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Open Access Publications from the University of California

Encapsulation of Biocatalysts (Cell/Enzyme) with High Retaining Activity

  • Author(s): Liu, Tao
  • Advisor(s): Lu, Yunfeng
  • et al.

Enzymes are always considered as great gifts from nature since they are holding brilliant properties, including high activity, selectivity and specificity. Nowadays, a variety of enzymes have been applied to many industry processes. However, challenges are still needed to be addressed while applying enzymes. It is worth to point out that enzymes are sensitive to the change of ambient conditions. Most of enzymes are unstable and work under certain sort of temperature and pH conditions. Since enzymes could be denatured when subject to unnatural conditions, their work environment has to be controlled.

Researchers have been developed a variety of methods to improve the stability of bio-catalysts under various non-biological conditions. However, the immobilization process might harm the activity of enzymes. Therefore, even though immobilization approach has stabilized the stability of bio-catalysts, alternative strategies are still necessary to maintain the enzymes' activity during the encapsulation process.

In my research, two novel strategies were successfully developed to maintain enzymes' activity during encapsulation processes. Enzyme-based microgels and nanogels were successfully synthesized at cellular and enzymatic level for various applications, which are briefly outlined below:

Cellular level: An approach was envisioned in this section to improve biocatalyst stability, while maintaining their activities at the maximum during the encapsulation process. The new technology employs materials self-assembly to form a protective layer coating on cells surface. Enzymes are restricted within the cell all the time, without disturbing the structure during the encapsulation process. Therefore, this strategy maintains enzymes' activity at maximum. What's more, the protective polymer coating significantly increases biocatalyst viability in harsh thermal environment, different pH conditions, while allowing rapid transport of substrates into the biocatalyst without significant activity compromise. Compared with the conventional enzymes' encapsulation method, such robust microgels exhibit significantly improved activity and catalytic stability. Meanwhile, such robust single cells make the immobilized whole cells much cheaper to use than an immobilized enzyme.

Enzymatic level: In this section, surface coating with zwitterionic polymers was studied at the single enzymatic level without disturbing the enzyme structure during the encapsulation process in order to maintain enzymes' activity. The protective polymer coating can significantly increase biocatalyst viability while allowing rapid transport of substrates into the biocatalyst without significant activity compromise. Zwitterionic polymer shells have an efficient antibiofouling property which reduce the protein or cell adsorption, reduce immune response and prolong the circulation time of nanogels in blood circulation system.

Overall, my researches focus on maintaining enzymes' activity during the encapsulation process. Protective layers stabilize enzymes and create new surface functions. The encapsulation process is without disturbing enzymes' 3D structure. The resulted enzyme microgels or nanogels gain high activity and various new functionalities. With these technologies, we can envision a promising prospect in environmental, therapeutic and analytical applications of enzymes.

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