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Conversion of stranded waste-stream carbon and nutrients into value-added products via metabolically coupled binary heterotroph-photoautotroph system

Bohutskyi, Pavlo, Kucek, Leo A., Hill, Eric, Pinchuk, Grigoriy E., Mundree, Sagadevan G., Beliaev, Alexander S.
Bioresource technology 2018 v.260 pp. 68-75
Bacillus subtilis, Haematococcus pluvialis, algae, astaxanthin, biomass, carbon, carbon dioxide, chemical oxygen demand, coculture, mass transfer, nitrogen content, nutrients, oxygen, phosphorus, photosynthesis, value-added products, waste treatment, wastes
Growth of heterotrophic bacterium Bacillus subtilis was metabolically coupled with the photosynthetic activity of an astaxanthin-producing alga Haematococcus pluvialis for conversion of starch-containing waste stream into carotenoid-enriched biomass. The H. pluvialis accounted for 63% of the produced co-culture biomass of 2.2 g/L. Importantly, the binary system requires neither exogenous supply of gaseous substrates nor application of energy-intensive mass transfer technologies due to in-situ exchange in CO2 and O2. The maximum reduction in COD, total nitrogen and phosphorus reached 65%, 55% and 30%, respectively. Conducted techno-economic assessment suggested that the astaxanthin-rich biomass may potentially offset the costs of waste treatment, and, with specific productivity enhancements (induction of astaxanthin to 2% and increase H. pluvialis fraction to 80%), provide and additional revenue stream. The outcome of this study demonstrates a successful proof-of-principle for conversion of waste carbon and nutrients into value-added products through metabolic coupling of heterotrophic and phototrophic metabolisms.