Immobilization of Chitosan‐Invertase Neoglycoconjugate on Carboxymethylcellulose‐Modified Chitin

Immobilization of cell wall invertase modified with glutaraldehyde for continuous production of invert sugar

Yeast cell wall invertase (CWI) was modified with dimethyl suberimidate, glutaraldehyde, formaldehyde, and sodium periodate. Retained activity after modification was 45% for CWI modified with formaldehyde, 77% for CWI modified with sodium periodate, 80% for CWI modified with glutaraldehyde, and 115% for CWI modified with dimethyl suberimidate. Chemically modified and native CWIs showed significantly broad pH stability (pH 3-11), whereas after incubations at 50, 60, and 70 °C, CWI modified with glutaraldehyde showed the highest thermostability. Optimum pH for CWI modified with glutaraldehyde was between 4 and 5, whereas optimum temperature was at 60 °C. Comparison to CWI modified with glutaraldehyde after immobilization within alginate beads showed broader pH optimum (4.0-5.5) as well as broader temperature optimum (55-70 °C). Column bed reactor packed with the immobilized CWI modified with glutaraldehyde was successfully used for the 95% inversion of 60% (w/w) sucrose at the flow rate of 3 bed volumes per hour, pH 4.9, and 45 °C. A 1 month productivity of 3844 kg of inverted sugar/kg of the immobilisate was obtained.

Glycosaminoglycans as polyelectrolytes

One of the barriers to understanding structure-property relations for glycosaminoglycans has been the lack of constructive interplay between the principles and methodologies of the life sciences (molecular biology, biochemistry and cell biology) and the physical sciences, particularly in the field of polyelectrolytes. To address this, we first review the similarities and differences between the physicochemical properties of GAGs and other statistical chain polyelectrolytes of both natural and abioitic origin. Since the biofunctionality and regulation of the structures of GAGs is intimately connected with interactions with their cognate proteins, we particularly compare and contrast aspects of protein binding, i.e. effects of both GAGs and other polyelectrolytes on protein stability, protein aggregation and phase behavior. The protein binding affinities and their dependences on pH and ionic strength for the two groups are discussed not only in terms of observable differences, but also with regard to contrasting descriptions of the bound state and the role of electrostatics. We conclude that early studies of the heparin-Antithromin system, proceeding to a large extent through the methods and models of protein chemistry and drug discovery, established not only many enabling precedents but also constraining paradigms. Current studies on heparan sulfate and chondroitin sulfate seem to reflect a more ecumenical view likely to be more compatible with concepts from physical and polymer chemistry.

Characterization of free and immobilized (S)-aminotransferase for acetophenone production

Enzyme immobilization often improves process economics, but changes in kinetic properties may also occur. The immobilization of a recombinant thermostable (S)-aminotransferase was made by entrapment on calcium alginate-3% (w/v)-and tested with (S)-(-)-(alpha)-methylbenzylamine for acetophenone production. The best immobilization results were obtained for beads of concentration of 10 mg of spray-dried cells (containing recombinant (S)-aminotransferase) per milliliter of sodium alginate bead. As a result of immobilization, the properties of immobilized spray-dried cells differed from the properties of free spray-dried cells. V (m) for the immobilized enzyme was between 0.08 and 0.09 mM/min, while the V (m) for free enzyme was 0.06-0.07 mM/min. K (m) values differed for immobilized and free spray-dried cells by a factor of between 3 and 5 for (S)-(-)-(alpha)-methylbenzylamine (6.05 mM for immobilized, 1.78 mM for free) and pyruvate (5.0 mM for immobilized, 1.01 mM for free) at 55 degrees C. Optimum pH values were 7.7 and 8.1 for the free spray-dried cells and the immobilized formulation, respectively. The maximum activity for free spray-dried cells was measured at 55 degrees C, whereas for immobilized ones, it was at 60 degrees C. Activation and deactivation energy values for free spray-dried cells were 15.13 and 41.73 kcal/mol, while those for immobilized spray-dried cells were 8.86 and 48.88 kcal/mol, respectively. Overall, as a result of immobilization, an increase in V (m) was measured for the (S)-aminotransferase by 28 to 33% with respect to free enzyme; K (m) increased by a factor of three- to fivefold and had a shift of 5 degrees C in optimum temperature, and the activation energy was 41% lower than the activation energy of free (S)-aminotransferase.