**4.4 Fermentation of pentose**

Pentoses like arabinose, ribose, and xylose, among other related carbohydrates, like gluconate, may all be broken down by several LABs. These compounds are processed through the phosphoketolase pathway after being taken in by cells through permeases [23, 24]. Pentose phosphate is then metabolized by epimerases or isomerases who phosphorylate the pentoses to create ribulose 5-phosphate or xylulose 5-phosphate [23].

## **4.5 Fermentation of disaccharides**

Disaccharides are substances composed of two simple sugars (monosaccharides). LAB breaks down (metabolize) and splits disaccharides into simple sugars (two monosaccharides) for easy absorption into the bloodstream. Lactose, cellobiose, maltose, melibiose, sucrose, and other disaccharides are among those digested by LAB [24]. These sugars are transferred as free sugars or phosphorylated sugars passing through the cell membrane and then splitting into two monosaccharides or a monosaccharide and a monosaccharide phosphate [30]. Even though disaccharide fermentation appears to be more complicated than monosaccharide fermentation, some LABs prefer disaccharides as growth substrates; lactose fermentation by dairy LAB and maltose fermentation by sourdough LAB are two examples [24].
