Optimization of culture conditions for CO2 fixation by a chemoautotrophic microorganism, strain YN-1 using factorial design

Culture conditions for CO2 fixation by a chemoautotrophic microorganism, strain YN-1, were optimized by statistical analysis using factorial design. Statistical analysis was performed by SAS software and then predicted the levels of four factors, H2 (X1), O2 (X2), CO2 (X3) concentration and pH (X4) which were required to obtain the optimum culture conditions. For the fractional factorial design 34−1, total 27 experimental runs by combination of each factor were carried out in a 5 L-jar fermentor, and the three-dimensional response surfaces were plotted to find out the optimum level of each factor for maximum CO2 fixation. Dry cell weight in optimized culture condition was predicted as 11.4 g/L in 48 h under the condition of 37.5 × 10−3 mol/min H2, 9.38 × 10−3 mol/min O2, 4.91 × 10−3 mol/min CO2, and pH 6.7. As compared with CO2 fixation rate before optimizing culture conditions, the improvement of CO2 fixation rate under optimized culture conditions was experimentally confirmed.