Microbiologically　influenced　corrosion　(MIC)　is　a　major　problem　in　the　oil　and　gas　industry　as　well　as　in　many　other　industries.　Current　treatment　methods　rely　mostly　on　pigging　and　biocide　dosing.　Biocide　resistance　is　a　growing　concern.　Thus,　it　is　desirable　to　use　biocide　enhancers　to　improve　the　efficacy　of　existing　biocides.　D-Amino　acids　are　naturally　occurring.　Our　previous　work　demonstrated　that　some　D-amino　acids　are　biocide　enhancers.　Under　a　biocide　stress　of　50　ppm　(w/w)　hydroxymethyl　phosphonium　sulfate　(THPS)　biocide,　1　ppm　D-tyrosine　and　100　ppm　D-methionine　used　separately　successfully　mitigated　the　Desulfovibrio　vulgaris　biofilm　on　carbon　steel　coupons.　The　data　reported　in　this　work　revealed　that　50　ppm　of　an　equimolar　mixture　of　D-methionine,　D-tyrosine,　D-leucine,　and　D-tryptophan　greatly　enhanced　50　ppm　THPS　biocide　treatment　of　two　recalcitrant　biofilm　consortia　containing　sulfate　reducing　bacteria　(SRB),　nitrate　reducing　bacteria　(NRB),　and　fermentative　bacteria,　etc.,　from　oilfield　operations.　The　data　also　indicated　that　individual　D-amino　acids　were　inadequate　for　the　biofilm　consortia.