Evaluation of crude oil biodegradation using mixed fungal cultures.

The use of potent fungal mixed cultures is a promising technique for the biodegradation of crude oil. Four isolates of fungi, namely, Alternaria alternata (AA-1), Aspergillus flavus (AF-3), Aspergillus terreus (AT-7), and Trichoderma harzianum (TH-5), were isolated from date palm soil in Saudi Arabia. The mixed fungal of the four isolates have a powerful tool for biodegradation up to 73.6% of crude oil (1%, w/v) in 14 days. The fungal consortium no. 15 containing the four isolates (1:1:1:1) performed significantly better as a biodegradation agent than other consortium in a variety of environmental factors containing crude oil concentration, incubation temperature, initial pH, biodegradation time and the salinity of the medium. The fungal consortium showed better performance in the biodegradation of normal alkanes (n-alkanes) than that of the polycyclic aromatic hydrocarbons (PAHs); the biodegradation efficiency of normal alkanes of the fungal consortium (67.1%) was clearly high than that of the PAHs (56.8%).

Crystal structure and immunologic characterization of the major grass pollen allergen Phl p 4.

BACKGROUND: Phl p 4 is a major pollen allergen but exhibits lower allergenicity than other major allergens. The natural protein is glycosylated and shows cross-reactivity with related and structurally unrelated allergens. OBJECTIVE: We sought to determine the high-resolution crystal structure of Phl p 4 and to evaluate the immunologic properties of the recombinant allergen in comparison with natural Phl p 4. METHODS: Different isoallergens of Phl p 4 were expressed, and the nonglycosylated mutant was crystallized. The specific role of protein and carbohydrate epitopes for allergenicity was studied by using IgE inhibition and basophil release assays. RESULTS: The 3-dimensional structure was determined by using x-ray crystallography at a resolution of 1.9 Å. The allergen is a glucose dehydrogenase with a bicovalently attached flavin adenine dinucleotide. Glycosylated and nonglycosylated recombinant Phl p 4 showed identical inhibition of IgE binding, but compared with natural Phl p 4, all recombinant isoforms displayed a reduced IgE-binding inhibition. However, the recombinant protein exhibited an approximately 10-fold higher potency in basophil release assays than the natural protein. CONCLUSION: The crystal structure reveals the compact globular nature of the protein, and the observed binding pocket implies the size of the natural substrate. Plant-derived cross-reactive carbohydrate determinants (CCDs) appear to reduce the allergenicity of the natural allergen, whereas the Pichia pastoris-derived glycosylation does not. Our results imply yet undescribed mechanism of how CCDs dampen the immune response, leading to a novel understanding of the role of CCDs.