Low stability of transgenes and high variability of their expression levels among the obtained transformants are still pending challenges in the nuclear genetic transformation of microalgae. We have generated a new multicistronic microalgal expression plasmid, called Phyco69, to make easier the large phenotypic screening usually necessary for the selection of high-expression stable clones. This plasmid contains a polylinker region (PLK) where any gene of interest (GOI) can be inserted and get linked, through a short viral self-cleaving peptide to the amino terminus of the aminoglycoside 3′-phosphotransferase (APHVIII) from Streptomyces rimosus, which confers resistance to the antibiotic paromomycin. The plasmid has been validated by expressing a second antibiotic resistance marker, the ShBLE gene, which confers resistance to phleomycin. It has been shown, by RT-PCR and by phenotypic studies, that the fusion of the GOI to the selective marker gene APHVIII provides a simple method to screen and select the transformants with the highest level of expression of both the APHVIII gene and the GOI among the obtained transformants. Immunodetection studies have shown that the multicistronic transcript generated from Phyco69 is correctly processed, producing independent gene products from a common promoter.

The identification of new functional food constituents is a priority to improve the prognosis and prevention of colorectal cancer (CRC). In this study, several bacterial and algal phytoene-enriched extracts were obtained, and their potential activity against oxidative damage and their ability to inhibit proliferation and cell migration in several human colon-adenocarcinoma-derived cell lines were assessed. The main conclusions indicate that total extracts of Sphingomonas echinoides and Chlorella sorokiniana exhibited the highest protective effect against oxidative damage. All extracts enhanced the activity of detoxifying enzymes, particularly importantly the increase of NAD(P)H:quinone oxidoreductase activity, which reached a value 40% higher than that of untreated control cells upon exposure to Escherichia coli extracts. Staphylococcus haemolyticus and transgenic E. coli extracts significantly arrested the migration capacity of both cell lines, while S. haemolyticus and C. sorokiniana extracts inhibited cell proliferation by 15 to 20% compared to untreated cells. These results point to these extracts as potential antioxidant complements able to protect cells against oxidative damage and with a moderate ability to inhibit the proliferation and migration of CRC tumor cells, paving the way to design functional foods or probiotic formulations with preventive properties against oxidative stress-related diseases, such as cancer, or as starting point for purifying anticancer compounds.

The search for antioxidant compounds from aquatic or marine environments to cope with the harmful effects of reactive oxygen species (ROS) is one of the major challenges in contemporary blue biotechnology. Among marine microorganisms, microalgae have emerged as promising candidates for the discovery and production of natural bioactive molecules with antioxidant properties. This review highlights the potential of microalgae and cyanobacteria as a sustainable source of antioxidant compounds and examines their growing relevance in biotechnology and pharmaceutical applications. A broad range of antioxidant metabolites produced by microalgae, including carotenoids, fatty acids, vitamins, polyphenols, and flavonoids, has also been discussed, with particular emphasis on their antioxidant mechanisms and bioactive properties. This review also integrates antioxidant mechanisms with the physiological and metabolic responses, underlying antioxidant production and sustainable strategies used to enhance their accumulation. Furthermore, microalgae offer the advantage of sustainable production systems, with the potential to enhance the biosynthesis and accumulation of valuable compounds through optimized cultivation strategies. Thus, different sustainable approaches aimed at increasing antioxidant compound production or reducing operational costs in microalgae cultivation are discussed to identify efficient and economically viable processes that maximize the biotechnological potential of these microorganisms for future industrial applications.