Safety evaluation of DAS-44406-6 soybeans in Wistar rats.

A 90-day in-country feeding trial in Wistar rats was conducted at Tianjin Laboratory in China to assess toxicity of diets containing DAS-44406-6 soybean meal. There were no treatment-related changes observed when compared with the non-GM isoline control groups but histopathologically, 2 of 10 high-dose females were reported to show kidney lesions. However, these findings contrasted with the absence of any treatment-related kidney lesions in 3 separate 90-day toxicity studies previously conducted in Sprague Dawley rats. Strain difference is not expected in the kidney response, and based on the low incidence and contrary evidence from previous studies, it is likely that these lesions were of spontaneous origin, or artefactual. To determine that the lesions observed were not treatment-related in Wistar rats, a specific follow-up confirmatory study was conducted under Good Laboratory Practices (GLP) in the Wistar strain of rats following an identical study design to the Tianjin study. To increase the power of detecting effects, twice the number of animals per group (20/sex/group) were used, and no treatment-related kidney histopathological changes were observed. Based on these results and entire weight of evidence evaluation, it is concluded that the histopathological changes previously noted in the 2 female Wistar rats of Tianjin study were not treatment-related and that DAS-44406-6 soybeans are as safe as conventional non-GM soybeans.

Genetic manipulation of Xanthophyllomyces dendrorhous and Phaffia rhodozyma.

The yeasts Xanthophyllomyces dendrorhous (teleomorph) and Phaffia rhodozyma (anamorph) are of basidiomycetous affinity and have the unique property among yeasts of producing the carotenoid pigment astaxanthin. Astaxanthin imparts the attractive coloration to salmonids, crustaceans, and several birds such as the flamingo, and it has considerable economic value. Microbiological and genetic techniques for manipulation are rudimentary in the yeast, while their utility would be valuable for strain development including hypermutants that overproduce astaxanthin. Here we describe methods for manipulation of the yeast, including induction of the sexual stage with basidiospore formation, methods for isolation of mutants (particularly mutants affected in carotenoid biosynthesis) as well as techniques for isolation and analysis of carotenoids. These methods are valuable for understanding the biology and enhancing the biotechnology value of the yeast.