Lactobacillus amylolyticus L6 produces a novel maltogenic amylase with stable catalytic activity

Abstract

Lactobacillus amylolyticus is rich in starch hydrolases, but the maltogenic amylase (MA), an anti-staling additive in the food baking industry, was not characterised. Herein, we investigated the MA from L. amylolyticus L6 (LAMA), a strain isolated from the naturally acidified tofu whey, the LAMA gene was firstly obtained by PCR amplification, and subsequently the recombinant enzyme was expressed, purified, and its catalytic activity was finally characterised. The optimum pH and temperature were 5.5–6 and 37–48 °C, respectively, the temperature range broad (40–65 °C), the pH stability high (pH 4.5–8.5), and the half-life long (444 h). Fe3+ and Triton X-100 improved enzyme activity to some extent, but enzymatic activity was not dependent on metal ions. Cyclodextrin was the preferred substrate, and hydrolytic activity was ranked β-cyclodextrin > α-cyclodextrin > γ-cyclodextrin. Molecular docking simulations verified the preference of LAMA and revealed the binding poses and sites of both substrates and LAMA. Among them, Tyr41 and Asn40 may be the key to influencing the binding ability of both substrates. Thus, L. amylolyticus L6 containing LAMA may have a bright future in application on bakery products.