Scientists Engineer E.Coli to Produce Key Precursor of Spandex

Scientists Engineer E.Coli to Produce Key Precursor of Spandex

The Future: Bacteria Produced Hot Pants?

Scientists from the company Genomica have genetically engineered E.Coli to produce 1,4-Butanediol (BDO), a key chemical in the production of Spandex, clothing of choice for superheroes, glam rockers and 80’s disco enthusiasts.

The work, published in the journal Nature Chemical Biology, has the potential to drastically change the way BDO is produced. Currently one million metric tons are produced per year and all of this is derived from oil and natural gas. Almost half of the BDO produced globally is dehydrated to produce Tetrahydrofuran. This can then be polymerised to polytetramethylene oxide, the primary use of which is in fibres such as spandex.

The researchers faced several challenges whilst trying to produce their engineered bacteria. The first of which being identifying a synthesis mechanism, as there is no known naturally occurring biological synthesis pathway for BDO. Instead they had to compute all potential pathways from the typical E. coli metabolites to BDO. The computer algorithm they used  identified over 10,000 four-six step pathways that could result in synthesis of BDO from common metabolites, including acetyl-CoA, succinyl-CoA and glutamate.

These methods were then narrowed down based on theoretical yield, pathway length and thermodynamic feasibility. After this they picked out the following pathway as the best way for E.Coli to produce BDO:

The BDO synthesis pathway. Each number indicates an enzyme: (1) 2-oxoglutarate decarboxylase; (2) succinyl-CoA synthetase; (3) CoA-dependent succinate semialdehyde dehydrogenase; (4) 4-hydroxybutyrate dehydrogenase; (5) 4-hydroxybutyryl-CoA transferase; (6) 4-hydroxybutyryl-CoA reductase; (7) alcohol dehydrogenase. Steps 2 and 7 occur naturally in E. coli, whereas the others are encoded by heterologous genes introduced in this work.

With an elucidated pathway, then came the challenge of how to get a bacterium to carry it out. Not all the enzymes required for the pathway are present in the wildtype E.Coli. As a result of this, the group identified several different mechanisms for generating the intermediate 4-Hydroxybulymate (4HB) settling on; the addition of three genes sucCD (E. coli), sucD and 4hbd (P. gingivalis).

The final stage in the process, 4HB to BDO, also required some manipulation. The change requires two reduction steps, catalyzed by dehydrogenases. This can occur by the addition of exogenous 4HB to wild-type Clostridium acetobutylicum. However, for efficient production they needed to have the process contained within E.Coli. So instead  they expressed the 4-hydroxybutyryl-CoA transferase (cat2) gene from P. gingivalis for the conversion of 4HB to 4HB-CoA. The final stages then involved the action of  4-hydroxybutyryl-CoA reductase and the native alcohol dehydrogenase, finally resulting in a viable BDO product.

Whilst this discovery does not directly result in the production of spandex or other useful fibres by bacteria. This could prove to be an efficient and environmentally friendly way to produce crime-fighting and disco outfits at some point in the future!

ScIPhone: Science in the world of Apps

ScIPhone: Science in the world of Apps

Science is everywhere, nowhere more so that the smartphone arena. But along with the high-tech that makes up the devices, science has also invaded the App market. Whether it be the, pseudoscientific apps which tell you when you are going to die or apps for peer-reviewed research. In this post I will review some of the science Apps that are out there:

NEJM Image Challenge (download here)

It is an interesting App idea, showing pictures medical conditions and then quizzing you on what it could be. It made me feel a little bit like I was House and I can see the app being useful for med students (I was rubbish at it!). However, there was one slight draw back to the app, when you are on the tube you don’t particularly want a big photo of deformed or diseased genitalia appearing on your phone…it tends to make people look at you like you are a crazy person!

Pros: Scientifically accurate and informative

Cons: Very difficult without a trained medical background, costs money, awkward commuting experiences.

Physics Box

This is an App claiming to contain a series of physics games. In one game “Ragdoll Shooter” you fire manikins at a target and the other you fire bombs. The physics claim is only due to them using a physics engine to power the dolls movements. The ragdoll game is quite fun, but there is really no difference between it and the bomb game.

Pros: Quite fun, free

Cons: No actual science, no variation in Game play

Merk – PSE HD (download here)

This is a periodic table app made by Merk pharmaceuticals. It looks very nice and polished and by clicking on the elements it contains lots more information about them.

Pros: Very informative, scientifically accurate.

Cons: Doesn’t do anything extraordinary with the app format

Genetic Code (download here)

Now this may be quite a geeky admission but I think this is a very cool little app. It let’s you enter three DNA bases and it will tell you what it codes for. I imagine this would be pretty useful for researchers.

Pros: Free, science geek novelty factor, could be useful for actual research.

Cons: Little practical use for most people.

So there we have a quick sample I am aware that there are many more science apps out there. If you have any good suggestions for apps to be reviewed drop me a comment below. This potentially may become a regular feature.

Beer Bottle Full or Empty: Which is Best as a Weapon?

Beer Bottle Full or Empty: Which is Best as a Weapon?

It’s a question that I am sure many of you have asked yourself. If that angry looking person over there decided to hit me over the head with a bottle, would it be better if it were finished or full? Well thankfully a research paper has the answer and contains my ‘Research Quote of the Week’!

“Fights are commonly carried out with fists, feet, furniture and drinking vessels”

So, why would you want to research this? Well, Dr Bolliger and his Switzerland based team wanted to see “if the amount of energy exceeds the energy necessary to inflict serious injuries to a victim”, with the goal of aiding forensic science.

