Figure 4 - uploaded by Karen Saerens
Content may be subject to copyright.
Alkylglucoside acceptor specificity of GTII (UgtB1) involved in sophorolipid production by S. bombicola. Activities were determined as% decrease in substrate peak area and expressed relatively to the activity observed for the natural glucolipid substrate. GL = 17-O-glucopyranosyloctadecenoic acid or the natural substrate; C10 = decylglucoside; C8 = octylglucoside; C6 = hexylglucoside; C4 = butylglucoside. Values plotted are mean values from two experiments.
Source publication
Altering glycolipid structure by genetic engineering of S. bombicola is a recently started research topic and worthy alternative to the unsuccessful selective feeding strategies conventionally applied to reach this goal. One question to be addressed when expressing heterologous proteins in S. bombicola is the activity of the subsequent biosynthetic...
Context in source publication
Context 1
... Because such compounds are commercially not avail- able and cannot simply be derived by other means, the speci- ficity was tested toward several alkylglucosides with different carbon chain lengths. Apart from the missing free carboxyl group, those substrates structurally resemble well the natural glucolipid acceptor. The results are shown in Fig. 4. As for GTI, also GTII shows significant specificity toward the chain length of its acceptor though it is less pronounced. While a shorten- ing to a C12 carbon chain length did not yield any glucosy- lated product from GTI, a decrease in the alkylglucoside lipid tail to C10 resulted in 83% activity and still 30.5% activity was found if ...
Similar publications
The enzyme UDP-glucose:glycoprotein glucosyltransferase (UGGT) mediates quality control of glycoproteins in the endoplasmic reticulum by attaching glucose to N-linked glycan of misfolded proteins. As a sensor, UGGT ensures that misfolded proteins are recognized by the lectin chaperones and do not leave the secretory pathway. The structure of UGGT a...
The physiological regulation of seasonal cambial growth is a longstanding unanswered question. Our evidence indicates that coniferin and the gene expression underlying CAGT activity, although capable of contributing to lignification, are more fundamentally linked to the overall control of seasonal cambial growth in conifers. No other metabolite or...
Calycosin-7-O-β-D-glucoside (Cy7G) is one of the principal components of Radix astragali. This isoflavonoid glucoside is regarded as an indicator to assess the quality of R. astragali and exhibits diverse pharmacological activities. In this study, uridine diphosphate-dependent glucosyltransferase (UGT) UGT88E18 was isolated from Glycine max and exp...
Almost one-third of proteins synthesized by eukaryotic cells belong to the secretory pathway, entering the endoplasmic reticulum (ER) either co- or posttranslationally. In the ER, proteins acquire their native tertiary fold, disulfide bonds are formed, and in some cases, they assemble into oligomeric structures. Numerous folding-assisting enzymes a...
Sucrose synthase (SUS), which catalyzes the reversible conversion of sucrose and uridine diphosphate (UDP) into fructose and UDP-glucose, is a key enzyme in sucrose metabolism in higher plants. In this study, we used reverse genetic approaches and carbohydrate analysis to investigate the role of cucumber sucrose synthase gene 4 (CsSUS4) in the grow...
Citations
... The lack of acetic acid consumption in the non-producing sugars is likely linked to the inhibition previously mentioned in the start of this section, however the acetic acid consumption and improved production appear strongly linked. Acetic acid and its anion acetate have not been previously explored for their ability to improve SL production and it has not been shown to be a component of the metabolic pathway and requires further exploration [36,42]. It would appear that acetic acid, a by-product of lignocellulose degradation and autoclaving, may be a beneficial component for SL production and demonstrates the capability of S. bombicola to utilize feedstocks that contain components that may otherwise inhibit other fermentation processes. ...
