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Purification and Characterization of a Thermostable Starch‐Saccharifying Alpha‐1,4‐Glucan‐Glucohydrolase Produced by Bacillus licheniformis
Author(s) -
Ghani Maria,
Ansari Asma,
Haider Muhammad Samee,
Asif Tayyaba,
Ibrahim Fariha,
Qader Shah Ali Ul,
Aman Afsheen
Publication year - 2019
Publication title -
starch ‐ stärke
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.62
H-Index - 82
eISSN - 1521-379X
pISSN - 0038-9056
DOI - 10.1002/star.201800352
Subject(s) - bacillus licheniformis , starch , mutant , biochemistry , hydrolysis , molecular mass , enzyme , potato starch , fermentation , glucan , chemistry , amino acid , food science , biology , bacteria , bacillus subtilis , gene , genetics
To alleviate the difficulties of starch processing industries, it is necessary to improve the enzyme yield of commercially important alpha 1,4‐glucan‐glucohydrolase (glucoamylase) and explore new thermostable glucoamylases that have strong starch saccharifying capabilities. The current investigation is based on the purification and characterization of glucoamylase from wild and mutant strains of Bacillus licheniformis . Glucoamylase is purified up to homogeneity. The purified glucoamylase exhibits 67‐ and 506‐fold purification from wild ( B. licheniformis KIBGE‐IB3) and mutant ( B. licheniformis KIBGE‐IB3M67) strains, respectively, with a molecular weight of ≈185 kDa. Glucoamylase from wild and mutant strains hydrolyzes the starch at 50 °C in 5 min. V max and K m values from KIBGE‐IB3 are 107.07 kU mg −1 and 0.07 mg mL −1 whereas, for glucoamylase from KIBGE‐IB3M67 are 386.56 kU mg −1 and 0.12 mg mL −1 , respectively. End product analysis reveals that glucoamylase from mutant strain have strong saccharifying capability for potato starch. N‐Terminal protein sequence discloses that the first two amino acids (SSNKLTTSWG) in the wild‐type are replaced by other amino acids in the mutant strain (MDNKLTTSWG). After reviewing potential kinetic properties of glucoamylase, it is suggested that glucoamylase from KIBGE‐IB3M67 has remarkable potential to withstand harsh industrial environment and can straightforwardly saccharify potato starch into glucose molecules.