Bioprocessing Approaches to Synthesize Bio-based Surfactants and Detergents - Food and Industrial Bioproducts and Bioprocessing - page 251

and caprylic (8:0) acid, the latter at 20-fold excess, were dissolved in hexane and treated
with immobilized phospholipase A 2 or immobilized R. miehei lipase at 40 °C. The former
enzyme produced a 45% yield of the desired product, phospholipid that contained one
caprylic acyl group per molecule, and 52% of the undesired product, phospholipids
containing two caprylic acyl groups per molecule, formed as a result of acyl migration of
incorporated caprylic acyl group from the 2- to the 1-glycerol position. The product
distribution using lipase as biocatalyst was similar, and the yield of desired product was
slightly less than that achieved using phospholipase A 2 , 39%. Therefore, this result suggests
the preparation of structured phospholipids must be accompanied by selective separations
schemes, since multiple products are formed for each step of a synthesis scheme, consistent
with previous examples in the literature (Xu et al ., 2008 ; Guo et al ., 2005 ).

10.6 PREPARATION OF BIOSURFACTANTS VIA
FERMENTATION

In addition to employing enzymes for bio-based surfactant via in vitro systems, microor-
ganisms can produce bio-based surfactants in vivo (Kitamoto et al ., 2009 ; Lang, 2003 ;
Muthusamy et al ., 2008 ; Rahman and Gakpe, 2008 ; Pinzon et al ., 2009 ). Fermentative
synthesis of bio-based surfactants, referred to as “biosurfactants,” possess many of the
advantages described above for enzymatic synthesis, particularly enhanced sustainability
(lower energy utilization, the absence of solvents, etc.). Biosurfactants are typically com-
posed of lipid, protein, and carbohydrate moieties and often are associated with cell walls
or membranes. Initial interest stemmed from their high biocompatibility and biodegrada-
bility. However, in recent years, research has shown their unique behavior in self-assembly
systems, suggesting their potential applications in biomedicine and nanotechnology
(Kitamoto et al ., 2009). Applications of biosurfactants in food products was recently
reviewed (Nitschke and Costa, 2007).
Biosurfactants are divided into four categories: glycolipid-type, fatty acid-type (includ-
ing phospholipids, which were discussed above), lipopeptide-type, and polymer-type
(Kitamoto et al ., 2009). Glycolipid biosurfactants include rhamnolipids, sophorolipids,
mannosylerythritol lipids, and trehalose esters (Figure 10.7). Rhamnolipids, produced
from Pseudomonas sp. or Burholderia sp. bacteria, may have a single rhamnose monosac-
charide unit, as depicted in Figure 10.7, or two, with a single product often containing a
mixture of mono- and di-rhamnolipid, with variability in acyl chain length as well. Also,
the lipophilic moiety can consist of a chain of two 2- β -hydroxy acids esterified together.

Sophorolipids consist of sophorose (2-O- β -D-glucopyranosyl, β -D-glucopyranose) with

an ether linkage between its reducing end and the hydroxyl of an -1- hydroxyl fatty

acyl group of 16-18 carbons. The carboxylic moiety of the fatty acid component can be
free, or can form an ester bond with the 4

ω or ω

′ hydroxyl of sophorose, as depicted in

Figure 10.7. Also, the 6 and/or 6 hydroxyl groups of the sophorose unit can be acylated,

as depicted in Figure 10.7, or free. Typically, the product obtained from fermentation is a
mixture of both types.
Rhamnolipids are secondary metabolites produced during a stationary growth stage,
often when deprived of a nutrient such as nitrogen, and often utilize long-chain lipophilic or
non-traditional carbon-energy sources, such as seed oils and alkanes (Pinzon et al ., 2009 ).
Their recovery from the fermentation can be challenging due to the frequent occurrence of
foaming (Pinzon et al ., 2009 ).

′