Abstract: A process for expression of a protein product in Aspergillus oryzae is disclosed. The process comprises transforming Aspergillus oryzae with a vector system comprising DNA-sequences encoding functions facilitating gene expression, a suitable marker for selection of transformants, and a DNA-sequence encoding the desired protein product. The process enables industrial production of many different polypeptides and proteins in A. oryzae. Examples of such products are chymosin or prochymosin and other rennets, proteases, lipases and amylases. Also disclosed is an effective promoter for expression of a protein in Aspergillus. A preferred promoter is the TAKA-amylase promoter or functional parts thereof. There is also provided a process for the production of a recombinant Humicola lipase. The recombinant Humicola lipase from A. oryzae differs from the native lipase in having a greater glycosylation and in exhibiting an improved thermostability.