The consumption of vegetable oil is an important way for the body to obtain tocols. However, the impact of oil types and grades on the tocopherol and tocotrienol contents in vegetable oils is unclear. In this study, nine types of traditional edible oils and ten types of self-produced new types of vegetable oil were used to analyze eight kinds of tocols. The results showed that the oil types exerted a great impact on the tocol content of traditional edible oils. Soybean oils, corn oils, and rapeseed oils all could be well distinguished from sunflower oils. Both sunflower oils and cotton seed oils showed major differences from camellia oils as well as sesame oils. Among them, rice bran oils contained the most abundant types of tocols. New types of oil, especially sacha inchi oil, have provided a new approach to obtaining oils with a high tocol content. Oil refinement leads to the loss of tocols in vegetable oil, and the degree of oil refinement determines the oil grade. However, the oil grade could not imply the final tocol content in oil from market. This study could be beneficial for the oil industry and dietary nutrition.

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High-performance chromatography method was developed and validated for essaying α-tocopherol and cholesterol in cryopreservation media. Chromatographic separation was performed on isocratic system, using a C-18 column. The mobile phase was composed of a mixture of methanol: acetonitrile: water 68:28:4 (v/v/v), using a flow rate of 1.5 ml/min and 20 μl injection volume, at a wavelength of 208 nm. The method was validated according to ICH guidelines. The method proved to be specific, accurate, precise and linear with correlation coefficients greater than 0.996 over a wide concentration range of both analytes. Vitamin E and cholesterol presented limits of detection of 0.002 mg/ml, 0.026 mg/ml and limits of quantitation of 0.006 mg/ml, 0.086 mg/ml, respectively. This method shows simple, rapid, high precision and accuracy and offers the advantage of simultaneous assay of vitamin E and cholesterol (alone, in cyclodextrins complexes or in liposome loaded) on semen cryopreservation media.

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Delta-tocotrienol as a vitamin E isomer has received much attention because of its diverse biomedical applications. Microbial biosynthesis of delta-tocotrienol is a promising strategy for its economic and environmental advantages. Here, we accomplished complete biosynthesis of delta-tocotrienol in Saccharomyces cerevisiae from glucose. We first constructed and incorporated a heterologous pathway into the genome of S. cerevisiae by incorporating the genes hpd (from Pseudomonas putida KT2440), hpt (from Synechocystis sp. PCC 6803), and vte1 (from Arabidopsis thaliana) for the biosynthesis of delta-tocotrienol. We further enhanced the biosynthesis of the precursor geranylgeranyl diphosphate by overexpressing the thmg1 and ggppssa (from Sulfolobus acidocaldarius) genes, leading to a production titer of delta-tocotrienol of 1.39 ± 0.01 mg/L. Finally, we optimized the fermentation medium using the response surface methodology, enabling a high-titer production of delta-tocotrienol (3.56 ± 0.25 mg/L), ∼2.6-fold of that of the initial culture medium. Fed-batch fermentation in a 2 L fermenter was further used to enhance the production titer of delta-tocotrienol (4.10 ± 0.10 mg/L). To the best of our knowledge, this is the first report on the de novo biosynthesis of delta-tocotrienol in S. cerevisiae, and the highest titer obtained for microbial production of delta-tocotrienol.

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