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Almost all industrial systems that are in contact with water suffer from biofilm formation.The emerging biofilms impede the function of many systems, as water filtration membraneswhere the biofilm prevents the production of clean water by exerting hydraulic drag. In othercases the biofilms cause other negative side effects, like in textiles where they producemalodorous byproducts that decrease consumer comfort. Biofilm formation on somematerials, including textiles, is poorly understood, making it difficult to design effectivemethods to counter them. Although other biofilms have been more extensively studied, suchas in membrane systems, novel cleaning methods still need to be developed that are bothgentle to the environment and the membrane itself. Enzymes are good candidates for biofilmremoval in many industrial systems. The aim of this PhD thesis was therefore twofold: Toexamine the bacterial colonization of textiles and to identify enzymes that can destabilizebiofilm on reverse osmosis (RO) membranes. To illuminate the mechanisms of biofilmrecalcitrance in textiles a novel in vitro biofilm model was designed and used to study theinfluence of fiber hydrophobicity. Bacteria adhered better in more hydrophobic textilesbefore drying, while almost all bacteria adhered irreversibly within both textiles after dryingdue to insufficient hydrophilicity. Bacteria are therefore more difficult to remove duringwashing from hydrophobic textiles. The hydrophobic fibers also absorbed larger amounts ofsebum, which increased bacterial activity by serving as a nutrient source. To preventrecalcitrant biofilm formation, textile fibers could be rendered more hydrophilic. However,this decreases textile breathability, and is therefore not desirable. The superior strategy wouldinstead be to focus future research on developing more effective cleaning, preferably byenzymes, or by seeding the textiles with probiotic bacteria which could degrade the sebumwithout producing malodorous compounds. To identify enzyme for biofilm degradation, aplatform was developed to facilitate high-throughput screening on both in situ and in vitrogrown biofilms. To demonstrate the utility of the platform, a large enzyme library wasscreened against both in vitro-grown membrane biofilms and biofilms on fouled ROmembranes. The two biofilms were largely vulnerable to different enzymes, indicating thatomitting in vitro studies while instead screening directly on in situ biofilms is the beststrategy to identify biofilm-degrading enzymes. The identified enzymes were found todestabilize the membrane biofilms more than conventional chemical cleaning agents,indicating that enzymatic cleaning could replace chemical cleaning. To illuminate how theenzymes influence the biofilm, the biofilm volume was analyzed before, during and afterenzyme treatment. The biofilms swelled while the ultimate strength decreased upon treatmentwith cellulase and inulinase. The platform could thus be applied to systematically studyingthe behavior of in situ biofilms within a range of applications. |
