Comparative biochemical characterization of soluble and chitosan immobilized β-galactosidase from Kluyveromyces lactis NRRL Y1564

• Published in: Process biochemistry (1991) 2013-03, Vol.48 (3), p.443-452
• Main Authors: Lima, Ariosvana Fernandes, Cavalcante, Kenia Franco, de Freitas, Maria de Fátima Matos, Rodrigues, Tigressa Helena Soares, Rocha, Maria Valderez Ponte, Gonçalves, Luciana Rocha Barros
• Format: Article
• Language: English
• Subjects: beta-galactosidase; carbon; Chitin; chitosan; enzyme activity; fermentation; Immobilization; immobilized enzymes; Kluyveromyces; Kluyveromyces lactis; Kluyveromyces marxianus var. lactis; Lactose; temperature; Thermal stability; Whey
• ISSN: 1359-5113; 1873-3298
• DOI: 10.1016/j.procbio.2013.02.002

► Kluyveromyces strains were screened for β-galactosidase production on whey. ► Kluyveromyces lactis NRRL β-galactosidase Y1564 was immobilized onto chitosan. ► High operational stability of the immobilized enzyme was observed. ► High storage stability of the immobilized enzyme was observed for 93 days at 4°C. An investigation was conducted on the production of β-galactosidase (β-gal) by different strains of Kluyveromyces, using lactose as a carbon source. The maximum enzymatic activity of 3.8±0.2U/mL was achieved by using Kluyveromyces lactis strain NRRL Y1564 after 28h of fermentation at 180rpm and 30°C. β-gal was then immobilized onto chitosan and characterized based on its optimal operation pH and temperature, its thermal stability and its kinetic parameters (Km and Vmax) using o-nitrophenyl β-d-galactopyranoside as substrate. The optimal pH for soluble β-gal activity was found to be 6.5 while the optimal pH for immobilized β-gal activity was found to be 7.0, while the optimal operating temperatures were 50°C and 37°C, respectively. At 50°C, the immobilized enzyme showed an increased thermal stability, being 8 times more stable than the soluble enzyme. The immobilized enzyme was reused for 10 cycles, showing stability since it retained more than 70% of its initial activity. The immobilized enzyme retained 100% of its initial activity when it was stored at 4°C and pH 7.0 for 93 days. The soluble β-gal lost 9.4% of its initial activity when it was stored at the same conditions.