The effective diffusion coefficient (
Deff) and partition coefficient (
P) of fatty acids and alcohols with carbon numbers of 4 to 14 as substrates of an enzyme reaction were measured in di-2-ethylhexyl sodium sulfosuccinate (AOT)-gelatin combination microemulsion-based organogels (MBGs). The correlation equations between the effective diffusion coefficient and the molar volume of substrate (υ) were obtained as follows:
for fatty acid:
Deff[10
-10m
2s
-1] = 6.55×10
-12υ
-0.43(109.0≤;υ[10
-6m
3mol
-1]≤331.0)
for alcohol:
DeffAL[10
-10m
2s
-1] = 2.67×10
-13υ
-0.71(103.6≤υ[10
-6m
3mol
-1]≤325.6)
The partition coefficient of substrate, the molar ratio of MBG phase to bulk organic phase, decreased with increasing carbon number of substrate and remained almost constant at a carbon number of 8 or above as follows:
PFA = 2.03 (butanoic acid), 1.17 (hexanoic acid), ca. 0.85 (octanoic acid, decanoic acid, dodecanoic acid and tetradecanoic acid);
PAL = 4.01 (butanol), 1.70 (hexanol),
ca. 1.50 (octanol, decanol, dodecanol and tetradecanol). The partition coefficients of alcohols were about 2-fold higher than those of fatty acids.
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