Microbial Carotenoids From Fungi Methods and Protocols
Carotenoids are a family of yellow to orange-red terpenoid pigments synthesized by photosynthetic organisms and many bacteria and fungi. They have beneficial health effects protecting against oxidative damage, and may be responsible for the colours associ
- PDF / 338,154 Bytes
- 12 Pages / 504.57 x 720 pts Page_size
- 0 Downloads / 217 Views
1. Introduction The ability of the basidiomycetous yeast Xanthophyllomyces dendrorhous (Phaffia rhodozyma) to accumulate the antioxidant, astaxanthin, as its major carotenoid is responsible for the industrial use of this yeast as a microbial source of pigments for aquaculture (1). Astaxanthin is economically important because it is the most expensive aquaculture feed component (2); it is used for the artificial pigmentation of fish and crustaceans (3). Astaxanthin is, in fact, one of the most expensive components of salmon farming, accounting for about 15% of total production costs (4). Original isolations of X. dendrorhous, which have served for most of the studies involving this species, were carried out in the 1960s by Phaff et al. (5). These isolates were obtained from slime exudates of various broad-leaved trees in different mountainous regions in the northern hemisphere, such as Japan and Canada. José-Luis Barredo (ed.), Microbial Carotenoids From Fungi: Methods and Protocols, Methods in Molecular Biology, vol. 898, DOI 10.1007/978-1-61779-918-1_12, © Springer Science+Business Media New York 2012
183
184
D. Libkind et al.
More recently, isolations of this species have been carried out in Italy (6), Germany (7), Argentina (8), and the USA (9). The isolations carried out in Argentina (NW Patagonia) were the first to be reported in the southern hemisphere, and unlike all previous isolations, they were not from sap flow, but rather from ascostroma of Cyttaria hariotii (8) parasiting the tree Nothofagus dombeyi. A few isolates were also obtained from a mountain lake. Patagonian strains of X. dendrorhous bear genetic differences with collection X. dendrorhous strains. These differences have been hypothetically explained by geographic isolation and habitat specificity (8). Even more recently, a new astaxanthin producing yeast isolate was obtained from a leaf of Eucalyptus globulus in Chile (10). This strain is remarkably different from all previous strains regarding the rRNA genes containing the internal transcribed spacers (ITS) sequences. These differences probably imply that the Chilean strain represents a novel species in the genus Xanthophyllomyces. Thus, it becomes clear that the natural geographic distribution of Xanthophyllomyces is wider than expected, and that its habitat is not restricted to slime fluxes, but rather, includes sugary rich fungal stromata, leaves, and freshwater. Furthermore, the genetic variability of this astaxanthin producing yeast is also more diverse than what was previously thought, and it is likely that there is more than one species in the genus. The biotechnological potential of the recently discovered Patagonian isolates has only been preliminary assessed (11). In this chapter, we describe the strategies currently used in our laboratory for the effective isolation of Xanthophyllomyces sp. from environmental samples, the accurate identification of the strains, the analysis of their astaxanthin content, and the proper conservation of the isolates.
2. Materials Prepare all soluti
Data Loading...
