Continue sentence after enumeration — comma needed/advised?

I have a sentence that continues after an enumeration, such as the following:

Due to X, it is difficult for researchers, lecturers and students, 
but also expert engineers, to apply Y.

I'm wondering whether or not the comma after engineers is needed. My gut feeling says yes, for the reason that it separates the enumeration from the continuing sentence.

Unfortunately, I can't find any source that discusses this situation. Does anybody here know a source, or has good arguments for/against the comma?

Solution 1:

It is necessary, but not because it separates an enumerated list, rather it marks off a parenthetical insertion. The phrase "but also expert engineers" is inserted and needs to be set off with commas (or dashes):

Due to X, it is difficult for researchers, lecturers and students to apply Y.

Due to X, it is difficult for researchers, lecturers and students, but also expert engineers, to apply Y.

Note that because "it is difficult" is a positive statement [albeit stating an undesirable situation], you can't use the negative but. You need and.

You can use but if the overall sentence is negative, say with not only:

Due to X, it is difficult for researchers, lecturers and students, and also expert engineers, to apply Y.

Due to X, it is difficult not only for researchers, lecturers and students, but also expert engineers, to apply Y.