Chuan Wang1, Lianli Yang2, Lunan Luo2, Shichao Tang2, Qiang Wang2. 1. College of Bioengineering, Sichuan University of Science & Engineering, No. 180, Xueyuan Street, Huixing Road, Zigong, 643000, Sichuan, People's Republic of China. watpc57944@163.com. 2. College of Bioengineering, Sichuan University of Science & Engineering, No. 180, Xueyuan Street, Huixing Road, Zigong, 643000, Sichuan, People's Republic of China.
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.
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, ricestarch 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.