- Carotenoids are a diverse group of naturally occurring pigments synthesized by plants, algae, fungi, and some bacteria. These compounds are responsible for the yellow, orange, and red colors found in many fruits, vegetables, and microorganisms.
- Chemically, carotenoids are tetraterpenoids, composed of 40 carbon atoms arranged in a conjugated double-bond system, which gives them their distinctive color and antioxidant properties. They are broadly classified into two categories: carotenes, which are purely hydrocarbons (e.g., β-carotene and lycopene), and xanthophylls, which contain oxygen atoms (e.g., lutein, zeaxanthin, and astaxanthin).
- In photosynthetic organisms, carotenoids play essential roles in light harvesting and photoprotection. They are embedded within chloroplast membranes, where they assist in capturing light energy and transferring it to chlorophyll molecules for photosynthesis. Importantly, carotenoids also protect plant cells from photooxidative damage by quenching reactive oxygen species (ROS) and dissipating excess energy as heat through a process known as non-photochemical quenching. In fungi and some bacteria, carotenoids serve as protective agents against ultraviolet radiation and oxidative stress.
- In the animal and human diet, carotenoids are vital micronutrients, especially since humans cannot synthesize them and must obtain them through food. Some carotenoids, like β-carotene, α-carotene, and β-cryptoxanthin, are precursors of vitamin A, a crucial nutrient for vision, immune function, and cell differentiation. Others, such as lutein and zeaxanthin, are important for eye health, accumulating in the macula of the retina where they help filter harmful blue light and reduce the risk of age-related macular degeneration. Additionally, carotenoids like lycopene and astaxanthin have been linked to antioxidant, anti-inflammatory, and anticancer activities, although these effects are still being explored in clinical research.
- Carotenoids have numerous industrial applications across food, cosmetics, pharmaceuticals, and animal feed industries. In the food industry, they are used both as colorants and nutritional additives. For example, β-carotene is used to color margarine and other processed foods, while astaxanthin is added to aquaculture feeds to enhance the pink-red coloration of salmon and shrimp. In cosmetics, carotenoids are valued for their antioxidant properties, contributing to skin protection and anti-aging products. In pharmaceuticals and nutraceuticals, carotenoids are being incorporated into supplements aimed at supporting eye health, cardiovascular health, and general immunity.
- Microbial production of carotenoids, especially by fungi like Blakeslea trispora and Phycomyces blakesleeanus, as well as certain yeasts and bacteria, is an area of increasing interest for sustainable biotechnology. Microorganisms offer advantages over plant sources due to faster growth, ease of cultivation, and the potential for genetic manipulation to enhance yield and specificity. These microbial systems are being optimized for commercial carotenoid production using cost-effective substrates and bioprocessing techniques.
- In summary, carotenoids are multifunctional, biologically important compounds that serve essential roles in photosynthesis, photoprotection, and human nutrition. Their vibrant colors, antioxidant potential, and diverse health benefits make them valuable across a wide spectrum of scientific and commercial fields. As research and biotechnological innovation continue, carotenoids are poised to play an even greater role in health, agriculture, and sustainable industry.
