Strategies using Phytase

You should have come up with at least three different strategies for using phytase. This enzyme is found in the ubiquitous bacterium, Escherichia coli, as well as various fungi including Aspergillus niger. So what are the strategies?

First, you could produce this enzyme and add it to animal feed. A benefit of this strategy is that the animal will also have access to more phosphate for growth and development, thereby contributing to a reduction in phosphorus being eliminated from the animal. This has been done with fungal phytase and you buy it at your local feed store. Unfortunately, phytase is expensive.

• What factors affect enzyme activity?
• What enzyme activity criteria would you need to consider when selecting the source of the enzyme to add to animal feed?
• Why isn't it necessary to add phytase to the food of ruminant livestock?

Second, you could modify the grains fed to these animals. Phytase does exist in soybeans, but it is not synthesized until the seed germinates. If the enzyme is already in the seed, this would not only make more phosphorus available to the animal, but also free up other minerals and proteins that the animal needs. This would save the farmer some extra money. At Virginia Tech there is research being conducted on the effects of feeding animals soybeans that have a fungal phytase gene in the soybean genome. The result is that the phosphate is already in a soluble form while the animal is digesting the food. Chickens fed the transgenic soybeans grew larger, had more bone growth, and eliminated less phosphorus that chickens that were fed unaltered soybeans.

The third way would be to alter the animal so that as it eats its food, the enzyme can break down the insoluble phosphate. Researchers at the University of Guelph have produced an "Enviropig." This pig has the bacterial gene incorporated into its body and the salvia produced during eating contains the phytase enzyme. Animals with this gene had 20 to 50% less phosphorous in their manure.

• Of the three strategies to reduce phosphorous pollution, which one do you think would be the most useful? Defend your answer.