Sequential co-immobilization of β-glucosidase and yeast cells on single polymer support for bioethanol production
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Co-immobilization of enzymes and microorganism is an effective way to enable cells to use nonmetabolizable substrates and accelerate reaction rate of overall process. Herein, a facile strategy to separately co-immobilize β-glucosidase (BG) and yeast cells on non-woven fabrics was developed. The BG was firstly in situ entrapped into poly(ethylene glycol) (PEG) network grafted on non-woven fabrics by visible light induced living/controlled graft polymerization. Then re-graft polymerization was performed on the as-formed BG loaded layer by taking advantage of living-grafting polymerization on its surface to in situ encapsulate yeast cells into the second PEG network layer. This layered structure of co-immobilization avoided possible interference between enzyme and cells. Viability assay of yeast cells demonstrated that most of cells were viable after immobilization. While immobilized BG showed decreased Vmax compared to free BG, indicating that entrapping BG into inner PEG network layer restricted its accessibility with substrates. This co-immobilization sheet could successfully convert cellobiose to ethanol and a maximum of 98.6% bioethanol yield can be obtained after 48 h of simultaneous saccharification and fermentation (SSF). The co-immobilization sheet showed excellent reusability and could still reach more than 60% of original ethanol yield after reusing for 7 batches. Compared with the mixed co-immobilization, the sequential layered immobilization in this system showed better stability and higher ethanol yield.
Keywordsimmobilization graft polymerization bioethanol enzyme yeast cells
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This work was supported by the National Natural Science Foundation of China (51521062, 51103009, 51473015), the Innovation and Promotion Project of Beijing University of Chemical Technology and the Beijing Natural Science Foundation (2162035).
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