SAFETY GUIDELINES FOR HANDLING ENZYMES
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The enzymes suggested for work in this booklet are safe to use, provided they are handled appropriately. While all the enzymes are food-grade products, items made with them should not be consumed. There are two reasons for this. Firstly, the proportions of enzyme products used in the activities suggested here are far greater than are normally used in the food industry. This is so that investigations can be conducted within the time of a normal practical session. Secondly, the enzymes have not been handled aseptically, so they (and the products made using them) may have been contaminated.
Please note: This is general advice from the NCBE for the use of enzymes in school investigations. It is not intended as a guide to industrial or research practice.
Safety guidelines for practical work with enzymes in schools
Enzyme activity units
The internationally-recognised unit of enzyme activity is the Katal (abbreviated to kat). It is defined as the enzyme activity which transforms 1 mole of substrate per second under optimal conditions.
In practice, few enzyme suppliers use the Katal, preferring instead units that reflect the preferences of their typical customers. For example, bakers are familiar with amylase activity expressed in 'SKB units', whereas brewers traditionally refer to amylase activity (which they call diastatic activity) in 'Degrees Lintner'. To obtain these various measures of enzyme activity, different assay methods have been used, and unfortunately there is no means of comparing dissimilar tests without conducting further practical work.
Planning your own enzyme tests
A solution to this problem is to develop your own tests. This is not as difficult or time-consuming as it might seem, and will almost certainly save you time (and money) in the long run.
Pushing enzymes to their limits
Sometimes it is not possible to achieve an optimum environment for enzyme activity in the classroom. Perhaps a water bath is not available, or it is difficult to accurately adjust the pH of the substrate. However, enzymes can and do operate under non-ideal conditions, and it may be useful to bear the following points in mind:
Sometimes lowering the temperature will broaden the effective pH range of an enzyme. e.g., Novozymes Lactozym will hydrolyse the lactose in acidic whey from home made soft cheese, at room temperature, even though the enzyme's optimum pH is around 7.0.
Consider high temperature/rapid processing. The Q1O rule states that for every 10 °C rise in temperature, the enzyme will react twice as fast. Of course, this is only true up to a point i.e., until the enzyme is denatured, but substantial catalysis can still be achieved in a short time if lesson timing demands it e.g., washing powder proteases can clear particular types of photographic film in just five minutes at 65 °C.
Increase the substrate concentration. High levels of substrates tend to stabilise enzymes, even under non-ideal conditions. The enzyme optimum and stability curves on Novozymes data sheets are often obtained from reactions where the substrate concentration is 10% w/w or less. If you use substantially greater levels of substrate, you may be able to raise the temperature or reduce the enzyme dose. Note: Some enzymes, such as invertase, are inhibited by high substrate concentrations.
This advice on using enzymes in schools, by Dean Madden, first appeared in the NCBE Newsletter in Summer 1991.
SPECIAL ENZYME PACK
The NCBE supplies the individual enzymes required for the practical work described in this booklet. The Centre also sells, at a substantial discount, a pack containing all of the enzymes (five types in total) together with a printed copy of 'In a jam and out of juice'.
For further information, please see the 'MATERIALS' section of the NCBE Web site.