Starch Rich Chlorella vulgaris: High-Throughput Screening and Up-Scale for Tailored Biomass Production

Abstract

The use of microalgal starch has been studied in biorefinery frameworks to produce bioethanol or bioplastics, however, these products are currently not economically viable. Using starch-rich biomass as an ingredient in food applications is a novel way to create more value while expanding the product portfolio of the microalgal industry. Optimization of starch production in the food-approved species Chlorella vulgaris was the main objective of this study. High-throughput screening of biomass composition in response to multiple stressors was performed with FTIR spectroscopy. Nitrogen starvation was identified as an important factor for starch accumulation. Moreover, further studies were performed to assess the role of light distribution, investigating the role of photon supply rates in flat panel photobioreactors. Starch-rich biomass with up to 30% starch was achieved in cultures with low inoculation density (0.1 g L−1) and high irradiation (1800 µmol m−2 s−1). A final large-scale experiment was performed in 25 L tubular reactors, achieving a maximum of 44% starch in the biomass after 12 h in nitrogen starved conditions.

Fine-tuned regulation of photosynthetic performance via γ-aminobutyric acid (GABA) supply coupled with high initial cell density culture for economic starch production in microalgae

“…One of the strategies raised to deal with this problem is to adopt a two-stage mode, where in the first stage, the algae cells are cultivated in an optimal condition to achieve high biomass accumulation and then transferred into a stressful condition under a specific physiological status for starch production as the second stage. The initial cell density (ICD) for the second stage is a key factor that affects biomass and starch productivity especially under the photoautotrophic cultivation mode (Carnovale et al 2021 ; Cheng et al 2017 ; Ivanov et al 2021 ; Yao et al 2013a ; Giraldo et al 2021 ). High cell density influences the accessibility of light penetration through the culture medium due to the mutual shading, thus altering the mean light intensity that individual algal cell would receive (Brányiková et al 2011 ; Carnovale et al 2021 ; Yao et al 2013a ).…”

“…The initial cell density (ICD) for the second stage is a key factor that affects biomass and starch productivity especially under the photoautotrophic cultivation mode (Carnovale et al 2021 ; Cheng et al 2017 ; Ivanov et al 2021 ; Yao et al 2013a ; Giraldo et al 2021 ). High cell density influences the accessibility of light penetration through the culture medium due to the mutual shading, thus altering the mean light intensity that individual algal cell would receive (Brányiková et al 2011 ; Carnovale et al 2021 ; Yao et al 2013a ). Therefore, a reduced starch content can be usually observed due to the decreased light accessibility, although the biomass and starch yield could be improved (Carnovale et al 2021 ; Cheng et al 2017 ; Ivanov et al 2021 ; Yao et al 2013a ).…”

“…High cell density influences the accessibility of light penetration through the culture medium due to the mutual shading, thus altering the mean light intensity that individual algal cell would receive (Brányiková et al 2011 ; Carnovale et al 2021 ; Yao et al 2013a ). Therefore, a reduced starch content can be usually observed due to the decreased light accessibility, although the biomass and starch yield could be improved (Carnovale et al 2021 ; Cheng et al 2017 ; Ivanov et al 2021 ; Yao et al 2013a ). Moreover, high cell density cultures can often suffer from extra stress, such as photorespiration, because of the oxygen accumulation (Formighieri et al 2012 ; Molina et al 2001 ) and the excretion of inhibitory metabolites with a prolonged cultivation (Richmond et al 2003 ), which could on the contrary impede the biomass and starch production.…”

Microalgae from Nordic collections demonstrate biostimulant effect by enhancing plant growth and photosynthetic performance

“…In this work, we developed a rapid and affordable phenotyping pipeline for evaluating plant biostimulant effects of microalgae. Microalgae can be a feasible resource for producing high‐value products if suitable strains, cultivation, and extraction methods are utilized (Carnovale et al, 2021; Kapoore et al, 2021). For industrial potential, advantageous microalgae should meet the minimum requirement of scalability (Allahverdiyeva et al, 2021; Barone et al, 2019).…”

Explorative characterization and taxonomy‐aligned comparison of alterations in lipids and other biomolecules in Antarctic bacteria grown at different temperatures

“…Total lipid content and fatty acid profiles were analysed by gas chromatography (GC), while Fourier transforms infrared (FTIR) spectroscopy was used to evaluate changes in the total cellular biochemical profile. FTIR spectroscopy was chosen due to its advantages and wide application in microbiology and biotechnology for the overall biochemical characterization of microbial cells and their metabolites (Carnovale et al, 2021 ; Forfang et al, 2017 ; Kohler et al, 2015 ; Kosa, Shapaval, et al, 2017 ; Olsen et al, 2023 ; Shapaval et al, 2017 , 2023 ). One of the main advantages of FTIR analysis is that it can be performed on non‐destructed or little‐processed microbial biomass and combined with automated sample preparation to increase throughput (Li et al, 2016 ; Xiong et al, 2019 ).…”