Purification and characterization of glucoamylase of Aspergillus oryzae from Luzhou-flavour Daqu

Biotechnol Lett. 2020 Nov;42(11):2345-2355. doi: 10.1007/s10529-020-02956-4. Epub 2020 Jul 4.

Abstract

Objective: To obtain novel glucoamylase from Daqu microbe.

Results: A dominant strain known as LZ2 with high activity of hydrolyzing starch was isolated from Luzhou Daqu, a Chinese traditional fermentation starter. The LZ2 was identified as Aspergillus oryzae by 18S rDNA sequence analysis. Glucoamylase from LZ2, named as GA-LZ2, was purified to homogeneity and showed a single band with expected molecular mass of 60 kD. The GA-LZ2 effectively degraded amylose, rice starch and wheat starch. Optimal temperature and pH value of enzyme were 60 °C and pH 4.0 respectively. The GA-LZ2 displayed significant thermal stability and pH stability at moderate temperature and low pH. Intriguingly, the thermostability was enhanced in the presence of starch. In addition, GA-LZ2 exhibited insensitivity to glucose, independence of metal ions and tolerance to organic solvents. The GA-LZ2 retained complete activity in the presence of 100 mM glucose and 5% ethanol and methanol.

Conclusion: Glucoamylase GA-LZ2 displayed broad substrate specificity, strong stability and tolerance, suggesting that GA-LZ2 carry potential for industrial application in bioethanol production.

Keywords: Aspergillus oryzae; Characteristics; Daqu; Glucoamylase; Purification.

MeSH terms

  • Amylose / chemistry
  • Aspergillus oryzae / classification*
  • Aspergillus oryzae / enzymology
  • Aspergillus oryzae / genetics
  • Aspergillus oryzae / isolation & purification
  • DNA, Fungal / genetics
  • DNA, Ribosomal / genetics
  • Enzyme Stability
  • Fermented Foods and Beverages
  • Fungal Proteins / isolation & purification
  • Fungal Proteins / metabolism
  • Glucan 1,4-alpha-Glucosidase / chemistry
  • Glucan 1,4-alpha-Glucosidase / isolation & purification*
  • Glucan 1,4-alpha-Glucosidase / metabolism
  • Hot Temperature
  • Hydrogen-Ion Concentration
  • Phylogeny
  • RNA, Ribosomal, 18S / genetics*
  • Sequence Analysis, DNA / methods*

Substances

  • DNA, Fungal
  • DNA, Ribosomal
  • Fungal Proteins
  • RNA, Ribosomal, 18S
  • Amylose
  • Glucan 1,4-alpha-Glucosidase