Downstream processing of mannosylerythritol lipids produced byPseudozyma aphidis

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

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.

A review on the upstream production and downstream purification of mannosylerythritol lipids

Biosurfactants are natural compounds with remarkable surface-active properties that may offer an eco-friendly alternative to conventional surfactants. Among them, mannosylerythritol lipids (MELs) stand out as an intriguing example of a glycolipid biosurfactant. MELs have been used in a variety of sectors for various applications, and are currently commercially produced. Industrially, they are used in the pharmaceutical, cosmetic, food, and agricultural industries, based on their ability to reduce surface tension and enhance emulsification. However, despite their utility, their production is comparatively limited industrially. From a bioprocessing standpoint, two areas of interest to improve the production process are upstream production and downstream (separation and purification) product recovery. The former has seen a significant amount of research, with researchers investigating several production factors: the microbial species or strain employed, the producing media composition, and the production strategy implemented. Improvement and optimization of these are key to scale-up the production of MELs. On the other hand, the latter has seen comparatively limited work presented in the literature. For the most part traditional separation techniques have been employed. This systematic review presents the production and purification methodologies used by researchers by comprehensively analyzing the current state-of-the-art with regards the production, separation, and purification of MELs. By doing so, the review presents different possible approaches, and highlights some potential areas for future work by identifying opportunities for the commercialization of MELs.

A comprehensive review of biosurfactant production and its uses in the pharmaceutical industry

Biosurfactants are naturally occurring, surface-active chemicals generated by microorganisms and have attracted interest recently because of their numerous industrial uses. Compared to their chemical equivalents, they exhibit qualities that include lower toxic levels, increased biodegradable properties, and unique physiochemical properties. Due to these traits, biosurfactants have become attractive substitutes for synthetic surfactants in the pharmaceutical industry. In-depth research has been done in the last few decades, demonstrating their vast use in various industries. This review article includes a thorough description of the various types of biosurfactants and their production processes. The production process discussed here is from oil-contaminated waste, agro-industrial waste, dairy, and sugar industry waste, and also how biosurfactants can be produced from animal fat. Various purification methods such as ultrafiltration, liquid-liquid extraction, acid precipitation, foam fraction, and adsorption are required to acquire a purified product, which is necessary in the pharmaceutical industry, are also discussed here. Alternative ways for large-scale production of biosurfactants using different statistical experimental designs such as CCD, ANN, and RSM are described here. Several uses of biosurfactants, including drug delivery systems, antibacterial and antifungal agents, wound healing, and cancer therapy, are discussed. Additionally, in this review, the future challenges and aspects of biosurfactant utilization in the pharmaceutical industry and how to overcome them are also discussed.

Substrates of Opposite Polarities and Downstream Processing for Efficient Production of the Biosurfactant Mannosylerythritol Lipids from Moesziomyces spp

Biosurfactants can replace fossil-driven surfactants with positive environmental impacts, owing to their low eco-toxicity and high biodegradability. However, their large-scale production and application are restricted by high production costs. Such costs can be reduced using renewable raw materials and facilitated downstream processing. Here, a novel strategy for mannosylerythritol lipid (MEL) production explores the combination of hydrophilic and hydrophobic carbon sources sideways with a novel downstream processing strategy, based on nanofiltration technology. Co-substrate MEL production by Moesziomyces antarcticus was threefold higher than using D-glucose with low levels of residual lipids. The use of waste frying oil instead of soybean oil (SBO) in co-substrate strategy resulted in similar MEL production. Moesziomyces antarcticus cultivations, using 3.9 M of total carbon in substrates, yields 7.3, 18.1, and 20.1 g/L of MEL, and 2.1, 10.0, and 5.1 g/L of residual lipids, for D-glucose, SBO, and a combination of D-Glucose and SBO, respectively. Such approach makes it possible to reduce the amount of oil used, offset by the equivalent molar increase in D-glucose, improving sustainability and decreasing residual unconsumed oil substrates, facilitating downstream processing. Moesziomyces spp. also produces lipases that broken down the oil and, thus, residual unconsumed oils are in the form of free fatty-acids or monoacylglycerol, which are smaller molecules than MEL. Therefore, nanofiltration of ethyl acetate extracts from co-substrate-based culture broths allows to improve MEL purity (ratio of MEL per total MEL and residual lipids) from 66 to 93% using 3-diavolumes.

