Yeast cell concentration

All novel bioreactors attempt to increase productivity by increasing yeast cell concentration or by reducing ethanol inhibition and much work has been reported on ethanol production in fluidized beds by Bauer, Hayes, Moebus, Rottenbacher, Teuber and their co-workers aqueous glucose solutions can be atomised within a bed of yeast particles with the latent heat for vaporisation of both ethanol and... 

An early example of an MIP-QCM sensor was a glucose monitoring system by Malitesta et al. (1999). A glucose imprinted poly(o-phenylenediamine) polymer was electrosynthesized on the sensor surface. This QCM sensor showed selectivity for glucose over other compounds such as ascorbic acid, paracetamol, cysteine, and fructose at physiologically relevant millimolar concentrations. A unique QCM sensor for detection of yeast was reported by Dickert and coworkers (Dickert et al. 2001 Dickert and Hayden 2002). Yeast cells were imprinted in a sol-gel matrix on the surface of the transducer. The MIP-coated sensor was able to measure yeast cell concentrations in situ and in complex media. A QCM sensor coated with a thin permeable MIP film was developed for the determination of L-menthol in the liquid phase (Percival et al. 2001). The MIP-QCM sensor displayed good selectivity and good sensitivity with a detection limit of 200 ppb (Fig. 15.7). The sensor also displayed excellent enantioselectivity and was able to easily differentiate the l- and D-enantiomers of menthol. 

It is generally agreed that yeast cells do not really play a role in membrane fouling [12,30,32]. Gan proved that increasing yeast cell concentration had almost no appreciable effect when the fractional mass concentration of large particles increased from 0.015% to 0.059% [32]. 

As can be seen in Fig. 26, only half of the QCM surface was imprinted thus eliminating the elfects of nonspecific adsorption upon the sensor output. The microbalance was imprinted with yeast cells and Escherichia coli. The microbalances were able to measure yeast cell concentrations in the range 10" -10 per mL under flow conditions of 10 mL min and were able to distinguish between the template cells and other microorganisms in complex mixtures. However, the microbalances proved to be less sensitive towards imprinted bacterial cells. 

The following errors in the brewing process listed in Table 5.11 can result in extreme values for the parameters measmed high fermentation/maturation temperature, insufficient aeration, long maturation time (yeast excretion), very strong yeast growth/ propagation, FAN deficiency, low yeast cell concentration, and short maturation. 

FIGURE 7.24 Effect of temperature (a) and yeast cell concentration (b) on hydration of aqueous suspensions of yeast cells containing 5 wt% of Si02. 

FIGURE 19.3 (a) Response surface as a function of pH and yeast cells concentration (Y). (b) Response surface as a function of lactose (L) and yeast cells concentration (Y), (the other variables were fixed at middle level). 

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