title: β-galactosidase Production by Aspergillus niger ATCC 9142 Using Inexpensive Substrates in Solid-State Fermentation: Optimization by Orthogonal Arrays Design.
abstract: Enzymatic hydrolysis of lactose is one of the most important biotechnological processes in the food industry, which is accomplished by enzyme β-galactosidase (β-gal, β-D-galactoside galactohydrolase, EC 3.2.1.23), trivial called lactase. Orthogonal arrays design is an appropriate option for the optimization of biotechnological processes for the production of microbial enzymes.
  
  
  
  Design of experimental (DOE) methodology using Taguchi orthogonal array (OA) was employed to screen the most significant levels of parameters, including the solid substrates (wheat straw, rice straw, and peanut pod), the carbon/nitrogen (C/N) ratios, the incubation time, and the inducer. The level of β-gal production was measured by a photometric enzyme activity assay using the artificial substrate ortho-Nitrophenyl-β-D-galactopyranoside.
  
  
  
  The results showed that C/N ratio (0.2% [w/v], incubation time (144 hour), and solid substrate (wheat straw) were the best conditions determined by the design of experiments using the Taguchi approach.
  
  
  
  Our finding showed that the use of rice straw and peanut pod, as solid-state substrates, led to 2.041-folds increase in the production of the enzyme, as compared to rice straw. In addition, the presence of an inducer did not have any significant impact on the enzyme production levels.
authors.affiliation: Vice-Chancellor of Research and Technology, Guilan University of Medical Sciences, Rasht, Iran.
authors.forename: Samaneh
authors.initials: S
authors.lastname: Kazemi
authors.affiliation: Department of Chemical Engineering, Faculty of Engineering, University of Guilan, Rasht, Iran.
authors.forename: Gholam
authors.initials: G
authors.lastname: Khayati
authors.affiliation: Department of Microbiology, Faculty of Science, Islamic Azad University, Lahijan Branch, Lahijan, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Faezi-Ghasemi
keywords: Beta-galactosidase; Aspergillus niger; Solid waste