Article pubs.acs.org/Langmuir
Encapsulation of Amylase in Colloidosomes Polly H. R. Keen, Nigel K. H. Slater, and Alexander F. Routh* Department of Chemical Engineering and Biotechnology, BP Institute, University of Cambridge, Madingley Road, Cambridge CB3 0EZ, United Kingdom ABSTRACT: Aqueous core colloidosomes encapsulating the enzyme amylase were manufactured with a shell comprising polymer latex particles of diameter 153 nm. The colloidosomes were sealed with calcium carbonate by precipitation between an inner phase of Na2CO3 and an outer phase of CaCl2. This seal allowed the retention of small molecules, such as dyes, as well as larger enzyme molecules, for several months. The encapsulated material could be released by dissolution of the CaCO3 with acid, upon a large dilution in water, or by applying a sufficient shear. The degree of release could be controlled since the greater the mass of CaCO3 precipitated onto the colloidosome shell, the greater the dilution or shear required to achieve release. The calcium carbonate seal protected encapsulated amylase from the detrimental effects of components in a liquid laundry detergent for several months so that, on triggered release, the enzyme retained its high activity.
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INTRODUCTION Enzymes are playing an increasing importance in many areas of industry thanks to their high chiral and regiospecific selectivity under mild and sustainable conditions.1 Over 500 commercial products covering 50 applications are made using enzymes.2 In 2009, the industrial enzyme market reached $5.1 billion3 divided into the following applications: 34% detergents, 28% food, 16% agriculture and feed, 10% textile processing, and 10% pulp and paper, leather, and chemicals.4 Enzymes in Detergents. The presence of enzymes in laundry detergents can improve cleaning efficiency because of their excellent ability to break down biological material. Enzymes for this application must be compatible with detergents, stable over at least the temperature range 20− 50 °C, active at alkaline pH, and have a long shelf life.5 Recent figures show that, of all laundry detergent products sold, more than 80% in the US and 85% in Europe contain enzymes.6 Liquid laundry detergents are more popular than powders because of their convenience and lack of solubility issues, which are particularly noticeable at low temperatures.7,8 Catalytic properties of enzymes derive from the specific conformation of their amino acid chains. The active conformations are thermodynamically fragile so are susceptible to chemical degradation pathways leading to loss of structure and hence activity. Surfactants, bleaches, and water-softening © 2014 American Chemical Society
builders are all necessary ingredients in a viable detergent product. However, these compounds can be detrimental to enzymes, altering the overall structure, or changing the active site, denaturing it, and lowering activity and, critically, the cleaning performance. In liquid detergents, stabilization of the enzymes is more difficult than in powders because the alkalinity, high water content, and surfactants present in the washing system can cause denaturation. In addition, the physical separation of enzymes from harmful detergent components is difficult.9 To reduce water hardness, chelators are common ingredients in laundry detergents. However, their ion-binding capacity can deprive the active site of the enzymes of calcium ions, thus reducing enzyme stability.10 For the desired long product shelf life, these obstacles need to be overcome. There are numerous patented methods for minimizing these problems. Existing technologies include the reduction of water activity using solvents or chemical additives such as enzyme stabilizers or inhibitors.9 Liquid detergents can be formulated as structured liquids by using salts and polymers so that the surfactant remains in the structured liquid and enzymes remain Received: December 13, 2013 Revised: January 31, 2014 Published: February 11, 2014 1939
dx.doi.org/10.1021/la4047897 | Langmuir 2014, 30, 1939−1948
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separate in the aqueous phase.11 Disadvantages of using chemical additives to stabilize the enzymes are cost and their extra volume in the final product.9 Enzymes are a small volume fraction of the detergent (
