Amylase enzymes have been produced on an industrial scale for at least 50 years if not much longer. There is an extensive literature on production/fermentation protocols, both recombinant and native. Just review the older literature for the organisms similar to those you are interested in.
It is important to consider the range of optimum pH and temperature during which the amylase is most active. This will most likely be an important factor for determining the scope of end users and market size