Evaluation of cross-linked enzyme aggregates of Lactobacillus cell-envelope proteinases, for protein degradation

• Cell-envelope proteinases have been prepared as cross-linked enzyme aggregates.
• Cross-linking conditions have been optimized to achieve high enzyme activity.
• Cross-linking improves recyclability and stability of cell-envelope proteinases.
• Proteolytic performance has been evaluates using several food proteins.

Enzymatic hydrolysis is a widely used approach to improve the functional, nutritional and physiological properties of food proteins. In this study, cross-linked enzyme aggregates (CLEAs) have been prepared from cell-envelope proteinases (CEPs) of Lactobacillus delbrueckii subsp. lactis 313 and their proteolytic properties have been evaluated using several food proteins. We have optimized cross-linking conditions including ammonium sulphate concentration, incubation temperatures, agitation speed, glutaraldehyde cross-linker concentration, reaction time and the addition of proteic feeders. Particularly, the presence of BSA improves retained activity of cross-linked CEP aggregates (CLCEPAs) from 21.5% to 40.9%. Blocking unreacted cross-linking groups on aggregates is important to enhance recyclability of CLCEPAs. CLCEPAs had attractive thermal stability at 50 °C and it showed enhanced catalytic activity over long-term storage after lyophilization. We have demonstrated that CLCEPAs has proteolytic properties on different food proteins including complex (chicken egg albumin, skimmed-milk protein), fractionated (bovine casein, whey protein isolate), and purified (bovine serum albumin) proteins. Being the first report of CLEAs from lactobacilli CEPs, this study demonstrates the feasibility of using LDL 313 CLCEPAs for degradation of various food proteins.