Characterization of thermostable β-amylase isozymes from Lactobacillus fermentum

A strain of Lactobacillus fermentum producing two isozymes of a 20kDa β-amylase was isolated from the faecal sample of a newborn. The starin was identified by sequencing its 16S rRNA gene. The two β-amylase isozymes were resolved and visualized by two dimensional protein gel electrophoresis (2-D gel electrophoresis). Some of the physical and biochemical properties of the enzymes were characterized. The β-amylase displayed two optimum pH s, 5.0 and 10.0 and two optimum temperatures, 45°C and 37°C, respectively. The isozymes hydrolyzed different substrates: glycogen at pH 5.0, and corn starch at pH 10.0. The activity did not require Ca²⁺, though the activity at pH 10.0 was enhanced in the presence of 5.0mM and 10.0mM CaCl_2, 110% and 130%, respectively.