Novel Organic Solvent Nanofiltration Approaches for Microbial Biosurfactants Downstream Processing

Glycolipid biosurfactants are the most prominent group of microbial biosurfactants, comprising rhamnolipids, sophorolipids and mannosylerythritol lipids (MELs). Usually, large amounts of hydrophobic substrates (e.g., vegetable oils) are used to achieve high titers (~200 g/L) of a crude product of low purity at values limited to 50-60%, contaminated with unconsumed triacylglycerol and residual free fatty acids and monoacylglycerides. The methods reported for the removal of these contaminants use a mixture of organic solvents, compromising solvent recyclability and increasing final process costs. This study reports, for the first time, an innovative downstream method for MELs, in which 90% of the triacylglycerols are separated from the crude MEL mixture in a first stage and the other lipid derivatives (free fatty acids, mono- and diacylglycerols) are removed by organic solvent nanofiltration (OSN). Three commercially available membranes (GMT-oNF-2, PuraMEm-600 and DuramMem-500) and several homemade membranes, casted from 22, 24 or 26% (w/v) polybenzimidazole (PBI) solutions, were assessed for crude MELs purification by diafiltration. A final purity of 87-90% in the MELs was obtained by filtering two diavolumes of methanol or ethyl acetate solutions through a PBI 26% membrane, resulting in MELs losses of 14.7 ± 6.1% and 15.3 ± 2.2%, respectively. Higher biosurfactant purities can be archived using the PBI 26% membrane at higher DV, but at the cost of higher product losses. Namely, in MeOH, the use of 6 DV leads to losses of 32% for MELs and 18% for sophorolipids. To obtain MELs at reagent grade with purities equal or higher than 97%, a two-sequential cascade filtration approach was implemented using the commercial membrane, GMT-oNF. In such a process, MELs with 98% purity was obtained at the cost of 11.6% MELs losses. Finally, decoloration, important in some applications, was successfully assessed using activated carbon. Overall, this study reports a unique solution for microbial biosurfactants production with minimal product losses, enabling solvent recycling and potentially reducing costs.

Microbial surfactants: A journey from fundamentals to recent advances

Microbial surfactants are amphiphilic surface-active substances aid to reduce surface and interfacial tensions by accumulating between two fluid phases. They can be generically classified as low or high molecular weight biosurfactants based on their molecular weight, whilst overall chemical makeup determines whether they are neutral or anionic molecules. They demonstrate a variety of fundamental characteristics, including the lowering of surface tension, emulsification, adsorption, micelle formation, etc. Microbial genera like Bacillus spp., Pseudomonas spp., Candida spp., and Pseudozyma spp. are studied extensively for their production. The type of biosurfactant produced is reliant on the substrate utilized and the pathway pursued by the generating microorganisms. Some advantages of biosurfactants over synthetic surfactants comprise biodegradability, low toxicity, bioavailability, specificity of action, structural diversity, and effectiveness in harsh environments. Biosurfactants are physiologically crucial molecules for producing microorganisms which help the cells to grasp substrates in adverse conditions and also have antimicrobial, anti-adhesive, and antioxidant properties. Biosurfactants are in high demand as a potential product in industries like petroleum, cosmetics, detergents, agriculture, medicine, and food due to their beneficial properties. Biosurfactants are the significant natural biodegradable substances employed to replace the chemical surfactants on a global scale in order to make a cleaner and more sustainable environment.

Production of mannosylerythritol lipids: biosynthesis, multi-omics approaches, and commercial exploitation

Compilation of resources regarding MEL biosynthesis, key production parameters; available omics resources and current commercial applications, for smut fungi known to produce MELs.

Fermentative Production of Mannosylerythritol Lipids using Sweetwater as Waste Substrate by Pseudozyma antarctica (MTCC 2706)

Mannosylerythritol lipids are glycolipid biosurfactants with promising industrial applications. However, their commercial production is hindered due to its high production cost. The current study investigates the use of sweetwater, a by-product of the fat-splitting industry in combination with soybean oil for the production of mannosylerythritol lipids using Pseudozyma antarctica (MTCC 2706). The optimum sweetwater and soybean oil concentration of 22% and 7% (w/v) yielded 7.52 g L–1and 21.5 g L–1 mannosylerythritol lipids at shake flask and fermenter level respectively. The structure and functional groups of mannosylerythritol lipids were confirmed by fourier transform infrared (FTIR) spectroscopy, liquid chromatography-mass spectrometry (LC/MS) and 1H- and 13C-nuclear magnetic resonance (NMR) analysis. Surfactant properties, such as surface tension, critical micelle concentration, foaming and emulsification of mannosylerythritol lipids were also explored.

