Protease on milk agar plate

Trypsin is an active protease.

Many fruits also produce proteases.

Kiwi fruit is a rich source of protease. Like papaya, it can be used as 

a natural meat tenderizer because

protease pre-digests part of the proteins in muscle.

Protease, the enzyme that digests protein, is available from a diversity of sources.

Preparation of milk agar plates.

To do this experiment, one has to mobilise a lot of resources (2007).

Circular " well(s) " are dug on the milk agar plates by the use of cork borer.

Note that the same cork borer must be used throughout 

to ensure a fair comparison of results.

The circular agar blocks can be easily taken off by the use of tooth-pick.

Any enzyme extract could be put into the wells by dropper.

All the milk agar plates are put inside an incubator which is set at about 37 deg C.

How to measure the results ? Discussion. 

ANSWER - THE ACTUAL AREA OF THE CLEAR ZONE !

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Previous results.

In this particular specimen result (of a student),

the inhibitory effect of ethanol on trypsin is not evident.

Quite surprisingly, trypsin, even when mixed wih 90% ethanol, 

could still digest milk casein to yield a circular clear zone. 

This is in contrast to our pre-laboratory testing result which showed that ethanol at above 70% inhibited trypsin. 

When the enzyme was mixed with 90% ethanol, the digestive effect was minimal.

The digestive effect of protease is demonstrated with a variety of sources.

The same photograph of result is digitally processed to reveal different digestive effect of various extracts. Both the size of the clear zone and the degree of clarity of the zone are indicators of casein digestion.

The paper labels show the dilution factor. Is there evidence to suggest that the digestive effect of protease in Kiwi fruit extract is concentration dependent ?

Business as usual, school as normal under the SARS threat in May 2003.

Link to other enzyme experiments