Selection of microbial consortia for treating metal-working fluids

The aim of this research was to determine the effectiveness of a strategy for constructing microbial consortia for treating chemically mixed industrial effluent, based on a more thorough understanding of communities within waste metal-working fluids (MWFs). Complementary phenotypic and genotypic methods revealed that the microbial communities in spent MWFs had low diversity and were very similar in species composition in samples originating from different locations and uses. Of 65 bacterial isolates studied, only 9 species were identified using fatty acid methyl ester (FAME) analysis. The results of genotypic analysis by denaturing gradient gel electrophoresis (DGGE) were congruent with observations made using FAME analysis. The metabolic potential of the isolates was assessed in terms of assimilation ability and tolerance of co-contaminants. The three isolates, selected (Clavibacter michiganensis, Methylobacterium mesophilicum, and Rhodococcus erythropolis) to form a consortium, were representative of three of the four most abundant populations and when combined could utilise or tolerate all of the individual MWF components, including the biocide and the recalcitrant compound benzotriazole.