Sho Shindo

Development of novel carrier using natural zeolite and continuous ethanol fermentation with immobilized Saccharomyces cerevisiae in a bioreactor

A natural zeolite, easily vitrified and blown at 1300 °C with a high porosity and diam. of 5–100 μm, was used to immobilize Saccharomyces cerevisiae at 3.6 × 108 cells ml−1 carrier. When the abilities of natural zeolite carrier were compared with glass beads, the capacity for immobilization and alcohol fermentation activity were, respectively, 2′-fold higher and 1.2-fold higher than that of glass beads. Continuous alcohol fermentation was stable for over 21 d without breakage of the carrier.

Control of acetate ester formation during alcohol fermentation with immobilized yeast

Abstract The effect of sugar composition on the formation of acetate esters using immobilized yeast was investigated. When the immobilized yeast was incubated in maltose medium lacking unsaturated fatty acids, the production of ethyl acetate and isoamyl acetate was poor when compared to glucose medium, although in maltose medium the production of acetyl-CoA was less than in glucose medium. Ester production was stimulated using the immobilized yeast and wort treated with glucoamylase to hydrolyze maltose. With this method, acetate esters were produced at normal levels compared to those of beer fermented in the conventional manner.

Immobilization of yeast with hollow PVA gel beads

Abstract We constructed a novel immobilization system of yeast cells with PVA gel beads. The PVA gel beads formed hollows, so they could be prevented from breaking by flotation by the CO 2 gas that filled the hollow part. Activity of this immobilized yeast on hollow PVA gel beads was about 1.4-fold higher than that on calcium alginate. Neither destruction of the carrier nor diminishing of yeast activity were observed even after 40 d of fermentation. The optimal immobilization of yeast cells was done with 8% PVA and 2% sodium alginate, and the inoculum size was 1.0 × 10 5 cells per ml of gel beads.

Relationship of production of succinic acid and methyl citric acid pathway during alcohol fermentation with immobilized yeast

SummaryImmobilized yeast cells produced succinic acid during alcohol fermentation When the uptake amounts of isoleucine and valine into the yeast cells were compared, which are related to the production of α-acetolactate, more iso-leucine than valine was consumed by the immobilized yeast cells. It was suggested that the isoleucine was metabolized to succinic acid through the methyl citric acid pathway and the metabolic activity of isoleucine to succinic acid was greatly increased in immobilized yeast cells compared with free yeast cells.

Control of diacetyl precursor [α-acetolactate] formation during alcohol fermentation with yeast cells immobilized in alginate fibers with double gel layers

Abstract During alcohol fermentation with yeast cells immobilized in single-layered gel beads, 0.94 mg/ l of α-acetolactate, which is a diacetyl precursor, was produced. However, by immobilizing the yeast cells in double-layered gel fibers, only 0.16 mg/ l of α-acetolactate was formed. The free cells which leaked from the gel carrier made no significant contribution to the formation of α-acetolactate. The effectiveness of double-layered gel fibers in reducing α-acetolactate formation could be attributed to a more anaerobic condition inside the gel fibers.