Of course. Library Management Systems are adding Digital Library functions, for example Koha. For now you can catalog stuff, add files to a record and show it in the OPAC.
Another possibility is to connect different systems and integrate Digital Library software into LMS. For example with OAI-PMH connectors a lot of systems can interact. You should have a LMS that can import stuff through OAI-PMH and organize it.
I have found one software which gives interface to search in both Digital library and Library management system (Software: VuFind).But here i was searching for the technique where we can easily integrate the most used software's like Koha and Dspace without disturbing their functionality. Is their such research available which is carried out earlier.