Stability and Activity of β‐Galactosidase in Sonicated Cultures of Lactobacillus delbrueckii ssp. bulgaricus 11842 as Affected by Temperature and Ionic Environments

Abstract

ABSTRACT:Stability of β‐galactosidase and related lactose hydrolyzing activity in sonicated cultures of Lactobacillus bulgaricus 11842 was investigated in the presence of Na+ or K+ ions. After sonication in Na+ or K+ buffers at various pH levels, cultures were held at various temperatures, before adding test lactose solutions. Hydrolysis was monitored by cryoscopy. Cultures sonicated in K+ buffer had higher activity and stability than those in Na+ buffer; both were highest at pH 6 and 7. Stability was unaffected at pH 6 and 7 below 56 °C. Holding at 61 °C for 60 min caused 70% activity loss with K+ ions at pH 6 and 7, while with Na+, activity loss was almost complete.