Scale-up and intensification of a microalgae cultivation process for the production of high-added value biochemicals

Abstract

The upscale and intensification of the Stichococcus sp. cultivation process was accomplished in this work with the prospect of maximizing the production of high-added value biochemicals, namely, carbohydrates, proteins and lipids. Initially, this study focused on the successful scale-up of individual strategies, developed experimentally for the optimal production of biomass and/or selected biochemicals in flasks to the photo-bioreactor level. Thereupon, further bioprocess performance improvement was facilitated by the manipulation of key-process variables. It was found that the light intensity time-profile, coupled with the culture agitation time-profile, exhibited the major impact on the biomass growth and biochemicals accumulation. In addition, the aeration, nitrogen source and CO2 feeding rates significantly affected the overall bioprocess behavior. Emphasis was also placed on the progressive adaptation of the above process variable, in association with the culture growth rate and physiological state. Thus, a satisfactory transition of the process operation from the smaller to the larger scale was achieved. The operational policy designated for the maximization of the total biochemical products concentration was of primary priority for scaling-up to the photo-bioreactor level. Subsequently, additional strategies were designed for the intensified production of either carbohydrates, or proteins or lipids, as targeted products. The analysis of the theoretical predictions vs. the experimental results revealed the significant qualitative and quantitative effect of the selected conditions on the culture efficiency and resulted to the identification of individual optimization strategies, depending on the intended bioproduct.