Effect of CO2 and metal-rich waste water on bioproduct potential of the diazotrophic freshwater cyanobacterium, Tolypothrix sp

Chinnathambi Velu; Samuel Cirés; Diane L Brinkman; Kirsten Heimann

doi:10.1016/j.heliyon.2019.e01549

Effect of CO₂ and metal-rich waste water on bioproduct potential of the diazotrophic freshwater cyanobacterium, Tolypothrix sp

Heliyon. 2019 Apr 29;5(4):e01549. doi: 10.1016/j.heliyon.2019.e01549. eCollection 2019 Apr.

Authors

Chinnathambi Velu¹, Samuel Cirés^{1

2}, Diane L Brinkman³, Kirsten Heimann^{4

1}

Affiliations

¹ College of Science and Engineering, James Cook University, Townsville, Australia.
² Department of Biology, Autonoma de Madrid University, Madrid, ES, 28049, Spain.
³ Australian Institute of Marine Science (AIMS), Townsville, 4810, Queensland, Australia.
⁴ Centre for Marine Bioproduct Development, Flinders University, Bedford Park, SA, 5042, Australia.

Abstract

Continued economic growth is reliant on stable, affordable energy, requiring at present fossil fuel-derived energy production. Coal-fired power stations produce metal-rich but macro-nutrient-poor waste waters and emit flue gas, containing ∼10% CO₂. Algae and cyanobacteria remediate metals and CO₂, but use of N₂-fixing (diazotrophic) cyanobacteria can reduce nitrogen-fertilization costs. The resulting biomass represents a promising source for biofuel and bio-product development. This study investigated the effect of CO₂- and trace metals on growth performance, biochemical profiles and metal content of the freshwater diazotrophic cyanobacterium Tolypothrix sp. to assess bioproduct potential. Aerated 2 L batch cultures were grown in simulated ash-dam water (SADW) and BG11 without nitrogen (BG11(-N) controls). Supplied air was supplemented with either 15% CO₂ or not (non-CO₂ controls). CO₂ supplementation resulted in 2.4 and 3.3-fold higher biomass productivities and 1.3 and 1.2-fold higher phycocyanin and phycoerythrin contents, whilst metals (media) had no effect. Al, Cu, Ni and V were more efficiently removed (50-90%) with CO₂-addition, while As, Mo, Se and Sr removal was higher (30-87%) for non-CO₂ controls. No significant effect on Zn and Fe removal was evident. Calculated biomass metal concentrations, at quantities required to meet N-requirements of wheat, suggests no metal toxicity when applied as a mineral-nitrogen biofertilizer. With a carbohydrate content of 50%, the biomass is also suitable for bioethanol production. In summary, Tolypothrix sp. raised in ash dam waste water supplemented with flue gas CO₂ could yield high-value phycobiliproteins, bioethanol or biogas, and mineral-rich nitrogen fertilizer which would offset remediation costs and improve agricultural productivity.

Keywords: AD, anaerobic digestion; ADW, ash dam water; Agriculture; BSA, bovine serum albumin; Biochemistry; Biotechnology; DW, dry weight; EPS, exocellular polymeric substances; FA, fatty acids; GHG, greenhouse gas; MUFA, mono-unsaturated fatty acids; PBP, phycobiliproteins; PC, phycocyanin; PE, phycoerythrin; PUFA, polyunsaturated fatty acids; Plant biology; SADW, simulated ash dam water; SFA, saturated fatty acids; TFA, total fatty acids; Yprod, production year.