Production and monitoring of biomass and fucoxanthin with brown microalgae under outdoor conditions

Abstract

The effect of light on biomass and fucoxanthin (Fx) productivities was studied in two microalgae, Tisochrysis lutea and Phaeodactylum tricornutum. High and low biomass concentrations (1.1 and 0.4 g L−1) were tested in outdoor pilot‐scale flat‐panel photobioreactors at semi‐continuous cultivation mode. Fluorescence spectroscopy coupled with chemometric modeling was used to develop prediction models for Fx content and for biomass concentration to be applied for both microalgae species. Prediction models showed high R2 for cell concentration (.93) and Fx content (.77). Biomass productivity was lower for high biomass concentration than low biomass concentration, for both microalgae (1.1 g L−1: 75.66 and 98.14 mg L−1 d−1, for T. lutea and P. tricornutum, respectively; 0.4 g L−1: 129.9 and 158.47 mg L−1 d−1, T. lutea and P. tricornutum). The same trend was observed in Fx productivity (1.1 g L−1: 1.14 and 1.41 mg L−1 d−1, T. lutea and P. tricornutum; 0.4 g L−1: 2.09 and 1.73 mg L−1 d−1, T. lutea and P. tricornutum). These results show that biomass and Fx productivities can be set by controlling biomass concentration under outdoor conditions and can be predicted using fluorescence spectroscopy. This monitoring tool opens new possibilities for online process control and optimization.

Effect of Nitrogen Concentration on the Alkalophilic Microalga Nitzschia sp. NW129-a Promising Feedstock for the Integrated Production of Lipids and Fucoxanthin in Biorefinery

“…Therefore, under conditions of nitrogen scarcity, cells tend to degrade them actively to reuse nitrogen and transfer it to the synthesis of those proteins that are indispensable for cell survival. P. tricornutum with high Fx content (0.2-16.51 mg g −1 ) has been widely concerned, which was several times more abundant than that in macroalgae (Kim et al, 2012a;Gomez-Loredo et al, 2016;Wu et al, 2016;Ishika et al, 2017;Gao et al, 2020). It has been reported that Fx content obtained from Nitzschia sp.…”

“…As to Fx, the nitrogen enrichment generally promoted the accumulation of biomass and Fx content at the same time, which would undoubtedly increase Fx productivity (Sun et al, 2019). Interestingly, it was found that the higher Fx content was caused by high biomass concentration and higher biomass and Fx productivities were induced by low biomass concentration (Gao et al, 2020). These results suggested the microalgae presented different responses in terms of the productivities of lipid and Fx under nitrogen replete and limited conditions, which it was difficult to obtain high Fx and lipid productivities in the meantime.…”

On-Line Monitoring of Biological Parameters in Microalgal Bioprocesses Using Optical Methods

“…Chemometric models for fucoxanthin content and biomass concentration of T. lutea and P. tricornutum were developed by Gao et al [63], using 2D fluorescence excitationemission matrices (EEM) obtained by off-line measurements in a cuvette as the only inputs. Biomass models predicted the BC with R 2 between 0.93 and 0.96.…”

“…Another chemometric model, mentioned already in Section 2.3.2, was developed for estimation of fucoxanthin content and biomass concentration [63]. Fucoxanthin models predicted its contents with R 2 between 0.63 and 0.77.…”

“…In a series of publications, Sa and various co-authors [40,41,[48][49][50] and other authors [32,63] developed data-driven chemometric models based on 2D fluorometry (EEMs) as inputs for estimation of several biological variables in microalgal cultivations, including cell count, cell viability and concentrations of nitrate, chlorophylls a and b, carotenoids, fatty acids as total, saturated and unsaturated, and eicosapentaenoic acid fraction in the TAG content. Such models could potentially be used for real time on-line estimation of various process variables by acquiring the real time data used as input for models automatically on-line through suitably designed and placed fiber probes measuring fluorescence just as they are used in the series for measuring samples drawn from the PBR.…”