Evaluation of Tolerant to CO2 Excess Microalgae for the Production of Multiple Biochemicals in a 3G Biorefinery

To date, the positive environmental impact of microalgae-based technologies has been demonstrated in numerous studies. However, there is still a number of major technical and economic obstacles to overcome. Therefore, further research and innovation are needed for the development and commercial exploitation of large-scale integrated and sustainable processes, based on robust 'industrial' microalgal strains and novel photobioreactors (PBRs). Note that the advancement of intensified microalgal cultivation processes can facilitate the economically feasible co-production of microalgal biomass and value-added biochemicals. In this context, the goal of the present investigation was to compare several microalgal strains based on a set of productivity criteria, including the maximum biomass growth and the maximum concentration of total biochemicals (i.e., carbohydrates, proteins, and lipids) under CO2 excess conditions (10% v/v). It was found that the wild type strain of Stichococcus sp. fully meets the above productivity criteria. In particular, a biomass concentration of 1.68 g center dot L-1 and a concentration of total biochemical products of 1.4 g center dot L-1 were measured in batch cultivation experiments in flasks using the selected strain. Further studies were performed in two different PBRs. Cultivation in a conventional stirred tank PBR showed successful scaling of the bioprocess, whereas cultivation in an innovative tubular recirculating PBR resulted in maximization of both biomass concentration (3.66 g center dot L-1) and total biochemical products concentration (3.33 g center dot L-1).