Biomass gasification is a process known for its high potential in enabling the exploitation of residual biomass in the production of renewable electricity. At present one of the most favorable patterns from both an environmental and a sustainability point of view is air gasification coupled with an Internal Combustion Engine (ICE) for decentralized production. In order to have the best performances of the ICE to be run with the produced gas, the required technical specifications on gas purity can be achieved at an appropriate level by means of wet scrubbing. In wet gas cleaning approach, stages based on organic liquids (e.g. biodiesel) and water can be jointly adopted for the removal of contaminants. In the present work preliminary results for the regeneration of the wastewater stream produced at a gasification plant whose gas cleaning is carried out with a purification train based on biodiesel and water scrubbing are presented. To this aim three different fungal strains were selected and tested for their bioremediation potential, i.e. Bjerkandera adusta, Arthrinium sp, and Pleurotus ostreatus. Laboratory tests gave an overall positive response on the effectiveness of wastewater treatment by Bjerkandera adusta and Arthrinium sp. thus demonstrating that these microorganisms are able to metabolize, and therefore remove, both aromatic molecules typical of tar produced in gasification processes, and esters of fatty acids constituting the biodiesel used for gas washing in the first stage.