1. Chemical modification of sophorolipids towards a platform of new derivatives
Elisabeth I.P. Delbeke1, K.M. Van Geem2, C.V. Stevens1
1 SynBioC Research Group, Ghent University
2 Laboratory for Chemical Technology, Ghent University

2. Physico-chemical properties
Introduction
Sophorolipids: Building blocks for chemical derivatization
Renewable resource
High production
cost (2-5 €/kg)
Non-pathogenic yeast
Biosurfactant
Starmerella bombicola
Biological activity
Physico-chemical properties
High production
quantity (400 g/L)
Complex structure

3. Results 1. Synthesis of intermediate sophorolipid aldehyde
Influence of fermentation conditions on methanolysis reaction
Protection of the sugar head proved necessary
Optimized ozonolysis conditions to prevent to formation of stable secondary ozonides

4. Results 2. Synthesis of innovative derivatives
Intermediate sophorolipid amines
Quaternary ammonium sophorolipids
Sophorolipid amine oxides
Bolaamphiphilic sophorolipids
Most interesting derivatives: Quaternary ammonium sophorolipids with octadecyl chain

5. Results 2.1. Antimicrobial evaluation
Performed by the Laboratory for Microbiology (Ghent University)
Gram-positive strains:
Gram-negative strains:
Staphylococcus aureus
Bacillus subtilis
Escherichia coli
Klebsiella pneumoniae
Significant growth inhibition against Gram-positive strains:
- 8 peracetylated quaternary ammonium sophorolipids
- 3 deprotected quaternary ammonium sophorolipids
MIC determination for active compounds against Gram-positive strains:
Staphylococcus aureus
Bacillus subtilis
Enterococcus faecium
Streptococcus pneumoniae
Control: Gentamicin sulfate

6. Results (µg/mL) 5a 5b 6a 6b Gentamicin sulfate S. aureus 10 5
E. faecium
B. subtilis
S. pneumoniae 25
(µM) 5a 5b 6a 6b
Gentamicin sulfate
S. aureus 8 6 5 10
E. faecium 21
B. subtilis
S. pneumoniae 52

7. Results Synthesis of deglycosylated derivatives
Evaluation of influence carbohydrate head
Synthesis of deglycosylated derivatives
Hydroxylated and non-hydroxylated quaternary ammonium salts

8. Results
Comparison of antimicrobial activity with quaternary ammonium sophorolipids
Performed by the Laboratory of Pharmaceutical Microbiology (Prof. Tom Coenye, Ghent University)
S. aureus
ATCC 6538
MU50
(µg/mL)
MIC
MBC 5a
7,81
31,25
62,5 5b
250 6a
1,95
3,9
15,63 6b 9a 9b
11a
125
11b
SL lactone
SL acid
>1000
S. aureus
ATCC 6538
MU50
(µM)
MIC
MBC 5a
6,59
26,36
52,72 5b
6,36
204
50,91 6a
2,18
8,76
4,37
17,53 6b
2,09
4,18
16,73 9a
3,44
55,08
110 9b
3,21
51,28
103
11a
56,68
227
11b
26,33
105
211
SL lactone
45,40
90,79
SL acid
>1607
Acetylated
SL quat
Deprotected
SL quat
Hydroxylated
quat
Non-hydrox.
quat

9. Results 2.2. Transfection efficiency evaluation
Performed by CEMCA UMR 6521 and INSERM UMR 1078 (Prof. Paul-Alain Jaffrès, Brest University)
Formulation of liposomal solutions
Only homogenous formulation for 6a and 6b
Evaluation of influence carbohydrate head
Formulation with DOPE nescessary
Complexation of pDNA at different CR (charge ratio)
6a/DOPE
6b/DOPE
9a/DOPE
9b/DOPE
11b/DOPE
11b/DOPE
LFM = lipofectamine

10. Results DNA transfection to different cell lines
Evaluation of cell viability
Transfection efficiency
6a/DOPE
6b/DOPE
9a/DOPE
9b/DOPE
11b/DOPE
11b/DOPE
Cell vialbility
6a/DOPE
6b/DOPE
9a/DOPE
9b/DOPE
11b/DOPE
11b/DOPE
LFM = lipofectamine

11. Conclusions
Synthesis of a four different sophorolipid libraries accomplished:
Sophorolipid amines
Quaternary ammonium sophorolipids
Sophorolipid amine oxides
Bolaform sophorolipids
Promising antimicrobial and transfection efficiency results
Positive influence of carbohydrate head was demonstrated

12. Acknowledgements Prof. dr. ir. C. Stevens Prof. dr. ir. K. Van Geem
Prof. dr. ir. G. Marin
InBio Research Group
Prof. T. Coenye
Prof. P.-A. Jaffrès
The research leading to these results has received funding from the Long Term Structural Methusalem Funding by the Flemish Government (grant number BOF09/01M00409)