Preparation of cross-linked enzyme aggregates by using bovine serum albumin as a proteic feeder.

Addition of bovine serum albumin (BSA) as a proteic feeder facilitates obtaining cross-linked enzyme aggregates (CLEAs) in cases where the protein concentration in the enzyme preparation is low and/or the enzyme activity is vulnerable to the high concentration of glutaraldehyde required to obtain aggregates. CLEAs of Pseudomonas cepacia lipase and penicillin acylase were prepared. CLEA of lipase prepared in the presence of BSA retained 100% activity whereas CLEA prepared without BSA retained only 0.4% activity of the starting enzyme preparation. Lipase CLEA showed 12-fold increase in activity over free enzyme powder when the CLEA was used in transesterification of tributyrin. For the transesterification of Jatropha oil, while free enzyme powder required 8 h and 50 mg lipase to obtain 77% conversion, CLEA required only 6 h and 6.25 mg lipase to obtain 90% conversion. In the case of penicillin acylase, 86% activity could be retained in CLEA prepared with BSA whereas CLEA made without BSA retained only 50% activity. CLEA prepared without BSA lost 20% activity after 8 h at 45 degrees C whereas CLEA with BSA retained full activity. CLEA prepared with BSA showed Vmax/Km of 36.3 min-1 whereas CLEA prepared without BSA had Vmax/Km of 17.4 min-1 only. Scanning electron microscopy analysis showed that CLEAs prepared in the presence of BSA were less amorphous and closer in morphology to CLEAs of other enzymes described in the literature.