Impact of Pressurized Liquid Extraction and pH on Protein Yield, Changes in Molecular Size Distribution and Antioxidant Compounds Recovery from Spirulina

Abstract

The research aims to extract nutrients and bioactive compounds from spirulina using a non-toxic, environmentally friendly and efficient method—Pressurized Liquid Extraction (PLE). In this work, Response Surface Methodology (RSM)–Central Composite Design (CCD) was used to evaluate and optimize the extraction time (5–15 min), temperature (20–60 °C) and pH (4–10) during PLE extraction (103.4 bars). The multi-factor optimization results of the RSM-CCD showed that under the pressure of 103.4 bars, the optimal conditions to recover the highest content of bioactive compounds were 10 min, 40 °C and pH 4. Furthermore, the compounds and antioxidant capacity of PLE and non-pressurized extraction extracts were compared. The results showed that under the optimal extraction conditions (10 min, 40 °C and pH 4), PLE significantly improved the antioxidant capacity (2870.5 ± 153.6 µM TE), protein yield (46.8 ± 3.1%), chlorophyll a (1.46 ± 0.04 mg/g), carotenoids (0.12 ± 0.01 mg/g), total polyphenols (11.49 ± 0.04 mg/g) and carbohydrates content (78.42 ± 1.40 mg/g) of the extracts compared with non-pressurized extraction (p < 0.05). The protein molecular distribution of the extracts was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and the results showed that there were more small-molecule proteins in PLE extracts. Moreover, Liquid Chromatography Triple Time of Flight Mass Spectrometry (TOF–LC–MS–MS) was used to analyze the phenolic profile of the extracts, and the results showed the extracts were rich on phenolic compounds, such as p-coumaric acid and cinnamic acid being the predominant phenolic compounds in the PLE extract. This indicates that PLE can promote the extraction of bioactive compounds from Spirulina, which is of great significance for the application of PLE technology to obtain active substances from marine algae resources.

Comparative study of factors affecting the recovery of proteins from malt rootlets using pressurized liquids and ultrasounds

“…Extraction of proteins by PLE was promoted at low-medium percentages of EtOH, medium-high temperatures, and high times. The positive effect of high temperatures and times on the protein yield was also observed in the case of Spirulina ( Zhou et al, 2021 ) while the addition of low-medium percentages of EtOH and high temperatures enabled to increase the extraction of proteins from brewer's spent grain ( González-García et al, 2021 ) and pomegranate seeds ( Guzmán-Lorite et al, 2022 ). Nevertheless, the extraction of proteins from pomegranate peels ( Hernández-Corroto et al, 2020 ) required the use of high EtOH percentages and temperatures.…”

“…Indeed, the solubility of proteins in water is low due to aggregation and association to cell walls. In other cases, PLE has been employed to obtain extracts with the highest content in bioactives, e.g., extracts with high antioxidant activity ( de la Fuente et al, 2021 ; Zhou et al, 2021 , 2022 ). These extracts contained many molecules (polyphenols, vitamins, saponins, chlorophyll, etc.…”

Valorization of biomass for food protein via deep eutectic solvent extraction: Understanding the extraction mechanism and impact on protein structure and properties

“…However, their study did not investigate deeper into the effects of the precipitation techniques on the protein structure and, subsequently, their functional properties. Ultrasound processing can disrupt cell walls, leading to greater release of proteins into the extracellular environment, whereas PLE promotes greater cell wall disruption and solvent diffusion, as well as perturbation of protein structure as a result of high temperature and pressure, thus unfolding the protein and exposing more surface area to the solvent and increasing solubility (Zhou et al, 2021). In summary, syn-…”

“…Here, complementary extraction methods combined together extracted more proteins than singular methods. Ultrasound processing can disrupt cell walls, leading to greater release of proteins into the extracellular environment, whereas PLE promotes greater cell wall disruption and solvent diffusion, as well as perturbation of protein structure as a result of high temperature and pressure, thus unfolding the protein and exposing more surface area to the solvent and increasing solubility (Zhou et al., 2021). In summary, synergistic processing techniques may allow increased protein extraction yields where stand‐alone DES use is insufficient.…”

Progress of Research on Antioxidants and Carriers for Skin Wound Repair

“…Spirulina contains antioxidants such as chlorophyll a and carotenoids, which play an important role in its antioxidative system [30]. Microalgae contain a variety of antioxidants such as carotenoids, ascorbic acid and glutathione, and these antioxidants play an important role in maintaining the normal life activities of microalgae [31].…”