Fig. 1

Calcium as a metal cofactor in the α-amylase of Clostridium sp. strain BOH3. a Ca²⁺ concentration in α-amylase and cell lysate without or with supplementation of CaCO₃; b CaCO₃-induced increases in the activities of α-amylase, NADPH- and NADH-dependent butyraldehyde and butanol dehydrogenases. Increases in activity are expressed as fold differences between the CaCO₃-supplemented fermentation broth and the CaCO₃-free fermentation broth