Magnetic cross-linked enzyme aggregates (CLEAs): A novel concept towards carrier free immobilization of lignocellulolytic enzymes

• Carrier free immobilization of lignocellulolytic enzymes (CLEAs).
• Preparation of novel magnetite (mag-CLEAs) and calcium magnetite (Ca-mg-CLEAs) CLEAs.
• Increase in activity and stability with mag-CLEAs and Ca-mag-CLEAs due to metal ions.
• Successful recycling of mag-CLEAs and Ca-mg-CLEAs using lignocellulosic substrates.
• Increase in sugar hydrolysis with mag-CLEAs and Ca-mg-CLEAs compared to free enzyme.

The enzymatic conversion of lignocellulosic biomass into biofuels has been identified as an excellent strategy to generate clean energy. However, the current process is cost-intensive as an effective immobilization approach to reuse the enzyme(s) has been a major challenge. The present study introduces the concept and application of novel magnetic cross-linked enzyme aggregates (mag-CLEAs). Both mag-CLEAs and calcium-mag-CLEAs (Ca-mag-CLEAs) exhibited a 1.35 fold higher xylanase activity compared to the free enzyme and retained more than 80.0% and 90.0% activity, respectively, after 136 h of incubation at 50 °C, compared to 50% activity retained by CLEAs. A 7.4 and 9.0 fold higher sugar release from lime-pretreated and NH4OH pre-treated sugar bagasse, respectively, was achieved with Ca-mag-CLEAs compared to the free enzymes. The present study promotes the successful application of mag-CLEAs and Ca-mag-CLEAs as carrier free immobilized enzymes for the effective hydrolysis of lignocellulolytic biomass and associated biofuel feedstocks.