What's wrong with static utility classes, versus beans?
Static helper classes makes testing harder. Nick Malik has a good article on this topic: Killing the Helper class, part two. 

Mocking non-static methods is closer to OOP and easier than static ones. Another gain is that you'll have simple tests: simple tests for the utility/helper class and simple tests for the clients of the utility class; the tests of the client classes don't have to know the internals of the utility class, and you don't need a DatabaseUtilsTestHelper class to keep in one place the mocking logic for the helper class. The linked article is worth the reading.

Some other notes: 


Try not using short variable names like ng. They are hard to read.
persistArticle does not close the transaction in every path. You should rollback it in the finally block if it's still active:

final EntityTransaction transaction = em.getTransaction();
transaction.begin();
try {
    ...    
    transaction.commit();
} finally {
    if (transaction.isActive()) {
        transaction.rollback();
    }
}

persistArticle does not use the value of max, therefore the getMax call seems unnecessary.