Production of Mannosylerythritol Lipids (MELs) to be Used as Antimicrobial Agents Against S. aureus ATCC 6538

Antimicrobial resistance (AMR) is a current major health issue, both for the high rates of resistance observed in bacteria that cause common infections and for the complexity of the consequences of AMR. Pathogens like Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Mycobacterium tuberculosis among others are clear examples of antibiotic-resistant threats. Biosurfactants have recently emerged as a potential new generation of anti-adhesive and anti-biofilm agents; mannosylerythritol lipids (MELs) are biosurfactants produced by a range of fungi. A range of structural variants of MELs can be formed and the proportion of each isomer in the fermentation depends on the yeast used, the carbon substrate used for growth and the duration of the fermentation. In order to allow assessment of the possible functions of MELs as antimicrobial molecules, small quantities of MEL were produced by controlled fermentation. Fermentations of the yeast Pseudozyma aphidis using rapeseed oil as a carbon source yielded up to 165 g_MELs/kg_Substrate. The MELs formed by this strain was a mixture of MEL-A, MEL-B, MEL-C and MEL-D. The MELs produced were tested against S. aureus ATCC 6538 on pre-formed biofilm and on co-incubation biofilm experiments on silicone discs; showing a disruption of biomass, reduction of the biofilm metabolic activity and a bacteriostatic/bactericidal effect confirmed by a release of oxygen uptake \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p_{{{\text{O}}_{2} }}$$\end{document}pO2, the reduction of citrate synthase activity and scanning electron microscopy. The results show that MELs are promising antimicrobial molecules for biomedical technological applications that could be studied in detail in large-scale systems and in conjunction with animal tissue models.

Production and characterization of a new glycolipid, mannosylerythritol lipid, from waste cooking oil biotransformation by Pseudozyma aphidis ZJUDM34

Mannosylerythritol lipids (MELs) are glycolipids possessing unique biosurfactant properties. However, the prices of substrates currently used for MEL formation caused its unsustainable commercial development. Waste cooking oil poses significant ecological and economical problems. Thus, the production of MELs from used waste cooking oil using the biotransformation route is one of the better alternatives to utilize it efficiently and economically. This work aims at the production of MELs using waste cooking oil instead of soybean oil and evaluating the major characteristics and compositions of MELs. The titers reached 61.50 g/L by the optimization of culture medium, higher than the counterpart (10.25 ± 0.32 g/L) of the nonoptimized medium. MELs exhibited good surface activity and better performance in contrast to MELs grown on soybean oil. The water phase behavior of MEL-A was also evaluated. The process showed higher productivity of MELs with better surface activity and application stability than the conventional process using soybean oil. The findings of this study imply that the use of inexpensive fermentation substrates associated with straightforward downstream processing is expected to have a great impact on the economy of MEL production.

Biosurfactant production by fungi as a sustainable alternative

ABSTRACT: A wide variety of bacteria is far more exploited than fungi as biosurfactants (BS) or bioemulsifiers (BE), using renewable sources. BS are considered to be environmentally safe and offer advantages over synthetic surfactants. However, the BS yield depends largely on the metabolic pathways of the microorganisms and the nutritional medium. The production of BS or BE uses several cultural conditions, in which a small change in carbon and nitrogen sources affects the quantity of BS or BE produced. The type and quantity of microbial BS or BE produced depend mainly on the producer organism, and factors such as carbon and nitrogen sources, trace elements, temperature and aeration. The diversity of BS or BE makes it interesting to apply them in the pharmaceutical and cosmetics industries, agriculture, public health, food processes, detergents, when treating oily residues, environmental pollution control and bioremediation. Thus, this paper reviews and addresses the biotechnological potential of yeasts and filamentous fungi for producing, characterizing and applying BS or BE.

Characterization, enhancement and modelling of mannosylerythritol lipid production by fungal endophyte Ceriporia lacerate CHZJU

The glycolipid biosurfactants mannosylerythritol lipids (MELs) attract great attention for their biodegradability, super emulsifying properties and versatile bioactivities. In this study, the MEL deriving from Ceriporia lacerate CHZJU was identified as MEL-A, and its critical micelle concentration and emulsifying activities were assessed. To examine the production of MELs from Ceriporia lacerate, a Plackett-Burman design and response surface methodology were used to optimize the culture nutrients. The optimal medium contains 1g/L yeast extract, 1.5g/L (NH₄)₂SO₄, 0.5g/L KH₂PO₄, 0.04g/L CaCl₂, 119.6mL/L soybean oil and 0.297g/L MnSO₄. Subsequent verification revealed that the yield of MELs was 129.64±5.67g/L. Furthermore, an unstructured kinetic model was developed for mycelial growth, MEL production and substrate utilization. This work provides insight into Ceriporia lacerate CHZJU, a predominant fungus producing MEL-A. Optimization using response surface methodology enhanced the mannosylerythritol lipid recovery. Importantly, we developed fermentation kinetic modelling for mannosylerythritol lipid production.

