Monitoring the mode of action of synthetic and natural biocides against Aeromonas hydrophila by Raman spectroscopy and chemometrics

Megha Mehta,Yang Liu,Geoff Holmes,Mark Waterland

doi:10.1186/s42825-021-00062-3

Megha Mehta, Yang Liu + Show 2 more

Open Access

https://doi.org/10.1186/s42825-021-00062-3

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Abstract

We have investigated the mode of action of synthetic biocides, (2-(thiocyanomethylthio) benzothiazole(TCMTB), dichlorophen, (commonly used in leather industry for preservation) and natural biocides, oregano and eucalyptus oils, on Aeromonas hydrophila using Raman spectroscopy in collaboration with multivariate analysis and 2D correlation spectroscopy to evaluate whether Raman spectra acquired contained valuable information to study the action of biocides on bacterial cells. The growth of A. hydrophila in clear and outer edge zone of inhibition differ in their reaction with different biocides, which allows us to highlight the differences as a characteristic of two kinds of bacteria. Such classification helps identify oregano oil as the most effective biocide by altering clear and outer edge zone of bacteria. Standard disk diffusion assay method was used for screening biocide bacteria interactions and later analysed by Raman spectroscopy. The paper also presents the introduction of TCMTB and oregano oil into leather processing stages to examine and determine the antimicrobial effect as an application to real-world setting. Therefore, we conclude that Raman spectroscopy with appropriate computational tools constitutes a powerful approach for screening biocides, which provide solutions to all the industries using biocides including leather industry, considering the potentially harmful effect of biocides to humans and the environment.Graphical abstract

Highlights

Microorganisms are present everywhere in different proportions, sizes, and diverse habitats
The identified strain of A. hydrophila was cultured for 24 h at 37 °C and stored for downstream application as stock cultures at − 80 °C in Luria Broth (LB) medium with 30% glycerol [19]. 30% 2(thiocyanomethylthio)benzothiazole (TCMTB; trade name Busan 30) was obtained from Buckman laboratories, USA, 30% dichlorophen was obtained from Prime Trading Company, New Zealand, eucalyptus oil
After leaving it for a day to allow biocide to induce bacteria-biocide interactions, there is an appearance of two zones formed by bacteria; one shows a clear zone with bacterial inhibition and another outer edge zone with bacteria resistant to inhibition (Fig. 1)

Summary

Introduction

Microorganisms are present everywhere in different proportions, sizes, and diverse habitats. Microorganisms can be useful, harmful, dangerous, or degrade materials. -called “weapons” to fight against harmful micro-organisms are biocides intended to kill living microorganisms responsible for decomposition and destruction of valuable materials, disturb the. Will it be safe in use for humans and the environment?. The unavoidable use of chemicals in the leather industry and its production processes represents an environmental impact. Biocides are a must for the leather industry as there are no feasible alternatives that guarantee long-term protection of partially processed material, held in a wet state for many months during transport and storage. The globalization of the leather market and the resulting international trade of these materials in the wet state make it necessary to protect the goods using biocides [3]. Like pentachlorophenol (PCP), are hazardous for human health and life and have been withdrawn from use [5]

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