TS), with significant release of inter-fibrillary materials. The enzyme was produced
using solid-state fermentation with wheat bran as the substrate and showed equivalent fibre splitting with lower cost than chemical-based processes and commercially
used enzyme powder products. Alkaline-active amylases produced from such
inexpensive substrates are thus good candidates for the leather processing and can
also be used in treatment of alkaline waste water generated from the leather
processing.
5 Conclusion
Alkaline-active starch-modifying enzymes have significant real and potential
industrial applications. A lot of alkaline-active amylases have been heterologously
expressed in recombinant hosts in order to improve yields and optimize their
properties. An example is the recombinant alkaline-active and thermotolerant
amylase from Bacillus halodurans MS-2-5 which was cloned and expressed in
E. coli with 104-fold yield as compared to that of the parent strain, MS-2-5 [117].
In another strategy employing the atmospheric and room temperature plasma
(ARTP) mutation breeding technique, it was found that some Bacillus subtilis
mutants produced higher yields of recombinant alkaline α-amylase (AMY) as
compared to expression of the amylase in the wild-type Bacillus subtilis host [118].
Studies have also been conducted to continuously improve the properties of
these enzymes. Through site-directed mutagenesis, the oxidative stability of
alkaline-active amylase from Alkalimonas amylolytica was enhanced, while some
mutants also exhibited extended pH stability of up to pH 12 [119]. Such mutants
would be more suitable for the detergent and textile industries. The specific activity
and catalytic efficiency of alkaline-active α-amylase (AmyK) from Alkalimonas
amylolytica was further enhanced by using a novel protein engineering strategy
that involved the integration of terminal truncation and N-terminal oligopeptide
fusion [120]. This was done by partially truncating the C- or N-terminus of
AmyK, followed by fusion of an oligopeptide at the N-terminus of the truncated
AmyK. The truncation-fusion mutants were found to have higher catalytic efficiency
than AmyK. Higher flexibility around the active site was proposed to be the possible
reason for the improved catalytic efficiency of AmyK amylase. With enhanced
catalytic activity and stability through genetic engineering and nanotechnology,
greater potential can be realized from these robust enzymes.
References
1. Singh J, Kaur L, McCarthy OJ (2007) Factors influencing the physico-chemical, morphological, thermal and rheological properties of some chemically modified starches for food
applications – a review. Food Hydrocoll 21(1):1–22
238
S. O. Hashim
using solid-state fermentation with wheat bran as the substrate and showed equivalent fibre splitting with lower cost than chemical-based processes and commercially
used enzyme powder products. Alkaline-active amylases produced from such
inexpensive substrates are thus good candidates for the leather processing and can
also be used in treatment of alkaline waste water generated from the leather
processing.
5 Conclusion
Alkaline-active starch-modifying enzymes have significant real and potential
industrial applications. A lot of alkaline-active amylases have been heterologously
expressed in recombinant hosts in order to improve yields and optimize their
properties. An example is the recombinant alkaline-active and thermotolerant
amylase from Bacillus halodurans MS-2-5 which was cloned and expressed in
E. coli with 104-fold yield as compared to that of the parent strain, MS-2-5 [117].
In another strategy employing the atmospheric and room temperature plasma
(ARTP) mutation breeding technique, it was found that some Bacillus subtilis
mutants produced higher yields of recombinant alkaline α-amylase (AMY) as
compared to expression of the amylase in the wild-type Bacillus subtilis host [118].
Studies have also been conducted to continuously improve the properties of
these enzymes. Through site-directed mutagenesis, the oxidative stability of
alkaline-active amylase from Alkalimonas amylolytica was enhanced, while some
mutants also exhibited extended pH stability of up to pH 12 [119]. Such mutants
would be more suitable for the detergent and textile industries. The specific activity
and catalytic efficiency of alkaline-active α-amylase (AmyK) from Alkalimonas
amylolytica was further enhanced by using a novel protein engineering strategy
that involved the integration of terminal truncation and N-terminal oligopeptide
fusion [120]. This was done by partially truncating the C- or N-terminus of
AmyK, followed by fusion of an oligopeptide at the N-terminus of the truncated
AmyK. The truncation-fusion mutants were found to have higher catalytic efficiency
than AmyK. Higher flexibility around the active site was proposed to be the possible
reason for the improved catalytic efficiency of AmyK amylase. With enhanced
catalytic activity and stability through genetic engineering and nanotechnology,
greater potential can be realized from these robust enzymes.
References
1. Singh J, Kaur L, McCarthy OJ (2007) Factors influencing the physico-chemical, morphological, thermal and rheological properties of some chemically modified starches for food
applications – a review. Food Hydrocoll 21(1):1–22
238
S. O. Hashim