Recently, microalgal biotechnology has received increasing interests in producing valuable, sustainable and environmentally friendly bioproducts. The development of economically viable production processes entails resolving certain limitations of microalgal biotechnology, and fast evolving genetic engineering technologies have emerged as new tools to overcome these limitations. This review provides a synopsis of recent progress, current trends and emerging approaches of genetic engineering of microalgae for commercial applications, including production of pharmaceutical protein, lipid, carotenoids and biohydrogen, etc. Photochemistry improvement in microalgae and CO₂ sequestration by microalgae via genetic engineering were also discussed since these subjects are closely entangled with commercial production of the above mentioned products. Although genetic engineering of microalgae is proved to be very effective in boosting performance of production in laboratory conditions, only limited success was achieved to be applicable to industry so far. With genetic engineering technologies advancing rapidly and intensive investigations going on, more bioproducts are expected to be produced by genetically modified microalgae and even much more to be prospected.

Microalgal biotechnology has become a promising field of research for the production of valuable, sustainable and environmentally friendly byproducts, especially for carotenoids. Bulk accumulation of secondary carotenoids in microalgae are mostly induced by oxidative stress of cells. In this research, we investigated the effects of antioxidant enzyme activity inhibition on carotenogenesis in a microalga Dactylococcus dissociatus MT1. The activities of four major antioxidant enzyme families, namely superoxide dismutase (SOD), catalases (CAT), glutathione peroxydases (GPX) and ascorbate perxodases (APX), were inhibited by relevant inhibitors during the stressed cultivation of D. dissociatus to observe the effects on carotenogensis. A 91% decrease in activity was observed for CAT, comparing with controls without any inhibitors added, followed by 65%, 61%, and 47% for the enzymes SOD, APX, and GPX, respectively. Concomitantly, it was found that this partial inhibition had substantial influences on the accumulation of carotenoids, with the highest production levels obtained in CAT inhibition conditions and an increase of 2.6 times of carotenoid concentration observed, comparing with control cultivation conditions. We conclude that the modulation of antioxidant enzyme activities could lead to the overproduction of carotenoids in this microalgal cell culture, and we expect that this novel approach of optimizing carotenogenesis processes for D. dissociatus cell cultures could be transferrable to other cell culture systems and might have an important impact on the carotenoid production industry.

Diagram showing the cultivation of the native D. dissociatus MT1 isolated from the Algerian Sahara for tertiary wastewater treatment. The process includes microalgal experimental setup, biomass production, and wastewater treatment, resulting in high removal of nutrient and COD. Inadequately treated municipal wastewater remains a major environmental challenge in Algeria due to the limited efficiency of conventional treatment systems in removing nutrients and organic matter. In this context, preliminary evaluation of microalgae-based wastewater treatment using the native microalga ‘Dactylococcus dissociatus MT1’, previously isolated from the Algerian Sahara, highlighting its potential as sustainable and locally alternative for advanced wastewater polishing. Experiments were conducted using sterilised media, including raw secondary wastewater, filtered secondary wastewater, and synthetic wastewater (SWW), with bold basal medium used as a control. D. dissociatus adapted well to all media, exhibiting specific growth rates between 0.44 and 0.71 d− and maximum biomass concentrations of 960–1,490 mg/L. Nutrient removal assays revealed high bioremediation performance across all media, with ammonium removal reaching 99% and nitrate removal efficiencies of 91–98%. Orthophosphate was eliminated in most media, except SWW, where removal reached 83%. In contrast, SWW exhibited the highest chemical oxygen demand (COD) reduction (100%), compared with 93–97% in real wastewaters. As pH remained below 9 and bacterial activity was excluded, reduction in nutrients and organic matter may have been associated with microalgal uptake. However, the contribution of other physicochemical removal cannot be completely excluded and warrants further investigations.