Enzyme activity, loss

Table 2 presents the results obtained in the statistical modeling. Temperature and reduced density had a pronounced effect on enzyme activity loss, both showing a positive effect. At this point, it is important to mention that the cross-interaction temperature-exposure time had a significant negative effect. In the range investigated (10-200 kg/[m3-min]), the decompression rate had a weak negative effect on loss of enzyme activity. The same effect was observed with the exposure time (60-360 min). 

The results show that in all experimental conditions the enzyme activity loss was lower than 15%. When compared to the work presented by Habulin and Knez (8), this activity loss is considered low. Some works available in the literature point to the use of SCC02 as a satisfactory medium to inactivate some enzymes (8,9). It is important to mention that all these works used enzymes in native form, and the results presented herein are related to an immobilized enzyme (Novozym 435). On the other hand, our results are in perfect agreement with those obtained by Castellari et al. (9) for the system containing a polyphenoloxidase present in grape musts. 

Enzyme must be injected during the reaction to ensure constant activity in the case of enzyme activity losses [8]. A dropwise addition of peroxidase [86] usually results in higher enzyme consumption and, thus, lower turnover numbers than in... 

In a previous work, Tardioli et al. [9] have immobilized CGTase from Thermoanaerobacter sp. by covalent attachment into glyoxy 1-agarose particles and obtained an activity recovery of about 32%, that is, five times the highest values obtained in this work (6.94% with sol-gel encapsulation). It is thought that with the latter method, in addition to the causes listed above for immobilized enzyme activity loss, the immobilization conditions and reagents used by the sol-gel method contribute to enzyme deactivation. 

Enzyme activity loss because of non-productive adsorption on lignin surface was identified as one of the important factors to decrease enzyme effectiveness, and the effect of surfactants and non-catalytic protein on the enzymatic hydrolysis has been extensively studied to increase the enzymatic hydrolysis of cellulose into fermentable sugars [7, 9 19]. The reported study showed that the non-ionic surfactant poly(oxyethylene)2o-sorbitan-monooleate (Tween 80) enhanced the enzymatic hydrolysis rate and extent of newspaper cellulose by 33 and 14%, respectively [20]. It was also found that 30% more FPU cellulase activity remained in solution, and about three times more recoverable FPU activity could be recycled with the presence of Tween 80. Tween 80 enhanced enzymatic hydrolysis yields for steam-exploded poplar wood by 20% in the simultaneous saccharification and fermentation (SSF) process [21]. Helle et al. [22] reported that hydrolysis yield increased by as much as a factor of 7, whereas enzyme adsorption on cellulose decreased because of the addition of Tween 80. With the presence of poly(oxyethylene)2o-sorbitan-monolaurate (Tween 20) and Tween 80, the conversions of cellulose and xylan in lime-pretreated com stover were increased by 42 and 40%, respectively [23]. Wu and Ju [24] showed that the addition of Tween 20 or Tween 80 to waste newsprint could increase cellulose conversion by about 50% with the saving of cellulase loading of 80%. With the addition of non-ionic, anionic, and cationic surfactants to the hydrolysis of cellulose (Avicel, tissue paper, and reclaimed paper), Ooshima et al. [25] subsequently found that Tween 20 was the most effective for the enhancement of cellulose conversion, and anionic surfactants did not have any effect on cellulose hydrolysis. With the addition of Tween 20 in the SSF process for... 

Other biomedical and biological appHcations of mictocapsules continue to be developed. For example, the encapsulation of enzymes continues to attract interest even though loss of enzyme activity due to harshness of the encapsulation protocols used has been a persistent problem (59). The use of mictocapsules in antibody hormone immunoassays has been reviewed (60). The encapsulation of hemoglobin as a ted blood substitute has received much attention because of AIDS and blood transfusions (61). 

If the inhibitor combines irreversibly with the enzyme—for example, by covalent attachment—the kinetic pattern seen is like that of noncompetitive inhibition, because the net effect is a loss of active enzyme. Usually, this type of inhibition can be distinguished from the noncompetitive, reversible inhibition case since the reaction of I with E (and/or ES) is not instantaneous. Instead, there is a time-dependent decrease in enzymatic activity as E + I El proceeds, and the rate of this inactivation can be followed. Also, unlike reversible inhibitions, dilution or dialysis of the enzyme inhibitor solution does not dissociate the El complex and restore enzyme activity. 

