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BACKGROUND: Laccases are receiving increasing attention as potential industrial enzymes in various applications. Therefore, it is important to find inexpensive and optimized media for large-scale commercial production. The present work aims to valorize olive mill wastewater (OMW) by its use as base media for laccases production by Trametes trogii and use of the laccases produced for decolorizing textile dyes.

The removal of toxic phenolic compounds from industrial wastewater is an important issue to be addressed. Their presence in water and soil has become a great environmental concern, and effective methods for their removal need to be addressed. The feasibility of applying laccases for the degradation of phenolic compounds has received increasing attention. In the present work, the transformation of five phenolic compounds (catechol, hydroxytyrosol, tyrosol, guaiacol and p-coumaric acid), the main constituents of a typical wastewater derived from an olive oil factory, by Trametes trogii laccases was studied at concentrations ranging between 0.2 and 1.6 mM. High-performance liquid chromatography analysis showed high degradation rates of phenolic compounds by T trogii laccases. Independently of the used concentration, a complete transformation of guaiacol, p-coumaric acid, hydroxytyrosol and tyrosol occurred after 1 h of incubation. The transformation of catechol depends on its initial concentration. The liquid chromatography-mass spectrometry analysis showed that laccases catalysed transformation of p-coumaric acid and tyrosol, resulting in the formation of phenolic dimers. No reduction of enzyme activity has been observed during the oxidation of all phenolic compounds. These results suggest that the studied laccases were capable of efficiently removing phenolic compounds, as well as catalysing the production of novel phenolic dimers.

Background The Mentha rotundifolia L. (Lamiaceae family), is a medicinal herb used since the ancient times as an antiseptic, analgesic and anti-inflammatory agent. In the present work, metabolomic profiling of two Mentha rotundifolia L. ecotypes leaf tissues spontaneously growing in the North of Tunisia was achieved. Methods Phenolic contents (TPC, TFC and TTC) were assessed using colorimetric methods. Metabolomic profiling of leaf tissues extracts was assessed based on Gas Chromatography-Mass Spectrometry (GC/MS) analysis. The antioxidant ability of M. rotundifolia extracts was achieved based on two test systems namely DPPH and FRAP assays. Antimicrobial activity against a set of Gram negative and Gram positive bacteria was estimated by measuring ID, MIC and MBC values. Results Fifty metabolites were identified as belonging mainly to phenolics, fatty acids, terpenes, steroids and aldehydes classes with qualitative and quantitative variability. Most of the identified compounds are reputed bioactive with potent antioxidant, antimicrobial and anti-inflammatory among others effects. To confirm these findings common in vitro biological activities were achieved. The investigated extracts showed significant antioxidant abilities based on both 1,1-diphenyl-2-picrylhydrazyl (DPPH) and Ferric reducing antioxidant potential (FRAP) assays. Furthermore, the extracts revealed promising antimicrobial ability against tested Gram+ and Gram- bacterial strains (ID: 12.5–14.5 mm, MIC: 3.125–25 (µg/mL), MBC: 6.25–100 (µg/mL)). Conclusions Based on our findings Mentha rotundifolia L. leaves extracts present a potential source of natural antioxidants and diverse bioactive compounds which could be used in green pharmacy, food preservation, alternative medicine and natural therapies.