Enhanced separation and analysis procedure reveals production of tri-acylated mannosylerythritol lipids by Pseudozyma aphidis

Mannosylerythritol lipids (MELs) are one of the most promising biosurfactants because of their high fermentation yields (>100 g l−1) and during the last two decades they have gained a lot of attention due to their interesting self-assembling properties and biological activities. In this study, MELs were produced by fed-batch bioreactor fermentation of rapeseed oil with Pseudozyma aphidis MUCL 27852. This high-level MEL-producing yeast secretes four conventional MEL structures, -A, -B, -C and -D, which differ in their degree of acetylation. During our research, unknown compounds synthesized by P. aphidis were detected by thin-layer chromatography. The unknown compounds were separated by flash chromatography and identified as tri-acylated MELs by high-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS). The third fatty acid chain on the tri-acylated MELs was positioned on the primary alcohol of the erythritol moiety and comprised long-chain acids, mainly oleic and linoleic acid, which are not found in conventional di-acylated MELs. Furthermore, the LC–MS analysis time of conventional MELs was reduced to almost one-third by switching from HPLC–MS/MS to ultraperformance liquid chromatography tandem mass spectrometry (UPLC–MS/MS). Provided optimization of the fermentation yield, P. aphidis could be an interesting novel producer of tri-acylated MELs and, thereby expand the supply and applicability of biosurfactants.

Selective recovery of acidic and lactonic sophorolipids from culture broths towards the improvement of their therapeutic potential

Sophorolipids (SLs) were produced by Starmerella bombicola. The separation and purification of SLs are a complex process, since they are produced as a mixture of compounds with few structural differences. Solvent extraction is commonly used in downstream processing. In this work, an environmental friendly approach was developed for SLs recovery and purification, based on neutral polymeric sorbents, Amberlite XAD16N^TM, XAD18^TM, and XAD1600N^TM. In batch microassays, key parameters of sorption/desorption process (e.g., contact time, temperature, sorbents, and SLs concentrations) were optimized for separation of acidic and lactonic SLs. Sorption equilibrium was reached after 2-3 h, for all the sorbents tested. Among them XAD1600N^TM showed a higher sorption capacity (q _max 230 mg g^-1), a higher removal (≈100 %) of acidic and lactonic SLs [1 and 2.5 % (w/v)], and the best selectivity. Methanol, ethanol, and acetone were suitable for SLs elution. A selective desorption of SLs was attained with acetonitrile aqueous solutions (v/v): (1) 25 % led to 88.3 % of acidic SLs and (2) 55 % followed by methanol solution (100 %) led to 93.2 % of purified lactonic SLs. This achievement was particularly important regarding SLs potential therapeutic applications, since acidic and lactonic SLs show different biologic activities. In fact, acid SLs show higher virucidal and pro-inflammatory cytokine activity, while lactonic SLs show stronger spermicidal and anti-cancer activity.

Glycolipid biosurfactants: Potential related biomedical and biotechnological applications

Glycolipids, consisting of a carbohydrate moiety linked to fatty acids, are microbial surface active compounds produced by various microorganisms. They are characterized by highly structural diversity and have the ability to decrease the surface and interfacial tension at the surface and interface respectively. Rhamnolipids, trehalolipids, mannosylerythritol-lipids and cellobiose lipids are among the most popular glycolipids. Moreover, their ability to form pores and destabilize biological membrane permits their use in biomedicine as antibacterial, antifungal and hemolytic agents. Their antiviral and antitumor effects enable their use in pharmaceutic as therapeutic agents. Also, glycolipids can inhibit the bioadhesion of pathogenic bacteria enabling their use as anti-adhesive agents and for disruption of biofilm formation and can be used in cosmetic industry. Moreover, they have great potential application in industry as detergents, wetting agents and for flotation. Furthermore, glycolipids can act at the surface and can modulate enzyme activity permitting the enhancement or the inhibition of the activity of certain enzymes.

