Haloarchaeal Carotenoids: Healthy Novel Compounds from Extreme Environments

Abstract

Haloarchaea are halophilic microorganisms belonging to the archaea domain that inhabit salty environments (mainly soils and water) all over the world. Most of the genera included in this group can produce carotenoids at significant concentrations (even wild-type strains). The major carotenoid produced by the cells is bacterioruberin (and its derivatives), which is only produced by this kind of microbes and few bacteria, like Micrococcus roseus. Nevertheless, the understanding of carotenoid metabolism in haloarchaea, its regulation, and the roles of carotenoid derivatives in this group of extreme microorganisms remains mostly unrevealed. Besides, potential biotechnological uses of haloarchaeal pigments are poorly explored. This work summarises what it has been described so far about carotenoids from haloarchaea and their production at mid- and large-scale, paying special attention to the most recent findings on the potential uses of haloarchaeal pigments in biomedicine.

Deciphering Pathways for Carotenogenesis in Haloarchaea

“…Lycopene is one of the key molecules in the global carotenogenesis because it is the precursor for several branches sustaining carotenogenesis. Thus, relevant carotenoids in nature like lutein and its precursors and derivatives [40][41][42], neurosporaxanthin, and the C 50 -carotenoid called bacterioruberin [43] are synthesized from lycopene. Neurosporaxanthin is a carboxylic xanthophyll synthesized from geranylgeranyl pyrophosphate through the activity of four enzymes, encoded by the genes carRA, carB, carT, and carD [44].…”

“…It is mainly produced by fungi, being Fusarium and Neurospora, the genera from which its synthesis has been characterized [45,46]. Bacterioruberin is the main carotenoid synthesized by microorganisms belonging to the haloarchaea group, and only a few species of Micrococcus genus apart from haloarchaea can produce it [43,47]. The following sections are focused on the elucidation of the potential pathways that may be involved in the synthesis of bacterioruberin in haloarchaea.…”

Haloferax volcanii for biotechnology applications: challenges, current state and perspectives

“…Due to their remarkable properties such as antioxidants, colouring and light absorption, carotenoids are of great interest in biotechnology and medicine (Eggersdorfer and Wyss 2018;Fiedor and Burda 2014;Zhang et al 2014a). Recently, there has been growing interest in naturally derived carotenoids owing to the increasing demand for bioactive compounds of natural origin with higher bioaccessibility and environmentally benign bioprocessing methods (Giani et al 2019). The carotenoid biosynthesis pathway in H. volcanii begins with a condensation of two C 20 molecules into C 40 phytoene, a reaction catalysed by phytoene synthase, encoded by the crtB (HVO_2524) gene.…”

Heterologous and Homologous Expression of Proteins from Haloarchaea: Denitrification as Case of Study

“…Archaea has been the focus of scientific attention during the last three decades, not only due to their biology but also due to the potential applications of the molecules that they produce (enzymes, bioplastics, carotenoids, antibiotics, etc.) [23][24][25]. Thus, enzymes from alkaliphiles, thermophiles, or halophilic archaea revealed as active and stable catalyzers at high-temperature and high salinity conditions, which are environments generally adverse to other enzymes, have potential applications in industry and biotechnology [26][27][28][29][30][31][32].…”