Amylolytic strains of Lactobacillus plantarum isolated from barley

Abstract

Two α-amylase-producing strains of Lactobacillus plantarum were isolated from South African barley. The extracellular α-amylase activity produced by strain A.S1.2 coincided with cell growth, while strain B.S1.6 produced α-amylase mainly during stationary growth. Cell wall α-amylases in both strains were approximately five times higher than recorded for extracellular α-amylases. Both strains demonstrated highest extracellular α-amylase activity in 2% (w/v) maltose, followed by 2% (w/v) malt extract and 2% (w/v) starch, respectively. The α-amylase produced by the two strains functioned optimally at 50°C and under alkaline conditions. The two strains of L. plantarum fermented carbohydrates naturally present in barley, and produced cell-bound and cell-free α-amylase at alkaline conditions. The two strains may be developed into starter cultures to facilitate the germination of barley and produce malt with a higher fermentable sugar content.

Key words: Lactobacillus plantarum, starch hydrolysis, barley, malting