Glucose‐to‐fructose conversion at high temperatures with xylose (glucose) isomerases from Streptomyces murinus and two hyperthermophilic Thermotoga species

Abstract

The conversion of glucose to fructose at elevated temperatures, as catalyzed by soluble and immobilized xylose (glucose) isomerases from the hyperthermophiles Thermotoga maritima (TMGI) and Thermotoga neapolitana 5068 (TNGI) and from the mesophile Streptomyces murinus (SMGI), was examined. At pH 7.0 in the presence of Mg(2+), the temperature optima for the three soluble enzymes were 85 degrees C (SMGI), 95 degrees to 100 degrees C (TNGI), and >100 degrees C (TMGI). Under certain conditions, soluble forms of the three enzymes exhibited an unusual, multiphasic inactivation behavior in which the decay rate slowed considerably after an initial rapid decline. However, the inactivation of the enzymes covalently immobilized to glass beads, monophasic in most cases, was characterized by a first-order decay rate intermediate between those of the initial rapid and slower phases for the soluble enzymes. Enzyme productivities for the three immobilized GIs were determined experimentally in the presence of Mg(2+). The highest productivities measured were 750 and 760 kg fructose per kilogram SMGI at 60 degrees C and 70 degrees C, respectively. The highest productivity for both TMGI and TNGI in the presence of Mg(2+) occurred at 70 degrees C, pH 7.0, with approximately 230 and 200 kg fructose per kilogram enzyme for TNGI and TMGI, respectively. At 80 degrees C and in the presence of Mg(2+), productivities for the three enzymes ranged from 31 to 273. A simple mathematical model, which accounted for thermal effects on kinetics, glucose-fructose equilibrium, and enzyme inactivation, was used to examine the potential for high-fructose corn syrup (HFCS) production at 80 degrees C and above using TNGI and SMGI under optimal conditions, which included the presence of both Co(2+) and Mg(2+). In the presence of both cations, these enzymes showed the potential to catalyze glucose-to-fructose conversion at 80 degrees C with estimated lifetime productivities on the order of 2000 kg fructose per kilogram enzyme, a value competitive with enzymes currently used at 55 degrees to 65 degrees C, but with the additional advantage of higher fructose concentrations. At 90 degrees C, the estimated productivity for SMGI dropped to 200, whereas, for TNGI, lifetime productivities on the order of 1000 were estimated. Assuming that the most favorable biocatalytic and thermostability features of these enzymes can be captured in immobilized form and the chemical lability of substrates and products can be minimized, HFCS production at high temperatures could be used to achieve higher fructose concentrations as well as create alternative processing strategies.

Production of glucose and fructose syrups from cassava (Manihot esculenta Crantz) starch using enzymes produced by microorganisms isolated from Brazilian Cerrado soil

“…Kinetic parameters (K M and V max ) were determined at best conditions for (PONTOH;LOW, 1995). Finally glucose-isomerase (GI) converts glucose to a mixture of about 26 to 59% of fructose, depending on the enzyme source and/or production conditions (BANDLISH et al, 2002). These syrups are largely used in pharmaceutical applications as well as in food industries (VORAGEN, 1998).…”

“…These syrups are largely used in pharmaceutical applications as well as in food industries (VORAGEN, 1998). Although, such processes are consolidated, a large number of researches are conducting studies in order to decrease the production costs and find a new and economically attractive starch source for this process (SANJUST et al, 2004;VORAGEN, 1998;BANDLISH et al, 2002;SAUER et al, 2000; VAN DER VEEN; VAN DER GOOT;BOOM, 2005).…”

“…The culture plates were incubated for 7 days at 30 °C. After growth, the species were subjected to taxonomic studies also according to Gilman (1971 (BANDLISH et al, 2002;SNEHALATA;BHOSALE;VASATI, 1996). the enzymatic analysis by measuring the initial reaction yields with soluble starch at various concentrations (1-25 mg.mL −1 ) for GA and for glucose solution at various concentrations (1-100 µg.mL -1 ) for GI.…”

Development of Fuzzy Logic Controller for Packed Bed Reactor

“…Selain itu, aktiviti enzim turut dipengaruhi dengan perubahan pH dan suhu. Perubahan pH yang kecil mampu menyahaslikan enzim dan proses pengisomeran pada suhu yang tinggi diperlukan untuk meningkatkan kadar tindak balas dan menolak anjakan keseimbangan kepada penghasilan produk (Bandish et al 2002). Oleh itu, satu perisian kawalan yang bersesuaian perlu direka untuk memastikan proses berlaku pada tahap optimum.…”

Characterization of a thermostable adenosine 5′-monophosphate deaminase gene in Streptomyces murinus

“…murinus is known to produce a thermostable xylose isomerase, which has been used for isomerization in sugar manufacturing for many years (Ashby et al, 1987;Bandlish et al, 2002). As mentioned above, Mizuguchi et al (2005) found a thermostable AMPD that is not denatured and that remains active at up to 65 C at its optimum pH of 5.6 in the culture medium of S. murinus.…”