**2. The depolymerization of the pectin polymer into a simpler form**

The pectin depolymerization occurred either physical, chemical, or enzymatic methods, **Figure 2**.

**Figure 2.**

*The different depolymerization processes of various types of pectin [inspired from Satapathy et al., 2020 [19]].*

#### **2.1 Physical process**

Includes high-pressure treatment, ultrasonication, radiation, and photolysis. At a pH value lower or higher than 3.5, the acetyl, methoxyl, and neutral sugar groups are eliminated, and the polymer backbone is cleaved.

### **2.2 Chemical process**

Acid or base hydrolysis can catalyze the splitting of chains by the β-elimination reaction. The dissolution takes place at a glycosidic linkage next to an esterified **GalA**. As a result of the higher methoxylation degree (DM) of pectin becomes extra susceptible to base-catalyzed reactions rather than a low DM pectin. However, by acid hydrolysis (pH < 3.0), pectin hydrolyses with low DM are faster in comparison to pectin with high DM [20].

### **2.3 Enzymatic process**

Wide range of enzymes used for the polymer degradation allowing regionselective depolymerization under mild conditions. So that, using enzymic degradation gain the interest of many researchers.
