Assessment of Heterotrophic Nitrification Capacity in Bacillus spp. and its Potential Application in the Removal of Nitrogen from Aquaculture Water

Abstract

The accumulation of nitrogen (-N) is a serious problem in aquaculture as it could lead to mass mortality events of the cultivated species. Chemilitotrophic nitrification is the most recognized in nitrogen removal underestimating the role of heterotrophic nitrifiers. In the present study, the heterotrophic nitrification capacity of 8 bacterial strains isolated from mangrove soil, periphyton and biofilters was evaluated. The strains were grown in heterotrophic nitrification base medium (HNM medium) with three different nitrogen sources, ammonium, nitrite or nitrate at a final concentration of 8 mg L -1 , 5 mg L -1 and 80 mg L -1 respectively. The concentration of nitrogen (-N) and OD (600 nm) were determined periodically. Only in 4 strains belonging to the Bacillus genus was the capacity for heterotrophic nitrification and aerobic denitrification observed. Among these strains, SM4 strain presented a good removal profile of ammonium, nitrite and nitrate, achieving an average nitrification efficiency of 98. 33 ± 2.89%, 83.67 ± 7.51% and 98.00 ± 0.01% respectively, and a nitrification rate (mg L -1 h -1 ) of 1.71 ± 0.70, 0.13 ± 0.07 and 0.21 ± 0.06 respectively. The nxrB, nirS, nirK genes in the selected strains were identified by PCR. Additionally, several proteins (enzymes) involved in the nitrogen cycle were identified by proteomic analysis, reporting for the first time the presence of the enzymes ammonia monoxygenase (AMO) and nitrite oxide reductase (NXR) in the genus Bacillus. These findings suggest that the strains studied would have a potential use in the biological removal of nitrogen in aquaculture systems.

Denitrification Characteristics of the Low-Temperature Tolerant Denitrification Strain Achromobacter spiritinus HS2 and Its Application

“…The enzyme of a strain might have multiple enzyme genes coexisting [ 40 ]. The strain HS2 possesses both Nap and NarG; similarly, Luz et al [ 41 ] found that Bacillus spp. possessed both NiRS and NiRK nitrite reductase enzymes.…”

Effect of symbiotic administration on growth and intestinal microbiota variation of pacú (Piaractus mesopotamicus) in recirculating aquaculture systems

“…Our results partially coincide with those, since Firmicutes were detected in the FGC of the fishes throughout the culture, standing out Asaccharospora irregularis (Firmicutes/Clostridiales) detected in all the experimental conditions, and Turicibacter sanguinis (Firmicutes) mainly in the control treatment; while another Firmicutes (Bacillus horti), was detected in MP treatment. The habitat of Bacillus is very wide and its application in aquaculture is widely documented (Mendoza et al, 2019;Soltani et al, 2019;Thurlow et al, 2019). Microbacterium aerolatum (Actinobacteria) isolated from marine environments has been detected in the activated symbiotic (Fig.…”

Denitrification Characteristics of the Low-Temperature Tolerant Denitrification Strain <em>Achromobacter spiritinus</em> HS2 and Its Application

“…A strain might have multiple enzyme genes coexisting [43]. Luz et al [44] found Bacillus spp. possessed both NiRS and NiRK nitrite reductase enzymes, the same as the strain HS2 possesses both Nap and NarG.…”