# Impacts of feed gases for micro-nano bubble water treatments: Antimicrobial efficacy against Escherichia coli and Staphylococcus aureus on ‘Fan Retief’ guava fruit

## TL;DR

This study explores using micro-nano bubble water with different gases to reduce bacteria on guava fruits, offering a safer alternative to chlorine.

## Contribution

The study introduces micro-nano bubble water with ozone as a novel decontamination method for fresh produce.

## Key findings

- O3-MNB reduced E. coli on guava fruits significantly after 60 minutes.
- S. aureus was more resistant to MNB treatments than E. coli.
- Cell damage from O3-MNB was confirmed via electron microscopy.

## Abstract

Microbes on fresh produce are often controlled by chlorine-based sanitizers, due to there is growing demand for safe alternatives. This work investigated effects of micro-nano bubble (MNB) water generated using air, oxygen (O2), or ozone (O3) against bacteria contaminants encountered along the fresh produce value chain. Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923) broth were treated with distilled water (DW), sodium hypochlorite (NaOCl, 200 mg/L, 5 min), air-MNB, O2-MNB, and O3-MNB for 30- and 60-min. Scanning-transmission electron microscopy confirmed that the bacterial survival population was reduced via various types of cell damage under O3-MNB. S. aureus was more resistant than E. coli to the MNB treatments. This could be due to the thicker layer of peptidoglycan surrounding the cell membrane protecting against oxidative species. On guava fruits, O3-MNB-60 min lowered E. coli counts immediately after treatment (p < 0.05). MNB water offers a new paradigm for fruit decontamination.

The online version contains supplementary material available at 10.1007/s10068-025-01897-w.