De Sutter scored in the 50th minute and substitute
Lokeren remains third in the table, but now trails second-placed Zulte-Waregem by four points.
Zulte-Waregem was a comfortable 2-0 winner over Lierse, which slipped a place to 15th in the 16-team league.
Karel D'Haene put Zulte-Waregem on its way with a 28th-minute opener, and its second goal arrived after 52 minutes with Franck Berrier the scorer.
Beerschot nudged ahead of Lierse after a goalless draw at home against Mons.
With the race for top-six places warming up, Genk, which currently occupies sixth place, fell to a 2-1 defeat against pursuer KV Mechelen.
Mechelen, which climbed to seventh place with the win, four points behind Genk, went ahead through
In lower mid-table, Waasland-Beveren withstood the dismissal of
Blondelle was ordered off in the 56th minute, but
Gent took a first-leg advantage in its play-off with Standard Liege for the Pro League's final UEFA Europa League place.