Affiliation:
1. Fermentation Laboratory, Centro de Microbiología y Biología Celular, I.V.I.C., Apartado 1827, Caracas 101, Venezuela
Abstract
Lactase (β-
d
-galactosidase) was produced by
Candida pseudotropicalis
grown in deproteinized whey. Maximum enzyme production in 2% whey was obtained by supplementation with 0.15% yeast extract, 0.1% (NH
4
)
2
SO
4
, and 0.05% KH
2
PO
4
(wt/vol). Highest enzyme values (4.35 U/mg of cells and 68 U/ml) were obtained with 10 to 12% whey, while enzyme yield was maximal in 2% whey (0.87 U/mg of whey). Optimal initial pH for cultivation was 3.5. The best conditions for extraction included 2% (wt/vol) chloroform, 10 h of treatment, pH 6.6 and higher, and 30 to 37°C. Optimum pH and temperature for enzyme activity were 6.2 and 47°C. The enzyme had a
K
m
for
O
-nitrophenyl-β-
d
-galactopyranoside of 3.06 × 10
−3
M and the initial
V
max
was estimated as 6.63 × 10
−8
M per min. It hydrolized 50 and 100% of the lactose in whey and milk within 4 and 5 h, respectively, at 37°C. The lyophilized enzyme retained 95% of activity for 3 months when stored at −20°C.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
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