Evaluating the potential of carbohydrate-rich microalga Rhodosorus sp. SCSIO-45730 as a feedstock for biofuel and β-glucans using strategies of phosphate optimization and low-cost harvest

With the increase of global energy consumption, bioenergy from microalgae has been recognized as a potential alternative choice. A novel carbohydrate-rich microalgal strain, isolated from Xisha Islands (China), was identified as Rhodosorus sp. SCSIO-45730. To accumulate biomass for bioenergy production, strategies of phosphate optimization and chitosan flocculation were used to evaluate its potential for the production of biomass, total carbohydrates, and beta-glucans. The biomass of this alga reached 12.3 +/- 0.1 g L-1 in vertical bubble column photobioreactors at the phosphate concentration of 120 mg L-1, and the productivities of total carbohydrates and beta-glucans maximized up to 242.6 +/- 2.3 mg L-1 day(-1) and 108.1 +/- 4.0 mg L-1 day(-1), respectively. Simultaneously, flocculation results demonstrated that the recovery rate of the biomass, total carbohydrates, and beta-glucans were over 90% at a low chitosan concentration of 3 mg L-1. The flocs were easily collected and washed through a 300-mesh bolting cloth, presenting an ultralow harvest cost of 2.93 US$ per tonne of biomass. In summary, addition of suitable phosphate and flocculation with low chitosan concentration could be effective strategies to enhance the commercial potential of Rhodosorus sp. SCSIO-45730 as a feedstock for biofuel and beta-glucans.