Characterization of earthworm α-amylases for dietary supplement development and biomass utilization

Abstract

Earthworms are useful soil-decomposing animals that possess various saccharification enzymes such as cellulases and amylases. Earthworms have also been traditionally used as antipyretic agents and medicines for preventing thrombotic diseases such as brain infarction. We previously developed a novel earthworm dietary supplement with fibrinolytic, cellulase, and amylase activities using high-pressure technology. However, the optimal temperature and pH required for amylase activity in bioindustry have not yet been investigated. In the present study, we purified and characterized two α-amylases of Eisenia fetida Waki, EfAMY1 and EfAMY2, which were monomeric enzymes of 63.8 kDa and 64.0 kDa, with specific activities of 69.2 and 40.4 units/mg, respectively. The optimal pH was 5.5 for both enzymes, and the optimal temperatures were 45 °C and 35 °C for EfAMY1 and EfAMY2, respectively; however, the enzymes were stable over a wide pH range (5–10) and at high temperature (up to 40 °C). These amylases showed higher specific activity and cold tolerance than those previously reported. These data should help to promote the development of E. fetida AMYs as functional dietary supplements and in biomass utilization.