Finding a Needle in a Haystack: Producing Antimicrobial Cutin-Derived Oligomers from Tomato Pomace

Abstract

Agro-industrial residues comprise a rich diversity of plant polymers and bioactive compounds, constituting promising sources for the development of materials, including bioplastics, and food supplements, among other applications. In particular, the polyester cutin is abundant in fruit peel, a plentiful constituent of pomace agro-industrial residues. The potential of diverse fruit pomaces as a source for the development of cutin-derived materials/products has been extensively sought out. This study expands the established knowledge: it sets proof of concept for the production of antimicrobial oligomers from cutin-rich materials isolated in a single step from tomato pomaces generated by two remote agro-industries. Specifically, it first analyzed how the chemical signature (nuclear magnetic resonance (NMR) and gas chromatography–mass spectrometry (GC–MS)) of a pomace (and of its major constituents) mirrors that of the corresponding cutin-rich material isolated using an ionic liquid extractant. The cutin-rich materials were then deconstructed (using mild hydrolyses), and the resultant mixtures were chemically characterized and screened for bactericidal activity against Escherichia coli and Staphylococcus aureus . The presence of esterified structures, linear and/or branched, likely comprising dioic acids as a major building block (but not exclusively) is a prerequisite for activity against E. coli but not against S. aureus that was susceptible to monomers as well. Further studies are required to optimize the production of broad bactericidal oligomers from any cutin-rich pomace source, moving ahead toward their circular usage.

Cutin-Derived Oligomers Act as Damage-Associated Molecular Patterns inArabidopsis thaliana

“…Cutin was purified from tomato pomace since its high availability as an agroindustry residue (European Commission, 2021) enables the production of large amounts of polymeric structures. Moreover, previous studies showed that cutin purified with an ionic liquid from tomato pomace (consisting of peels, seeds and stems) is virtually similar to that obtained from the tomato peel fraction alone (Escórcio et al, 2022).…”

“…S2). Cutin hydrolysates, which are obtained by an extensive hydrolysis of the cutin, consist almost exclusively of aliphatic monomers with a few aromatic monomers (Escórcio et al, 2022). These hydrolysates also did not elicit a ROS burst (Fig.…”

“…ratio enzyme:inhibitor) . Cutin hydrolysates (mixture of all hydrolysable cutin monomers) also contain low levels of phenolic compounds (Escórcio et al, 2022). There are alternative methods for ROS measurement; for example, DAB staining has been used to detect the accumulation of intracellular ROS in response to treatment with cutin aliphatic monomers, specifically hydroxy palmitic acid (HPA) Park et al, 2008).…”

“…COM preparations have been shown to consist of oligomers and monomers (Escórcio et al, 2022). During infection, pathogens can secrete enzymes able to hydrolyze ester-type linkages present in cutin (Serrano et al, 2014); breaking the structural integrity of the cutin barrier to allow pathogen invasion of the infected plant tissue.…”

From Tomato Pomaces Biorefinery to Biobased Shape-Memory Semicrystalline Polyester Networks

“…Conversely, tomato cuticles are rich in cutin polyester, whose monomer composition is highly homogeneous (tomato cutin mainly consists of 9(10)-16 dihydroxyhexadecanoic acid). Tomato pomace is currently the largest and growing source of cutin-rich wastes, ranging from 6 to 9.10 6 tons per year. − After separation from seeds and pulp, tomato peels, containing more than 60% cutin, can be hydrolyzed by alkali treatment to yield fatty acid extracts containing mostly 9(10)-16 dihydroxyhexadecanoic acid with typically less than 10% of impurities such as α,ω-dicarboxylic fatty acids and phenolic compounds.…”