Kinetics of net photosynthetic oxygen production of a microalgae suspension at small doses of sulfide

A new empirical model for the net oxygen production rate of an alkaliphilic microalgae consortium (AMC) with prominent members of Picochlorum and Pseudoanabaena was developed as a function of sulfide at concentrations up to 1.50 mM. The kinetic model consists of a non-continuous function with two domains for sulfide concentration, which describes the enhancement and the inhibition of net photosynthetic oxygen production. Small doses of sulfide can foster the photosynthetic activity evaluated by a Gaussian type of kinetic model; while, at a total sulfide concentration higher than 1.00 mM, the photosynthetic activity was inhibited following a linear inverse response. This study shows that small sulfide concentrations around 0.60 mM improved the photosynthetic activity by up to 90% compared to assays without sulfide. Moreover, the sulfide influence on the oxygenic photosynthetic activity of the AMC was confirmed after one year, suggesting that the kinetic model could be helpful for the design and operation of photobioreactors to improve the performance of microalgae cells exposed to hydrogen sulfide.