans sp. HO-1, with particular emphasis on extracellular polymeric substances (EPS) characteristics, microbial community structure, and nitrogen transformation pathways. Three parallel sequencing batch reactors (SBRs) were operated for 70 days: a control reactor (RN), and two bioaugmented reactors inoculated with ACI-9 (RA) and HO-1 (RH), respectively. Bioaugmentation preserved granule structural stability and enhanced overall nitrogen removal performance. Relative to the control, ACI-9 bioaugmentation reduced nitrate accumulation by 19.26%, whereas HO-1 exerted a comparatively weaker effect. Microbial community analyses revealed increased community diversity and the selective enrichment of taxa associated with floc formation, endogenous carbon turnover, and nitrogen reduction processes. Functional gene profiling suggested coordinated shifts in genes involved in nitrate processing and downstream denitrification following bioaugmentation. In particular, ACI-9 showed a stronger late-stage nosZ-associated signal than HO-1, while the Dirammox-related gene dnfABC remained detectable in all reactors, suggesting persistent Dirammox-related genetic potential in the MBGS system. Overall, ACI-9 induced more pronounced structural and functional responses than HO-1, underscoring the critical role of strain-specific pathway integration in mitigating nitrate accumulation and improving nitrogen removal efficiency in MBGS systems.
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