Dependence of microalgae culture specific endogenous loss rate and gross productivity on irradiance

Abstract

Microalgal growth rate is determined by the difference between gross productivity and endogenous biomass loss rate. Gross productivity is a function of surface irradiance and reaches the maximal value under saturating light intensity. Endogenous biomass consumption of microalgal cells is mainly due to the respiration which can be sub-divided into growth and maintenance respiration. The paper proposes equations for calculating microalgae culture gross productivity and specific loss rate based on production characteristics. Verification of the obtained equations was performed for Arthrospira platensis and Dunaliella salina cultivated under constant illumination with different irradiance. It was demonstrated that gross productivity and specific loss rate increase linearly with increasing irradiance. Specific loss rate varied from 0,01 to 0,58 h-1 in A. platensis and from 0,04 to 0,35 day-1 in D. salina. Specific maintenance respiration rate was determined to be 0,01 h-1 in A. platensis and 0,01–0,04 day-1 in D. salina. The proposed calculation method enables a sufficiently accurate determination of productivity and loss rates based on culture density dynamics measures.