Resumo

The technology of membrane osmosis systems (MOS) has been seen as a clean technology with low environmental impact, and has been used by diverse industries, including oil refineries, in order to treat and reuse water, and consequently reduce discharge. However, MOS are prone to microbial biofilm development and biofouling, i.e. the degradation of materials resulted from biofilm activity. Biofilms are microbial communities developed on surfaces which are formed by initial adhesion of planktonic bacteria or by bacteria that are incorporated onto the preformed biofilm. In both cases, the feed water is seen as a source of contamination. Bacterial motility is known as an important feature involved in the ability of bacteria to form biofilms. Thus, this work aimed to isolate bacteria from feed water of a MOS and investigate the bacterial motility. Feed water was inoculated onto different culture media surface (Nutrient Agar - NA, Triptone Soya Agar - TSA and Yeast Malt Extract Agar - ISP2), and incubated at 30^oC for 5 days. For motility characterization, bacteria were rinsed and suspended in distilled and sterilized water and inoculated in King B culture medium containing 1.5% and 0.5% agar for twitching and swarming test, respectively, and incubated at 35 ^oC for 48 h. A total of 352 CFU were isolated and, based on macromorphology, 29 isolates were selected for motility tests after which 6 isolates were positive for twitching and 3 positive for swarming assays. These results revealed the presence of diverse bacteria colonizing the feed water of the MOS which may be involved in biofilm development and consequent biofouling. Although motility is not a critical feature to biofilm formation, bacteria defective in biofilm formation lack the ability to produce structures involved in bacterial motility, e.g. pili and flagella. Thus, the detection of motile bacteria indicates the presence of phenotypes that are adapted for initiation of biofilm. Additionally, bacterial identification based on 16S rRNA gene sequencing and evaluation of the ability of in vitro biofilm formation are currently being performed. The identification and characterization of these bacteria may lead to further development of sanitizing processes to prevent biofilm formation.