Investigation of finishing of leather for inside parts of the shoes with a natural biocide

Elżbieta Bielak,Ewa Marcinkowska,Justyna Syguła-Cholewińska

doi:10.1038/s41598-020-60285-y

Abstract

The prevention of decrease of quality caused by microbial activity in footwear materials entails the use of biocides. However, these substances may pose a hazard to humans and to the natural environment. The paper presents the results of antimicrobial effect investigation for cowhide leather treated with oregano oil. In these studies oil was applied by spraying onto the finished leather surface and examined to determine its antimicrobial activity by using the Agar Diffusion Plate Test. These results were compared with those where a cowhide leather was treated with oil at the stage of fatliquoring. In addition, the oregano oil toxicity level was assessed and compared with biocides used in the tanning industry. Introducing oregano oil into the leather at the stage of fatliquoring provides a better antimicrobial effect than by spraying, however hygienic finishing of leather can be obtained by introducing oil into the raw material by these both methods. The oregano oil is characterised by the lowest number of hazards and toxicity as compared with commercial biocides. The use of essential oils as natural biocides in the tanning industry seems to be especially important and suitable solution considering the harmful effects of synthetic biocides to humans and the environment.

Highlights

The prevention of decrease of quality caused by microbial activity in footwear materials entails the use of biocides
When assessing antimicrobial effect of leather fatliquored with oregano oil (3%) after one month, a very good antimicrobial activity of the leather was confirmed by considerable zones of growth inhibition for mould Scopulariopsis brevicaulis (>32 mm), yeasts Candida albicans (16 mm), bacteria Staphylococcus aureus and Staphylococcus epidermidis (10–11 mm) and the strain of Escherichia coli (9 mm)[34]
The results presented allowed to conclude that lining leather fatliquored with the addition of oregano oil at a concentration of 3% by leather mass is characterised by good and durable antimicrobial effect persisting even for 12 months

Summary

Introduction

The prevention of decrease of quality caused by microbial activity in footwear materials entails the use of biocides. According to Annex V to the said document, biocides used in the tanning industry for leather preservation are intended to prevent harmful effects of microbes by preventing the settlement of microorganisms on the surface of materials, hampering the development of unpleasant odours, and to gain other benefits from the activity of biocides[2] It follows from the definition of biocidal products given above that they may pose a hazard to humans and their surrounding environment because of their properties. According to REACH6 for DMF the restriction imposed limits the possible content of this substance in a product or even in its parts to a concentration not exceeding 0.1 mg/kg Another example is pentachlorophenol (PCP), an agent hazardous to human health and life[7] which was used to protect hides and skins in the pickling process; it has, been withdrawn from use for environmental reasons[8]. The fact that the presence of harmful chemicals in products and tanning wastewater is a topical and important issue is supported by numerous studies carried out for many years[12,13,14] and aimed at making the tanning industry more ecological and environmentally friendly

Methods

Results

Conclusion