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).

Automated summary

The positive environmental impact of microalgae-based technologies has been proven in many studies, but there are still major technical and economic obstacles to be overcome. Further research and innovation are necessary for the development and commercial exploitation of large-scale, sustainable processes using industrial microalgae strains and novel photobioreactors. The investigation aimed to compare different microalgae strains based on productivity criteria, and the wild type strain of Stichococcus sp. met the criteria with a biomass concentration of 1.68 g·L-1 and a concentration of total biochemical products of 1.4 g·L-1 in batch cultivation experiments. Cultivation in an innovative tubular recirculating photobioreactor resulted in the highest biomass and biochemical product concentrations of 3.66 g·L-1 and 3.33 g·L-1, respectively.