Influence of the pH of glutaraldehyde and the use of dextran aldehyde on the preparation of cross-linked enzyme aggregates (CLEAs) of lipase from Burkholderia cepacia

The preparation of cross-linked enzyme aggregates (CLEAs) of lipase has been a challenge due the low amount of lysine residues that lipases have on their surface. The results show that CLEAs prepared using dextran aldehyde (100-200KDa) have a higher hydrolysis activity and particle size (activities between 3186 +/- 21 U/g of CLEA and 4800 +/- 30 U/g of CLEA and particle sizes between 52.6 +/- 18.7 mu m and 126.2 +/- 53.5 mu m) than CLEAs prepared with glutaraldehyde (0.1 KDa) (activities between 894 +/- 16 U/g of CLEA and 2874 +/- 20 U/g of CLEA and particle sizes between 21.2 +/- 5.1 mu m and 83.4 +/- 24.9 mu m); Thermal stability assays of bioctalysts at 60 degrees C at pH 7.0 using phosphate buffer 25 mM showed that CLEAs prepared with dextran aldehyde have lower residual activity after 50 hrs (maximum residual activity of 46.8% in the CLEA) than CLEAs prepared with glutaraldehyde (maximum residual activity of 70.2% in CLEA). When considering hydrolysis activity, thermal stability and residual activity of CLEAs as a criteria for selecting the best preparation conditions, it has been found that the best condition for CLEAs preparation are to use glutaraldehyde as cross-linking reagent at pH 9.5, at a concentration of 3.5 g/l, and an enzyme/albumin ratio of 15.