Biosynthesis of pigment by bacteria isolated from antarctica

Abstract

Known as one of the world's most extreme environments, Antarctica is a region that has attracted researchers from around the world, boasting dozens of creatures, structures, and formations yet to be discovered. Human technology, as it has developed to date, has the capacity to gradually expand our horizons beyond the known by unlocking the mysteries of this continent. It serves as a guiding light for us in sustainable living and clean energy technologies, which are among the most important issues of our time, as well as in the protection of people and the planet. Every study done for this continent is a treasure, providing inspiration and ideas to advance deep research, learning and technology in every field, from microorganisms and metabolites to ocean life and its diverse habitats, from geological formations to the rich structure of its minerals. This study emerged as a result of interest and curiosity in the microorganisms living on this remarkable continent. Antarctica hosts a diverse range of microbial communities, and the ways these communities adapt to extreme conditions compared to what we might call the world's normally temperate regions is being closely studied today. Due to the microorganisms' easy biodegradability, ease of controlled production in a laboratory setting, and rich variety of contents, scientific research on natural pigments derived from microorganisms has gained momentum in recent years as an alternative to synthetic pigment production. Many studies are focused on improving microbial pigments by bioengineering methods and generating scientific data on the adequate understanding of their metabolic formation pathways and on improving the biotechnological utilization of organic pigments. As a result, technologies based on chemical pigments, which harm humans and the ecosystem, are beginning to give way to natural solutions and transform. In this study, pigment activities on Rhodococcus fascians isolated from ice cores from the Horseshoe, Hovgaard, and Nansen Islands of Antarctica, as well as Brevibacterium sp. and Microbacterium sp. isolated from the Ross Sea that belong to the Italian Maria Zucchelli Station, are analyzed experimentally. An optimization study (Plackett-Burman Design-PBD) was carried out to investigate the responses of bacteria to medium components and environmental factors, and appropriate pH and temperature values were investigated. To ascertain the chemical structure, FTIR, UV-Vis, NMR, and TLC analyses were carried out. The disk diffusion method was used to test its antibacterial activity, and DPPH (Free Radical Scavenging Test) tests were performed to determine its antioxidant capacity, and the results were shared in this study. Spectroscopically, the pigment structure obtained from R. fascians shows the presence of a carotenoid-based pigment at 456 nm, as reported in the literature. The structure of isorenieratene, a carotenoid-derived pigment, at 405-408 nm in Brevibacterium sp., and neurosporene, a carotenoid-derived pigment also reported in previous studies, at 407-417 nm in Microbacterium sp., are strikingly similar. An optimization study was conducted to determine the most efficient production conditions for three different bacterial species. The highest total carotenoid concentration was obtained in Rhodococcus fascians (485.00 µg/g), followed by Microbacterium sp. (179.89 µg/g) and Brevibacterium sp. (63.62 µg/g). Pigments were extracted from the isolates and their antimicrobial activities were determined to inhibit both Gram (+) and Gram (-) bacteria. FTIR spectra for pigment production in these three Actinomycete bacterial species confirmed the presence of functional groups associated with carotenoid-like pigments. The FTIR analysis revealed strong O-H, C-H, and C=O stretching vibrations, which supported the pigment structures suggested by the UV-Vis data. DPPH was evaluated in detail for Rhodococcus fascians pigment by the free radical scavenging test. DPPH inhibition increased from 17.46% to 84.99%, indicating high antioxidant properties with IC₅₀ value = 0.36 µg/µL based on linear regression analysis (R²=0.8817). Further analysis of the chemical structure of the pigment obtained from R. fascians using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy revealed that it was a carotenoid pigment of the zeaxanthin and lutein varieties. Microbial studies conducted in extreme environments like space and Antarctica demonstrate that microorganisms are more adaptable than their counterparts living under normal conditions. Researching Antarctic-origin microorganisms is very valuable in the search for solutions to existing problems in the space environment, from biofilm formation to natural polymers and the use of natural carotenoid pigments. Expeditions to the Moon and Mars will be able to make significant gains in the coming years, such as preventing infections, reducing cell decay, recycling waste, protecting against radiation, and improving food content, thanks to microorganism-based technological solutions.