Metagenomic and Mineral Characterisation of Biofloc Cultured With Anaerobically Treated Distillery Spent Wash

This study characterised the microbial community and mineral composition of biofloc cultured in three independently managed 50 t indoor raceway tanks (R1, R2 and R3) using anaerobically treated distillery spent wash as the exogenous carbon source. The mineral profile of the biofloc was determined for each tank by inductively coupled plasma mass spectrometry, whereas the microbial community was characterised by whole metagenome shotgun sequencing of a single composite library pooled across all nine biofloc samples. Eleven minerals were quantified, with calcium (Ca) the most abundant (26.71 mg g −1 ), followed by phosphorus (26.43 mg g −1 ) and sodium (14.87 mg g −1 ). Mineral content did not differ significantly among the three replicate tanks ( p > 0.05). Sequencing of the composite library yielded 11,154,421 high‐quality read pairs (2 × 150 bp; 3.31 Gb), from which 489,136 genes were predicted. Bacteria dominated the classified fraction at kingdom level (305,573 genes; 62.47% of predicted genes), and Proteobacteria was the most gene‐rich phylum (101,622 genes; 33.3% of bacterial genes), within which Alphaproteobacteria was the most abundant class (46,390 genes). Below class level, the most abundant single lineage was cyanobacterial: Oscillatoriales (30,631 genes) at order level, Leptolyngbyaceae (17,892 genes) at family level, Leptolyngbya (11,702 genes) at genus level and Leptolyngbya sp. JSC (10,682 genes) at species level. Functional annotation identified carbohydrate metabolism as the most highly represented SEED subsystem. Under these conditions the dried biofloc had high total mineral concentrations, and the pooled metagenome encoded a broad range of functional genes; neither nutritional value nor microbial activity was assessed. These data characterise this system rather than establish a comparative treatment effect. Controlled comparative studies, contaminant screening and animal performance trials are required before practical benefits can be claimed.