BACKGROUND A major problem in the orange industry is ‘delayed’ bitterness, which is caused by limonin, a bitter compound developing from its non‐bitter precursor limonoate A‐ring lactone (LARL) during and after extraction of orange juice. The glucosidation of LARL by limonoid UDP‐glucosyltransferase (LGT) to form non‐bitter glycosyl‐limonin during orange maturation has been demonstrated as a natural way to debitter by preventing the formation of limonin. RESULT Here, the debittering potential of heterogeneously expressed glucosyltransferase, maltose‐binding protein (MBP) fused to cuGT from Citrus unishiu Marc (MBP‐cuGT), which was previously regarded as LGT, was evaluated. A liquid chromatography – mass spectrometry (LC–MS) method was established to determine the concentration of limonin and its derivatives. The protocols to obtain its potential substrates, LARL and limonoate (limonin with both A and D ring open), were also developed. Surprisingly, MBP‐cuGT did not exhibit any detectable effect on limonin degradation when Navel orange juice was used as the substrate; MBP‐cuGT was unable to biotransform either LARL or limonoate as purified substrates. However, it was found that MBP‐cuGT displayed a broad activity spectrum towards flavonoids, confirming that the enzyme produced was active under the conditions evaluated in vitro. CONCLUSION Our results based on LC–MS demonstrated that cuGT functionality was incorrectly identified. Its active substrates, including various flavonoids but not limonoids, highlight the need for further efforts to identify the enzyme responsible for LGT activity to develop biotechnology‐based approaches for producing orange juice from varietals that traditionally have a delayed bitterness. © 2020 Society of Chemical Industry
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.