Evaluation of microbial pollution, biofilm formation, and malodor generation in household washing machines in Wuxi, China

Abstract

Abstract Microbial contamination in household washing machines (WMs) often leads to the formation of stubborn stains and the generation of unpleasant odors. In this study, 16s RNA sequencing was employed to detect the microbiota in the rubber ring, drum wall, and drainage outlet of WMs. As a result, Sphingobium, Pseudomonas, and Acinetobacter were found to persist over extended periods of time. Additionally, the dominant fungi identified in WMs were Paraphoma, Knufia, and Cladophialophora. The composition of the biofilm varied among different locations within each WM, reflecting differences in microbial composition. One significant component contributing to the odors in WMs is dimethyl disulfide(DMDS, C2H6S2), which is produced by common bacteria isolated from these WMs. While silver ions exhibited good inhibitory effects on most microorganisms found in WMs, they did not have a noticeable killing effect on Pseudomonas putida and Meyerozyma guilliermondii. On the other hand, the use of isothiazolinone as a bacteriostatic agent proved effective in inhibiting the growth of all isolated strains from WMs. These findings provide valuable insights into the composition of contaminated microorganisms, biofilm formation, and effective bacteriostatic methods for cleaning household WMs.