β-Galaktosidase (laktase) digunakan dalam produksi susu rendah laktosa untuk konsumsi penderita intoleransi laktosa. Dalam proses metabolismenya, enzim ini dapat menghidrolisis laktosa menjadi glukosa dan galaktosa. Lactobacillus lactis merupakan salah satu bakteri asam laktat yang dapat menghasilkan β_galaktosidase secara intraseluler. Dalam penelitian ini β_galaktosidase dari Lactobacillus lactis diekstraksi melalui tiga jenis pelarut, yaitu isoamyl Alkohol, SDS-Kloroform, dan Toluen-Aseton. Hasil ekstraksi dilakukan karakterisasi pada variasi pH, suhu, dan waktu fermentasi terhadap aktivitas β_galaktosidase. Penentuan aktivitas β-galaktosidase dilakukan dengan penambahan substrat oNPG dan diukur nilai absorbansi pada λmax 420 nm. Pada penelitian ini, pelarut toluen-aseton lebih baik dari pelarut isoamil alkohol dan SDS-kloroform karena menghasilkan nilai oNP tertinggi yaitu sebesar 8,206 µmol, pada pH 7 dengan waktu fermentasi Lactobacillus lactis dan suhu inkubasi β-galaktosidase masing masing 24 jam dan 37oC. Aktivitas β-galaktosidase tertinggi diperoleh sebesar 13,02 U/mL dengan waktu inkubasi β-galaktosidase dan waktu fermentasi Lactobacillus lactis masing-masing 15 menit dan 24 jam. Perbandingan aktivitas β_galaktosidase yang dihasilkan antara Lactobacillus lactis dengan Lactococcus lactis telah menunjukkan bahwa walaupun family dan bentuk sel berbeda, namun nilai aktivitas enzim yang dihasilkan tidak berbeda secara signifikan. Nilai pH dan suhu optimal untuk aktivitas β-galaktosidase dalam menghidrolisis substrat oNPG masing-masing pH 7 dan 37oC.

β-Galactosidase (lactase) is used in the production of low-lactose milk for consumption by people with lactose intolerance. In its metabolic process, this enzyme can hydrolyze lactose into glucose and galactose. Lactobacillus lactis is one of the lactic acid bacteria which can produce β-galactosidase intracellularly. In this study, β-galactosidase from Lactobacillus lactis was extracted through three types of solvents, isoamyl alcohol, SDS-Chloroform, and Toluene-Acetone. The results of the extraction were characterized by variations in pH, temperature, and fermentation time on β-galactosidase activity. Determination of β-galactosidase activity was carried out by adding oNPG substrate and measuring the absorbance value at λmax 420 nm. In this study, toluene-acetone was better than isoamyl alcohol and SDS-chloroform because it produced the highest oNP value of 8.206 µmol, at pH 7 with fermentation time of Lactobacillus lactis and β-galactosidase incubation temperature, respectively 24 hours and 37oC. The highest β_galactosidase activity was obtained at 13,02 U / mL with the incubation time of β-galactosidase and Lactobacillus lactis fermentation time of 15 minutes and 24 hours. Comparison of β-galactosidase activity produced by Lactobacillus lactis and Lactococcus lactis has shown that although the family and cell shape are different, the result of enzyme activity values are not significantly different. The optimal pH and temperature values for β-galactosidase activity in hydrolyzing the oNPG substrate were pH 7 and 37oC.

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