Optimization of the Key Medium Components and Culture Conditions for Efficient Cultivation of G. sulfurreducens Strain PCA ATCC 51573 Using Response Surface Methodology

Abstract

Microbial electrolysis cell (MEC) is a promising method for hydrogen production by microorganisms. The culture conditions were optimized for Geobacter sulfurreducens PCA ATCC 51573 using response surface methodology involving central composite design (CCD). Effects of sodium bicarbonate, sodium acetate, sodium fumarate, incubation temperature, and initial pH value of culture on cell growth of G. sulfurreducens PCA ATCC 51573 were studied. Experimental data obtained from CCD were utilized to generate a second-order polynomial regression model and to evaluate the effect of the variables studied on the optical density (OD) as the main response of bacterial growth of the strain PCA ATCC 51573. The statistical analysis showed that sodium bicarbonate, sodium acetate, and sodium fumarate had significant effect on OD value (P < 0.01). Similar results revealed sodium bicarbonate had significant interaction with sodium acetate and sodium fumarate (P < 0.05). On the other hand, quadratic term of temperature and initial pH value had a significant effect on OD value at 99% probability level (P < 0.01). Furthermore, interaction between culture temperature and initial pH value significantly affected OD value (P < 0.01). The optimum conditions suggested by the model for obtaining high OD value were 3.11 g/L NaHCO3, 4.10 g/L NaC2H3O2, 16.24 g/L Na2C4H2O4, 28.31 °C incubation temperature, and 6.80 pH value. The statistical model predicted that an OD value of 0.88 could be attained under optimum conditions. Result of verification experiment showed OD value of 0.87 was obtained which confirmed the adequacy of the model for the determining optimum conditions.