Enzymatic time-temperature integrator

Two different types of enzymatic time-temperature integrators are described. The first, under the tradename of I-point, is based on a lipase-catalyzed hydrolysis reaction (125). The lipase is stored in a nonaqueous environment containing glycerol. The indicator contains two components that are mixed when the indicator is activated. The operating principle is as follows Upon activation, two volumes of reagents are mixed with each other. Lipase is thereby exposed to its substrate, here a triglyceride. At low temperatures there will be almost no hydrolytic reaction. As the temperature increases, hydrolysis accelerates and protons are liberated. A pH indicator is dissolved in the system. The indicator is selected to shift color after a certain amount of acid has been liberated by the enzyme-catalyzed process. Since the catalytic activity is influenced both by temperature and time, this indicator strip is said to be a time-temperature integrator. 

Dilute H2S04 is a well-studied pretreatment system that has been shown to be effective but expensive. Limited studies on carbonic acid have shown that this mild acid offers some benefit compared to liquid hot water (4,5), but that performance is generally less effective than optimized dilute H2S04. Laboratory investigations of carbonic acid pretreatment have shown that pretreatment effectiveness is primarily a function of time and temperature, and that high C02 pressure enhances hydrolysis on some substrates such as corn stover (8) but offers little benefit on aspen wood (6,7). Thus, for certain substrates such as aspen wood, lower pressure values are likely to offer performance similar to higher pressures. To date, no study integrating carbonic acid pretreatment, enzymatic hydrolysis, and fermentation has been carried out to determine the overall ethanol yield compared to similar. 

The hydrolysis of aromatic polyesters hke poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) at room temperature or under environmental conditions is an extremely slow reaction and no significant direct microbial or enzymatic attack on pure PET or PBT have been observed [138]. Natural environmental processes are, thus, unable to break down products made of PET and they maintain their strength and integrity for a long period of time [139,140]. Blown PET bottles exposed to 45% relative humidity, wet soil and 100% relative humidity at 20 °C have life expectancies of 48, 35 and 27 years, respectively [139]. The life expectancies at relative humidities lower than 45% are considerably longer than that. 

Goto et al. demonstrated the integration of a bioassay system that illustrated all processes required for a bioassay, that is, cell culture, chemical stimulation of cells, chemical and enzymatic reactions, and detection, on a chip using CFCP (Figure 35.10). By using the temperature control device, spatial temperature control of the system was possible, with areas on the chip maintained at different temperatures. Nitric oxide released from macrophage-like cells stimulated by lipopolysac-charide was successfully monitored by this system. The total assay time was reduced from 24 to 4 h, and the detection limit for nitric oxide was improved from 1 x 10 m to 7 x 10 M compared with the conventional batch methods. Moreover, the system could monitor a time course of the release, which is difficult to measure by conventional methods. 

Figure 71. Measuring cell for absolute calorimetric GOD-based glucose determinations. The opening must be minimized because otherwise the water evaporates too fast and interferes with the measurement by its heat of evaporation. In order to accelerate the enzymatic reaction peroxidase was added simultaneously. As soon as the drop of blood was added the temperature - time course was recorded and integrated. The glucose concentration can then be directly calculated via the published value for AW for this reaction as Figure 72 demonstrates...

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