Introduction of β-Carotene
β-Carotene, a prevalent carotenoid in the human diet, is found in various tissues, including blood, and is extensively used in medicine due to its high bioactivity. Its crucial role in supplying provitamin A impacts embryonic development, growth, and vision. Additionally, it acts as a gene inhibitor, displaying anticancer and antioxidant properties. Beyond its bioactivity, β-carotene's significance lies in its industrial use as a food additive and coloring agent. In the food industry, it imparts an orange-red hue to beverages, fats, cheese, pastry, and ice cream. In pharmaceuticals, it serves as a tablet colorant, while in cosmetics, it functions as a protective bioactive ingredient against oxidation and UV radiation.
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Fig. 1 Chemical structure of beta-carotene.
Properties of β-Carotene
β-Carotene, a plant-synthesized secondary metabolite, belongs to the unoxidized carotenoid compound group. Its acyclic structure, C40H56, boasts a polyene compound with a chain of conjugated double bonds. High temperatures induce isomerization, brightening the resulting color. β-carotene holds the highest bioactivity as a vitamin A precursor, undergoing conversion in the small intestine. However, the conversion is incomplete, with 1 mg of retinol equivalent to 6 mg of β-carotene. Carotenoids, with β-ion rings, exhibit provitamin activity and accumulate in lipid phases, affecting biological processes like photosynthesis and vision. Unconverted β-carotene and retinal esters, transported via chylomicrons, impact biological functions.
Methods for β-Carotene Production
Methods for β-carotene production are diverse, encompassing physicochemical, chemical, and biotechnological approaches. Physicochemical methods involve the extraction of carotenoids from various plant parts, such as green plant tissues, flowers, fruits, seeds, roots, and tubers. The orange carrot is a prominent source of β-carotene. The extraction process includes purification, material shredding, juice pressing, protein coagulation, sedimentation, centrifugation, extraction with organic solvent, filtration, deodorization, evaporation, and crystallization. However, this method faces challenges like high costs, geographical constraints, and raw material seasonality. Efforts are underway to enhance carotenoid biosynthesis in plants through genetic modifications.
Chemical synthesis, dating back to the 1950s, has been a significant method for carotenoid production. Wittig reactions and Grignard compounds are employed to synthesize carotenoids, including β, and β-carotene.
Biotechnological methods, particularly microbial biosynthesis, are gaining prominence. Microorganisms such as algae (Dunaliella spp., Eustigmatos cf. Polyphem), bacteria (Rhodococcus maris, Rhodobacter sphaeroides), and yeast species are explored for their ability to produce β-carotene efficiently. Downstream processing is crucial for β-carotene extraction, with the microbial biomass being broken down to isolate the compound. Glycerol, a by-product in various processes, has become an economically important substrate for β-carotene production.
Industrial-scale production of β-carotene involves cultivating molds (Blakeslea trispora) or algae (Dunaliella salina). The process includes three main stages: inoculum multiplication, biomass biosynthesis, and carotenoid extraction. Conditions for alga cultivation, such as intense sunlight and saline water, impact β-carotene biosynthesis. Dunaliella salina is a major commercial source, with cultivation in open tanks under specific conditions. The extraction process varies depending on the desired commercial form, whether alga powder or carotenoid emulsion. Despite algae being a popular source of carotenoids, concerns about heavy metal accumulation necessitate careful sourcing to ensure safety for food applications.
References
- Gul K., et al. Chemistry, encapsulation, and health benefits of β-carotene-A review. Cogent Food & Agriculture. 2015, 1(1): 1018696.
- Bogacz-Radomska L., Harasym J. β-Carotene-properties and production methods. Food Quality and Safety. 2018, 2(2): 69-74.
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