Enzyme leaching

Moreover, the catalytic results clearly show that the lipase immobilization procedure strongly influences the final activity of the enzyme. Adsorption and entrapping procedures allow to preserve the open and active conformation of the enzyme whit respect to electrostatic ones. Using the entrapped lipase, the enzyme leaching can be avoided and the biodiesel total productivity strongly increases if compared with the one obtained by the free enzyme. 

Bajc, A.F. 1998. A comparative analysis of enzyme leach and mobile metal ion selective extractions case studies from glaciated terrain, northern Ontario. Journal of Geochemical Exploration, 61, 113-148. 

Fig. 2. t probability as a function of Student s t statistics for Enzyme Leach (a best case ) and Bioleach (b worst case )... 

For example, Asuri and his co-workers (Asuri et al., 2007) reported that the proteases attached to the surface of SWCNTs can create self-cleaning surfaces that resist protein adsorption. This kind of SWCNT-enzyme composite exhibited 30 times higher overall catalytic activity than control composites where the proteases were conjugated to a non-nanoscale graphite support. Importantly, the enzymes preserved more than 90% of their initial activity over 30% days in the liquid buffer, with only negligible amounts of enzymes leaching out. The result demonstrates that the nanocomposites of SWCNTs and polymers can act as hosts for enzymes and can prevent protein contamination on the surface of medical devices. We consider that SWCNTs may have the function as biocatalyst to improve the enzyme activity attached to the surface of CNTs. Our previous work also indirectly hints that CNTs could improve the bioactivity of enzymes such as Taq enzyme Cui et al. (2004). However, there are also adverse reports. CNTs can... 

Ag, As, Au, Cu, Mo, Re, Sb, Tl, U, and V. The highest ranking analytical methods were enzyme leach, cold hydroxylamine hydrochloride leach, and MMI. It should be noted that this matrix method did not take into account the added value of creating ratios (such as to total Fe or organic carbon) between related elements. The use of ratios may change the rank of evaluated analytical methods. Also, the soil gas hydrocarbons technique was treated separately, since the analyses are for organic compounds, rather than for the inorganic elements of the other methods. 

Based on the results of this matrix evaluation, cold hydroxylamine leach and enzyme leach methods were chosen for use in subsequent field seasons. 

Based in part on the above results, soils in 2008 were collected along a north-south traverse over the Pebble East zone to confirm the influence of large faults on surface geochemistry in the deeper portions of the deposit. The early results from the 2008 N-S traverse show a broad zone of high values. Figure 3 shows the distribution of molybdenum in a plan view from the combined 2007 and 2008 data. Enzyme leach values for Ag, As, Br, Ca, Cl, Mg, Re, S, Sb, Se, Tl, V, W show similar distribution patterns in the N-S... 

Fig. 2. West to east plot of vanadium by enzyme leach in soils on top of a cross section showing vanadium in drill core. Dashed line shows the subcrop of Cretaceous, granitic rock of Pebble East beneath the Palaeozoic/Eocene volcanic and sedimentary rock cover.

Fig. 3. Distribution of Mo in soil samples analyzed by the enzyme leach method.

Enzymes can also be entrapped within the pores of a matrix or network. Small molecules can diffuse in and out of the matrix, whereas the macromolecular enzyme is maintained within the network. Precise control of the pore size is not possible, and therefore mass transfer limitations and enzyme leaching always cause problems [59]. 

Enzymes can lose their activity because of protein denaturation and loss of active site.26 Glucose oxidase can also lose its activity when exposed to excessive amounts of hydrogen peroxide. Most enzymes utilized in the fabrication of biosensors for implantation are derived from nonmammalian proteins, which can lead to an allergic response if the enzymes leach (or leak out of the sensor) into the body. Enzyme leaching can result when the attachment or entrapment of the enzyme is not robust. For example, if a method of entrapment via cross-linking polymers is utilized and the reaction does not go to completion during entrapment, then the enzyme can leach out and cause a loss of signal.27... 

Clark, J.R., 1996. Unique significant enzyme leach anomaly patterns in areas of tropical/subtropical weathering. Proc. Conference Queen s University, Kingston, Onatrio, pp. 241-256. 

Clark, J.R., 1997. Concepts and models for interpretation of enzyme leach data for mineral and petroleum exploration. Internal report. Enzyme - Actlabs, 62 pp. 

In Novozym 435, the enzyme is not covalently linked to the carrier, but merely adsorbed. Therefore, as mentioned, enzyme leaching is a known issue with this product. The problem has been addressed by several authors [20, 21], Even though the enzyme performance has been satisfactory, there has been a need specifically for a non-leaching immobilized formulation. It has been shown that several physical and chemical treatments such as coating the immobilized particles can enhance the stability of Novozym 435 [20-22],... 

The activity of the reaction showed a dependence on temperature, achieving a maximum at 80°C and 10MPa. The productivity reached over 92% yield and a TON of 35.8 X lO mol product/mol enzyme. Furthermore, enzyme leaching was not observed. A comparative reaction using silica as the support for the IL had a productivity seven times lower than in the monolith. 

Thus, immobilisation should not lead to enzyme deactivation, make access to the enzyme active site difficult or let enzyme leach into the surrounding solution. The more common methodology for immobilisation of enzymes on electrode surfaces involves cross-linking with glutaraldehyde, aided by the protein bovine serum albumin (BSA) in order to increase the interaction with the enzyme molecules. In this section two other strategies will be described. 

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