Isolation, production and optimisation of beta-galactosidase by utilizing yeasts isolated from selected dairy products

Folake  Titilayo Afolabi; Oluwaseyi Peter Adewale; Stella Mojisola Adeyemo

doi:10.18502/jfsh.v8i3.11019

Folake Titilayo Afolabi Department of Microbiology, Faculty of Science, University of Ibadan, Ibadan, Nigeria.
Oluwaseyi Peter Adewale Department of Microbiology, Faculty of Science, University of Ibadan, Ibadan, Nigeria.
Stella Mojisola Adeyemo Department of Microbiology, Faculty of Science, Obafemi Awolowo University, Ile-Ife, Osun State, Nigeria.

DOI: https://doi.org/10.18502/jfsh.v8i3.11019

Keywords: β-galactosidase; Kluyveromycesmarxianus SLDY – 005; lactose; Nigerian local cheese; Ortho-nitrophenyl-β-Dgalactopyranoside (ONPG)

Abstract

β-galactosidase is an enzyme that converts lactose into glucose and galactose. It alleviates the issue associated with intolerance to lactose and pollution caused as a result of milk by-products (whey). This study aimed to isolate and select yeast strains that can produce β-galactosidase from fresh milk, yoghurt and locally made cheese. A total of 115 yeasts were isolated from the samples, 9 yeast isolates had the ability to produce β-galactosidase and three (3) were selected for further analysis. β-galactosidase producers were screened using Ortho-nitrophenyl-β-D-galactopyranoside (ONPG) assay. Kluyveromyces marxianus strain SLDY – 005 produced the highest β-galactosidase. It showed maximum enzyme activity (277U/mL) at temperature 30oC, pH 5.5, after an incubation period of 36 h. Glucose had a decrease in β-galactosidase production while yeast extract and urea were considered appropriate nitrogen sources for the best enzyme synthesis. Crude β-galactosidase produced by Kluyveromyces marxianus SLDY – 005 was purified. The partially purified enzyme after dialysis showed a specific activity of 165.12 U/mL and had a purification fold of 6.02 and yield of 45.91 %. The purified enzyme had an optimum temperature of 40oC and a pH 6.0. Kluyveromyces marxianus strain isolated from local cheese is a potential candidate for the production of βgalactosidase and it could be used for combating the problem of lactose intolerance.