Expression and characterization of a maltogenic amylase from Lactobacillus plantarum in Escherichia coli and its application in extending bread shelf life

Abstract

A Lactobacillus sp. was screened from various cereal sourdoughs and was designated as Lactobacillus plantarum YXY418 based on the 16S rRNA gene analysis. A putative Lactobacillus plantarum maltogenic amylase, LpMA, was discovered based on computer-aided analysis. Then, its encoding gene (lpma) was expressed in E. coli BL21(DE3). The expressed recombinant LpMA (reLpMA) was efficiently purified to 12.2-fold using the one-step nickel-nitrilotriacetic acid (Ni–NTA) affinity chromatography. The final recovery yield and specific activity of the purified reLpMA were 61% and 36.4 U/mg towards soluble starch, respectively. The purified reLpMA exhibited optimal amylolytic activity towards soluble starch at 45 °C and pH 6.0, with a good pH stability ranging from pH 5.0 to 8.0. Besides, the reLpMA also hydrolyzed soluble starch, β-CD and pullulan to maltose with specific activity of 96.4 SU/mL, 78.2 CU/mL and 2.0 PU/mL, respectively. The reLpMA hydrolytic activity was increased in the presence of metal ions especially Ca²⁺ and Zn²⁺, which could be applied to different processing processes. Baking test indicated after 7-day storage, the reLpMA at a dosage of 2000 U/300 g could significantly reduce hardness and chewiness by 29.5% and 26.4%, respectively, compared with the control. Adding reLpMA improved bread quality, increased bread volume and decreased hardness during storage, thus extending its shelf life.

Funding

National Natural Science Foundation of China,(21676117)

the Natural Science Foundation of Jiangsu Province for Youth of China,(No. BK20180622)