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% CO 2 . Algae and cyanobacteria remediate metals and CO 2 , but use of N 2 -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 CO 2 - 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% CO 2 or not (non-CO 2 controls). CO 2 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 CO 2 -addition, while As, Mo, Se and Sr removal was higher (30–87%) for non-CO 2 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 CO 2 could yield high-value phycobiliproteins, bioethanol or biogas, and mineral-rich nitrogen fertilizer which would offset remediation costs and improve agricultural productivity.

Tropical N 2 -fixing cyanobacteria offer an attractive alternative for production of biomass and bioproducts with potentially low cultivation and harvesting costs. The present study evaluated the biomass productivity of the N 2 -fixing cyanobacterium Tolypothrix sp. NQAIF319 grown in nitrogen-free medium in outdoor suspension and biofilm prototype cultivation systems in tropical Australia (Queensland). One-week cycles yielded maximum biomass productivitiesestimated based on ground area occupied by single systemsof 45-49 g dry weight m −2 day −1 (suspension) and 1.0-1.2 g dry weight m −2 day −1 (biofilm) with minimal biological contamination (Tolypothrix sp. biomass representing 94-98 % of the photosynthetic community). Moderate productivities of t h e pi g m e n t s ph y c o c y a n in/p hyc oe ryth rin ( 0.1 -2.8 g m −2 day −1 ), fatty acids (0.1-2.0 g m −2 day −1 ), and nitrogen stored in the biomass (0.1-5.9 g m −2 day −1 ) were reached in biofilm and suspension systems, respectively, opening avenues for production of low-value commodities with potentially big markets (nitrogen-rich biofertilizers and a q u a c u l t u r e f e e d ) a n d h i g h e r-v a l u e c h e m i c a l s (phycobiliproteins and fatty acids). Simulated multi-system arrangements yielded theoretical overall areal productivities four to six times lower than those in single systems thus highlighting the need for future tests fine-tuning inter-system separation to minimize shadowing while maximizing the efficiency in land use in larger-scale production plants. Biofilm and self-flocculated biomass showed 80-fold and 53-fold reduced extracellular-water contents compared to suspension cultures, respectively, which will need to be considered for techno-economic and water/carbon footprint evaluation of each of the possible bioproduct synthesis pathways. In conclusion, the flexible and simple prototypes developed together with the good properties of Tolypothrix sp. represent a promising platform for low-cost production of cyanobacterial bioproducts in tropical regions using low nitrogen-containing water sources.

Rising CO 2 levels, associated climatic instability, freshwater scarcity and diminishing arable land exacerbate the challenge to maintain food security for the fast growing human population. Although coal-fired power plants generate large amounts of CO 2 emissions and wastewater, containing environmentally unsafe concentrations of metals, they ensure energy security. Nitrogen (N 2 )-fixation by cyanobacteria eliminate nitrogen fertilization costs, making them promising candidates for remediation of waste CO 2 and metals from macronutrient-poor ash dam water and the biomass is suitable for phycocyanin and biofertilizer product development. Here, the effects of CO 2 and metal mixtures on growth, bioproduct and metal removal potential were investigated for the self-flocculating, N 2 -fixing freshwater cyanobacterium Tolypothrix sp. Tolypothrix sp. was grown outdoors in simulated ash dam wastewater (SADW) in 500 L vertical bag suspension cultures and as biofilms in modified algal-turf scrubbers. The cultivation systems were aerated with air containing either 15% CO 2 (v/v) or not. CO 2 -fertilization resulted in ∼1.25-and 1.45-fold higher biomass productivities and ∼40 and 27% increased phycocyanin and phycoerythrin contents for biofilm and suspension cultures, respectively. CO 2 had no effect on removal of Al, As, Cu, Fe, Sr, and Zn, while Mo removal increased by 37% in both systems. In contrast, Ni removal was reduced in biofilm systems, while Se removal increased by 73% in suspension cultures. Based on biomass yields and biochemical data obtained, net present value (NPV) and sensitivities analyses used four bioproduct scenarios: (1) phycocyanin sole product, (2) biofertilizer sole product, (3) 50% phycocyanin and 50% biofertilizer, and (4) 100% phycocyanin and 100% biofertilizer (residual biomass) for power station co-located and not colocated 10 ha facilities over a 20-year period. Economic feasibility for the production of food-grade phycocyanin either as a sole product or with co-production of biofertilizer was demonstrated for CO 2 -enriched vertical and raceway suspension cultures raised without nitrogen-fertilization and co-location with power stations significantly increased profit margins.

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The necessity to safeguard the environment has increased the potential of enzyme usage in textile processing to ensure eco-friendly production. Laccase enzyme formulation has been used in textile processing such as biobleaching, dyeing, rove scouring, finishing, neps removal, printing, wash-off treatment, dye synthesis and effluent treatment. However, a high cost associated with biocatalyst production is still a hindrance to their use. Pleurotus ostreatus is a white-rot fungus that produces a ligninolytic enzyme complex rich in several laccase iso-enzymes. The main objective of this study is optimize influence of pH and stability of divalent metal ion-immobilzed crude laccase enzyme towards decolourization of prototype textile dyes such as Reactive red 80 (Red F3B) and Reactive blue 21(T Blue G). Wheat bran is used as a lead candidature for production of lignolytic enzyme using Pleurotus osteratus by solid state fermentation. Two divalent metal ions such as Zn2 + and Ca2 + were selected to study the influence of metal ions towards the dye decolourization. Results revealed that Ca2 + ion was better compared to Zn2 + ion towards enzyme immobilization and its influence on dye decolourization in the optimal pH 5.5. Finally, interactions between laccase and dyes were studied exclusively using Insilco structure based molecular docking methods.