Green Microalgae Strain Improvement for the Production of Sterols and Squalene

Thraustochytrium sp. and Aurantiochytrium sp.: Sustainable Alternatives for Squalene Production

This study investigated a sustainable alternative to squalene production utilizing Thraustochytrium sp. and Aurantiochytrium sp., thereby reducing dependence on critically endangered sharks exploited for this compound. By optimizing fed-batch cultivation, a technique prevalent in industrial biotechnology, we have enhanced squalene yields and have demonstrated, through sensitivity analysis, the significance of this shift in preserving species at risk of extinction. Optimization of culture conditions led to the highest biomass concentrations for Thraustochytrium sp. being achieved at lower C-N ratios (<5.0), while the optimal biomass production for Aurantiochytrium sp. occurred in culture media with a high C-N ratio of 54:50. Regarding squalene production, Thraustochytrium sp. produced 26.13 mg/L in the fed-batch system after 72 h, and Aurantiochytrium sp. produced 54.97 mg/L in a batch system with 30 g/L glucose and 0.22 g/L nitrogen after 96 h, showcasing their potential for industrial applications. Moreover, the sensitivity analysis revealed that, on an industrial scale, both strains could produce up to 59.50 t of squalene annually in large-scale facilities, presenting a valuable and sustainable alternative for the biotechnological industry and significantly reducing the reliance on non-renewable and endangered sources such as shark liver oil and preventing the annual capture of over 156,661 sharks.

Solving Challenges in Microalgae-Based Living Materials

Engineered living materials (ELMs) integrate aspects of material science and biology into a unique platform, leading to materials and devices with features of life. Among those, ELMs containing microalgae have received increased attention due to the many benefits photosynthetic organisms provide. Due to their relatively recent occurrence, photosynthetic ELMs still face many challenges related to reliability, lifetime, scalability, and more, often based on the complicated crosstalk of cellular, material-based, and environmental variables in time. This Viewpoint aims to summarize potential avenues for improving ELMs, beginning with an emphasis on understanding the cell's perspective and the potential stresses imposed on them due to recurring flaws in many current ELMs. Potential solutions and their ease of implementation will be discussed, ranging from choice of organism, adjustments to the ELM design, to various genetic modification tools, so as to achieve ELMs with longer lifetime and improved functionality.

Algal lipids: A review on current status and future prospects in food processing

The consumer demand for functional foods derived from natural sources has been enhanced due to health-promoting effects. Algae are widely available globally as a sustainable source of proteins, lipids, and carbohydrates. Algal lipids are underexplored natural sources that exhibit several nutraceutical effects and applications in fortification, cosmetics, and pharmaceuticals. Both macro- and microalgae are composed of high-quality lipids. These latter involve polar lipids, nonpolar lipids, and essential fatty acids. Therefore, this review aimed to bring out knowledge on the chemistry of various lipids isolated and identified from micro- and macroalgae. Further, their extraction using traditional thermal (solid-liquid, and liquid-liquid) and advanced nonthermal (supercritical fluid, microwave-, ultrasound-, and enzyme-assisted) techniques has been explored. Along with this, bioactivities of algal lipids have been discussed. This study explored algal lipids in advancing sustainable food processing technologies that contribute positively to environmental sustainability and global health, in line with United Nations Sustainable Development GroupUnited Nations Sustainable Development Group UNSDGs.

Outdoor cultivation and metabolomics exploration of Chlamydomonas engineered for bisabolene production

Demonstrating outdoor cultivation of engineered microalgae at considerable scales is essential for their prospective large-scale deployment. Hence, this study focuses on the outdoor cultivation of an engineered Chlamydomonas reinhardtii strain, 3XAgBs-SQs, for bisabolene production under natural dynamic conditions of light and temperature. Our preliminary outdoor experiments showed improved growth, but frequent culture collapses in conventional Tris-acetate-phosphate medium. In contrast, modified high-salt medium (HSM) supported prolonged cell survival, outdoor. However, their subsequent outdoor scale-up from 250 mL to 5 L in HSM was effective with 10 g/L bicarbonate supplementation. Pulse amplitude modulation fluorometry and metabolomic analysis further validated their improved photosynthesis and uncompromised metabolic fluxes towards the biomass and the products (natural carotenoids and engineered bisabolene). These strains could produce 906 mg/L bisabolene and 54 mg/L carotenoids, demonstrating the first successful outdoor photoautotrophic cultivation of engineeredC. reinhardtii,establishing it as a one-cell two-wells biorefinery.

Random Mutagenesis as a Promising Tool for Microalgal Strain Improvement towards Industrial Production

Microalgae have become a promising novel and sustainable feedstock for meeting the rising demand for food and feed. However, microalgae-based products are currently hindered by high production costs. One major reason for this is that commonly cultivated wildtype strains do not possess the robustness and productivity required for successful industrial production. Several strain improvement technologies have been developed towards creating more stress tolerant and productive strains. While classical methods of forward genetics have been extensively used to determine gene function of randomly generated mutants, reverse genetics has been explored to generate specific mutations and target phenotypes. Site-directed mutagenesis can be accomplished by employing different gene editing tools, which enable the generation of tailor-made genotypes. Nevertheless, strategies promoting the selection of randomly generated mutants avoid the introduction of foreign genetic material. In this paper, we review different microalgal strain improvement approaches and their applications, with a primary focus on random mutagenesis. Current challenges hampering strain improvement, selection, and commercialization will be discussed. The combination of these approaches with high-throughput technologies, such as fluorescence-activated cell sorting, as tools to select the most promising mutants, will also be discussed.

Structural and Molecular Characterization of Squalene Synthase Belonging to the Marine Thraustochytrid Species Aurantiochytrium limacinum Using Bioinformatics Approach

The marine microorganisms thraustochytrids have been explored for their potential in the production of various bioactive compounds, such as DHA, carotenoids, and squalene. Squalene is a secondary metabolite of the triterpenoid class and is known for its importance in various industrial applications. The bioinformatic analysis for squalene synthase (SQS) gene (the first key enzyme in the tri-terpenoid synthesis pathway), that is prevailing among thraustochytrids, is poorly investigated. In-silico studies combining sequence alignments and bioinformatic tools helped in the preliminary characterization of squalene synthases found in Aurantiochytrium limacinum. The sequence contained highly conserved regions for SQS found among different species indicated the enzyme had all the regions for its functionality. The signal peptide sequence and transmembrane regions were absent, indicating an important aspect of the subcellular localization. Secondary and 3-D models generated using appropriate templates demonstrated the similarities with SQS of the other species. The 3-D model also provided important insights into possible active, binding, phosphorylation, and glycosylation sites.