To Örebro University

The thesis investigates the resistance mechanisms of Pseudomonas oleovorans strains, with an overarching goal of exploring biocide-free alternatives in construction materials and developing efficient formulations with minimal biocide content. The research focuses on the industrially significant P4A isolate, offering a detailed analysis of its unique characteristics compared to the reference strain 1045. Key findings reveal the superior resistance and tolerance of P4A to standard biocides commonly used in industrial coatings, such as BIT and CMIT, as demonstrated through minimum inhibitory concentration (MIC) analysis.

Whole genome sequencing (WGS) was employed to explore the genetic basis of biocide resistance. While no specific resistance genes or mutations aligned with existing databases, notable genomic differences suggest potential genetic contributors to antimicrobial resistance. The study also highlights the role of Serine/Threonine protein kinases in bacterial adaptation, with mutations in these kinases influencing survival and metabolic pathways.

Metabolic profiling provided insights into the effects of biocide exposure on bacterial metabolism, identifying changes in key metabolites such as tetradecenoic acid, 5-Hydroxyindole-3-acetic acid (5-HIAA), and amino acids. Pathway analysis revealed significant alterations in stress response, energy generation, and protein synthesis pathways, with a specific focus on peptidoglycan biosynthesis in the biocide-resistant strain P4A.

Additionally, the thesis examines the emissions of volatile organic compounds (VOCs) from industrial products treated with biocides and biocide-free alternatives. The findings demonstrate that both biocide-free and traditionally biocide-preserved products effectively protect against microbial contamination. However, while traditional biocide-treated products may exhibit slightly higher VOC emissions, these emissions are more significantly influenced by raw materials, such as solvents and plasticizers, rather than biocides alone.

Biocides were shown to contribute substantially to the long-term durability and microbial protection of products. By selecting low-VOC biocides and optimizing formulations, manufacturers can achieve a balance between microbial efficacy and environmental impact. The results indicate that biocide-free products offer notable environmental advantages, while biocide-preserved products remain crucial for ensuring microbial safety in industrial applications.