The transcriptomic profile of Pseudozyma aphidis during production of mannosylerythritol lipids

The basidiomycetous fungus Pseudozyma aphidis is able to convert vegetable oils to abundant amounts of the biosurfactant mannosylerythritol lipid (MEL) with a unique product pattern of MEL-A, MEL-B, MEL-C, and MEL-D. To investigate the metabolism of MEL production, we analyzed the transcriptome of P. aphidis DSM 70725 under MEL-inducing and non-inducing conditions using deep sequencing. Following manual curation of the previously described in silico gene models based on RNA-Seq data, we were able to generate an experimentally verified gene annotation containing 6347 genes. Using this database, our expression analysis revealed that only four of the five cluster genes required for MEL synthesis were clearly induced by the presence of soybean oil. The acetyltransferase encoding gene PaGMAT1 was expressed on a much lower level, which may explain the secretion of MEL with different degrees of acetylation in P. aphidis. In parallel to MEL synthesis, microscopic observations showed morphological changes accompanied by expression of genes responsible for cell development, indicative of a coregulation between MEL synthesis and cell morphology. In addition a set of transcription factors was identified which may be responsible for regulation of MEL synthesis and cell development. The upregulation of genes required for nitrogen metabolism and other assimilation processes indicate additional metabolic pathways required under the MEL-inducing conditions used. We also searched for a conserved gene cluster for cellobiose lipids (CL) but only found seven genes with limited homology distributed over the genome. However, we detected characteristic TLC spots in fermentations using P. aphidis DSM 70725, indicative of CL secretion.

Analytical characterization of mannosylerythritol lipid biosurfactants produced by biosynthesis based on feedstock sources from the agrofood industry

Mannosylerythritol lipids (MELs) are currently one of the most promising biosurfactants because of their multifunctional applications and good biodegradability. Depending on the yeast strain and the feedstock used for the fermentation process, structural variations in the MELs obtained occur. Therefore, MELs produced by Pseudozyma aphidis DSMZ 70725 with a soybean oil feedstock were characterized by chromatography and mass spectrometry (MS). Column chromatography with silica provided fractionation of the different types of MEL. High-performance liquid chromatography combined with MS was employed for the analysis of the MEL fractions and crude mixtures. A characteristic MS pattern for the MELs was obtained and indications of the presence of new MEL homologues, showing the incorporation of longer and more unsaturated fatty acid chains than previously reported, were given. Gas chromatography-MS analysis confirmed the presence of such unsaturated fatty acid chains in the MELs, demonstrating the incorporation of fatty acids with lengths ranging from C(8) to C(14) and with up to two unsaturations per chain. The incorporation of C(16) and C(18) fatty acid chains requires further investigation. MS/MS data allowed the unambiguous identification of the fatty acids present in the MELs. The product ion spectra also revealed the presence of a new isomeric class of MELs, bearing an acetyl group on the erythritol moiety.

Bioconversion of crude glycerol to glycolipids in Ustilago maydis

Ustilago maydis is known to produce glycolipid-type biosurfactants. Here, we show that U. maydis is able to efficiently convert biodiesel-derived crude glycerol to glycolipids. We have optimized the medium composition and environmental factors for bioconversion of crude glycerol to glycolipids. The synthetic medium (MinCG) contains 50 g L(-1) crude glycerol and 20.3 mg L(-1) ammonium citrate as the carbon and nitrogen sources, respectively. The supplementation of trace amount of amino acids, Group-B vitamins and precursors of glycolipids, mannose and erythritol, also improved the final yield. At pH 4.0 and 30°C, 32.1 g L(-1) total glycolipids was produced in a 8.2-day fed-batch bioprocess. Methanol at 2% or above severely inhibited cell growth and production of glycolipids. Our results suggest that U. maydis is an excellent host for the bioconversion of crude glycerol to value-added products.

Mannosylerythritol lipids: a review

Mannosylerythritol lipids (MELs) are surface active compounds that belong to the glycolipid class of biosurfactants (BSs). MELs are produced by Pseudozyma sp. as a major component while Ustilago sp. produces them as a minor component. Although MELs have been known for over five decades, they recently regained attention due to their environmental compatibility, mild production conditions, structural diversity, self-assembling properties and versatile biochemical functions. In this review, the MEL producing microorganisms, the production conditions, their applications, their diverse structures and self-assembling properties are discussed. The biosynthetic pathways and the regulatory mechanisms involved in the production of MEL are also explained here.