What is Biotechnology? Part II
André van Ham already explained the term biotechnology in first Stahl Explains on Biotechnology and now he explains it further.
Besides genetic engineering, there is another major factor of influence on the success of biotechnology, which contributes to the technology part. This regards pretreatment of substrate, medium optimisation, bioreactor design, and downstream processing.
To explain these terms I would like to make a comparison to a farmer taking care of cattle. The feed for cattle is optimised to the needs of the animals as well as the production of their milk or meat. The feed also needs to be easily accessible and easy to digest. A microbe is no different; it is at its best when the circumstances are optimal for growth. This means that the food (called substrate) must be given so that it is easy to eat, or as we could say: pretreated.
Cattle are not only fed grass and hay, but farmers will give them concentrate as well and most of the time you can also find a mineral lick. The animals need an optimised diet to grow up healthy – with a lot of vitamins, minerals, protein and fat. By not supplying enough food the animals don’t grow up strong and healthy, which will result in less production of milk or meat. Microbes are no different, besides the fact that their diet is differently balanced. The goal of medium optimisation is thus to make the situation ideal for the microbes to grow and produce desired products.
Apart from giving the right substrate, bioreactor design is of importance as one must make sure that the conditions inside the reactor are favourable for microbes. Much like a farmer that ensures a good environment for the animals grow up in. When walking around in a farm, one could spot the stalls filled with sawdust, the occasional cow brush. A shed is never completely closed to allow fresh air for the animals to flow in. When the temperature is cold outside the shed is closed to prevent the animals from freezing and when it is hot outside the shed is open to allow the animals to cool down. Just like cattle, microbes are most happy when it is neither too warm nor too cold. Some microbes also need air, even though the preferred composition of this air can be different to the air we breathe. While some can live on regular air, others need more oxygen. In contrast, others dislike oxygen so much they might die if they come in contact with it: anaerobic microbes. There are more factors that are of importance, but these require a more deep understanding of the topic. The general idea is that all needs to be comfortable for the organism to grow, reproduce and produce. This is done through smart designing of the bioreactor where the microbes are kept.
Downstream processing is the art of removing the desired product from the reactor, and purifying the product to a certain grade. This could be compared to milking the cows and pasteurising the milk. A product is removed from the bioreactor with great care to not contaminate and damage the product. Just as well milk is removed from the cow and stored at a low temperature to prevent bacterial growth. When the product is removed from the bioreactor it is not at 100% purity. There are many different techniques to achieve a certain purity and depending on the application several techniques have to be used. In medical applications for instance, the purity needs to be quite high, while application in leather is less affected by purity. As you can imagine, this can be the most important part. Since there is no application possible in medicine when there are still leftovers from the fermentation such as bacteria or side-products in the end product.
After successful growth and reproduction a healthy population of cows can produce enough meat or milk so that a farmer can cover the expenses and earn some money. In the same way if microbes inside a bioreactor live in a healthy population and produce the desired product in a high enough concentration to cover expenses as well as generate some extra revenue, a company might decide to invest in such a system.
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