Amylolytic Potential of Lactic Acid Bacteria Isolated from Wet Milled Cereals, Cassava Flour and Fruits

Abstract

Aims: This research was conducted with the objective to evaluate amylolytic potential of lactic acid bacteria isolated from wet milled cereals, cassava flour and fruits. Methodology: Strains of lactic acid bacteria were isolated from food samples and screened for amylolytic potential using starch hydrolysis technique. The resultant Amylolytic Lactic acid bacteria (ALAB) isolates were then characterized and identified based on their morphological and physiological properties using both conventional methods and API 50CHL kit (Biomerieux, France). These isolates were further evaluated for their amylase yield (U/ml) and amylase activity (mg/ml) using standard procedures. Results: From this study, characteristics typical of the lactic acid bacteria showed that isolates were Gram positive rods, catalase negative, with growth occurring at 30, 37, 40, 45°C and 3, 6, 10% (w/v)NaCl. On the basis of amylolytic potential, only 14 isolates exhibited amylolytic properties with halo diameter of between 25.00 to 68.00 mm. Comparatively, isolates (AMZ5) obtained from maize flour gave the highest amylase potential. Occurrence of the ALAB species identified showed that; Lactobacillus plantarum 8(57.14%), Leuconostoc mesenteroides 2(14.29%), Lactobacillus fermentum 1(7.14%), Lactobacillus brevis 1(7.14%), Lactococcus lactis 1(7.14%) and Pediococcus acidolactici (7.14%) were predominant. Quantitatively, maximum amylase yield of between 0.38 (U/ml) to 1.10 (U/ml) was observed for the isolates at 24 h of incubation. Amylolytic Lactobacillus plantarum (AMZ5) from maize dough flour however, gave the highest amylase concentration (1.10 U/ml). As a criterion of strain selection, hydrolytic action of AMZ5 gave the highest reducing sugar concentration of 0.55 (mg/ml) after 24 hr. Among the isolates, Lactobacillus brevis (ATt) isolated from tomato on the other hand, had lowest reducing sugar concentration (0.30 mg/ml) even after 48 hr of incubation. Conclusion: Therefore, findings from this study indicate that cereal based products are rich sources of ALAB. Also the strain of Lactobacillus plantarum (AMZ5) isolated from maize flour possesses better starch degradation capability through production high extracellular amylase and reducing sugar yields.