Cellulase enzyme mixture

It is often desirable to enhance or deplete the cellulase enzyme mixture of one or more individual cellulase components. This is done if one or two components are particularly desired, or if one or more are deleterious to the application. In the extreme, only a single cellulase component is produced. In one example of this, pure Trichoderma endoglucanase III is produced by extracting it with polyethylene glycol [16]. 

Another simple example is an unclarified enzyme product. In this case, the cells in the fermenter produce a target molecule, for example, a cellulase enzyme mixture. The enzyme mixture is the product, but the cells remain in the final product. This approach is preferable when a product has very low purity requirements and a separation process is cost prohibitive. Cellulase enzyme mix is used to break down biomass into glucose which enables the use of cellulosic raw materials as fermentation feedstocks (Himmel et al., 1999). This application requires a very inexpensive enzyme mix at low purity. Cellulases are also used in textile applications, where they are required in a purified form. 

Another method which may become a useful technique for selective inactivation of cellulases in enzyme mixtures is the use of selective heat inactivation. While establishing the thermostability properties of crude xylanases from a fungal strain Y-94, Mitsuishi et al. (80) observed differential heat labilities of the cellulase and xylanase activities in the culture filtrate. After an incubation period of 20 minutes at 65°C, the xylanase activity was reduced by 5-10% whereas the Avicelase and /3-glucosidase activities were reduced by 100% and 60%, respectively. We have observed a similar temperature dependency of xylanase and cellulase activities in T. auranti-acus. As indicated in Figure 2, treatment of the culture filtrate at 70°C for 20 minutes resulted in less than a 5% loss in xylanase activity whereas cellulase activities were reduced by 40-50%. A similar effect has also been observed for the xylanases and cellulase enzymes produced in culture filtrates from T. harzianum (93). Further work in the area of heat treatments may improve the effectiveness of cellulase inactivation. Since the cellulase activities of some enzyme preparations can be more rapidly inactivated on... 

In the current work, we employed a modified approach, with predeposition of a secondary membrane of yeast (SMY) before starting the filtration of protein. Backflushing was employed periodically to remove the deposited secondary membrane to recover the flux, and a new secondary membrane was deposited subsequently with the start of each new cycle, prior to restarting the filtration of protein. Microfiltration experiments were performed with yeast as the secondary membrane and BSA-only solutions and yeast-BSA mixtures as the feed. Ultrafiltration experiments were performed with yeast as the secondary membrane deposition medium and cellulase enzyme solutions, used in the conversion of biomass into ethanol, as the feed. In this article, we also present direct visual observation images (19) of the formation of the secondary membrane and its subsequent removal. 

Beta-glucosidase is available within the complex mixture of crude cellulase enzymes. In addition, some microbes, including Aspergillus niger, produce beta-glucosidase with httle additional cellulase activity. 

Since the 1990s enzyme mixtures have been commonly used in heavy-duty liquids. Most products contain a minimum of a protease for removal of proteinaceous soils and an amylase to facilitate starchy food-based soil removal. Some products contain lipases for degrading fatty or oily soils and cellulases to improve fabric appearance by cleaving the pills or fuzz formed on cotton and synthetic blends. 

Mixtures of enzymes comprise detergent celluloses. There are three types of cellu-lases [31,62] cellobiohydrolases, which are exocellulases active on crystalline cellulose, endoglucanases, which catalyze the hydrolysis of amorphous cellulose, and -glucosidases, which lead to termination of the hydrolytic process yielding glucose tmits. Less detail is known about the structure of the cellulase enzymes than about the other detergent enzymes. 

Recently, Rlbeiro et al studied the effect of supplementing a barley-based diet with a familyll P glucan-binding domain, fused to a recombinant cellulase from C. thermocellum. The results showed that birds fed on diets supplemented with the recombinant proteins, containing the CBMll or the commercial enzyme mixture, have improved performance when compared to birds fed with diets without the enzyme supplement [162]. 

Extraction of the cellulase system. The culture of SSF from each flask (originally 5 g of substrate) was mixed well with more water to bring the final weight of the mixture (mycelium plus unutilized lignin, cellulose, and hemicelluloses) to 100 g. Tween 80 was added at a rate of 0.1%. The mixture was shaken for 0.5 h and centrifuged. The supernatant was used for enzyme determination. We estimated that about 7% to 10% cellulases remained adsorbed on the residues (mycelium and unutilized cellulose, hemicelluloses, and lignin) when the residues were suspended in water and Tween 80 as before and the supernatant was tested for cellulase titer. 

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