Production of canthaxanthin by Haloferax alexandrinus under non-aseptic conditions and a simple, rapid method for its extraction

Abstract.

The production of carotenoids from Haloferax alexandrinus strain TM^T was investigated at various concentrations of NaCl (10–25%) in culture media under non-aseptic conditions. PCR and dot blot hybridization assays were employed to monitor the growth of Hfx. alexandrinus in the culture under aseptic and non-aseptic conditions. The amplified PCR products of 16S rDNA from Hfx. alexandrinus grown under aseptic conditions were used as specific probes, which bound with amplified PCR products of 16S rDNA dots from both aseptic and non-aseptic conditions (20–25% NaCl). The results indicated that contamination of the culture was precluded at high NaCl concentrations (20–25%). Therefore, it is not necessary to perform asepsis during the biotechnological processes of carotenoid production by Hfx. alexandrinus. A 1-l-scale cultivation of the cells in flask cultures under non-aseptic conditions produced 3.12±0.5 g dry weight, 6.34±2.5 mg total carotenoids and 2,156.67±0.1 µg canthaxanthin. Further experiments in a batch fermenter, under non-aseptic conditions, also demonstrated increases in the biomass concentration and carotenoid production. When grown in a standard growth medium at 25% NaCl, the cells of Hfx. alexandrinus lysed spontaneously in fresh water and hence carotenoids could be extracted directly from the cells without any mechanical disintegration. These results demonstrate the feasibility and simplicity of commercial production of carotenoids using Hfx. alexandrinus.