Simultaneous production of raw starch degrading highly thermostable a-amylase and lactic acid by Lactobacillus fermentum 04BBA19

The widely used thermostable amylases were produced long time ago from Bacillus genus. Although, lactic acid bacteria (LAB) fermentation presents several advantages including the reduction of growth of pathogenic microorganisms, no study has yet reported thermostable amylases from lactic acid bacteria. An amylolytic LAB, Lactobacillus fermentum (04BBA19) isolated from starchy wastes of a soil sample from the western region of Cameroon was studied for amylase and lactic acid production. The bacterium exhibited maximal amylase and lactic acid production at temperature of 45°C, and within pH range of 4.0 to 6.5. Upon the optimization of various environmental and cultural conditions the yield of amylase and lactic acid reached 732.3±0.4 U/ml and 53.2±0.7 g/L respectively in fermented broth after 48 h of culture. The enzyme was identified as α-amylase, with a very high thermostability revealed by the retention of 100% of original activity after pre-incubation for 30 min at 80°C. The stability was improved significantly with the addition of 0.1% (w/v) CaCl2.2H2O; the half life of the enzyme in these conditions was 6 h at 80°C. Owing to its aptitude to exhibit a simultaneous production of thermostable amylase and lactic acid, L. fermentum (04BBA19) appeared as a potential candidate for the making of high density gruel from starchy material.Key words: Lactic acid bacteria, thermostable a-amylase, lactic acid, fermentation, high density gruel

Partial purification and characterization of alpha-amylases from Abrus precatorius, Burnatia enneandra and Cadaba farinosa

Leaves of Abrus precatorius, tubers of Burnatia enneandra and stems of Cadaba farinosa are used in savannah regions of Cameroon in traditional food processing, particularly in sweetening and liquefaction of gruels. α-amylase was extracted and partially purified from these plants using conventional methods of protein purification including ammonium sulfate fractionation and two steps of gel filtration. Purification achieved 58, 61 and 46 fold respectively for A. precatorius, B. enneandra and C. farinosa. The purified enzymes were then characterized in terms of molecular weight, optimum pH and stability, optimum temperature and stability, Km, Vmax and metals ions effects. The optimum pH of enzymes varied from 6.0 for amylases from B. enneandra and C. farinosa, to 7.0 for amylase from A. precatorius; while the optimum temperature was 60°C for amylases from A. precatorius and B. enneandra, and 65°c for amylase from C. farinosa. The three enzymes displayed, respectively for A. precatorius, B enneandra and C farinosa, a molecular weight of 60, 65 and 48.5 kDa, Km for hydrolyzing soluble starch of 3.25, 1.81 and 3.18 mg/ml, and strong individual activation by Ca2+, Co2+ and Fe3+. Li2+ appeared as a common activator for all the amylases, while Ag+, Hg2 +, Zn2+ and Cu2+ act as common inhibitors

Partial purification and characterization of alpha-amylases from Abrus precatorius, Burnatia enneandra and Cadaba farinosa

Leaves of Abrus precatorius, tubers of Burnatia enneandra and stems of Cadaba farinosa are used in savannah regions of Cameroon in traditional food processing, particularly in sweetening and liquefaction of gruels. α-amylase was extracted and partially purified from these plants using conventional methods of protein purification including ammonium sulfate fractionation and two steps of gel filtration. Purification achieved 58, 61 and 46 fold respectively for A. precatorius, B. enneandra and C. farinosa. The purified enzymes were then characterized in terms of molecular weight, optimum pH and stability, optimum temperature and stability, Km, Vmax and metals ions effects. The optimum pH of enzymes varied from 6.0 for amylases from B. enneandra and C. farinosa, to 7.0 for amylase from A. precatorius; while the optimum temperature was 60°C for amylases from A. precatorius and B. enneandra, and 65°c for amylase from C. farinosa. The three enzymes displayed, respectively for A. precatorius, B enneandra and C farinosa, a molecular weight of 60, 65 and 48.5 kDa, Km for hydrolyzing soluble starch of 3.25, 1.81 and 3.18 mg/ml, and strong individual activation by Ca2+, Co2+ and Fe3+. Li2+ appeared as a common activator for all the amylases, while Ag+, Hg2 +, Zn2+ and Cu2+ act as common inhibitors