Converting phototrophic biomass into value-added products

Introduction: Nowadays, a large proportion of chemicals and fuels are derived from fossil resources such as oil, gas and coal. The heavy reliance on these fossil resources results in excessive emissions of greenhouse gases, which are a major contributor to global warming (Khoo et al., 2019). Thus, the development of technologies for a more sustainable energy and chemical production attracts concerns worldwide. Much of the attention has been drawn to the utilization of microalgae, which convert sunlight, CO2 and water into organic compounds, and possess a number of advantages over traditional plant-based biomass (Singh & Olsen, 2011).

Goal: The aim of this study is to cultivate the phototrophic microalgae Galdieria sulphuraria and Cyanidioschyzon merolae in shake flasks, Multi-Cultivator photobioreactors as well as in custom-made flat panel photobioreactor and to utilize the resulting biomass as 3rd generation feedstock for the production of value-added compounds using heterotrophic platform organisms.

Results: Initial characterizations of the microalgae strains regarding temperature, illumination intensity and CO2 concentration were performed in Multi-Cultivator photobioreactors, with the highest growth rate of 0.05 h-1 reached at 42 °C, 400 µE and 5 % CO2. The scale-up to custom-made flat panel photobioreactors reduced the growth rate to 0.02 h-1, but enabled much higher optical density values of 35.7 ± 0.1. Heat-stable phycocyanin was identified as a valuable product extracted from algal biomass. The remaining algal biomass was successfully utilized by the biotechnological platform species Ustilago maydis for both growth and itaconic acid production.

Summary: This work provides blueprints for converting photosynthetic biomass into bioproducts essential for the pharmaceutical and polymer industries, supporting both carbon utilization and sequestration.

Singh, A., & Olsen, S. I. (2011). A critical review of biochemical conversion, sustainability and life cycle assessment of algal biofuels. Applied Energy, 88(10), 3548-3555. https://doi.org/https://doi.org/10.1016/j.apenergy.2010.12.012

Khoo, C. G., Dasan, Y. K., Lam, M. K., & Lee, K. T. (2019). Algae biorefinery: Review on a broad spectrum of downstream processes and products. Bioresource Technology, 292, 121964. https://doi.org/https://doi.org/10.1016/j.biortech.2019.121964