FISH probing applied to biofilm control in the paper industry

A great majority of the paper factories, specially those producing recycled paper, suffer from biofouling in their installations. Such phenomena are caused by certain bacteria that form colonies. These microorganisms have the capacity to excrete diferent polysacharids that form a protective and adhesive matrix (biofilm) that allows the bacteria to attach to the surface of pipes, tanks and other equipment.

Once the initial attachment of the biofilm takes place, organic matter and other bacteria that lack the capacity to form a biofilm can anchor themselves to the formed colony. Biofilms can evolve into hardened crusts and create incrustations that are very hard to eliminate or can progressively free themselves from the original attachment site hindering both the process as well as the quality of the produced paper.

Traditionally, to avoid the formation of biofilms, wide spectrum biocides were used at different points through the process. Nevertheless, the toxicity of such agents, along with the development of resistance by some microorganisms, has forced the industry to seek new alternative treatments based on enzymes or biodispersants that have less environmental impact and are more specific in their action, affecting principally those species that are the main cause of the problems. In the paper industry, the main species of bacteria with capacity to form biofilms belong to the genus Enterobacter; the most common ones being Pantoea agglomerans, Enterobacter sp., Raoultella y Klebsiella sp.

The cellulose and paper research group from the department of chemical engineering, working in collaboration with the department of microbiology (animal health) biochemistry and molecular biology at the Universidad Complutense, have developed and patented a new method to detect these bacterial species in the paper industry by means of a probe based on “in situ” hybridization (that does not require biofilms to be cultured) and fluorescent markers (FISH). This method is based on the selective reacction of a molecular marker designed to react by attaching to the specific DNA of a particular mircroorganism. Once attached, part of the marker molecule called fluorophor activates and produces fluorescence. By taking a microscopic image of the medium in wich the reaction takes place and procesing it digitally, it is posible to carry out reliable counting of the number of bacteria of each type that are present per unit volume of the sample. In this way, by knowing the bacterial species present in the installations and the concentration, antimicrobial treatments can be tailored for the detected flora and can be done so with a better adjusted dosage. The aplication of this technique in the paper industry would generate a reduction of the costs of maintaining the installations and greatly reduce the enviromental impact associated with the treatments that use biocides.

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