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Electronic Journal of Biotechnology ISSN: 0717-3458 © 2008 by Pontificia Universidad Católica de Valparaíso -- Chile DOI: 10.2225/vol11-issue4-fulltext-12

Vol.11 No.4, Issue of October 15, 2008 Received April 10, 2008 / Accepted August 4, 2008

RESEARCH ARTICLE

Optimization of β-galactosidase production using Kluyveromyces lactis NRRL Y-8279 by response surface methodology
Seval DagbagliDepartment of Food Engineering Faculty of Engineering Ege University 35100 Bornova İzmir, Turkey Tel: 90 232 3884000. Ext. 3003 Fax: 90 232 3427592 E-mail: seval.dagbagli@ege.edu.tr

Yekta Goksungur*
Department of Food Engineering Faculty of Engineering Ege University 35100 Bornova İzmir, Turkey Tel: 90 537 405 29 24 Fax: 90 232 3427592 E-mail: yekta.goksungur@ege.edu.tr Financial support:This research was supported by the State Planning Organization (Turkey) through Project no: DPT.2005K120570 and Scientific and Technical Research Council of Turkey (TÜBİTAK) through Project no: TOVAG 104 O 270. Keywords: β-galactosidase, Kluyveromyces lactis, response surface methodology, shake flask culture, synthetic medium. Abbreviations: DNS: dinitrosalicylic acid ONP: o-nitrophenol ONPG:ο-nitrophenol-β-D-galactopyranoside P: probability RSM: response surface methodology SDS: sodium dodecyl sulfate

This paper investigates the production and optimization of β-galactosidase enzyme using synthetic medium by Kluyveromyces lactis NRRL Y-8279 in shake flask cultures. Among the different cell disintegration methods used, the highest specific activity was obtained when the cells werepermeabilized using isoamyl alcohol. Response surface methodology was used to investigate the effects of four fermentation parameters (agitation speed, pH, initial substrate concentration and incubation time) on β-galactosidase enzyme production. Results of the statistical analysis showed that the fit of the model was good in all cases. Maximum specific enzyme activity of 4218.4 U g-1 was obtained at theoptimum levels of process variables (pH 7.35, agitation speed 179.2 rpm, initial sugar concentration 24.9 g l-1 and incubation time 50.9 hrs). The response surface methodology was found to be useful in optimizing and determining the interactions among process variables in β-galactosidase enzyme production. The enzyme β-galactosidase (lactase, EC 3.2.1.23) catalyzes the hydrolysis of lactose toglucose and galactose. This enzyme is industrially important because it can be
*Corresponding author

used to avoid lactose crystallization in sweetened, condensed and frozen dairy products such as ice cream and condensed milk and solve problems associated with whey utilization and disposal. In addition, β-galactosidase is used to avoid the problems of lactose intolerance by individuals who aredeficient in lactase (Artolozaga et al. 1998). New applications for β-galactosidase, such as in the production of biologically active galacto-oligosaccharides, have also been reported in the literature (Boon et al. 2000; Albayrak and Yang, 2002). Commercial β-galactosidases are produced from yeasts such as Kluyveromyces lactis and Kluyveromyces marxianus (formerly known as Kluyveromyces fragilis andSaccharomyces fragilis), and moulds such as Aspergillus niger and Aspergillus oryzae (Shaikh et al. 1997; Santos et al. 1998). β-galactosidases produced by yeasts are the most employed for the treatment of milk, sweet whey and neutral pH dairy products since their optimum pH is between 6.5-7.0 (Santos et al. 1998). The activity and stability of enzymes is influenced by the type of strain,cultivation conditions (temperature, pH, aeration, agitation, incubation time) and the growth medium composition (particularly carbon and nitrogen

This paper is available on line at http://www.ejbiotechnology.info/content/vol11/issue4/full/12/

Dagbagli, S. and Goksungur, Y.

grits or wheat bran moistened with deproteinized milk whey. No previous work has used RSM or other statistical...