... UDP-glucose enters into the biosynthesis to form glucolipid and then a nonacetylated acid sophorolipid is formed. Subsequently, a series of reactions occur to convert this last compound to lactones both in monomeric or in dimeric structures, since sophorolipid exists in two forms acidic and lactonic (Van Bogaert et al 2011;Saerens et al 2015;Wongsirichot, Fig. 3 An overview of factors influencing biosurfactant production. The selection of microbial culture as well as the use of adequate fermentation systems and novel technological developments are important for the optimization of microbial surfactant production et al 2021) (Fig. 5). ...
... A series of reactions occur to convert non-acetylated acid sophorolipid to lactones both in monomeric or in dimeric structures. Sophorolipid exists in two forms acidic and lactonic (redrawn from Van Bogaert et al 2011;Saerens et al 2015;Wongsirichot, ...
The increasing influence of human activity and industrialization has adversely impacted the environment via pollution with organic contaminants, which are minimally soluble in water. These hydrophobic organopollutants may be present in sediment, water or biota and have created concern due to their toxic effects in mammals. The ability of microorganisms to degrade pollutants makes their use the most effective, inexpensive and ecofriendly method for environmental remediation. Microorganisms have the ability to produce natural surfactants (biosurfactants) that increase the bioavailability of hydrophobic organopollutants, which enables their use as carbon and energy sources. Due to microbial diversity in production, and the biodegradability, nontoxicity, stability and specific activity of the surfactants, the use of microbial surfactants has the potential to overcome problems associated with contamination by hydrophobic organopollutants.
This review provides an overview of the current state of knowledge regarding microbial surfactant production, mode of action in the biodegradation of hydrophobic organopollutants and biosynthetic pathways as well as their applications using emergent strategy tools to remove organopollutants from the environment. It is also specified for the first time that biosurfactants are produced either as growth-associated products or secondary metabolites, and are produced in different amounts by a wide range of microorganisms.
... A possible alternative to chemically produced surfactants are biosurfactants which are a structurally diverse group of surface-active compounds and synthesized by the microorganisms [18][19][20][21][22][23][24][25]. These Q4 compounds have been reported to have several advantages compared to chemically produced surfactants, e.g., they are less toxic, readily biodegradable, highly selective, etc. [17,[26][27][28]. From an economic point of view, biosurfactants are not yet competitive compared to surfactants obtained by chemical processes, so the development of a cost-effective production process is still necessary. ...
... SLs are mainly produced by various yeast species such as Candida bombicola, Candida apicola, and Candida bogorensis as an extracellular product. SL production requires a sugar source and a fatty acid source [15][16][17][18][19][20][26][27][28]. Advantages of this method are a high production rate and a good industrial applicability. ...
Among glycolipids, mannosylerythritol lipids (MEL), are mild and environmentally friendly surfactants used in various industrial applications. MELs are produced by biofermentation using non-traditional oils with various water-soluble carbon sources as cell growth booster. This substrate affects the production yield and cost of MEL. In this research work, the non-traditional oils jatropha oil, karanja oil and neem oil were used as new substrates along with glucose, glycerol and honey as new water-soluble substrates. All these oils are new feedstocks for the production of MEL using Pseudozyma antarctica (ATCC 32657). Jatropha oil, karanja oil and neem oil with honey as substrates resulted in higher MEL yields of (8.07, 7.75, and 1.86) g/L and better cell growth of (8.07, 7.75, and 1.86) g/L, respectively, than non-traditional oils with glucose and glycerol as substrates. Neem oil gave a lower yield of MEL (1.54 g/L) as well as cell growth (6.06 g/L) compared to jatropha oil and karanja oil (7.03 and 6.17) g/L, respectively. Crude MEL from the fermentation broth was detected by thin-layer chromatography (TLC), Fourier transform infrared spectrommetry (FT-IR), high performance liquid chromatography (HPLC) and proton nuclear magnetic resonance spectroscopy (1H NMR). Purified MEL has been used as an antimicrobial agent in cosmetic products associated with gram-positive and gram-negative bacteria and fungi.
