Enterobacter aerogenes metabolites enhance Microcystis aeruginosa biomass recovery for sustainable bioflocculant and biohydrogen production

Highlights: • Bioflocculant from E. aerogenes is involved in the bioflocculation of M. aeruginosa. • M. aeruginosa is the substrate for bioflocculant and biohydrogen production. • Bioflocculant yield from 20 g/L of wet biomass of M. aeruginosa was 3.6 ± 0.1 g/L. • The highest yield of biohydrogen was 35 mL of H₂/g (dw) algal biomass. • The metabolic pathways of bioflocculant and biohydrogen production were determined. We report a recycling bioresource involving harvesting of Microcystis aeruginosa using the bioflocculant (MBF-32) produced by Enterobacter aerogenes followed by the recovery of the harvested M. aeruginosa as the main substrate for the sustainable production of MBF-32 and biohydrogen. The experimental results indicate that the efficiency of bioflocculation exceeded 90% under optimal conditions. The harvested M. aeruginosa was further recycled as the main substrate for the supply of necessary elements. The highest yield (3.6 ± 0.1 g/L) of MBF-32 could be obtained from 20 g/L of wet biomass of M. aeruginosa with an additional 20 g/L of glucose as the extra carbon source. The highest yield of biohydrogen was 35 mL of H₂/g (dw) algal biomass, obtained from 20 g/L of wet biomass of M. aeruginosa with an additional 10 g/L of glycerol. Transcriptome analyses indicated that MBF-32 was mainly composed of polysaccharide and tyrosine/tryptophan proteins. Furthermore, NADH synthase and polysaccharide export-related genes were found to be up-regulated.