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Indexed/Abstracted in: EMBASE, Science Citation Index Expanded (SciSearch), Scopus
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Doostmohammadi M. 1, Esfandiari M. 1, Asadollahi M. A. 1, Kamali M. 2, Nahvi I. 3
1 Department of Biotechnology, Faculty of Advanced Sciences and Technologies, University of Isfahan, Isfahan, Iran;
2 Chemical Processes Research Department, Engineering Research Center, University of Isfahan, Isfahan, Iran;
3 Department of Biology, Faculty of Science, University of Isfahan, Isfahan, Iran
AIM: The main goal of the present study was to study biotransformation of benzaldehyde to L-phenylacetyl carbinol (L-PAC) by free and immobilized cells of Saccharomyces cerevisiae. Yeast cells were immobilized both in calcium alginate and calcium alginate-PVA-boric acid beads.
METHODS: Yeast cells were immobilized with calcium alginate and calcium alginate-PVA-boric acid beads. Free or immobilized cells were added to biotransformation medium containing benzaldehyde and acetaldehyde and incubated at 30 oC and 200 rpm in anaerobic conditions. Samples were taken every two hours. Concentrations of benzaldehyde, L-PAC, and benzyl alcohol were determined by gas chromatography. Effect of benzaldehyde concentration on L-PAC formation was investigated. Fed batch fermentation was performed using immobilized yeast cells in a 3 L bioreactor.
RESULTS: The optimum biotransformation of benzaldehyde to L-PAC was obtained at 2 g/L of benzaldehyde. Cells immobilized in calcium alginate-PVA beads produced approximately 2 g/L of L-PAC using 2 g/L of benzaldehyde in the second and third cycles. In fed batch fermentation, a concentration of nearly 3 g/L L-PAC was achieved. The highest obtained yields of L-PAC for free cells, immobilized cells in calcium alginate, immobilized cells in calcium alginate-PVA-boric acid, and fed batch fermentation were 0.55, 0.55, 1, and 0.64 g L-PAC per each gram of consumed benzaldehyde, respectively.
CONCLUSION: This study showed that higher L-PAC titers can be obtained using immobilized yeast cells. Besides improved mechanical properties, cells immobilized in calcium alginate-PVA-boric acid beads exhibited higher production of L-PAC and lower amount of benzyl alcohol as compared to the cells immobilized in calcium alginate beads.