Accumulation characteristics of soluble algal products (SAP) by a freshwater microalga Scenedesmus sp. LX1 during batch cultivation for biofuel production

Algae cultivation is the essential basis for microalgal biofuel production. Soluble algal products (SAP) are significant obstacle to large-scale, high-cell-density cultivation processes. SAP accumulation during batch cultivation of Scenedesmus sp. LX1 (a unique strain accumulating lipid substantially while growing fast under low-nutrient conditions) with different initial nitrogen concentrations (7.4–34.0 mg N L−1) was investigated. The SAP content varied in the range of 3.4–17.4 mg DOC L−1 at stationary phase, with average yield per cell of 0.5–2.5 pg DOC cell−1. High SAP accumulation up to 15.2–17.4 mg DOC L−1 were observed with initial nitrogen above 20.2 mg N L−1. The maximum SAP production rate per unit culture volume (rSAP) was 2.6 mg DOC (L d)−1 and that per cell (νSAP) was 1.5 pg DOC (cell d)−1. The rSAP increased with cell growth rate and decreased with cell density linearly. The SAP accumulation was majorly due to the release of growth-associated products.