In the present study, the main characteristics and functions of amylase enzymes are summarized. Furthermore the identification and characterization of a new amylase from Photobacterium halotolerans isolated from salt marsh of Tarquinia, Viterbo Italy is described. For a more efficient expression of this enzyme, the Pichia pastoris expression system is studied and optimized with a specific flow rate of methanol during the glycerol-methanol transition phase, using a semiconductor gas sensor for methanol detection from the exhaust air of the fermentor.