Non-catalytic hydrolysis

Solution for early stage degradation by non-catalytIc hydrolysis... 

Non-catalytic hydrolysis (k2 =0) without the assumption of early stage degradation and 1... 

In the case shown in Figure 3.9, and were set as zero to represent pure random scission. The ratio kjk, reflecting the relative rate of autocatalytic hydrolysis to non-catalytic hydrolysis, was varied from 0 to inflnity to cover a wide range of different polymers. It can be observed from Figure 3.9 that in all the cases the accumulation of short chains is insignificant until the molecnlar weight reaches a very small value. This means any measurable mass loss cannot be expected before the device breaks apart. 

It will prove useful to write the governing equations in a non-dimensional format. However non-dimensionalisation of the equations is not unique. Here we chose to use the autocatalytic hydrolysis as a reference for all the other time-dependant processes (non-catalytic hydrolysis and TCP dissolution). This is because autocatalytic hydrolysis is expected always to occur in the polyesters considered in this chapter. The scission rate equation,... 

In Equations [7.2] and [7.3], and are rates for the non-catalytic hydrolysis and auto-catalytic hydrolysis reactions, respectively, a and P are related to the production rate of the small molecules by chain scission, m is the average degree of polymerisation of the small molecules, and n is the exponent for acid dissociation, which is usually taken as 0.5. D is the diffusion coefQcient of the small molecules in a degrading polymer, which is calculated by... 

Femia, R. E. and Weinberger, R., Determination of reducing and non-reducing carbohydrates in food products by liquid chromatography with post-column catalytic hydrolysis and derivatization comparison with refractive index detection, /. Chromatogr., 402, 127, 1987. 

Non-catalytic reaction pathways and rates of reaction of diethyl ether in supercritical water have been determined in a quartz capillary by observing the liquid- and gas-phase XH and 13C NMR spectra.37 At 400 °C, diethyl ether undergoes, competitively, proton-transferred fragmentation and hydrolysis as primary steps. The former path generates acetaldehyde and ethane and is dominant over the wide water density range up to... 

G. Schmidtke, S. Emch, M. Groettrup, and H. G. Holzhuetter. Evidence for the existence of a non-catalytic modifier site of peptide hydrolysis by the 20S proteasome. /. Biol. Chem., 275 22056-22063, 2000. 

The solubilized Fi has the active sites of the entire enzyme and catalyzes ATP hydrolysis. Similar to mitochondrial Fi,42) K coli Fi has six nucleotide binding sites (three for catalytic and three for non-catalytic sites).43) The role(s) of the non-catalytic sites is still unknown. The . coli Fi having at least two vacant catalytic sites, or Fi having less than one vacant catalytic site could be prepared.44 ... 

Characteristic of the cGB-PDEs is the ability of isobutyl nethylxanthine (IBMX) to promote cGMP binding while inhibiting the enzyme due to enhanced binding at a non-catalytic site. IBMX acts as a competitive inhibitor of cGMP hydrolysis. In feet, a... 

With this conqtound in hand, the original conditions were repeated. However the nucleophilic character of the NaOtBu base resulted in a product fi om a non-catalytic attack of the t-butoxide anion at the fluorine and subsequent hydrolysis of the t-butyl ether during workup to give phenol 14 (eq 3). 

Non-ionic Surfactants and Non-Catalytic Protein Treatment on Enzymatic Hydrolysis of Pretreated Creeping Wild Ryegrass... 

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... 

Although lots of work has been done on additives for enhancement of enzymatic hydrolysis of various substrates such as wood, com stover, and wheat straw, saline Creeping Wild Ryegrass (CWR) has not previously been studied with addition of additives. Furthermore, the mechanisms for the enhancement of enzymatic hydrolysis by additives are not clear. Thus, more in-depth studies are needed to investigate such mechanisms. Two non-ionic surfactants (Tween 20 and 80) and a non-catalytic protein (BSA) were employed to do this study. 

Non-ionic surfactants (Tween 20 and 80) and non-catalytic protein (BSA) were used to investigate if the enzymatic hydrolysis of pretreated CWR can be improved with various surface-active additives. The enzyme protein concentration and activities in solution were measured during enzymatic hydrolysis. Based on these data, the effect of additives on enzyme protein and activity was determined. All the experiments and experimental conditions are summarized in Table 1. 

As shown in Fig. 1, the presence of Tween 80, Tween 20, BSA or (BSA + Tween 20) improved the enzymatic hydrolysis of pretreated CWR by 8 to 14% after 72 h of hydrolysis. The initial hydrolysis rate was also increased to some extent The cellulose conversion was increased from approximately 75% (no additives) to 89, 88, and 83% with the presence of Tween 20, Tween 80, and BSA, respectively. Of all three additives. Tween 20 was the most effective additive on the improvement of cellulose conversion, followed by Tween 80 and BSA. The treatment of Tween 20, Tween 80, or BSA gave similar results at an enzyme loading of 15 FPU/g cellulose to those at enzyme loading of 30 FPU/g cellulose but without additive addition (Fig. 1). Therefore, the addition of surfactants and/or non-catalytic protein could help save enzyme loading without decreasing the hydrolysis yield. In addition, it was found that Tween 20 and BSA gave no further increase in cellulose conversion. Thus, the effect of Tween 20 on the hydrolysis of pretreated CWR might be similar to that of BSA [7]. 

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