Abstract
Due to its superior antioxidant capabilities and higher activity than other carotenoids, astaxanthin is used widely in the nutraceutical and medicine industries. The most prolific natural producer of astaxanthin is the unicellular green microalga Haematococcus pluvialis. The correct identification of any contaminants in H. pluvialis cultures is both essential and nontrivial for several reasons. Firstly, while it is possible to distinguish the main microalgal contaminant Coelastrella sp. (in H. pluvialis cultures), in practice, it is frequently a daunting and error-prone task for personnel without extensive experience in the microscopic identification of algal species. Secondly, the undetected contaminants may decrease or stop production of astaxanthin. Lastly, the presence of other contaminants such as fungi can eventually infect and destroy the whole algae collection. In this study, high-resolution melting (HRM) analysis was developed to detect microalgal and fungal contamination. The developed diagnostic procedure allowed to distinguish pure H. pluvialis samples from cultures contaminated with low amounts (1.25 ng/ml) of microalgal DNA and fungal DNA (2.5 ng/ml). Such discrimination is not possible with the use of microscopy observations and allows fast and efficient collection testing.
Highlights
Astaxanthin (C40H52O4, 3,3’-dihydroxy-β,β-carotene-4,4’dione) is a red ketocarotenoid with extraordinary antioxidant capabilities
The tested samples described in the experiment belong to two strains of H. pluvialis: H. pluvialis G 1002 Flotow obtained from the Culture Collection of Algae of Charles University Department of Botany and H. pluvialis HPM obtained by the company AlgaeLabs Ltd. (Table 1)
The Sanger sequencing of amplicons was possible only in the samples containing pure control strain of H. pluvialis and samples very highly contaminated with Coelastrella sp
Summary
Astaxanthin (C40H52O4, 3,3’-dihydroxy-β,β-carotene-4,4’dione) is a red ketocarotenoid with extraordinary antioxidant capabilities. For many years, it has been produced synthetically and used mainly in aquaculture and poultry business as a pigmentation source, with an annual turnover of over $200 million (Li et al 2011) and a selling price of roughly $5000–6000 per kilo as of July 2012. Natural astaxanthin is over 50 times and 20 times stronger in singlet oxygen quenching and free radical elimination, respectively, than synthetic astaxanthin (Capelli et al 2013) This is due to the different composition of synthesized metabolite mixtures, as the natural product is predominantly a mixture of esters of a single enantiomer (3S, 3’S), while the artificial synthesis of astaxanthin results in a mixture of enantiomers in non-esterified form. Natural astaxanthin mixes are produced by various plants, bacteria, fungi, and green algae
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