Effect of Salt Stress on the Phenolic Compounds, Antioxidant Capacity, Microbial Load, and In Vitro Bioaccessibility of Two Microalgae Species (Phaeodactylum tricornutum and Spirulina platensis)

Abstract

Microalgae have gained attention as alternative food sources due to their nutritional value and biological effects. This study investigated the effect of salt stress on the antioxidant activity, phenolic profile, bioavailability of bioactive compounds, and microbial counts in the blue-green algae Spirulina platensis and diatom species Phaeodactylum tricornutum. These microalgae were cultured in growth mediums with different salt concentrations (15–35‰) We observed the highest antioxidant activity and phenolic compounds in the control groups. S. platensis (20‰) exhibited higher antioxidant activity compared to P. tricornutum (30‰), which decreased with increasing salt stress. Using HPLC-DAD-ESI-MS/MS, we identified and quantified 20 and 24 phenolic compounds in the P. tricornutum and S. platensis culture samples, respectively. The bioavailability of these compounds was assessed through in vitro digestion with the highest amounts observed in the intestinal phase. Salt stress negatively affected the synthesis of bioactive substances. Microbial counts ranged from 300 to 2.78 × 104 cfu/g for the total aerobic mesophilic bacteria and from 10 to 1.35 × 104 cfu/g for yeast/mold in P. tricornutum samples while the S. platensis samples had microbial counts from 300 to 1.9 × 104 cfu/g and the total aerobic mesophilic bacteria from 10 to 104 cfu/g, respectively. This study suggests that adding salt at different ratios to the nutrient media during the production of P. tricornutum and S. platensis can impact phenolic compounds, antioxidant capacity, microbial load evaluation, and in vitro bioaccessibility of the studied microalgae.

Enhancing algal production strategies: strain selection, AI-informed cultivation, and mutagenesis

“…Identification through DNA barcoding, mainly 18S rRNA gene sequencing, is a precise and widely used method for strain determination (Darienko et al, 2015;Hadi et al, 2016;Zou et al, 2016). After identification, candidate bioactive compounds are extracted and subjected to various assays to ascertain their bioactivity (Uzlasir et al, 2023;Yang et al, 2023;Zhou et al, 2023). Recent bioprospecting endeavors have unveiled a plethora of microalgal strains with promising bioactivities.…”

Phaeodactylum tricornutum as a stable platform for pilot scale production and investigation of the viability of spirulina fucoxanthin as a commercial lipolysis active novel compound

“…Phaeodactylum tricornutum is widely used as a model organism due to its genomic sequence and ease of culture. This unicellular eukaryotic diatom microorganism belongs to the group Pennateae (Uzlasir et al, 2023). It is characterized by a length of 5-27 µm length and a width of 3-4 µm, and belongs to the family Phaeodactylaceae.…”