Purification and characterization of a novel alkali-stable α-amylase from Chryseobacterium taeanense TKU001, and application in antioxidant and prebiotic

Chryseobacterium taeanense TKU001 was isolated from soils using red-koji rice as the sole carbon/nitrogen sources. Mung bean is a widely used traditional oriental food material and has been reported as a healthy food. For further investigating the possibility of microbial reclamation of mung bean, TKU001 was tested for producing α-amylase using mung bean powder as the sole carbon/nitrogen source. Following fermentation, an α-amylase was purified from the culture supernatant. The α-amylase has a molecular mass of 46,000 and 47,000 estimated by SDS-PAGE and gel filtration, respectively. The optimum pH, optimum temperature, pH stability, and thermal stability of the α-amylase were 9, 50 °C, 6-11, and <60 °C, respectively. The enzyme efficiently hydrolyzed soluble starch to yield glucose and maltose as the end products. Addition of 5 mM Ca²⁺ and 2% (v/v) Tween 40 into the medium could increase amylase activity by 3.52 and 3.27 fold, respectively. Besides, when 1.5% mung bean powder was used as the carbon/nitrogen source, the culture supernatant had strong antioxidant activity and could enhance the growth of Lactobacillus paracasei subsp. paracasei TKU010.