Enzymatic Production of Lauroyl and Stearoyl Monoesters of d-Xylose, l-Arabinose, and d-Glucose as Potential Lignocellulosic-Derived Products, and Their Evaluation as Antimicrobial Agents

Forestry and agricultural industries constitute highly relevant economic activities globally. They generate large amounts of residues rich in lignocellulose that have the potential to be valorized and used in different industrial processes. Producing renewable fuels and high-value-added compounds from lignocellulosic biomass is a key aspect of sustainable strategies and is central to the biorefinery concept. In this study, the use of biomass-derived monosaccharides for the enzymatic synthesis of sugar fatty acid esters (SFAEs) with antimicrobial activity was investigated to valorize these agro-industrial residues. With the aim to evaluate if lignocellulosic monosaccharides could be substrates for the synthesis of SFAEs, d-xylose, l-arabinose, and d-glucose, lauroyl and stearoyl monoesters were synthetized by transesterification reactions catalyzed by Lipozyme RM IM as biocatalyst. The reactions were performed using commercial d-xylose, l-arabinose, and d-glucose separately as substrates, and a 74:13:13 mixture of these sugars. The proportion of monosaccharides in the latter mixture corresponds to the composition found in hemicellulose from sugarcane bagasse and switchgrass, as previously described in the literature. Products were characterized using nuclear magnetic resonance (NMR) spectroscopy and showed that only the primary hydroxyl group of these monosaccharides is involved in the esterification reaction. Antimicrobial activity assay using several microorganisms showed that 5-O-lauroyl-d-xylofuranose and 5-O-lauroyl-l-arabinofuranose have the ability to inhibit the growth of Gram-positive bacteria separately and in the products mix. Furthermore, 5-O-lauroyl-l-arabinofuranose was the only product that exhibited activity against Candida albicans yeast, and the four tested filamentous fungi. These results suggest that sugar fatty acid esters obtained from sustainable and renewable resources and produced by green methods are promising antimicrobial agents.