Kraft lignin as a partial replacement for a traditional surfactant in thymol-based biocidal suspensions: physical and chemical features

Abstract

Thymol is a renewable substance and has a high antimicrobial efficiency, which indicates that it could be used to produce sustainable biocides. In this study, we used kraft lignin as a partial replacement for a traditional surfactant in order to solubilize thymol in water. In this sense, this article reports an unprecedented method for using a kraft lignin solution to stabilize a thymol-based biocide with high fungicidal activity. The results showed that the lignin was crucial for stabilizing the suspensions. When the lignin was not added to the surfactant, there was a water-oil phase separation and the thymol crystallized after its rest for 30 days. Results obtained by in vitro experiments indicated that one of the studied lignin:thymol suspension (volume ratio of 1:0.1) presented an excellent fungal resistance. Furthermore, even the sample with the smallest thymol concentration (c.a. 0.5%) was able to inhibit the mycelial growth of the bracket fungus (Ganoderma applanatum), which is a promising feature for a biocidal application.

HIGHLIGHTS

• This research addresses multidisciplinary concepts for obtaining sustainable products;

• Lignin is a good renewable stabilizer for thymol suspensions in water;

• Thymol and lignin, at three different mass ratios, were successfully applied for obtaining stable suspensions;

• Lignin-thymol suspensions seem to be promising biocides.

Keywords:

• Lignocellulosic biomass
• essential oil
• renewable material
• suspensions
• sustainable product

Author contributions

The article was written through the contributions of all authors and all of them have approved the final version of the article. A.K.S and W.L.E.M developed the experiments and analyzed the results. A.K.S and A.L.M. proposed experimental solutions, validated the initial objectives of the project, and wrote the original draft. W.L.E.M and D.A.G. helped with the funding acquisition. R.A.D. M.A.U.G. and X.E. helped for reviewing, editing, and correcting both spelling and grammar errors.

Declaration of interest statement

The authors have no potential conflict of interest to declare.

Additional information

Funding

The authors are grateful for the support of the Brazilian CNPq, CAPES (PNPD scholarship - Grant number 88887.475364/2020-00) and Embrapa Florestas.