  Myelin figures (MFs) -- cylindrical lyotropic liquid crystalline structures
consisting of concentric arrays of bilayers and aqueous media -- arise from the
hydration of the bulk lamellar phase of many common amphiphiles. Prior efforts
have concentrated on the formation, structure, and dynamics of myelin produced
by phosphatidylcholine (PC)-based amphiphiles. Here, we study the myelinization
of glycolipid microbial amphiphiles, commonly addressed as biosurfactants,
produced through the process of fermentation. The hydration characteristics
(and phase diagrams) of these biological amphiphiles are atypical (and thus
their capacity to form myelin) because unlike typical amphiphiles, their
molecular structure is characterized by two hydrophilic groups (sugar,
carboxylic acid) on both ends with a hydrophobic moiety in the middle. We
tested three different glycolipid molecules: C18:1 sophorolipids and
single-glucose C18:1 and C18:0 glucolipids, all in their nonacetylated acidic
form. Neither sophorolipids (too soluble) nor C18:0 glucolipids (too insoluble)
displayed myelin growth at room temperature (RT, 25 C). The glucolipid C18:1
(G-C18:1), on the other hand, showed dense myelin growth at RT below pH 7.0.
Examining their growth rates, we find that they display a linear L $\alpha$ t
(L, myelin length; t, time) growth rate, suggesting ballistic growth,
distinctly different from the L $\alpha$ t^(1/2) dependence, characterizing
diffusive growth such as what occurs in more conventional phospholipids. These
results offer some insight into lipidic mesophases arising from a previously
unexplored class of amphiphiles with potential applications in the field of
drug delivery.
