I use OWIN + Microsoft.AspNet.Identity.Owin (v.2.0.0.0) in Web application. I register UserManager/DbContext per web request, as widely recommended:
app.Crea
The memory leak in AppBuilderExtensions class has been already fixed in latest version of Microsoft.AspNet.Identity.Owin library (2.2.1).
I have checked the code by using Reflector and also by putting a breakpoint into Dispose() methods of objects created by AppBuilderExtensions.CreatePerOwinContext().