Continuous Microalgal Cultivation for Antioxidants Production

Abstract

Microalgae, including cyanobacteria, represent a valuable source of natural compounds that have remarkable bioactive properties. Each microalga species produces a mixture of antioxidants with different amounts of each compound. Three aspects are important in the production of bioactive compounds: the microalga species, the medium composition including light supplied and the photobioreactor design, and operation characteristics. In this study, the antioxidant content and productivity performance of four microalgae were assessed in batch and continuous cultures. Biomass productivity by the four microalgae was substantially enhanced under continuous cultivation by 5.9 to 6.3 times in comparison with batch cultures. The energetic yield, under the experimental conditions studied, ranged from 0.03 to 0.041 g biomass kJ−1. Phenols, terpenoids, and alkaloids were produced by Spirulinaplatensis, Isochrysisgalbana, and Tetraselmissuecica, whereas tocopherols and carotenoids were produced by the four microalgae, except for phycocyanin and allophycocyanin, which were only produced by S. platensis and Porphyridiumcruentum. The findings demonstrate that the continuous cultivation of microalgae in photobioreactors is a convenient method of efficiently producing antioxidants.

Sequential Continuous Mixotrophic and Phototrophic Cultivation Might Be a Cost-Effective Strategy for Astaxanthin Production From the Microalga Haematococcus lacustris

“…In continuous cultivation, the longer the residence time, the higher the substrate utilization, and thus, the cell biomass concentrations are higher at lower dilution rates than those at higher dilution rates ( Liu, 2013 ). Under steady-state cultivation, the dilution rates of continuous cell cultures are, in fact, equivalent to the cell growth rates ( López-Hernández et al, 2020 ). However, the maximum biomass productivity of 0.104 ± 003 g L −1 d −1 was attained at a dilution rate of 0.54 days −1 under a light intensity of 160 μmol photons m −2 s −1 in mixotrophic cultures.…”

Extraction and characterization of microalgae‐derived phenolics for pharmaceutical applications: A systematic review

“…El‐Baky et al [24] reported that Zarrouk's medium containing l ‐phenylalanine (100 mg/L) and sodium nitrate (3.77 g/L) have a remarkable influence on total phenolic content (4.51–16.96 mg/g DW), total flavonoid content (1.32–5.12 mg/g DW) and phenolic composition (gallic, vanillic and ferulic acid) in axenic cultures of S. maxima . The culture medium supplement with 1.9 or 2.5 g/L of sodium nitrate increased the content of phenolic compounds in axenic cultures of S. platensis [78]. Strejckova et al [68] reported that low concentrations of NiCl 2 (5 μM), CdCl 2 (20 μM), and CuCl 2 (40 μM) significantly increased the accumulation of phenolic acid (phenyl pyruvic) and 2DR in axenic cultures of S. quadricauda , Chlorella sorokiniana , and Scenedesmus acuminatus exposed to sublethal doses of copper (25 and 50 µM, respectively) showed a marked enhancement in the accumulation of phenolic compounds to mitigate the oxidative damage [71].…”

“…Hanachi et al [77] reported that high temperature (28°C) increases the content of antioxidant phenolic compounds in axenic cultures of Monoraphidium species . S. platensis exposed to high temperatures (35°C) showed high content of phenolic compounds in their biomass [78]. Low temperature (16°C) favored the production of phenolic compounds (56.70 ± 1.07 µg/g DW) in axenic cultures of Selenastrum capricornutum [79].…”

“…Temperature is a critical factor affecting the production of phenolic compounds in microalgae [71,78]. Sozmen et al [61] reported that temperature substantially affects the accumulation of phenolic compounds (caffeic acid, flavanones, flavonols, and hydroxycinnamic acid) in an axenic culture of C. miniata.…”

“…Several researchers have used different types of photobioreactors to enhance the production of phenolic compounds [80,89]. López-Hernández et al [78] demonstrated that continuous cultivation of S. platensis, Isochrysis galbana, and T. suecica photobioreactors is a convenient method for the efficient production of phenolic compounds. Researchers also found that small-sized cells of Tetraselmis tetrathele cultured in annular photobioreactor have 1.6 times higher phenolic content (2.99 ± 0.14 mg GAE/g) than large-sized cells.…”