Inhibition of biofilm formation on washing machine drawer

Biofilm formation has been a problem for many years on industrial water lines, production lines, various surfaces and domestic conditions. Biofilms that form in areas where human contact is particularly high, such as food, are a threat to health. For this reason, the fight against biofilm has been a crucial topic for many years. Microbial accumulation occurs in many areas in domestic conditions and causes biofilm. Especially in areas such as kitchens, bathrooms and surfaces that are constantly damp, it creates a suitable environment for biofilm formation. In addition to these, it is observed that microbial occurrences on the household products such as refrigerators, washing machines, dishwashers due to usage conditions over time. Washing machine, which is one of the most used white goods products in particular today, is the most problematic product in this issue. The washing machine is used to remove the contaminants in textile products. In addition to physical and chemical dirt such as sludge and paint, microbiological contaminants can also be collected on textile products. Textile-contaminated microorganisms are mostly originated by humans and the environment they are in. It is known that there are some microorganisms passing from pets in some cases. These microorganisms are transmitted from the textile to the washing machine during washing. Especially in recent years, low-temperature washing programs which save energy and bleach-free liquid detergents have begun to use for washing of textiles. Therefore, microorganisms on textiles and washing machines are not removed effectively. The constant dampness on the parts of washing machine such as the detergent drawer provide a suitable environment for the growth and accumulation of microorganisms. These microbial accumulations which are formed on detergent drawer parts of the washing machine, lead to the formation of biofilm over time and also cause visible irritating fouling. In some cases, there are odor formation caused from microbial accumulation in the machine, and smell formation is among the complaints for the washing machine. Due to these reasons, studies aiming to eliminate microbial contamination in the washing machine and to prevent biofilm formation gain importance. In this thesis, microbial accumulations in detergent drawer of washing machine and methods for eliminating these deposits were taken up. For this purpose, the problems encountered in the detergent drawer have been described first. For this, 5 detergent drawers with visual contamination of the washing machines used in the customer condition were supplied. The levels of microorganisms in the main wash and softener parts of the detergent drawers were determined. Therefore, microbial level of softener part was higher than the level of main wash part in all provided detergent drawer. Also, results showed that Pseudomonas levels and total viable counts in softener parts of drawers were found to reach levels of 106 - 107 CFU/mL. In order to better understand the problem, the accumulation on the detergent drawer was investigated by 20 times sequential washes in the washing machine at Daily 40 ° C program under controlled conditions. Here, the use of powder detergent and liquid detergent was examined as two different conditions and it was examined whether there was a difference in microbial accumulation between the two after the same number of washes. As a result of the tests, the microbial accumulation in the use of liquid detergent was found to be higher than the powder detergent. After sequential washing with liquid detergent, it was found that Pseudomonas, mold/yeast and total living species in both the main washing part and the softener part reached level of 106 CFU/mL. In the case of using powder detergent, these levels were around 104 CFU/mL in the main washing eye. After 20 washing cycles, no visible contamination was found in the detergent drawer, microbial accumulation was observed and the liquid detergent was more likely to have microbial accumulation. In addition, biofilm formation studies have been carried out on polypropylene discs in laboratory conditions in order to examine the biofilm formation stages and to test for biofilm removal methods. Rotating disc bioreactors and flowcell methods were used in biofilm formation studies using Pseudomonas aeruginosa microorganism and the level of microbial accumulation on the discs was determined at the end of the study. Microbial accumulation level of 109 CFU/mL was formed on the discs in the bioreactor when accumulation level of 107 CFU/mL was observed on the PP discs in the flow cell. For this reason, biofilm formation on coupons with the bioreactor was used while the removal efficiency of biofilm eradication methods were tested. After the microbial accumulation and biofilm formation stages of detergent drawer have been examined, studies have been carried out to remove microbial accumulation on the washing machine detergent drawer and to prevent biofilm formation. First of all, microbial accumulation removing studies with hot water application have been carried out. For this aim, Beko