LumiNUS integration does not allow for bulk submission on behalf of students.
However, if your intention is that the students should not see the similarity index and similarity report, this can be done.
You will have to set up the Turnitin submission folder.
Under the Optional Settings, look for Allow students to view Similarity Reports? Select No, then Submit.
Then ask your students tothemselves, and they will not see the similarity index nor the similarity report.