D-tyrosine　and　D-methionine　that　are　naturally　occurring　chemicals　were　investigated　as　enhancers　for　alkyldimethylbenzylammonium　chloride　(ADBAC)　against　the　Desulfovibrio　vulgaris　biofilm　on　C1018　coupons　surfaces　in　ATCC　1249　culture　medium.　The　7-day　biofilm　prevention　results　showed　that　the　D-amino　acids　alone　had　only　limited　effects　on　SRB　sessile　cell　counts.　Ten　ppm　(w/w)　ADBAC　alone　achieved　a　1-log　reduction　in　SRB　sessile　cell　count　compared　with　the　untreated　control.　The　combination　of　1　ppm　D-tyrosine　+　10　ppm　ADBAC　achieved　3　extra　log　reduction　and　50　ppm　D-methionine　+　10　ppm　ADBAC　achieved　2　extra　log　reduction　compared　with　the　10　ppm　ADBAC　alone　treatment.　In　the　biofilm　removal　test,　both　combinations　exhibited　2　extra　log　reduction　compared　with　the　10　ppm　ADBAC　alone　treatment.　These　results　were　supported　by　scanning　electron　microscope　images　and　confocal　laser　scanning　microscope　images　of　the　biofilms.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.