I wasn't able to find this information...
My question is related to amount of document libraries that I can create on a Document Center web app. There is a limit?
Does anyone knows that?
The primary difference between the Document Center and a Document Library are the templates they were created from - the Document Center from a Site Template and the Document Library is from a List Template.
As such, the limitations are governed by the Site itself which is constrained by content database limits (recommended < 200gb). In a practical scenario with optimal performance & storage for a Document Center, the results may vary based on the document check-in/check-out, versions & workflows, if any, are used. This post describes a Document Center example - Enterprise content storage planning (under section 'Large-scale authoring environment').
The number of document libraries under a site is contingent upon performance while viewing the list of libraries - I believe this limit is ~5000 items per view (default List View Threshold) for SharePoint 2010.
There are some recommendations related to capacity planning.
Start here: http://technet.microsoft.com/library/cc262787.aspx
Mark Kruger has a nice summary here: