Promising Application, Efficient Production, and Genetic Basis of Mannosylerythritol Lipids

Abstract

Mannosylerythritol lipids (MELs) are a class of glycolipids that have been receiving increasing attention in recent years due to their diverse biological activities. MELs are produced by certain fungi and display a range of bioactivities, making them attractive candidates for various applications in medicine, agriculture, and biotechnology. Despite their remarkable qualities, industrial-scale production of MELs remains a challenge for fungal strains. Excellent fungal strains and fermentation processes are essential for the efficient production of MELs, so efforts have been made to improve the fermentation yield by screening high-yielding strains, optimizing fermentation conditions, and improving product purification processes. The availability of the genome sequence is pivotal for elucidating the genetic basis of fungal MEL biosynthesis. This review aims to shed light on the applications of MELs and provide insights into the genetic basis for efficient MEL production. Additionally, this review offers new perspectives on optimizing MEL production, contributing to the advancement of sustainable biosurfactant technologies.

Keywords: biological activity; biosynthetic pathways; efficient production; fungi; gene clusters; mannosylerythritol lipids.

Figure 1

The chemical structures of four MEL homologs, MEL-A, MEL-B, MEL-C, and MEL-D. These homologs are categorized according to the carbon acetylation in the C-4 and C-6 (mannose).

Figure 2

A diagram showing the various biological properties of mannosylerythritol lipids. (A) MELs can interact with proteins. (B) MELs can induce differentiation of mammalian cells. (C) MELs have antibacterial activity. (D) MELs have antioxidant activity. (E) MELs exhibit skin- and hair-moisturizing efficacy. (F) MELs have depigmentary properties.

Figure 3

Molecular phylogenetic tree of some MEL-producing microorganisms. The phylogenetic tree was constructed using Mega X [122] based on the internal transcribed spacer (ITS). All sequences were retrieved from GenBank (https://www.ncbi.nlm.nih.gov/genbank/ accessed on 26 December 2023).

Figure 4

A schematic representation of the pathways and enzymes necessary for MEL biosynthesis in basidiomycetous yeasts belonging to the genera Ustilago, Pseudozyma, Moesziomyces, and Sporisorium. The genes for MEL biosynthesis encode four enzymes (EMT1, MAC1, MAC2, and MAT1) and one transport protein MMF1. EMT1 is needed for the synthesis of the hydrophilic carbohydrate backbone 4-O-β-D-mannopyranosyl-erythritol. Two peroxisomal acyltransferases Mac1 and Mac2 link MELs to fatty acid oxidation. Mat1 catalyzes the formation of acetylated MEL variants MEL-A, MEL-B, and MEL-C. The synthesis of the nonacetylated variant MEL-D does not need MAT1.

Figure 5

Gene clusters for the biogenesis of MEL in diverse strains. The exons of each of the five genes involved in MEL synthesis were labeled. The schematic diagram for all cluster genes is drawn according to their genomic loci shown in GenBank.