Carotenoids from Haloarchaea and Their Potential in Biotechnology

Abstract

The production of pigments by halophilic archaea has been analysed during the last half a century. The main reasons that sustains this research are: (i) many haloarchaeal species possess high carotenoids production availability; (ii) downstream processes related to carotenoid isolation from haloarchaea is relatively quick, easy and cheap; (iii) carotenoids production by haloarchaea can be improved by genetic modification or even by modifying several cultivation aspects such as nutrition, growth pH, temperature, etc.; (iv) carotenoids are needed to support plant and animal life and human well-being; and (v) carotenoids are compounds highly demanded by pharmaceutical, cosmetic and food markets. Several studies about carotenoid production by haloarchaea have been reported so far, most of them focused on pigments isolation or carotenoids production under different culture conditions. However, the understanding of carotenoid metabolism, regulation, and roles of carotenoid derivatives in this group of extreme microorganisms remains mostly unrevealed. The uses of those haloarchaeal pigments have also been poorly explored. This work summarises what has been described so far about carotenoids production by haloarchaea and their potential uses in biotechnology and biomedicine. In particular, new scientific evidence of improved carotenoid production by one of the better known haloarchaeon (Haloferax mediterranei) is also discussed.

Biocompounds from Haloarchaea and Their Uses in Biotechnology

“…Few studies stated that some haloarchaeal species (wild-type strains) produce significant concentrations of carotenoids, which are marked highly demanding [13]. Besides, carotenoid production by haloarchaea can be improved by genetic modification or even by modifying several cultivation aspects such as nutrition, growth pH, or temperature.…”

“…The conversion of two molecules of geranylgeranyl pyrophosphate (GGPP) to phytoene, a compound common to all C 40 carotenogenic organisms, constitutes the first reaction unique to the carotenoid branch of isoprenoid metabolism. From this step, slightly different reactions can be found in different organisms [13].…”

“…Animals are not able to synthesize carotenoids de novo, and consequently, they are acquired through diet. In most of the organisms, carotenoids show powerful antioxidant properties, which directly emerge from their molecular structure [13].…”

“…They are also involved in the reinforcement of the cell membrane, and they can be part of the rhodopsin complexes (light-driven proton pump highly important for haloarchaea cells to obtain energy) [13].…”

“…Thus, several biocompounds such as enzymes [12], carotenoids [13], PHAs/PHBs [14], and halocins (bacteriocin-like peptides) [15] have focused the attention of many researchers around the world. Many of the studies on these subjects were published between the 1990s and the first decade of the current century.…”