This study was supported by CONCYTEC-FONDECYT en el marco de la convocatoria ?Proyecto Investigaci?n B?sica 2019-01? (grant numbers 355-2019) and by the Vicerrectorado de Investigaci?n y Posgrado de la Universidad Nacional Mayor de San Marcos en el marco de la convocatoria ?Proyecto de Investigaci?n con financiamiento para Grupos de Investigaci?n 2021?. This study was also partially supported by the Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq grant numbers 404984/2018-5 and 301469/2018-0) and the Funda??o Carlos Chagas de Amparo ? Pesquisa do Estado do Rio de Janeiro, Brazil (FAPERJ, grant number E-26/202.909/2017).

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 prese...