BackgroundXanthophyllomyces dendrorhous is a basidiomycetous yeast that synthesizes astaxanthin, a carotenoid with great biotechnological impact. The ergosterol and carotenoid synthetic pathways derive from the mevalonate pathway and involve cytochrome P450 enzymes. Among these enzymes, the CYP51 family, which is involved in ergosterol biosynthesis, is one of the most remarkable that has C14-demethylase activity.ResultsIn this study, the CYP51 gene from X. dendrorhous was isolated and its function was analyzed. The gene is composed of ten exons and encodes a predicted 550 amino acid polypeptide that exhibits conserved cytochrome P450 structural characteristics and shares significant identity with the sterol C14-demethylase from other fungi. The functionality of this gene was confirmed by heterologous complementation in S. cerevisiae. Furthermore, a CYP51 gene mutation in X. dendrorhous reduced sterol production by approximately 40% and enhanced total carotenoid production by approximately 90% compared to the wild-type strain after 48 and 120 h of culture, respectively. Additionally, the CYP51 gene mutation in X. dendrorhous increased HMGR (hydroxy-methylglutaryl-CoA reductase, involved in the mevalonate pathway) and crtR (cytochrome P450 reductase) transcript levels, which could be associated with reduced ergosterol production.ConclusionsThese results suggest that the CYP51 gene identified in X. dendrorhous encodes a functional sterol C14-demethylase that is involved in ergosterol biosynthesis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-015-0428-2) contains supplementary material, which is available to authorized users.

Silicone rod extraction (SR) is a siloxane-based methodology for the extraction of organic pollutants from aqueous samples with similar principle extraction as the stir bar sorptive extraction (SBSE). In this study the SR was coupled with HPLC-DAD and employed for the extraction and quantification of selected UV filters in water and seawater samples. Chromatographic parameters were optimized as well as the main sorption/desorption conditions for 4-methylbenzylidene camphor (4MBC) and octyl-methoxy cinnamate (OMC) from both river water and seawater samples. After optimization of the proposed method the following variables were selected: 25,0 mL of sample volume, 3 hour extraction, 1250 rpm as stirring velocity and 2 mL methanol as desorption solvent. The recoveries from seawater samples were 76.6% for 4MBC and 85.9% OMC. In river water samples recoveries of 69.8% and 82.4 % for 4MBC and OMC, respectively, were observed when salt was added to the sample. Linear calibration curves were obtained in the corresponding matrix and quantification limits below 1.86 µg L-1 were obtained. A comparison between the proposed method and the SBSE alternative revealed that SR can be use as a reliably and cheap methodology for the determination of sunscreens.