Biofilm formation by Bacillus subtilis: Effect of Oxide Layers and Surface Roughness
(2025) KMBM01 20251Applied Microbiology
Biotechnology
Biotechnology (MSc)
- Abstract
- Biofilms in the dairy and food industry, particularly those formed by Bacillus subtilis, present significant contamination and food safety challenges. This thesis investigates the impact of stainless steel surface properties, specifically oxide layer formation and surface roughness of polished coupons, on biofilm development. Bacillus subtilis SA 22 (NCA 72-52; DSM 4181) was cultivated using a CDC Biofilm Reactor® (BioSurface Technologies Corporation), with stainless steel coupons subjected to various treatments, including citric acid passivation, polishing, and chemical cleaning. Surface wettability was assessed through contact angle measurements, while biofilm growth was quantified using relative fluorescence units (RFU) and UV... (More)
- Biofilms in the dairy and food industry, particularly those formed by Bacillus subtilis, present significant contamination and food safety challenges. This thesis investigates the impact of stainless steel surface properties, specifically oxide layer formation and surface roughness of polished coupons, on biofilm development. Bacillus subtilis SA 22 (NCA 72-52; DSM 4181) was cultivated using a CDC Biofilm Reactor® (BioSurface Technologies Corporation), with stainless steel coupons subjected to various treatments, including citric acid passivation, polishing, and chemical cleaning. Surface wettability was assessed through contact angle measurements, while biofilm growth was quantified using relative fluorescence units (RFU) and UV microscopy. Although surface treatments affected hydrophilicity, they did not significantly reduce biofilm formation. These results indicate that effective biofilm prevention in food processing environments requires more comprehensive strategies beyond surface modification. This study enhances understanding of microbial adhesion mechanisms and provides insights relevant to the design of safer food processing systems. (Less)
- Popular Abstract
- Imagine cleaning your kitchen, only to find that bacteria have returned stronger and harder to remove. This is the reality in the food and dairy industry, where tiny bacterial communities called biofilms can form stubborn layers on stainless steel equipment. These biofilms are especially hard to clean and can lead to spoiled food or even illness if left unchecked.
This project focused on understanding how the surfaces used in dairy industries, specifically stainless steel, can be changed to stop bacteria like Bacillus subtilis from sticking and forming biofilms. Could polishing the steel or applying protective chemical layers make a difference?
To find out, small steel coupons were cleaned, polished, or treated with citric acid (a... (More) - Imagine cleaning your kitchen, only to find that bacteria have returned stronger and harder to remove. This is the reality in the food and dairy industry, where tiny bacterial communities called biofilms can form stubborn layers on stainless steel equipment. These biofilms are especially hard to clean and can lead to spoiled food or even illness if left unchecked.
This project focused on understanding how the surfaces used in dairy industries, specifically stainless steel, can be changed to stop bacteria like Bacillus subtilis from sticking and forming biofilms. Could polishing the steel or applying protective chemical layers make a difference?
To find out, small steel coupons were cleaned, polished, or treated with citric acid (a mild acid found in lemons), then tested in a special reactor to grow bacteria under controlled conditions. We used techniques like water droplet tests (to see how wet or dry the surface is) and fluorescent dye (to make bacteria glow under UV light) to see how well the bacteria formed biofilms.
The results were surprising: while some treatments changed how water interacted with the surface (making it more or less "wettable"), this didn’t always stop the bacteria from forming biofilms. In other words, cleaner or shinier surfaces didn’t automatically mean fewer bacteria.
So, what does this mean? It suggests that keeping food processing equipment safe requires more than just polishing and cleaning. While surface treatments help, they must be combined with good hygiene practices and smart design choices. This research helps the industry take a step closer to safer, cleaner food production, and fewer invisible battles against bacteria. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9197036
- author
- Anowar Supti, Tasneem LU
- supervisor
- organization
- alternative title
- Biofilmbildning av Bacillus subtilis: effekten av oxidlager och ytjämnhet
- course
- KMBM01 20251
- year
- 2025
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Biofilm, Bacillus subtilis, Food and Dairy Industry, Stainless-steel, CDC Biofilm Reactor, Contact angle, Applied microbiology
- language
- English
- id
- 9197036
- date added to LUP
- 2025-06-12 13:37:35
- date last changed
- 2025-06-25 08:56:25
@misc{9197036,
abstract = {{Biofilms in the dairy and food industry, particularly those formed by Bacillus subtilis, present significant contamination and food safety challenges. This thesis investigates the impact of stainless steel surface properties, specifically oxide layer formation and surface roughness of polished coupons, on biofilm development. Bacillus subtilis SA 22 (NCA 72-52; DSM 4181) was cultivated using a CDC Biofilm Reactor® (BioSurface Technologies Corporation), with stainless steel coupons subjected to various treatments, including citric acid passivation, polishing, and chemical cleaning. Surface wettability was assessed through contact angle measurements, while biofilm growth was quantified using relative fluorescence units (RFU) and UV microscopy. Although surface treatments affected hydrophilicity, they did not significantly reduce biofilm formation. These results indicate that effective biofilm prevention in food processing environments requires more comprehensive strategies beyond surface modification. This study enhances understanding of microbial adhesion mechanisms and provides insights relevant to the design of safer food processing systems.}},
author = {{Anowar Supti, Tasneem}},
language = {{eng}},
note = {{Student Paper}},
title = {{Biofilm formation by Bacillus subtilis: Effect of Oxide Layers and Surface Roughness}},
year = {{2025}},
}