Amaranth and wheat grains tested as nucleation sites of microbial communities to produce bioflocs used for shrimp culture

The taxonomy profiles of bacterial communities contained in bioflocs produced with amaranth (BFT_Amaranth) and wheat (BFT_Wheat) grains as substrates, and used for shrimp culture were evaluated. The proliferation of heterotrophic bacteria was promoted by maintaining a carbon:nitrogen ratio of 12:1. High throughput sequencing of the 16S-rRNA gene revealed that the maximum difference between BFT_Amaranth and BFT_Wheat was registered at the beginning of the trial, when BFT_Wheat was dominated by Bacteroidetes (80-85%), whereas BFT_ Amaranth was dominated by Planctomycetes (42%), Proteobacteria (26%) and Bacteroidetes (16%). However, the taxonomic profile of both biofloc types were similar at the end of the trial, suggesting that the type of substrate affected the initial biofouling process, but the similar physicochemical conditions maintained during the trial favored the same heterotrophic communities in both treatments; herein, only 97 were shared between BFT_Wheat and BFT_Amaranth at the beginning of the trial, but 185 at the end. Thereafter, a better productive response in terms of survival, growth rate and FCR was registered for shrimp reared with BFT_Wheat, which corresponded to the biofloc registering the highest protein content at the end of the trial (18.5%), compared to BFT_Amaranth (12.7%). Finally, despite the high similarity detected among both biofloc types, this may not be strongly associated with their nutritional composition, nor the massification rate of these microbial communities.