Optimization of Growth and Carotenoid Production by Haloferax mediterranei Using Response Surface Methodology

Abstract

Haloferax mediterranei produces C50 carotenoids that have strong antioxidant properties. The response surface methodology (RSM) tool helps to accurately analyze the most suitable conditions to maximize C50 carotenoids production by haloarchaea. The effects of temperature (15–50 °C), pH (4−10), and salinity (5–28% NaCl (w/v)) on the growth and carotenoid content of H. mediterranei were analyzed using the RSM approach. Growth was determined by measuring the turbidity at 600 nm. To determine the carotenoid content, harvested cells were lysed by freeze/thawing, then re-suspended in acetone and the total carotenoid content determined by measuring the absorbance at 494 nm. The analysis of carotenoids was performed by an HPLC system coupled with mass spectrometry. The results indicated the theoretical optimal conditions of 36.51 or 36.81 °C, pH of 8.20 or 8.96, and 15.01% or 12.03% (w/v) salinity for the growth of haloarchaea (OD600 = 12.5 ± 0.64) and production of total carotenoids (3.34 ± 0.29 mg/L), respectively. These conditions were validated experimentally for growth (OD600 = 13.72 ± 0.98) and carotenoid production (3.74 ± 0.20 mg/L). The carotenoid profile showed four isomers of bacterioruberin (89.13%). Our findings suggest that the RSM approach is highly useful for determining optimal conditions for large-scale production of bacterioruberin by haloarchaea.

Haloarchaeal Carotenoids: Healthy Novel Compounds from Extreme Environments

“…Due to these adaptations, haloarchaea have become a promising and innovative renewable source of different molecules of high interest in biotechnology such as enzymes able to be active at high temperature and high ionic strength [12,13], poly(3-hydroxybutyrate) (PHB) and polyhydroxyalkanoate (PHA) [14,15,16,17], and carotenoids [18,19,20]. Besides, new roles for haloarchaea in wastewater bioremediation processes have also been reported [7,21,22].…”

Evaluation of the Antibacterial Material Production in the Fermentation of Bacillus amyloliquefaciens-9 from Whitespotted Bamboo Shark (Chiloscyllium plagiosum)

“…where Y is the predicted response, β 0 is the intercept term, β i represents the linear coefficients, β ii represents the quadratic coefficients, β ij represents the interactive coefficients, and x i and x j are the coded independent variables [19,51]. Other media concentrations remained at 8.5 , 3, and 0.5 g L −1 for Na 2 HPO 4 , KH 2 PO 4 and NaCl, respectively.…”

Deciphering Pathways for Carotenogenesis in Haloarchaea

“…In summary, although haloarchaea could synthesize other carotenoids apart from bacterioruberin (like β-carotene, lycopene, or in some species canthaxanthin), the major carotenoid is bacterioruberin and its relatives. The pathway deciphered in this work (Figure 2) sheds light on the knowledge of carotenogenesis in archaea and will contribute to the production of mutants over pigmented in order to upscale carotenoids production using archaea as biofactories [80,90]. Other issues like regulation of carotenogenesis [91] in haloarchaea and connections between carotenogenesis, synthesis of bacteriorhodopsin, and monooxygenases [69] should be explored into detail in the near future in order to understand the whole process making possible cellular pigmentation in this kind of microorganisms.…”

“…), haloarchaea could synthetize phytoene, phytofluene, γ-carotene, β-carotene, neurosporene, lycopene, zeacarotene and bacterioruberin (and its derivatives and precursors) ( Figure 2). The final concentration of each of those carotenoids, quantified from cellular extracts, will depend on the conditions of the culture as well as on the phase of growth in which the cells are harvested [80].…”