... The performance of the fermentation in this work is benefited by the procedural media optimisation and the inclusion of baffled flasks to improve mixing and mass transfer. The oxygenation of the fermentation broth was a major point of consideration for this SL fermentation, as the biphasic (water/oil) media and viscous properties of the product are known to cause a decline in mass transfer and impede productivity (Saerens et al., 2015;Dolman et al., 2017). ...
A key barrier to market penetration for sophorolipid biosurfactants is the ability to improve productivity and utilize alternative feedstocks to reduce the cost of production. To do this, a suitable screening tool is required that is able to model the interactions between media components and alter conditions to maximize productivity. In the following work, a central composite design is applied to analyse the effects of altering glucose, rapeseed oil, corn steep liquor and ammonium sulphate concentrations on sophorolipid production with Starmerella bombicola ATCC 222144 after 168 h. Sophorolipid production was analysed using standard least squares regression and the findings related to the growth (OD600) and broth conditions (glucose, glycerol and oil concentration). An optimum media composition was found that was capable of producing 39.5 g l–1 sophorolipid. Nitrogen and rapeseed oil sources were found to be significant, linked to their role in growth and substrate supply respectively. Glucose did not demonstrate a significant effect on production despite its importance to biosynthesis and its depletion in the broth within 96 h, instead being replaced by glycerol (via triglyceride breakdown) as the hydrophilic carbon source at the point of glucose depletion. A large dataset was obtained, and a regression model with applications towards substrate screening and process optimisation developed.
... Soon after this, the UGTB1 enzyme converts newly generated glucolipids to the non-acetylated acidic SLs (Saerens et al., 2011c). Thereafter, the acetyltransferase (AT) enzyme regulates two acetylation events transferring the acetyl groups from acetyl co-enzyme A (AcCoA), either simultaneously and independently from each other to newly synthesized glucolipids or SLs mainly at C6 ′ and C6 ′ ' positions De Graeve et al., 2018;Saerens et al., 2015Saerens et al., , 2011bVan Bogaert et al., 2013a). After acetylation, the non-, mono-or di-acetylated ASLs and some glucolipids are transported extracellularly by an MDR transporter, i.e. mainly via SbSLMdr.2 ...
... So far, only a few studies have been conducted to find out integral episomal plasmids in S. bombicola but no such fruitful accomplishments have yet been achieved. Therefore, routine gene deletions to transform S. bombicola strains were achieved through linear DNA fragments and efficient homologous recombination using specially designed gene cassettes containing hygromycin, zeocin or nourseothricin resistant genes (Ciesielska et al., 2014;Jezierska et al., 2020;Liu et al., 2020;Lodens et al., 2018;Saerens et al., 2015;Van Bogaert et al., 2008, 2009. ...
Sophorolipids are highly active green surfactants (glycolipid biosurfactants) getting tremendous appreciation worldwide due to their low toxicity, biodegradability, broad spectrum of applications, and significant biotechnological potential. Sophorolipids are mainly produced by an oleaginous budding yeast Starmerella bombicola using low-cost substrates. Therefore, the recent state-of-art literature information about S. bombicola yeast is hereby provided, especially the underlying production pathways, biosynthetic gene cluster, and regulatory enzymes. Moreover, the S. bombicola offers flexibility for regulating the structural diversity of sophorolipids, either genetically or by varying fermentative conditions. The emergence of advanced technologies like ‘Omics and CRISPR/Cas have certainly boosted rational engineering research for designing high-performing platform strains. Therefore, currently available genetic engineering tools in S. bombicola were reviewed, thereby opening up exciting new possibilities for improving the overall bioproduction titers, structural variability, and stability of sophorolipids. Finally, some technical perspectives to address the current challenges were discussed.
