Abstract:
Raw starch degrading enzyme specially glucoamylase with starch binding domain (SBD) has great values in the starch processing industry
because it digests the starch particles below the gelatinization temperature by releasing glucose from the non-reducing ends sequentially.
The purpose of the study was to measure the secretion levels of recombinant glucoamylase from Pichia pastoris, by using the α-mating
factor secretion signal peptide (α-MF) and the native signal peptide of glucoamylase from Aspergillus flavus NSH9. The Aspergillus flavus
NSH9 gene (with and without native signal sequences), encoding a pH and thermostable glucoamylase with an SBD, was successfully
cloned and expressed in Pichia pastoris to produce recombinant glucoamylases. The constructed recombinant plasmids pPICZB_GA2
(having a native signal peptides) and pPICZαC_GA2 (having the α-MF) were 5144 and 5356 bp in length respectively. Recombinant
pichia having α-MF signal sequence (plasmid, pPICZαC_GA2) gave the highest level of secretions of recombinant glucoamylase after 6
days of incubation period with 0.5% methanol. In conclusion, yeast expression vector signal peptide is more efficient for heterologous
expression/secretions of recombinant glucoamylase compared to its native signal sequences.
