Rhamnolipid is used correctly in the singular form when referring to the plural such as how the word fish is used. In some instances, we will use rhamnolipids to simplify an explanation.
Rhamnolipid is class of glycolipids. They are constructed of rhamnose sugar combined with beta- hydroxy fatty acids. Rhamnose is a sugar. Fatty acids are ubiquitous in animals and plants. The carboxyl end of the fatty acid end is connected to the rhamnose. Rhamnolipid is a compound of only 3 common elements, carbon, hydrogen and oxygen.
There are two major groups of rhamnolipid; mono-rhamnolipid and di-rhamnolipid. One “tail” –mono, two “tails” di-rhamnolipid.
Mono-rhamnolipids have a single rhamnose sugar ring. The basic formula (which is most often produced by P. aeruginosa) is: L-rhamnosyl-beta-hydroxydecanoyl-beta-hydroxydecanoate (often referred to as Rha-C10-C10) with a formula of C26H48O9 The IUPAC Name is 3-[3-[(2R,3R,4R,5R,6S)-3,4,5-trihydroxy-6-methyloxan-2- yl]oxydecanoyloxy]decanoic acid
Di-rhamnolipids have two rhamnose sugar rings. The basic formula is: L-rhamnosyl-L-rhamnosyl-beta-hydroxydecanoyl-beta-hydroxydecanoate (often referred to as Rha-Rha- C10-C10) with a formula of C32H58O13 The IUPAC Name is: 3-[3-[4,5-dihydroxy-6-methyl-3-(3,4,5-trihydroxy-6-methyloxan-2-yl)oxyoxan-2- yl]oxydecanoyloxy]decanoic acid
Di-rhamnolipids have two rhamnose sugar rings. The basic formula is: L-rhamnosyl-L-rhamnosyl-beta-hydroxydecanoyl-beta-hydroxydecanoate (often referred to as Rha-Rha- C10-C10) with a formula of C32H58O13 The IUPAC Name is: 3-[3-[4,5-dihydroxy-6-methyl-3-(3,4,5-trihydroxy-6-methyloxan-2-yl)oxyoxan-2- yl]oxydecanoyloxy]decanoic acid.
To simplify these pages and avoid browser character set issues we will not use those naming conventions.
Rhamnolipids have been found with combinations of the following fatty acids: Hydroxyoctanoyl = C8 Hydroxydecanoyl = C10 Hydroxydecanate = C10 Hydroxydodecanoyl = C12 Hydroxydodecanate = C12 Hydroxytetradecanoyl = C14 Hydroxytetradecanate = C14
A compound where the total carbon count is the same, but the C10-C12 is switched to C12-C10 is called a structural isomer, meaning that the formula is the same for both molecules, but the bonds or links are connected differently.
In various papers instead of mono-rhamnolipid as Rha-, it may be abbreviated as Rh or RL2. Similarly, instead of Rha-Rha- designating a di-rhamnolipid, Rh-Rh- or RL1 is used. For historical reasons “rhamnolipid 2” is a mono-rhamnolipid and “rhamnolipid 1” is a di-rhamnolipid. This actually leads to some ambiguity in the usage or “RL1” and “RL2” in the literature.
In various studies the following rhamnolipids have been detected as produced by the following bacteria: (C12:1, C14:1 indicate fatty acyl chains with double bonds.)
Rhamnolipids produced by P. aeruginosa (mono-rhamnolipids): Rha-C8-C10, Rha-C10-C8, Rha-C10-C10, Rha-C10-C12, Rha-C10-C12:1, Rha-C12-C10, Rha-C12:1- C10
Rhamnolipids produced by P. aeruginosa (di-rhamnolipids): Rha-Rha-C8-C10, Rha-Rha-C8-C12:1, Rha-Rha-C10-C8, Rha-Rha-C10-C10, Rha-Rha-C10-C12:1, Rha- Rha-C10-C12, Rha-Rha-C12-C10, Rha-Rha-C12:1-C12, Rha-Rha-C10-C14:1
Rhamnolipids produced by P. aeruginosa (unidentified as either mono- or di-rhamnolipids): C8-C8, C8-C10, C10-C8, C8-C12:1, C12:1-C8, C10-C10, C12-C10, C12:1-C10, C12-C12, C12:1-C12, C14-C10, C14:1-C10, C14-C14.
Rhamnolipids produced by P. chlororaphis (mono-rhamnolipids only): Rha-C10-C8, Rha-C10-C10, Rha-C12-C10, Rha-C12:1-C10, Rha-C12-C12, Rha-C12:1-C12, Rha-C14- C10, Rha-C14:1-C10
Rhamnolipids produced by Burkholdera pseudomallei (di-rhamnolipids only): Rha-Rha-C14-C14
Rhamnolipids produced by Burkholdera (Pseudomonas) plantarii (di-rhamnolipids only): Rha-Rha-C14-C14