Formulation enzyme stabilization

Formulations. Any formulation is a compromise between the previously mentioned requirements. For example, the fermentation broth may contain enzyme-stabilizing substances, but the appHcation of the enzyme or precipitation problems in the formulation may demand a high degree of purification that eliminates the stabilizers. Alternatively, the pH necessary for good microbial or physical stabiHty may differ from the pH that gives optimum enzyme stabiHty, or a preservative that is effective at the optimum pH for enzyme stabiHty may have a denaturing effect on the enzyme. 

The low content of water in these formulations promotes improved stabilization of enzyme and bleach additives. The combination of LAS and AE in a low-water-content formulation is effective at solubilizing enzymes and preserving enzyme stability when the sum of the LAS and water levels ranges between 25% and 45% [53],... 

Different industries pose different challenges to the protein formulator. Many feed enzymes are sold as formulated liquid concentrates. In this case, the major requirements for a liquid formulation are enzymatic stability and preservation against microbial growth. It is sometimes not appreciated that the dominant factor affecting enzyme stability is the intrinsic stability of the enzyme itself formulation can do very little to correct for a structurally labile protein. Therefore, it is advisable to make stability an important criterion of the initial enzyme screening process. 

Liquid products are approximately 50 to 60 percent water, with the remainder being a combination of surfactants, builders, foam regulators, enzymes and enzyme stabilizers, hydrotropes, antiredeposition polymers, optical brighteners, corrosion inhibitors, dye, and perfume. Two-in-one formulations also contain antistatic and fabric softening ingredients. Liquid systems require careful selection and blending of raw materials to achieve a stable product. Special attention is necessary for the following items. 

The patent literature contains numerous examples of enzyme stabilization schemes based on the use of various chemical additives. Common themes are to either lower the amount of water in the formulation while retaining solubility of other components, or to add specific enzyme stabilizer/inhibitors. Some examples are highlighted in Table 4, and many others can be found in the review by Crutzen and Douglass. Few published articles have addressed the mechanisms of enzyme stabilization by additives. One study examines protease stabilization by carboxylic acid salts and another discusses the use of borate in conjunction with propylene glycol to inhibit protease activity. ... 

The primary disadvantages of using chemical additives as enzyme stabilizers are their cost and that valuable formulation space is lost without any direct benefit to detergent performance. Thus, an alternative... 

A disadvantage of using LAS in HDLDs is their detrimental effect on enzymes. With the increasing use of enzymes it becomes necessary to devote a sizable portion of the formulation space and cost to enzyme stabilization. Alternative approaches using surfactants that are more compatible with enzymes can be employed. 

Unlike sodium LAS, alcohol ether sulfates are more tolerant to hardness ions and as a result do not require an accompanying high level of builder in the formulation. Figure 8.11 shows the relative insensitivity of AEOS to hardness ions. Small amounts of AEOS when added to LAS were found to improve the interfacial properties. They are more compatible with enzymes, which can also reduce the cost of enzyme stabilizers in the formulation. They are also milder to the skin and, as a result, are frequently used in hand dishwashing applications. The superior detergency performance of this surfactant is demonstrated by its superior efficacy in most stain categories. 

The recovered broth has to be formulated into a final product to comply with requirements appropriate to its final application. In formulation, whether for a solid or liquid product, different issues are addressed. Maintaining the activity of enzyme from the time of manufacture to the time of application through storage is one of the main factors tested during formulation. Other stability issues such as microbial stability and physical stability are important as well. Depending on the final application of the enzyme, the physical appearance can be customized (e.g., colored). A specific example of formulation is immobilization (see also Chapter 2). 

Ciystallization of stabilizer system and impact on enzyme stability during freeze drying residual activity of P-galactosidase in marmitol sodium phosphate formulations after freeze-drying. (Data taken from Ref 34.)... 

HLADH has also been used for the preparative reduction of water-insoluble substrates such as cinnamaldehyde [113], cyclohexanone [112], and the steroid eticholane-3/f-ol-17-one [112] with simultaneous oxidation of low molecular weight alcohols. With sodium dodecyl sulfate (SDS) or AOT as surfactant, enzyme activity was very dependent on the amount of water added. Relatively high water content gave the highest reaction rate and also the best enzyme stability. A properly formulated microemulsion gave a higher reaction rate than an aqueous buffer [112]. 

The liquid product formulation process is usually integrated with the downstream production process. After the enzyme has been concentrated, the enzyme stabilizers are added followed by a filtration process. The filtration is done to remove any undissolved solids and/or to reduce the level of microbial burden in the formulated product. The filtration process can be done using standard filtration equipment such as an RVDF, plate and Ifame, or depth filtration. The resulting products are transparent and commonly range Ifom clear to amber in color. 

Liquid formulation in this context means nonsolid formulations. The vast majority of liquid formulations are based on water with a varying degree of other components present, although liquid nonwater formulations of enzymes have been described. The most important of the issues listed in Table 27.2, when working with liquid formulations, is the stability of the formulated enzyme product as well as the final liquid detergent. A comprehensive overview of the stability issues of enzymes in detergents is given in Ref. 11. Stability can be divided into enzymatic, physical, and microbial stability. 

Keeping the pH near neutral in the detergent formulation also increases the enzyme stability. A pH increase upon dilution both increases the enzyme efficacy and the detergency of other formulation ingredients [71]. 

Uses Anti redeposition agent which boosts detergency in liq. detergent formulations improves stability of enzymes lime soap dispersant for It.- and heavy-duty detergents... 

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