Irradiance penetration distribution and flashing light frequency simultaneously affected with microalgal cell absorption and CO2 bubble scattering in a raceway pond

Spirulina (Arthrospira) cultivation in photobioreactors: From biochemistry and physiology to scale up engineering

Spirulina (Arthrospira) has been extensively applied in CO2 biofixation, wastewater purification, and value-added bioproducts preparation. Light availability plays a pivotal role in Spirulina photoautotrophic cultivation, which is primary determined by characteristics of incident light and distribution of light within photobioreactors (PBRs). To clarify the role of light in Spirulina photoautotrophic cultivation, this review first analyzes the processes of light delivery and conversion in suspended PBRs. Then, effects of key light characteristics, including light intensity, spectrum, and photoperiod, on Spirulina growth and intracellular biochemical components synthesis are comprehensively summarized. Recent advancements in innovative PBR designs aimed at enhancing light utilization efficiency and promoting Spirulina growth are also highlighted. Finally, potential future research directions in the field of Spirulina photoautotrophic cultivation are outlined. Overall, this work provides a theoretical foundation and technical guidance for improving Spirulina production and specific target products synthesis from prespectives of light conditions regulation and PBRs design.

Photobioreactor configurations in cultivating microalgae biomass for biorefinery

Microalgae, highly prized for their protein, lipid, carbohydrate, phycocyanin, and carotenoid-rich biomass, have garnered significant industrial attention in the context of third-generation (3G) biorefineries, seeking sustainable alternatives to non-renewable resources. Two primarily cultivation methods, open ponds and closed photobioreactors systems, have emerged. Open ponds, favored for their cost-effectiveness in large-scale industrial production, although lacking precise environmental control, contrast with closed photobioreactors, offering controlled conditions and enhanced biomass production at the laboratory scale. However, their high operational costs challenge large-scale deployment. This review comprehensively examines the strength, weakness, and typical designs of both outdoor and indoor microalgae cultivation systems, with an emphasis on their application in terms of biorefinery concept. Additionally, it incorporates techno-economic analyses, providing insights into the financial aspects of microalgae biomass production. These multifaceted insights, encompassing both technological and economic dimensions, are important as the global interest in harnessing microalgae's valuable resources continue to grow.