1. Development of a bench-scale photobioreactor with a novel recirculation system for continuous cultivation of microalgae.
- Author
-
Tavares, João, Silva, Tiago P., Paixão, Susana M., and Alves, Luís
- Subjects
- *
MICROALGAE , *MANUFACTURING processes , *CHEMOSTAT , *CARBON dioxide , *WASTE gases , *CARBON fixation , *DILUTION - Abstract
Microalgae cultivation can be used to increase the sustainability of carbon emitting processes, converting the CO 2 from exhaust gases into fuels, food and chemicals. Many of the carbon emitting industries operate in a continuous manner, for periods that can span days or months, resulting in a continuous stream of gas emissions. Biogenic CO 2 from industrial microbiological processes is one example, since in many cases it becomes unsustainable to stop these processes on a daily or weekly basis. To correctly sequester these emissions, microalgae systems must be operated under continuous constant conditions, requiring photobioreactors (PBRs) that can act as chemostats for long periods of time. However, in order to optimize culture parameters or study metabolic responses, bench-scale setups are necessary. Currently there is a lack of studies and design alternatives using chemostat, since most works focus on batch assays or semi-continuous cultures. Therefore, this work focused on the development of a continuous bench-scale PBR, which combines a retention vessel, a photocollector and a degasser, with an innovative recirculation system, that allows it to operate as an autotrophic chemostat, to study carbon sequestration from a biogenic CO 2 -rich constant air stream. To assess its applicability, the PBR was used to cultivate the green microalga Haematococcus pluvialis using as sole carbon source the CO 2 produced by a coupled heterotrophic bacterial chemostat. An air stream containing ≈0.35 vol% of CO 2, was fed to the system, and it was evaluated in terms of stability, carbon fixation and biomass productivity, for dilution rates ranging from 0.1 to 0.5 d−1. The PBR was able to operate under chemostat conditions for more than 100 days, producing a stable culture that generated proportional responses to the stimuli it was subjected to, attaining a maximum biomass productivity of 183 mg/L/d with a carbon fixation efficiency of ≈39% at 0.3 d−1. These results reinforce the effectiveness of the developed PBR system, making it suitable for laboratory-scale studies of continuous photoautotrophic microalgae cultivation. [Display omitted] • A novel bench-scale PBR for continuous cultivation of microalgae was developed. • This PBR integrates three units and presents an innovative recirculation system. • This PBR operates as an autotrophic chemostat. • Steady states for dilution rates from 0.1 to 0.5 d−1 were studied in this PBR system. • Maximum productivity (Pv) of 183 mg/L/d, with a CFE of 39% at dilution rate of 0.3 d−1. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF