Producing Chlorella vulgaris in Ricotta Cheese Whey Substrate

Abstract

Ricotta cheese whey (RCW) is a by-product with nutritional potential, but its use in thehuman diet is limited due to its high salinity. Chlorella vulgaris can use RCW as a substrateto enhance biomass productivity. The aim of this work was to evaluate different conditionsfor C. vulgaris growth in RCW, during scaling-up analysis. After preliminary assays toselect growth conditions, two systems were prepared as follows: 500 mL Erlenmeyerflasks (control-system) and a 3 L Bioreactor. Microfiltrated RCW was used as a substratefor C. vulgaris LPMA39 production. Biomass was measured and productivity at 96 h,cell growth kinetics behaviour, biomass biochemical characterisation, and the efficiency ofnutrient removal were determined. Both systems presented the same biomass concentrationat 96 h (2.2–2.8 g·L−1) and productivity (0.021–0.027 g·L−1·h−1). Nevertheless, 11 h lagperiodfor cell adaptation to the 3 L Bioreactor was required; thereafter, cells grew faster(μmax: 0.32 ± 0.08 h−1) than control-system. Finally, slight but significantly lower Cmax:2.14 ± 0.08 was obtained when comparing it to control-system. Lipids, proteins, andpigment contents decreased by the scaling-up; meanwhile, higher reduction in chemicaloxygen demand (COD), total phosphorus, and total nitrogen were recorded in the 3 LBioreactor. Identifying the operating conditions that improve C. vulgaris performance innon-diluted RCW remains a challenge from a sustainability standpoint.