# Xylan Degradation in the Halotolerant Bacterium Bacillus altitudinis relies on glycosidic hydrolases from families 11 and 30

## TL;DR

This paper studies how a salt-tolerant bacterium breaks down xylan using two specific enzymes, which work together to convert xylan into usable sugars.

## Contribution

The study identifies and characterizes two novel xylanolytic glycoside hydrolases from a halotolerant bacterium with a unique genomic arrangement.

## Key findings

- BaGH11 and BaGH30 are salt-tolerant endoxylanases that produce different xylooligosaccharides.
- The two enzymes work synergistically to hydrolyze glucuronoxylan into xylose and xylobiose.
- The enzymes are encoded in distinct operons involved in xylan and xylose catabolism.

## Abstract

The breakdown of
xylan, a major hemicellulose component, involves
multiple xylanases.Bacillus altitudinis SRL571, a halotolerant endophytic bacterium, utilizes glucuronoxylan
and xylose as its sole carbon and energy sources. Genome analysis
revealed two sequences encoding putative secreted xylanolytic glycoside
hydrolases: one from family 11 (BaGH11) and another from family 30,
subfamily 8 (BaGH30). These genes are located in two distinct operons
involved in xylan and xylose catabolism, a genomic configuration unique
to this strain. Both enzymes are salt-tolerant and act as endoxylanases:
BaGH11 releases mainly short-chain xylooligosaccharides (e.g., xylobiose)
while BaGH30 produces medium-chain xylooligosaccharides. BaGH11 and
BaGH30 act synergistically to hydrolyze glucuronoxylan into xylose
and xylobiose, which are subsequently imported into cells via putative
sugar transporters. This study elucidates the biocatalytic basis of
xylan degradation in a halotolerant bacterium and highlights the importance
of complementary enzyme activities for effective biomass degradation
in saline environments.