Isolation, Identification and Preliminary Enzymology of an Acidic α-Amylase-producing Fungus
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Abstract:
An acidic α-amylase-producing fungal strain was isolated from the soil near a vinegar factory and was identified by morphology and ITS sequence analysis. Growth characteristics such as growth temperature and pH of the initial fermentation solution as well as the characteristics of the enzyme produced by this strain were examined. The strain was identified as Aspergillus niger and was named Aspergillus niger ZTL. The optimal growth and enzyme-producing temperatures were determined as 35 ℃ and 40 ℃, respectively, while optimum growth and enzyme-producing pH values were 6.0 and 5.0, respectively. The activity of α-amylase produced was above 80% within the pH range of 4.5 to 7.0. The optimum functional temperature range was between 40 ℃ and 50℃, and the enzyme was stable within this range, as determined by thermal stability analysis. Additionally, the enzyme stability decreased significantly when kept at 60 ℃ for some time. The enzyme was activated by Ca2+ to some extent and inhibited by Mg2+, Fe2+, and Cu2+, while Na+ showed no obvious effect. The Km value was 4.5×10-3 g/L. These results indicate that α-amylase produced by the strain isolated in this study has potential development value.
