Abstract

Amylases are among the most important enzymes in present-day biotechnology. The present study aimed at varying temperature, pH and incubation time to optimize the activities of amylolytic lactic acid bacteria isolated from fermented “Ogi” and retted cassava. Amylase positive bacterial strains were identified based on the clear zone formation around the bacterial growth. Amylase producing bacteria were grown on the starch production media in submerged fermentation method. Fermentation conditions were optimized by varying the following parameters, pH (3-9), temperature (20-70ºC), and incubation time (12-72 h). The most prominent amylolytic index (AI) recorded in isolate AK1 (Ogi), CA5 (cassava) and CA2 (cassava) were 2.63±0.06, 2.06±0.03 and 2.55±0.05 respectively. The highest enzyme activity (0.85±0.05U/ml) was exhibited by AK1. The three strains were identified as Lactobacillus plantarumFMO2(AK1), Lactobacillus plantarumZ2(CA5) and Lactobacillus pentosusBRS3(CA2) by 16S rRNA sequencing. The extracellular amylase activity produced by strain FMO2 coincided with the cell growth. The optimum pH range and temperature for the activity of amylase were found to be pH 6 and 45-50⁰C respectively. The amylase from Lactobacillus plantarumFMO2 was purified 2.63 fold with a specific activity of 0.10U/mg. The enzyme was stable at 50⁰C and 60⁰C up to 180 min. The residual enzyme activity of 85.1% was retained after 60mins of incubation at temperature of 70⁰C and affected by different metal ions in a dose dependent manner, although activated by CaCl₂ ion. The results showed that Ogi is a good substrate for amylase production. These bacteria strains may be developed into starter cultures to facilitate production of enzymes that can be used for industrial purposes since the enzyme they produced are thermostable.