... These groupings are facilitated by the acetylation and lactonization. Acetylation applies an acetyl group to the C6' and C6'' of the sophorose 31 group, producing di-or mono-acetylated sophorolipids (Saerens et al., 2015). Following this, 32 acetylated/non-acetylated sophorolipids may undergo lactonization, with esterification between the 33 fatty acid carboxyl group and the 4'' hydroxyl (and occasionally on the 6' or 6'' position) of the 34 sophorose, facilitated by the S. bombicola lactone esterase (SBLE) enzyme (Ciesielska et al., 2016). ...
The replacement of traditional petroleum-based surfactants with renewable biosurfactants is a key part of the transition towards a circular economy. Sophorolipids are the most commercially adopted biosurfactant due to the existence of high productivity fermentation process, excellent surface and interfacial tension properties and because the main producer organism Starmerella bombicola is non-pathogenic/non-GMO. However, the current large-scale production of sophorolipids still utilizes purified substrates such as glucose and oleic acid. This is a major reason their price is an order of magnitude higher than traditional surfactants, severely limiting their commercial adoption. Hence, implementation of sophorolipid production from alternative biomass byproducts and wastes is crucial. This review illustrates the potential performance of alternative feedstocks as sources of sugars, fatty acids and nitrogen for sophorolipid production. Important studies where alternative feedstocks outperformed purified substrates under the same conditions, as well as high overall production of sophorolipid using sophisticated fermentation schemes are highlighted. Promising performance such as productivities of up to 2.4 g/L/h currently exist with processes based on alternative feedstocks. Important knowledge gaps within the literature are also identified, such as the need to combine alternative feedstocks to eliminate the use of purified substrates. Future improvement of productivity on alternative feedstocks could be achieved via implementation of sophisticated fermentation schemes to either improve cell titer during growth or to improve SL production itself, such as in-situ separation of sophorolipids. Selection criteria were produced using key performance factors identified from the literature, together with other factors such as available quantity, price and logistics as well as the potential for integrated biorefining. These selection criteria were then applied to the UK as a case study. In the future, the framework developed could be applied to feedstock assessment and selection for localized sophorolipid production in various locations around the world.
... This, however, has not been achieved yet. Partly, it is due to the fact that enzymes of the sophorolipid synthesis pathway have a higher affinity to C16-C18 fatty acids rather than C12 or C10 [69,70]. Additionally, the fermentation of raw cooking oils results in a viscous, oily end product containing a mixture of sophorolipids of various structures. ...
Biosurfactants are a microbially synthesized alternative to synthetic surfactants, one of the most important bulk chemicals. Some yeast species are proven to be exceptional biosurfactant producers, while others are emerging producers. A set of factors affects the type, amount, and properties of the biosurfactant produced, as well as the environmental impact and costs of biosurfactant’s production. Exploring waste cooking oil as a substrate for biosurfactants’ production serves as an effective cost-cutting strategy, yet it has some limitations. This review explores the existing knowledge on utilizing waste cooking oil as a feedstock to produce glycolipid biosurfactants by yeast. The review focuses specifically on the differences created by using raw cooking oil or waste cooking oil as the substrate on the ability of various yeast species to synthesize sophorolipids, rhamnolipids, mannosylerythritol lipids, and other glycolipids and the substrate’s impact on the composition, properties, and limitations in the application of biosurfactants.
... At the interface of two phases, the hydrophobic part of the bioemulsifier is present at the surface in contact with the hydrophobic phase, whereas the hydrophilic moiety is oriented toward the hydrophilic phase. Because of their varied properties like Saerens et al. 2015) cleansing, foaming, wetting, emulsification, and reduction in viscosity, they find applications in pharmaceuticals, food, cosmetics, and bioremediation processes (Gautam and Tyagi 2006;Franzetti et al. 2010;Perfumo et al. 2010;Fracchia et al. 2012;Uzoigwe et al. 2015). ...
