A mini-review was recently published as a preliminary proof in ACS Omega, which provided extensive insights into the production of important bioactive compounds through the “alg nanobionics” approach. This study focused mainly on the role of carbon nanomaterials (CNM) in efficient algae growth.
Study: Explore the role of carbon-based nanomaterials in microalgae for sustainable production of bioactive compounds and more. Image credit: Chokniti Khongchum / Shutterstock.com
Microalgae: Composition and function
Microalgae are an important source of many important biostimulating products with added value; for example, bioactive compounds are widely used in the pharmaceutical industry. In addition, these have been used as an important food source for many centuries. Algae play an important role in reducing the carbon footprint.
Some of the main components of microalgae are chlorophylls, sterols, hydrocarbons, wax esters, carotenoids, proteins, carbohydrates, phycobilins, minerals, fatty acids and other bioactive compounds. The concentration of these components varies from one species of microalgae to another.
The bioactive compounds extracted from microalgae have many unique properties, including antimicrobial, anti-inflammatory, antioxidant and antitumor. These phytonutrients play an important role in improving human health. Researchers have pointed out some of the benefits of using algal drugs over synthetic drugs. They claimed that algal drugs are biodegradable, have superior biocompatibility and are non-toxic in nature.
One of the essential green microalgae is Chlorella sp., Which has been used to produce various refined components, such as natural lipids, lutein and β-carotene. The biggest advantage of this algae is that it is extremely fast-growing and thrives well in environmental stresses.
Carbon nanomaterials and microalgae
There are many types of CNM, such as fullerenes, graphene nanosheets, nanocarbon, nanodiamond, graphene oxide (GO) and graphene quantum dots (GQDs). CNM has many unique properties, including optical properties, large area-to-volume ratio, multifunctional surface morphology, immunogenicity and biocompatibility. Their sizes range from 1 to 100 nm. These nanomaterials are used in many research areas, such as drug delivery.
Among various CNMs, GO has significantly improved the rate of bioconversion by increasing the catalytic conversion of lipids to biodiesel from wet microalgae (Chlorella pyrenoidosa) biomass. Researchers found that sulfonated graphene oxide (SGO) exhibits the highest catalytic activity due to a higher concentration of hydrophilic hydroxyl group.
Carbon nanosheets (CNS) are two-dimensional (2D) structures that have a high surface-to-volume ratio, high chemical stability, lightweight materials and have superior thermal and electrical properties. The CNS can easily pass through the algal pores found in its cell wall due to its small size. Thereafter, internalization and distribution of nanoparticles in its cells and organelles, such as mitochondria, endoplasmic reticulum, chloroplast, and vacuoles, occur. Passive transfer and endocytosis are two methods associated with the internalization of the CNS in the algal cells. Passive internalization of the CNS in microalgae cells causes minimal damage and has significantly improved the biotransformation process.
Recently, enzyme-immobilized nanomaterials have been used for the conversion of microalgae because they have greater recyclability, antibacterial properties, do not require a filtration process and have better functionality.
The effect of carbon nanomaterials on microalgae
Nanobionics is an emerging technology that supports the incorporation of CNM into algal cell networks to improve biosynthetic pathways for increased production of bioactive compounds. For example, the introduction of carbon nanotubes (CNT) through the leaves of a plant increases the photosynthesis process and increases the production of secondary carotenoids. However, a similar phenomenon was not observed when using single-walled CNTs due to cytotoxic effects.
Several studies have shown that CNM can increase the photosynthetic processes within the algal biosystem. These can also modify the physico-chemical functions of the algae. Therefore, microalgae can be used as a sustainable source to produce important biologically active components with added value.
The introduction of CNM into the algal cell framework increases stress tolerance and the ability of microalgae to absorb more sunlight, which improves its photosynthesis process and results in increased biomass production.
Microalgae are usually grown in three different ways, namely mixotrophic, photoautotrophic and heterotrophic. Because the cost of growing and maintaining microalgae is high, it inhibits its widespread development. In this context, researchers reported that the use of CNM can significantly reduce the cultivation and maintenance costs of microalgae.
Researchers have planned the use of the CNS to adsorb algal cells in its surface, which promotes rapid cell growth and lipid accumulation. This is an environmentally friendly approach to promote the production of alternative fuels (biofuels). In addition, several microalgae are used as nutraceutical products and the bioactive compounds have medicinal applications.
Another strategy used to improve the catalytic activity and biocompatibility of CNMs is the doping technique, which modifies their physicochemical properties. For example, nitrogen doped CNS has greater photocatalytic activity with higher biocompatibility, which can be determined by the presence of amino and hydroxyl groups.
Researchers researching algae nanobionics have focused on improving their understanding of the inherent metabolic changes at nano-bio interfaces. This information can effectively improve the production of bioactive compounds. In addition, incorporation of nanomaterials into the algal system can create new nano-bio-hybrid organisms (algae nano-biohybrids) that can facilitate the superior production of biologically important active compounds. Researchers believe that alganobio hybrids can be used to promote sustainability in the medical, agricultural and pharmaceutical sectors.
Jeevanandham, S. et al. (2022) Explores the role of carbon-based nanomaterials in microalgae for sustainable production of bioactive compounds and beyond. ACS Omega. https://pubs.acs.org/doi/10.1021/acsomega.2c01009
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