Special guide means 7 are located in the interior of a loop reactor for circulating the reactor contents. The guide means 7 has at least one central gas supply means 1 with gas distribution means 2 attached thereto for gas charging into the guide means 7. These loop reactors are used, e.g., as biogas reactors for treatment of biowastes or renewable raw materials. The gas distribution means 2 as gas guide elements are open to the bottom and are located above the gas exit openings 3 of the central gas supply means 1.