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In this paper, we have performed the Lipozyme 435-catalyzed synthesis of xylose oleate in methyl ethyl ketone (MEK) from xylose and oleic acid. The effects of substrates’ molar ratios, reaction temperature, reaction time on esterification rates, and Lipozyme 435 reuse were studied. Results showed that an excess of oleic acid (xylose: oleic acid molar ratio of 1:5) significantly favored the reaction, yielding 98% of xylose conversion and 31% oleic acid conversion after 24 h-reaction (mainly to xylose mono- and dioleate, as confirmed by mass spectrometry). The highest Lipozyme 435 activities occurred between 55 and 70 °C. The predicted Ping Pong Bi Bi kinetic model fitted very well to the experimental data and there was no evidence of inhibitions in the range assessed. The reaction product was purified and presented an emulsion capacity close to that of a commercial sugar ester detergent. Finally, the repeated use of Lipozyme 435 showed a reduction in the reaction yields (by 48 and 19% in the xylose and oleic acid conversions, respectively), after ten 12 h-cycles.

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Citrus sinensis and Citrus limonia were obtained by germination from seeds, and isotopic-labeling experiments using d-[1-13C]­glucose were performed with the seedlings. After 60 days, the seedlings were analyzed by high-performance liquid chromatography–ultraviolet–solid-phase extraction–nuclear magnetic resonance, data and the 13C enrichment patterns of xanthyletin and seselin indicated that the pyran ring was formed by the methylerythritol phosphate pathway and that the coumarin moiety was derived from the shikimate pathway in both compounds. This information regarding the biosynthetic pathway can be used to increase resistance against phytopathogens, because xanthyletin and seselin are reported to have antimicrobial activity on the growth of Xylella fastidiosa, which causes citrus variegated chlorosis in orange.