Sophorolipids and Rhamnolipids

The biosurfactant molecule consists of sophorose, a diglucose, bound to a hydroxy fatty acid in a glycosidic bond. The sophorose moiety may contain acetyl groups at the 6 and/or 6 positions and the molecule itself may form a lactone through linking 

Surfactants from Renewable Resources Edited by Mikael Kjellin and Ingegard Johansson 2010 John Wiley Sons, Ltd 

Sophorolipids may be produced on substrates that are, in part, directly incorporated into the molecule as the hydrophobic moiety, as opposed to, for example, rhanmoUpids where the biosynthesis occurs with the de novo synthesis of the hydrophobic part. Specifically, when providing C. bombicola with oleic acid and an otherwise suitable medium, the yeast will incorporate this fatty acid into a sophorolipid. By contrast, when capric acid is provided to Pseudomonas aeruginosa, the fatty acid is not directly converted into a rhamnolipid but is metabolized instead. The possibility of direct incorporation is a clear indication as to why sophorolipid production is among the highest of all biosurfactants. 

As of yet, no direct studies have been performed on the biosynthetic pathway of sophorolipids. Several indirect studies have been performed, however, that allow for the construction of a theoretical pathway. These studies were executed on different species 

The activation of a fatty acid for sophorolipid synthesis occurs in step 5 through the creation of a hydroxyl group at the coot co-l position, depending on the length of the fatty acid. Ci6 chains will undergo terminal hydroxylation and Cig chains are hydroxylated subterminally. This difference in position of the hydroxyl group is a clear indication 

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Other studies [85] have shown that cationic bacitracin, anionic AOT, and nonionic Tween 80 all enhanced cellulose hydrolysis, implying that the charge of the surfactant was not an important consideration. In fact. Tween 80 (0.1%) increased the rate and extent of saccharification by up to 40% [82,85]. The structure of the hydrophilic head group of the surfactant also had little significance [85], Those with a sugar group, sophorolipid and rhamnolipid, worked well, as did bacitracin, which has a peptide hydrophilic group [85]. 

Renkin, M. (2003) Environmental profile of sophorolipid and rhamnolipid biosurfactants. Convention Giornate CID NolO, Milan, Italy, vol. 80, no. 4, pp. 249-252. 

The rhamnolipid B (70) has the molecular structure of biosurfactants, comprising a hydrophilic part (rhamnose moiety) and a hydrophobic part ((3-hydroxydecanoate moiety) [151]. The biosurfactant property of this glycolipid was supposed to confer the ability to intercalate into and disrupt the zoospore plasma membrane [152,153]. However, other glycolipids such as sophorolipids and trehalose lipids, which have chemical properties similar to the rhamnolipids, did not show zoosporicidal activity at concentrations up to 1000 pg/ml. 

Nguyen TTL, Edelen A, Neighbors B, Sabatini DA. Biocompatible lecithin-based microemulsions with rhamnolipid and sophorolipid biosurfactants Formulation and potential applications. Journal of Colloid and Interface Science. 2010 348(2) 498-504. 

Glycosides of hydroxy fatty acids are typified by rhamnolipid and sophorolipid (see Fig. 2.7). 

Similarly, naturally derived surfactants extracted from fermentation broths or prepared by partial hydrolysis of natural extracts can contain polysaccharides, proteins, and phospholipids. For example, rhamnolipids and sophorolipids have unique structural features that cause them to deposit on chemically similar surfaces and modify surface energy even at very low concentrations. Clearly, the emergence of biotechnology in the twenty-first century will drive the development of new surfactants from microbial fermentation, and improve the commercial viability of known surfactants from such processes. 

Transparency Market Research. Microbial biosurfactants market (Rhamnolipids, sophorolipids, mannosylerythri-tol lipids (MEL) and other) for household detergents, industrial institutional cleaners, personal care, oilfield chemicals, agricultural chemicals, food processing, textile and other applications. Global Industry Analysis, Size, Share, Growth, Trends and Forecast 2014. 2014—2020. 

Biosurfactants are classified based on their chemical composition and microbial origin. The chemical structure of biosurfactants contains hydrophilic and hydrophobic groups. Amino acids, peptides and polysaccharides can be present as hydrophilic moieties and saturated or unsaturated fatty acids can be present as hydrophobic moieties in the structure. Structure based classification has following major classes of biosurfactants (Guerra-Santos et al., 1987 Kooper and Goldenberg, 1987) (i) Glycolipids (Rhamnolipids, Trehalolipids and Sophorolipids) (ii) Lipopeptide and lipoprotein (iii) Fatty acids, phospholipids and neutral lipids (iv) Pol5mieric biosurfactants, and (v) Particulate biosurfactants. 

Sophorolipids possessing lactone rings are generally more lipophilic than rhanmoUpids and are less sensitive to pH, and often have a lower surface activity per mass than rhamnolipids. They are typically obtained from bacteria or yeasts, particularly from Candida sp. Fermentation is often conducted under nitrogen starvation conditions, with abundant dissolved oxygen being present (Pinzon et al., 2009). Sophorolipids can undergo chemical or enzymatic modification to further tune their surface-active properties (Ashby et al, 2009). 

An unpublished cradle-to-gate life cycle analysis (LCA) study subcontracted to Vito (Mol, Belgium) tried to identify environmental bottlenecks of rhamnolipid and sophorolipid production and compare them with those of market reference surfactants according to the ISO 1404x series. Experimental data for the pilot plant scale were complemented with LCA data from the Vito database as well as literature data for the upscaled production scenario. In order to compare the environmental profile of these biosurfactants with market reference surfactants data were used from Zah and Hischier [18]. The Eco-Indicator 99 methodology [19] was used to determine environmental impacts. 

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