## 2 Starch Modification Processes
### Enzymatic Process  
During enzymatic modification, starch is exposed to enzymes (hydratases) that accelerate the production of highly functional derivatives [38]. The enzymatic modification technique is mainly used to prepare glucose syrup, high fructose corn, or cassava syrup. The primary function of enzymatic modification is the depolymerization of starch into oligosaccharides or the transformation of starch by transferring glycosidic linkages and residues [38]. The role of the enzyme during this modification technique is breaking down the \(\alpha\)-1,4 bond between two glucose units [32]. Enzymatically modified starch is utilized in foodstuffs, cosmetics, pharmaceuticals, detergents, adhesives, and drilling fluids [32]. The main four types of starch converting enzymes are (i) endoamylses, (ii) exoamylases, (iii) debranching enzymes, and (iv) transferases [32]. Table 1 summarizes the examples of starch converting enzymes and their biological function.  
Among the four types of starch converting enzymes, debranching enzymes are widely employed in the industry. Figure 4 demonstrates the enzymatic hydrolysis of starch. As depicted in Figure 4, pullulanase, isoamylase, and oligo-1,6-glucosidase are mainly used to debranch the \(\alpha\)-1,6-glycosidic bonds in starch, giving linear amylose, whereas amylosucarse, \(\alpha\)-amylase, and amylomalatase are capable of debranching the 1,4 and 1,6 glycosidic bonds, resulting in small amylose or amylopectin chains.  
Table 2 summarizes the optimum reaction conditions for starch debranching enzymes. According to Figure 4, exoamylases such as glucoamylases, \(\alpha\)-glucosidase, and \(\beta\)-amylases are used to produce glucose, whereas cyclodextrin cleaves the \(\alpha\)-1,4-glycosic bond while connecting both reducing and nonreducing ends. The isoamylase enzyme has higher enzymatic activity compared to that of other enzymes [38]. Pullulanase is widely employed to prepare high-amylose starch utilized in adhesive products, resistance starch, corrugated boards, and the paper industry [38].  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Type of Starch** & **Biological Function** & **Example(s)** & **References** \\ \hline Endoamylses & \begin{tabular}{c} Cleave the \(\alpha\)-1,4-glucosidaseic bonds present in the inner \\ part of the amylose or amylopectin chain \\ \end{tabular} & \(\alpha\)-amylase & [39] \\ \hline Exoamylases & \begin{tabular}{c} Cleave both \(\alpha\)-1,4 and \(\alpha\)-1,6 bonds on amylose or \\ amylopectin’s external glucose residues from the \\ non-reducing end and produces only glucose \\ (glucoseamylase and \(\alpha\)-glucosidase). \\ \end{tabular} & Glucoamylases & [40] \\ \hline Debranching enzymes & \begin{tabular}{c} Catalyze the hydrolysis of \(\alpha\)-1,6-glucosidaseic bonds \\ in amylopectin. \\ \end{tabular} & \begin{tabular}{c} Amylo-1,6-glucosidaseic \\ Pullulanase \\ Isoamylase \\ \end{tabular} & [38] \\ \hline Transferases & \
\begin{tabular}{c} Cleave \(\alpha\)-1,4-glucosidaseic bond of the donor molecule and \\ transfer part of the donor to a glucosidic acceptor to \\ form a new glucosidic bond. \\ \end{tabular} &
\begin{tabular}{c} Amylomalatase \\ Cyclodextrin \\ \end{tabular} & [38] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Main types of starch converting enzymes and their biological function.  
Figure 4: Enzymatic hydrolysis of starch.  
Besides the previously mentioned enzymes, lipase and protease are also used for starch modification [41]. These enzymes are widely utilized to catalyze starch acetylation and achieve modified starch with high purity [42]. [PERSON] et al. [43] reported the green synthesis of corn starch-maleate using the lipase enzyme as a biocatalyst and maleic acid as an esterification agent. [PERSON] et al. [44] prepared esterified starch using lipase and ionic liquid.