Shortening the Light Path Length of Photobioreactors to Elevate the Cell Mass Concentration of Cyanobacterium Synechococcus sp. Strain PCC6301

To explore high-cell density cultivation of photolithotrophs in the production of high-value compounds, a model cyanobacterium Synechococcus sp. strain PCC6301 was grown in rectangular photobioreactors with light path lengths of 0.1, 0.3, 0.5, 1.4 and 5 cm. A mathematical model to correlate cell growth with medium concentration, light transmittance and light path length was formulated. Logarithmic and linear growth phase were prolonged, and linear growth rate was elevated by shortening the light path length and by avoiding monohydrogen phosphate ion depletion. With sufficient monohydrogen phosphate ions, a high cell mass concentration of 24.5 mg·mL–1 was accomplished using a 0.1 cm light path length photobioreactor.