BK 9121BT Model 9 kg / 1200 rpm washing machine and its drum cleaning program was used. The temperature of the water in the drum at this program is reached to approximately 70 °C, so this program is developed to clean the drum and to remove the microbial accumulation in the drum of the washing machine. In studies to use hot water sanitation at the drawer, hot water in the drum at drum cleaning program was directed to the detergent drawer. For this redirection of water, prototypes of three different detergent drawers and direction systems were prepared and these prototypes were tested in terms of removal effectiveness of microbial accumulation and biofilm in drawer. Therefore, firstly sequential washing cycles were made by using laundry with microbial contamination in washing machines. Microbial accumulation on drawer was formed as 104 – 106 CFU/mL. After the wash cycles, drum cleaning program on washing machine was run and hot water was directed from drum to drawer during 110 minutes. At the same time, biofilms were formed at 108 - 109 CFU/mL levels on the coupon in the bioreactor and the coupons were placed in the detergent drawer and the hot water was directed to the dispenser in the drum cleaning program. As a result of the hot water sanitation, microbial accumulation and biofilm on detergent drawer were completely removed for three different concept designs. However, the Concept 1 design has been failed due to the blockage by textile fibers during the test. The most efficient flow shape during hot water sanitation was obtained in Concept 2. For this reason, it is decided that it is the most suitable design that can be applied on the washing machine. Finally, antimicrobial additive studies have been carried out to participate in detergent drawer raw materials which is polypropylene plastic material to prevent microbial accumulation in the detergent drawer. It has been aimed to form antimicrobial detergent drawer by adding the additives which have antimicrobial activity to the polypropylene plastic material during the plastic injection process. For this purpose, 1-decyl-3-methyl-imidazolium chloride [DMIM] ionic liquid has been provided to take advantage of the antimicrobial activities of ionic liquids in the detergent drawer. Solutions were prepared between 1 to 25 mM concentrations of the supplied ionic liquid and impregnated into the textile and filter paper, and the antimicrobial activity of ionic liquid was directly examined by zone inhibition test. When the results were evaluated, it was found that the antibacterial activity even at a small concentration like 1 mM but the antifungal activity was low when 1-decyl-3-methylimidazolium chloride [DMIM] ionic liquid solutions was used directly. Later, ionic liquid solutions were prepared at different concentrations in the range of 25 - 500 mM using pure water and ethyl alcohol solvents and impregnated with 3M Accurel® XP / MP branded polypropylene foam. Therefore, ionic liquid was added to PP plates by plastic injection methods and antimicrobial activities of these plates were tested. Antibacterial activity was found in PP plates obtained using 300 and 500 mM ionic liquid, and no antifungal activity was observed. Consequently, it has been found that it is difficult to incorporate the ionic liquid into the PP material and the antimicrobial activity was lost during the process. At the same time with the ionic liquid studies, 1% KD-00-2A + 1% CP-00-1A and 1% GF-00-5A + 1% CP-00-1A code powdered antimicrobial additives were obtained, these are commercially available from Life Materials. The antimicrobial activities of these powdered additives are based on some antimicrobial compounds like Vanzide ZP and Topane. 1%, 1.5% and 2% powdered antimicrobial mixtures were added to the polypropylene material during the injection process to obtain additive plastic plates. Plateau zone inhibition and antimicrobial surface activity tests were performed to test the antimicrobial activities of these obtained powder antimicrobial-added polypropylene plates. As a result of the standard antibacterial surface test, 99.9998% of the microorganisms of Escherichia coli and Staphylococcus aureus on the plates were removed. In order to determine the antimicrobial activity lifetime of detergent drawers prepared with powder additives, aging tests were carried out at 60 ° C in a 1% standard detergent solution. The plates containing additive were soaked and mixed in this solution during 168 hours. The antimicrobial activity initially observed in 1.5% and 2% platelets continued after aging. As a result of the standard antibacterial surface test made on plates after aging, it was determined that Escherichia coli and Staphylococcus aureus microorganisms on plated plates were removed by 99.99%. As a result, it was determined that the hot water application had very good microbial accumulation removal efficiency. It was also found that PP plates obtained with commercial powdered antimicrobial additives show antibacterial and antifungal activity before and after aging. Consequently, hot water application and antimicrobial powder additives can be used to prevent biofilm formation in the detergent drawer.