Minimal and dynamic bacterial diversity in grease trap revealed by molecular analysis

Abstract

Grease traps are widely used in restaurants and food industry to reduce oil and grease discharge into public sewers. Although enhancement of grease trap performance often use microbial biomasses, yet little is known about the natural microbial assemblages that colonize and settle inside grease trap and may be used for grease degradation processes. This study evaluates the diversity and composition of bacterial assemblages colonizing the greasy layer in a public restaurant grease trap. Using a culture-independent approach, the dynamic of these assemblages have been studied before (Monday) and after (Friday) a week of restaurant activity. Bacterial diversity was quite low: 16S rRNA gene clones were affiliated with only three phyla, of which Firmicutes, Proteobacteria, and Bacteroidetes were represented in all libraries. Anaerobes, facultative anaerobes and microaerophilic taxa dominated the clone libraries. Sequences similar to Selenomonas spp., Lactobacillus spp. and Dialister spp. represented respectively 23.2%, 13.0% and 8.7% of the two libraries together. The Monday and Friday libraries were quite similar (70% similarity), however diversity indices showed that bacterial diversity seemed greater at the end of the week. Several taxa were only detected on Friday, including Acetobacter spp., Gulbenkiania spp., Aeromonas spp., Petrobacter sp., Escherichia sp. and Desulfovibrio sp. The description of metabolic capabilities of surveyed species is beyond the range of the clone libraries, however several taxa were fermenting or anaerobic-respiring organisms which could be likely involved in lipid degradation.