PUFA. For these trials, water conte

PUFA. For these trials, water content, temperature, and molar ratio of PC to fatty acid were kept at 1.0% (based on total substrate weight), 55 C, and 1:8, respectively. The effect of enzyme loading on the acidolysis reaction is shown in Fig. 4 The incorporation of n3 PUFA into PC increased significantly when enzyme loading increased up to 20%. However, the differences between the n3 PUFA contents achieved at enzyme loading of 20% and 30% were minimal. For example, at 12 h, the incorporation of n3 PUFA increased by 22.5 mol%, as enzyme loading was increased from 10% to 20%. However, the difference in the n3 PUFA contents achieved
between enzyme loading of 20% and 30% was only 4.3 mol%. It is important to reduce the enzyme loading for economic feasibility, although reactions, such as acidolysis and esterification, are proportional to enzyme loading (Blasi et al., 2009; Karabulut, Durmaz, & Hayaloglu, 2009). The yield of PC decreased sharply during the first 3 h of reaction and remained constant after 6 h for all enzyme loadings examined. With the higher enzyme loading, the lower yield of PC was
obtained. Previous studies have also reported that the extent of hydrolysis increased along with increased incorporation of fatty acid residues into PC when higher enzyme loadings were employed
(Doig & Diks, 2003; Vikbjerg, Mu, & Xu, 2005). Overall, during the acidolysis reaction, the yield of PC decreased significantly although the incorporation of n3 PUFA into PC increased. For enzyme loading, 20% was selected as the optimum for further study, when the incorporation of n3 PUFA into PC was primarily taken into con- sideration. The total n3 PUFA content in modified PC obtained after 24 h at this condition was 57.4 mol% and the yield of PC was 16.7 mol%. In addition, vacuum was applied in the next step to enhance the yield of PC.
3.2.4. Vacuum
It is well known that enzymatic reactions in non-aqueous media are critically sensitive to the water content of the system. There