Increasing biomass production yields is a critical challenge for macroalgae biorefineries. The continuous tumbling and mixing of free?floating algae through water or airflow has been shown to increase the productivity of algae in land?based cultivation systems. This approach has not been tested thoroughly in offshore cultivation. We report, here, a field feasibility study on the increase in green macroalga Ulva sp. growth rates in offshore cages, achieved by the combined effect of tumbling and mixing of the algae using influxes of water and air. The experimental system was tested in a shallow coastal area in central Israel, in the eastern Mediterranean Sea. A maximum daily growth rate of 19.2%, areal productivity of 33.72 g dry weight (DW) day−1 m−2, and volumetric yields of 37.78 g DW day−1 m−3, together with 38.47 ± 0.01% ash and 5.28% protein content on a dry matter basis were achieved in the cages with intensified cultivation in the first week of May 2017. Our study shows that cultivation with tumbling and mixing of biomass with air, and water exchange with the environment is a feasible method to increase Ulva sp. biomass productivity offshore. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd
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Figure S1. Temperature profile in aerated and not aerated cages in June?July 2017. Figure S2. DGR of Ulva biomass in the controlled, on land 1.5 L bottles with and without tumbling with air and mixing. The seawater and the excess of nutrients was changes daily. Figure S3. Monosaccharides content comparison between the biomass harvested from cages with intensified and extensive cultivation in May 2017. Gal – galactose, Glu?glucose, GluA?glucuronic acid, SA?other sugar acids, Rha? rhamnose, Xyl?xylose, Fru?fructose, UA?uronic acid. Table S1. Eluent gradients of the HPLC program used for glucuronic acid monitoring. Eluent A= ultrapure water, eluent B= NaOH 480mM, eluent C=Sodium Acetate 1M + NaOH 100mM. |
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