Comparison of suspended and immobilized yeast metabolism using 31P nuclear magnetic resonance spectroscopy

Abstract

SUM~RY:slP nuclear magnetic resonance has been employed to monitor noninvasively Suechoromy~es cet-evisiue anaerobic glucose metabolism in suspended and immobilized cells. Results show that cell entrapment in Ca-alginate beads alters cell metabolism compared to that in suspended cells. Assuming similar intracellular ionic strength, differences in intracellular phosphate chemical shift indicate that the internal pH of the immobilized cells is lower than the suspended cell internal pH. This result is consistent with higher ethanol production rates exhibited by immobilized yeast. INTRODUCTION:

Comparison of fermentation properties and specific enzyme activities of free and calcium-alginate-entrapped Saccharomyces cerevisiae

“…Altered concentration of an effector of a regulation step is an assumption also made by Galazzo and Bailey (1989), when they found differences in intermediate metabolite levels between free an Ca-alginate-entrapped S. cerevisiae by nuclear magnetic resonance analysis. Galazzo et al (1987) determined a lower intracellular pH in Ca-alginate-entrapped S. eerevisiae and suspected that this could be the reason for enhanced glucose turnover, because hexokinase and phosphofructokinase can be stimulated by a lower pH in vitro. As this study shows, the significant differences in kinase activities between free and immobilized cells were determined under identical test (pH) conditions.…”

In SituNMR Systems

“…In other words, changes in the local environment in terms of nutrients and products may cause the differences in metabolic behavior observed between immobilized cells and cell suspensions in this system. (29,52,53) and in particular, the glucose consumption rate is increased (31,53). Immobilized cells had more glucose-6-phosphate and less fructose-1,6-bisphosphate than suspended cells, as determined from 31 P NMR spectra.…”

“…A kinetic model indicated that the distribution of flux control in the glucose to ethanol pathway was altered upon immobilization (31) and increased membrane permeability was hypothesized for the increase in glucose uptake rates (53). Calculation of the observable intraparticle diffusion-reaction modulus and the internal and external mass transport ratio indicated the absence of both internal and external mass transport limitations in these kinetic measurements (29,52). Differences in cellular physiology in gel-immobilized cells versus cell suspensions may be dependent on the type of gel, the biological species, and the reactor configuration and operation.…”

Comparison of wild‐type and Reg 1 mutant saccharomyces cerevisiae metabolic levels during glucose and galactose metabolism using 31P NMR

“…The uptake process of glucose may trigger rapid extrusion of protons from endogenous sources . 32 Consequently, the intracellular acidification in the initial moments after glucose addition is a result of metabolism, not of glucose uptake itself. The uptake of galactose via galactose permease may be by active transport,I2 although it most likely occurs by facilitated diffusion since the ratio of intracellular to extracellular galactose concentration is less than l.3* Thus, galactose uptake, like glucose uptake, is probably not directly related to intracellular acidification.…”