... Hydrophobic substrate is hydrolyzed into fatty acids by esterase. However, in the absence of exogenous hydrophobic carbon source, cells can also synthesize fatty acids de novo using acetyl-CoA (AcCoA) derived from the glycolysis pathway (Saerens et al. 2015). With only alkane substrates, cells can generate fatty acids through a three-step oxidation reaction catalyzed by cytochrome P450 monooxygenase, alcohol dehydrogenase, and aldehyde dehydrogenase, respectively (Inoue and Ito 1982). ...
Sophorolipids (SLs), currently one of the most promising biosurfactants, are secondary metabolites produced by many non-pathogenic yeasts, among which Candida bombicola ATCC 22214 is the main sophorolipid-producing strain. SLs have gained much attention since they exhibit anti-tumor, anti-bacterial, anti-inflammatory, and other beneficial biological activities. In addition, as biosurfactants, SLs have a low toxicity level and are easily degradable without polluting the environment. However, the production cost of SLs remains high, which hinders the industrialization process of SL production. This paper describes SL structure and the metabolic pathway of SL synthesis firstly. Furthermore, we analyze factors that contribute to the higher production cost of SLs and summarize current research status on the advancement of SL production based on two aspects: (1) the improvement of strain performance and (2) the optimization of fermentation process. Further prospects of lowering the cost of SL production are also discussed in order to achieve larger-scale SL production with a high yield at a low cost.
Key points
• Review of advances in strain performance improvement and fermentation optimization.
• High-throughput screening and metabolic engineering for high-performance strains.
• Low-cost substrates and semi-continuous strategies for efficient SL production.
... Then, pyruvate dehydrogenase catalyzes the oxidative decarboxylation of pyruvate to acetyl-CoA, which enters the Krebs cycle and provides energy and intermediate metabolites for microbial growth and metabolism. Meanwhile, part of glucose converts to activated UDP-glucose for the synthesis of glycogen and other complex carbohydrates by phosphoglucomutase (PGM) and UDP-glucose pyrophosphorylase (UGPASE), serving as the primary composition part of SLs (Oliveira et al. 2014;Saerens et al. 2015;Van Bogaert et al. 2007;Van Bogaert et al. 2011b). ...
... If the medium contains no fatty acids, acetyl-CoA derived from glycolysis will convert into fatty acids by de novo synthesis. When only hydrophobic substrates are existing in the medium, part of the fatty acids will be converted to acetyl-CoA by β-oxidation for cell maintenance (Saerens et al. 2015). ...
... In a subsequent step, a second UDP-glucose is coupled to the C2′ position of the first glucose moiety by glycosyltransferase II (UGTB1) and non-acetylated acidic SLs are formed. Further modifications are performed by acetyltransferase (AT) to obtain acetylated acidic SLs at the 6′and/or 6″-position (Esders and Light 1972;Saerens et al. 2015). The genes involved in the SL biosynthesis pathway are found in the gene cluster (Van Bogaert et al. 2013). ...
Sophorolipids (SLs), mainly synthesized by yeasts, were a sort of biosurfactant with the highest fermentation level at present. In recent years, SLs have drawn extensive attention for their excellent physiochemical properties and physiological activities. Besides, issues such as economics, sustainability, and use of renewable resources also stimulate the shift from chemical surfactants towards green or microbial-derived biosurfactants. SLs’ large-scale production and application were restricted by the relatively high production costs. Currently, waste streams from agriculture, food and oil refining industries, etc., have been exploited as low-cost renewable substrates for SL production. Advanced cultivation method, uncommonly used substrates, and new genetically modified SL-producing mutants were also designed and applied to improve the productivity or the special properties of SLs. In this review, a systematic and detailed description of primary and secondary metabolism pathways involved in SL biosynthesis was summarized firstly. Furthermore, based on the pathways of SL biosynthesis from different carbon substrates, we reviewed the current knowledge and advances in the exploration of cost-effective and infrequently used hydrophilic and hydrophobic substrates for large or specialized SL production.