Since 1978, several papers have examined the potential of using immobilised cells in fuel production. Microbial cells are used advantageously for industrial purposes, such as Escherichia coli for the continuous production of L-aspartic acid from ammonium fur-marate.5,6 Enzymes from microorganisms are classified as extracellular and intracellular. If whole microbial cells can be immobilised directly, procedures for extraction and purification can be omitted and the loss of intracellular enzyme activity can be kept to a minimum. Whole cells are used as a solid catalyst when they are immobilised onto a solid support. 

In contrast to this, the enzyme resin is stressed less by gas sparging than by stirring (see Fig. 18 and 20). The same activity losses were observed first with 1 to 8 times greater specific adiabatic compression power Pj/ V than the maximum power density necessary for stirring. As in the case of the smooth disc, the effects of power input are only weak. The type of gas sparger and therefore the gas exit velocity are of no recognisable importance. The behaviour of the enzyme resin particles is thus completely different from that of the clay min-eral/polymer floes and the oil/water/surfactant droplet system, which are particularly intensively stressed by gas sparging. 

The experimental results in Fig. 27 show the influence of the reactor system (see Fig. 28) on the disintegration of enzyme activity. It was found that the low-stress bladed impeller results in less activity loss than the propeller stirrer which causes much higher maximum energy dissipation ,. The gentle motion the blade impeller produces means that stress is so low that its disadvantage of worse micro mixing in NaOH (in comparison with the propeller) is more than compensated. 

Fig. 27. Activity loss a/a of Acylase enzym resign with the reaction time t of the enzymatic deaccylation of Penicillin G to 6-Aminopenicillanic acid (reactor design see Fig. 28)...

The enzyme had a requirement for calcium. The addition of EDTA to the reaction mixtures, resulted in complete loss of activity, whereas the addition of CaCl2 increased the activity (figure 8). Presumably, sufficient contaminating calcium ions were present in the dialyzed enzyme and substrate mixture to permit the limited activity of the controls, but apparently these were removed by chelation with EDTA. The optimum concentration was in the range of 5 to 15 M, and higher concentration resulted in a decrease in activity. Phoma medicaginis var. pinodella synthesizes a pectin lyase that lacked an absolute requirement for calcium ions but maximum enzyme activity required the presence of 1 mM Ca [25]. The lyase from Fusarium solani f sp. phaseoli, that is active on pectin and pectic acid, is calcium-dependent [30]. Most of the pectate lyases characterized are calcium-dependent the pectate lyase from Rhizoctonia solani [34] and the endopectate lyase fi om Fusarium solani f sp. pisi [31]. 

Carney, J.M., Starke-Reed, P.E., Oliver, C.N., Landrum, R.W., Cheng, M.S. and Wu, J.F. (1991). Reversal of age-related increase in brain protein oxidation, decrease in enzyme activity, and loss in temporal and spatial memory by chronic administration of the spin-trapping compound N-tert-butyl-cr-phenylnitrone. Proc. Natl Acad. Sci. USA 88, 3633-3636. 

The above conclusion is supported by the results shown in figure 4. Just as inhibitors of the 5-HT uptake carrier can antagonize MDMA-induced [ H]5-HT release in vitro, coadministration of MDMA with an uptake inhibitor such as citalopram can completely block the acute depletion of 5-HT. Although citalopram also antagonized the MDMA-induced decrease in TPH activity, there was still a significant loss of enzyme activity when compared to control. This implies that if MDMA requires access to the interior of the nerve terminals to affect TPH activity, it does not require the activity of the uptake carrier to gain entrance. Hence, these results are consistent with the outcome of synaptosomal uptake experiments with [ HJMDMA (Schmidt et al. 1987), which show that MDMA is not actively concentrated by a carrier system. Furthermore, it is apparent that the loss of enzyme activity alone is not sufficient to reduce 5-HT concentrations, but that release via the carrier must occur simultaneously, to deplete the terminal once synthetic capacity is reduced. 

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