Development of novel acetate- and water-soluble fertilizer-based medium for Chlorella cultivation

Chlorella species grow quickly, with high protein content and tolerance to different kinds of stresses. It can be used for food, feed, fertilizer, wastewater treatment, carbon fixation and other purposes. However, the high cultivation cost limits its industrial application. Tris-acetate-phosphate (TAP) has been the most commonly used medium for Chlorella culture for decades because of its outstanding performance, but the medium is expensive and inconvenient for industrial use. To address these problems, a novel acetate-based water-soluble fertilizer (Ab-WSF) was developed on the basis of TAP media, where the trace and macroelements in TAP were replaced by water-soluble fertilizer (WSF). Additionally, HAc-NaAc was used to balance the pH of the culture medium and replace tris in TAP medium. Compared with TAP, Ab-WSF demonstrated better performance when tested in fed-batch and semicontinuous cultures of Chlorella sorokiniana. When C. sorokiniana was cultured in twelve liters of Ab-WSF. The biomass concentration, volumetric productivity and areal productivity were 4.5 g/L, 0.6 g/L/d, and 9.0 g/m²/d, which were 50.0 %, 36.0 % and 49.8 % greater than those obtained with TAP, respectively. Ab-WSF medium was used in ten tons of outdoor culture. Technoeconomic analysis indicated that the cost of Ab-WSF is 19.6 % that of TAP, while one twentieth of the time, Ab-WSF is used for preparation. These results suggest that the application of Ab-WSF not only reduces the cost of Chlorella production but also increases the biomass yield, potentially promoting industrialized microalgae production.