# A Hyperthermostable Archaeal GH78 Rhamnosidase Efficiently Hydrolyzes Flavonoid Glycosides for Juice Debittering

## TL;DR

This paper introduces a new archaeal enzyme that efficiently removes bitterness from fruit juices by breaking down specific compounds.

## Contribution

The first hyperthermostable archaeal GH78 α-L-rhamnosidase is identified and characterized for juice debittering.

## Key findings

- ArRha efficiently hydrolyzes α-1,2 and α-1,6 rhamnosyl linkages in flavonoid glycosides.
- ArRha achieves >95% conversion of naringin to prunin and naringenin in orange juices within 2 hours at 65 °C.
- The enzyme exhibits remarkable temperature stability, wide pH activity, and organic solvent tolerance.

## Abstract

α-L-Rhamnosidases are a class of glycosyl hydrolases
(GHs)
that catalyze the hydrolysis of terminal α-L-rhamnose residues
from diverse glycoconjugates. While extensively characterized in bacterial
and fungal sources, no archaeal α-L-rhamnosidases have been
characterized to date. Herein, we report the identification and characterization
of the first thermostable archaeal α-L-rhamnosidase (ArRha),
derived from the metagenomic data set of Pisciarelli solfatara hot
spring. ArRha, classified in glycoside hydrolase family GH78, efficiently
hydrolyzes α-1,2 and α-1,6 rhamnosyl linkages in flavonoid
glycosides with notable biological activities. The novel enzyme showed
remarkable temperature stability, wide-range pH activity, organic
solvent tolerance, and no metal dependence. Combined with a thermostable
β-glucosidase, ArRha converts naringin to prunin and naringenin
in sweet and blood orange juices, achieving >95% conversion within
2 h at 65 °C. This represents the first report of a hyperthermostable
archaeal GH78 α-L-rhamnosidase with promising applications in
industrial enzymatic juice debittering and sustainable flavonoid biotransformation.