PROCESS BIOCHEMISTRY (Impact Factor: 2.52). 02/2004; 39(6):749-753. DOI: 10.1016/S0032-9592(03)00185-7
Acetobacter aceti MIM 2000/28 was employed for the oxidation of 2-phenyl-1-ethanol. Oxidation in aqueous systems gave phenylacetic acid with high yields, while the use of a two-liquid phase system (composed of water and isooctane) allowed for the production of the corresponding aldehyde. Free cells showed poor operational stability and were immobilized in calcium alginate; immobilized cells had specific activity, substrate tolerance and stability higher than that obtained with free cells. Simple fed-batch operation with immobilized cells in an air-lift reactor allowed for the production of 23 g l−1 phenylacetic acid in 9 days without foam formation.
"f the encapsulated cells ( Figure 6 right ) was also investigated and a slightly decreased biotransforma - tion rate was observed . The cumulative concentra - tion of product ( Figure 7 ) after 7 days was 25 g / L . This is slightly higher than the product concentra - tion obtained after 9 - day cultivation in an air - lift reactor as described by Gandolfi et al . ( 2004 ) ."
[Show abstract][Hide abstract] ABSTRACT: A high-performance biocatalyst in the form of encapsulated cells of Gluconobacter oxydans have been developed for production of phenylacetic acid (PAA) as a natural flavor component. Polyelectrolyte complex (PEC) capsules consisting of sodium alginate, cellulose sulfate, poly(methylene-co-guanidine), CaCl2, and NaCl were used for highly controlled and mild encapsulation of cells. Utilization of encapsulated G. oxydans cells was a significant improvement on existing data on operational stability of cells and cumulative product concentration during biocatalytic production of PAA from 2-phenylethanol. Concerning operational stability, encapsulated cells were active over 12 cycles with a high biotransformation rate, while free cells were inactive after 7 cycles of use. The biocatalytic properties of encapsulated G. oxydans were tested in a bubble column reactor over 7 days with a final cumulative product concentration of 25 g/L. High cell viability (90%) was observed within PEC capsules by confocal laser scanning microscopy, performed before and after repetitive PAA production in the bubble column reactor. The surface microstructure of fully hydrated capsules with and without G. oxydans cells was investigated and compared using an environmental scanning electron microscope.
Biocatalysis and Biotransformation 06/2015; 33(2). DOI:10.3109/10242422.2015.1053470 · 0.69 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An immobilized whole cell system was successfully performed to produce the most powerful antioxidant, hydroxytyrosol. Bioconversion of tyrosol into hydroxytyrosol was achieved via the immobilization of Pseudomonas aeruginosa resting cells in calcium alginate beads. Immobilization was advantageous as it allows immobilized cells to tolerate a greater tyrosol concentration than free cells. The bioconversion yield reached 86% in the presence of 5 g L-1 of tyrosol when cells immobilized in alginate beads were carried out in single batches. Evaluation of kinetic parameters showed the maintenance of the same catalytic efficiency expressed as Kcat/Km for both free and immobilized cells. The use of immobilized cells in repeated batches demonstrated a notable activity stabilization since the biocatalyst reusability was extended for at least four batches with a molar yield greater than 85%.
Journal of Agricultural and Food Chemistry 01/2007; 54(26):9906-11. DOI:10.1021/jf062145g · 2.91 Impact Factor
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