Purification and characterization of glucoamylase of Aspergillus oryzae from Luzhou-flavour Daqu
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ORIGINAL RESEARCH PAPER
Purification and characterization of glucoamylase of Aspergillus oryzae from Luzhou-flavour Daqu Chuan Wang
. Lianli Yang . Lunan Luo . Shichao Tang . Qiang Wang
Received: 22 January 2020 / Accepted: 30 June 2020 Ó Springer Nature B.V. 2020
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,
C. Wang (&) L. Yang L. Luo S. Tang Q. Wang College of Bioengineering, Sichuan University of Science & Engineering, No. 180, Xueyuan Street, Huixing Road, Zigong 643000, Sichuan, People’s Republic of China e-mail: [email protected]
suggesting that GA-LZ2 carry potential for industrial application in bioethanol production. Keywords Daqu Aspergillus oryzae Glucoamylase Purification Characteristics
Introduction The glucoamylase functionality is attributed to starch glycosylation fermentation which facilitate absorption of nutrients and creation of energy. Currently, commercial glucoamylase is acquired mainly from fungi such as Aspergillus niger or Rhizopus niveus and R. delemar (Kumar and Satyanarayana 2009). The glucoamylases acquired from these resources carry moderate thermostability, acidic pH requirement, narrow substrate pattern, pretreatment of substrate and slow catalytic activities. Owing to these shortcomings, fungal glucoamylase made more energy consumption and process inconvenience in starch saccharification and fermentation. Therefore, there is an urgent and unmet demand to develop novel microbial glucoamylases suitable for evolving industrial applications. In recent decades, some representative novel glucoamylases were isolated from microorganism and were functionally characterized. Some microbial glucoamylase have shown activities at optimum temperature of 75 °C
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(Zheng et al. 2010) and 90 °C (Kim et al. 2004), and remained stable at pH2 and between pH 10–11 (Xian and Feng 2018; Spinelli et al. 1996). Nevertheless, these glucoamylases still need further study for industrial applications. Daqu,
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