Talk2clean: application of probiotics to control biofilm in industrial water circuits – a innovative application

Biofilms are omnipresent in industrial cooling water circuits and frequently lead to technical and economic problems. Yet, methods to remove biofilms may be inefficient, due to the EPS layer, which provides a protective layer against penetration of disinfectants. In combination with stricter legislation and increased environmental awareness, this has opened the search for alternative strategies to control biofilms in cooling water systems.

In this study we implement a novel biofilm removal strategy, in which we target the intercellular language involved in the formation of biofilm structures. This language consists of signalling molecules (autoinducers) excreted by biofilm forming bacteria, a process referred to as quorum sensing (QS). We aim to alter QS via the activation of an antagonistic process called quorum quenching (QQ). Quorum quenching is a process that naturally occurs in bacterial communities; hence the final product is environment, - and user-friendly and thus a valuable alternative to the oxidising chemical products that are often used to clean cooling water circuits.

Here we present the first application of a QQ-product tested on pilot scale using parameters that resemble industrial evaporative cooling towers. This setting is particularly interesting as it an open system, fed with various types of make-up water, and comprised of biofilms adjusted to high operating temperatures.

The QQ product was tested using a closed, tube-like system, under continuous flow, fed with a propionic, - and acetic acid rich synthetic medium. Hydraulic retention time (HRT) was gradually shifted over a time span of 6 weeks. Heterotrophic plate counts were acquired once per week from the planktonic and biofilm phase. A pilot without the addition of QQ was ran in parallel as a control.

Our results show that the QQ product reduced and delayed the formation of biofilm compared to the control. Interestingly, this difference diminished when the HRT was modified. Metagenomic analysis of the biofilm phase, revealed that 16S rRNA sequences corresponding to the QQ were also strongly reduced during this shift, indicating a wash-out of the QQ product. The exact interaction of HRT and presence of QQ will be analysed in more depth using QQ specific qPCR primers.