A comparative analysis of omics and microbial composition of biofloc based on carbon source and C:N ratio addition strategies

Biofloc technology transforms nitrogen wastes into microbial biomass, that can be consumed in situ by cultured animals. The process requires addition of an exogenous carbon source at a specific carbon-to-nitrogen (C:N) ratio. In this study, three carbon sources at 10:1, 18:1, and 26:1 C:N ratios were tested under super-intensive conditions (350 P.vannamei /m³): molasses (MOL, control), yeast (YST), with an initial brewer's yeast addition and polybutylene succinate (PBS, as slow-release carbon source). Through biofloc maturation, the water quality parameters remained optimal, with PBS strategy and low-to-intermediate C:N ratios exhibiting reduced nitrogen and phosphate levels. The mineral dynamics evidenced that seawater and biofloc experienced a decrease in Ca, K, Mg, and Sr while shrimp accumulated these elements over time. Additionally, the biofloc acted as a mineral reservoir accumulating several times more ions than water and shrimp. Carbon strategies influenced bacterial composition of biofloc differently, with YST treatment supporting dominant bacterial groups, while PBS favored less abundant taxa. Both MOL and YST promoted an increase in heterotrophic bacteria, however, MOL exhibited a more balanced distribution of key bacterial groups involved in the nitrogen cycle. Regarding shrimp performance, PBS produced the lowest specific growth rate despite showing better water quality and higher bacterial diversity, likely due to reduced heterotrophic bacteria. Finally, a principal component analysis highlighted the interactions between water quality, bacterial diversity and shrimp growth. Overall, the findings suggest that MOL carbon addition strategy at low-to-intermediate C:N ratios as the most recommendable based on its more balanced bacterial composition and good shrimp performance. • PBS strategy resulted in a higher diversity but lower shrimp specific growth. • The bacteria diversity increased as heterotrophic bacteria decreased. • Biofloc acted as a mineral sink, with ions 5–8 × higher than water or shrimp tissues. • MOL strategy ensured a more balanced key functions, especially in nitrogen cycle.