Native to designed: microbial α-amylases for industrial applications
Background. α-amylases catalyze the endo-hydrolysis of α-1,4-D-glycosidic bonds in starch into smaller moieties. While industrial processes are usually performed at harsh conditions, α-amylases from mainly the bacteria, fungi and yeasts are preferred for their stabilities (thermal, pH and oxidati...
Saved in:
Main Authors: | , |
---|---|
Format: | Article |
Published: |
PeerJ
2021
|
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Summary: | Background. α-amylases catalyze the endo-hydrolysis of α-1,4-D-glycosidic bonds in
starch into smaller moieties. While industrial processes are usually performed at harsh
conditions, α-amylases from mainly the bacteria, fungi and yeasts are preferred for
their stabilities (thermal, pH and oxidative) and specificities (substrate and product).
Microbial α-amylases can be purified and characterized for industrial applications.
While exploring novel enzymes with these properties in the nature is time-costly, the
advancements in protein engineering techniques including rational design, directed
evolution and others have privileged their modifications to exhibit industrially ideal
traits. However, the commentary on the strategies and preferably mutated residues
are lacking, hindering the design of new mutants especially for enhanced substrate
specificity and oxidative stability. Thus, our review ensures wider accessibility of the
previously reported experimental findings to facilitate the future engineering work.
Survey methodology and objectives. A traditional review approach was taken to
focus on the engineering of microbial α-amylases to enhance industrially favoured
characteristics. The action mechanisms of α- and β-amylases were compared to avoid
any bias in the research background. This review aimed to discuss the advances in
modifying microbial α-amylases via protein engineering to achieve longer half-life in
high temperature, improved resistance (acidic, alkaline and oxidative) and enhanced
specificities (substrate and product). Captivating results were discussed in depth,
including the extended half-life at 100 ◦C, pH 3.5 and 10, 1.8 M hydrogen peroxide as
well as enhanced substrate (65.3%) and product (42.4%) specificities. These shed light
to the future microbial α-amylase engineering in achieving paramount biochemical
traits ameliorations to apt in the industries.
Conclusions. Microbial α-amylases can be tailored for specific industrial applications
through protein engineering (rational design and directed evolution). While the critical
mutation points are dependent on respective enzymes, formation of disulfide bridge
between cysteine residues after mutations is crucial for elevated thermostability. Amino
acids conversion to basic residues was reported for enhanced acidic resistance while
hydrophobic interaction resulted from mutated hydrophobic residues in carbohydrate binding module or surface-binding sites is pivotal for improved substrate specificity. Substitution of oxidation-prone methionine residues with non-polar residues increases the enzyme oxidative stability. Hence, this review provides conceptual advances for the future microbial α-amylases designs to exhibit industrially significant characteristics. However, more attention is needed to enhance substrate specificity and oxidative
stability since they are least reported. |
---|