Computational analysis of successional changes in the microbial population and community diversity of the immobilized marine nitrifying bacterial consortium in a nitrifying packed bed bioreactor.

Nitrifying bioreactor (NBR) connected to the recirculating aquaculture system (RAS), has a greater emphasis on the biological treatment of wastewater. Nitrifying bacterial consortium (NBC) formed bio-film on the substratum activating the NBR, and it was observed with high nitrification potential in shrimp maturation systems. Scanning Electron Microscopy (SEM) revealed the integrity of the biofilm substantiated with biomineralization. The fate of the matured bio-film population on subsequent operation under RAS, and the aggregated population at different points of RAS, including the rearing water were determined using fingerprints of Denaturing Gradient Gel Electrophoresis (DGGE). Altogether, 38 OTUs of biofilm sample and 35 OTUs of water samples represented the bacterial communities; the shared and unique OTUs indicated the diversity of the population at different time intervals in the operation of the NBR. The mathematical (range-weighted richness) and statistical (diversity indices) interpretation unveiled the OTUs based high bacterial diversity in the biofilm supporting the compositional changes and determined the distance between the community cluster. Ordination analyses indicated the population shift and stability of the activated bio-film till the matured biofilm community got established in the RAS. The DGGE with mathematical and statistical analysis revealed microbial diversity (high Shannon index, species richness and evenness), abundance (relative intensity), consecutive change in the population composition (OTUs, Rr index), and the dynamics (Δt) in the system during the operation.

Community composition of marine and brackish water ammonia-oxidizing consortia developed for aquaculture application.

To mitigate the toxicity of ammonia in aquaculture systems, marine and brackish water ammonia-oxidizing bacterial consortia have been developed and are used for activation of nitrifying bioreactors integrated to recirculating aquaculture systems. To shed more light on to these biological entities, diversity of both the consortia were analyzed based on random cloning of 16S rRNA gene and ammonia-oxidizing bacterial specific amoA gene sequences. The dendrograms of representative clones on the basis of amplified ribosomal DNA restriction analysis generated 22 and 19 clusters for marine and brackish water nitrifying consortia, respectively. Phylogenetic analysis demonstrated the presence of various autotrophic nitrifiers belonging to α-, ß- and γ-Proteobacteria, anaerobic ammonia oxidizers, heterotrophic denitrifiers, Bacteroidetes, and Actinobacteria. Distribution patterns of the organisms within the two consortia were determined using the software Geneious and diversity indices were investigated using Mega 5.0, VITCOMIC and Primer 7. The abundance of ammonia oxidizers was found in the order of 2.21 ± 0.25 × 109 copies/g wet weight of marine consortium and 6.20 ± 0.23 × 107 copies/g of brackish water consortium. Besides, marine ammonia-oxidizing consortium exhibited higher mean population diversity and Shannon Wiener diversity than the brackish water counterparts.

Activated packed bed bioreactor for rapid nitrification in brackish water hatchery systems.

A packed bed bioreactor (PBBR) was developed for rapid establishment of nitrification in brackish water hatchery systems in the tropics. The reactors were activated by immobilizing ammonia-oxidizing (AMONPCU-1) and nitrite-oxidizing (NIONPCU-1) bacterial consortia on polystyrene and low-density polyethylene beads, respectively. Fluorescence in situ hybridization demonstrated the presence of autotrophic nitrifiers belong to Nitrosococcus mobilis, lineage of beta ammonia oxidizers and nitrite oxidizer Nitrobacter sp. in the consortia. The activated reactors upon integration to the hatchery system resulted in significant ammonia removal (P < 0.01) culminating to its undetectable levels. Consequently, a significantly higher percent survival of larvae was observed in the larval production systems. With spent water the reactors could establish nitrification with high percentage removal of ammonia (78%), nitrite (79%) and BOD (56%) within 7 days of initiation of the process. PBBR is configured in such a way to minimize the energy requirements for continuous operation by limiting the energy inputs to a single stage pumping of water and aeration to the aeration cells. The PBBR shall enable hatchery systems to operate under closed recirculating mode and pave the way for better water management in the aquaculture industry.