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Tagatose Production by Immobilized Recombinant Escherichia coli Cells Containing Geobacillus stearothermophilus l ‐Arabinose Isomerase Mutant in a Packed‐Bed Bioreactor
Author(s) -
Jung EunSook,
Kim HyeJung,
Oh DeokKun
Publication year - 2008
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1021/bp050078p
Subject(s) - chemistry , isomerase , bioreactor , arabinose , chromatography , immobilized enzyme , yield (engineering) , geobacillus stearothermophilus , escherichia coli , enzyme , substrate (aquarium) , biochemistry , fermentation , biology , xylose , organic chemistry , ecology , materials science , metallurgy , gene , thermophile
Abstract Using immobilized recombinant Escherichia coli cells containing Geobacillus stearothermophilus l ‐arabinose isomerase mutant (Gali 152), we found that the galactose isomerization reaction was maximal at 70 °C and pH 7.0. Manganese ion enhanced galactose isomerization to tagatose. The immobilized cells were most stable at 60 °C and pH 7.0. The cell and substrate concentrations and dilution rate were optimal at 34 g/L, 300 g/L, and 0.05 h ‐ 1 , respectively. Under the optimum conditions, the immobilized cell reactor with Mn 2+ produced an average of 59 g/L tagatose with a productivity of 2.9 g/L·h and a conversion yield of 19.5% for the first 20 days. The operational stability of immobilized cells with Mn 2+ was demonstrated, and their half‐life for tagatose production was 34 days. Tagatose production was compared for free and immobilized enzymes and free and immobilized cells using the same mass of cells. Immobilized cells produced the highest tagatose concentration, indicating that cell immobilization was more efficient for tagatose production than enzyme immobilization.