Growing Saccharomyces cerevisiae in calcium-alginate beads induces cell alterations which accelerate glucose conversion to ethanol

✍ Scribed by Jorge L Galazzo; James E. Bailey

• Publisher: John Wiley and Sons
• Year: 1990
• Tongue: English
• Weight: 925 KB
• Volume: 36
• Category: Article
• ISSN: 0006-3592
• DOI: 10.1002/bit.260360413

✦ Synopsis

Nongrowing Saccharomyces cerevisiae cells previously grown i n alginate exhibit ethanol production rates 1.5 times greater than cells previously grown in suspension. Analysis of glucose, ethanol, and glycerol formation data using quasi-steady-state pathway stoichiometry shows that alginate-grown cells possess phosphofructokinase (PFK), ATPase, and polysaccharide synthesis maximum activities which are approximately two-, two-, and ninefold larger, respectively, than in suspensiongrown cells. The estimated change in PFK maximum velocity is consistent with in vitro assays of PFK activity in extracts of suzpension-and alginate-grown yeast. Estimation of ethanol production flux control coefficients using in vivo nuclear magnetic resonance (NMR) spectroscopy measurements of intracellular metabolite concentrations and a previously proposed detailed kinetic model of ethanol fermentation in yeast shows that glucose uptake dominates flux control i n alginate-grown cells i n suspension while earlier research revealed that PFK and ATPase exert significant flux control i n suspension-grown cells. When placed in a calcium alginate matrix, alginate-grown cells produced ethanol 1.8 times more rapidly and accumulated substantially more polyphosphate than suspension-grown cells placed in alginate. Cells growing in alginate elicit responses at the genetic level which substantially alter pathway rates and flux control when these cells are used as either a suspended or an immobilized biocatalyst. These responses in gene expression to growth in alginate serve to reconfigure flux controls in alginate to a pattern which is similar t o that obtained for suspendedgrown cells in suspension.