Lumostatic cultivation of H. pluvialis on 30 L photobioreactor

초록

High-density cultivation of photosynthetic microbes requires a sophisticate control of light because because of decreasing light quantity per cell as the cells grow. The most efficient method of adjusting light intensity is the lumostatic operation using the specific light uptake rate (qe = ?S/XV). H. pluvialis was cultured under various qe to identify the optimal qe. Bubble column photobioreactors with 30 L working volume were constructed using pyrex glass with diameter of 17 cm and height of 150 cm. Each photobioreactor has 20 ea of linear fluorescent lamps (40 W) with an electronic light intensity control system per lamp. Aeration with 95% air and 5% CO2 was supplied at a flow rate of 0.1 vvm, or 3 L/min, which was determined by previous experiments. MBBM (modified Bold？s basal medium) with pH 6.5 was used as culture media at 25? and initial cell concentration and fresh cell weight were ~6X103 cell/mL and ~1 g/L, respectively. Experimental sets were consisted of a control (maintained at 30 ?ol/(m2∙s) of light intensity) and three lumostatically controlled sets at 2.5, 3.0 and 3.5 ?ol/(s∙g cell) of qe. Light intensity was adjusted for lumostatic operation every other day and sodium nitrate was also fed at the same frequency. Final cell concentration and fresh cell weight were improved ~2.5 (7.6X104/1.9X105 cell/mL) and ~4.5 (1.03/4.59 g/L) times, respectively, at 3.5 ?ol/(s∙g cell) of optimal qe compared to those of control.