Figure 1: The 'Weapon of Choice'

Now, its difficult enough making a choice what to drink when in your local pub, let alone to think about its potential use for research/weaponry. The researchers selected Feldschösschen in half litre bottles, the reasons for this choice were not made clear in the article (Figure 1). It was a small study, with 10 bottles used (4 full and 6 empty).

The strength of the bottles was then tested using a drop-tower (apparatus in which weights are dropped onto materials to test their properties. The bottles were place on their sides and had a wooden board attached to them (to cause a more dispersed impact similar to what the cranium would experience) and soft clay used to represent the brain soft tissue (As seen in Figure 2). A 1 kg heavy steel ball was dropped from different heights (minimum 2 m, maximum 4 m) onto the bottles.

They observed that full beer bottles tolerated energies of up to 25 J, but burst at 30 J. Whereas, empty shattered at 40J. Again, it is worth pointing out that this is a small study. But, the results are interesting ( especially for those with alcohol induced anger issues) as it indicates that the bottles make a much more suitable “club” than the traditional UK pint glass (shatters at 1.7 J). But, why does this difference occur, and which bottle would hurt more to get hit by!?

There are two main theories as to why the difference occurs:

  1. Beer is an almost “incompressible fluid” and even a slight deformation could lead to an increase of the pressure within the bottle and its destruction.
  2. As beer is carbonated. The gas pressure, and may assist in the destruction of the bottle.

Figure 2: The bottle in position

And the ouch factor? Well, as the study looked at impacts on the bottle and not made by the bottle as little mathematical recalculation is required to calculate the amount of work needed to swing the bottle and its imapact force. The researchers conclude the following:

“full bottle will strike a target with almost 70% more energy than an empty bottle. In other words, it takes less muscle work to achieve a greater striking energy when fighting with a full bottle, even though lifting the bottle requires slightly more energy.”

In terms of damage to the skull electrohydraulic experiments using human cadaver heads had previously shown that the skull is fractured by 14.1 – 68.5 J depending on the area hit. Implying, that both full and empty bottles could fracture areas of the skull.

So, there we have it. If you are a bit weak and want to cause harm an enemy with a beer bottle, either will do the job. But, choose a full bottle for that extra force in your hit.

ResearchBlogging.org

Bolliger, S., Ross, S., Oesterhelweg, L., Thali, M., & Kneubuehl, B. (2009). Are full or empty beer bottles sturdier and does their fracture-threshold suffice to break the human skull? Journal of Forensic and Legal Medicine, 16 (3), 138-142 DOI: 10.1016/j.jflm.2008.07.013

Science’s Search For Secret Of Heat Resistant Chocolate

Science’s Search For Secret Of Heat Resistant Chocolate

Why God!? Why!?

Science, it seeks to solve some of the biggest problems facing humanity. It tries to understand the nature of life, cure cancer and save the planet. However, now it seems to be dealing with THE big issue facing society, increasing the melting point of chocolate!

We’ve all been there, you hold a toffee crisp (or whatever happens to be your weapon of choice) for too long and you are left with horrible chocolatey sticky fingers. Well never fear, wipe away those tears…and the melted chocolate…because science is working on it! A new paper from the University of  Guelph, Canada, has reviewed many potential techniques for increasing the melting point of chocolate and have outlined 3 concepts:

  • Enhancing the microstructure of the materials
  • Addition of a polymer
  • Increasing the melting point of the fat phase.

But, how would you go about doing each…

Microstructure Enhancement

Photograph and full spectrum autofluorescence micrograph of chocolate confection showing (A) cream filling, (B) milk chocolate coating, (C) white chocolate coating.

One technique mentioned to do this was to add water. However, it’s not quite as simple as it sounds. There are several suggested complicated ways of incorporating the water. You could add it directly with the ‘Lataner’ technique  (4-20% water) ensuring that all the sugar is disolved. This will produce chocolate that “is said to be able to withstand any climatic conditions found in any part of the world”. However, it is also highly viscosous making it difficult to mould and not commercially viable.

The ‘Russell and Zenlea’  method is more complicated still, involving warm water addition with the chocolate being “stirred continuously in a steam jacketed mixer until a homogenous”. This produces chocolate that can withstand up to approximately 49 °C.

There are several other ways to directly add water to chocolate. However, they all have two major drawback, a susceptibiltiy to sugar bloom (what you see when the chocolate gets a weird white gray coat) and a reduction in the quality of the chocolate.

You can also add water indirectly. Frieman in 1921 as well as Kempf & Downey both produced high melting-point chocolate (HMC) this way. However, “chocolate likely had a high viscosity, poor texture and an unfinished flavor”. Other methods of water inclusion involved the use of water/fat emulsion. These prototypes produces chocolate able to withstand sufficient temperatures. But, there was a lack of taste testing of the products.

So, whilst overall these methods were are able to increase the melting point the quality was sacrificed. Clearly not an ideal situation.

Oil/fat binding polymer

This method of altering chocolate really came into its own in 2006 when Ogunwolu and Jayeola looked at adding cornstarch or gelatin. They were added at levels of 2.5, 5.0, 7.5, or 10.0% to other chocolate ingredients at the grinding and mixing stage. They then looked at the melting points and found that both caused it to increase (Figure 1)

Figure 1: Melting points of chocolate with addition of cornstarch or gelatin

These forms of chocolate also, like the previously mentioned methods, had their drawbacks. Sensory evaluation showed that 10% cornstarch chocolate whilst not significantly different than conventional milk chocolate in colour, taste and  smoothness, there was a significant decrease in sweetness of the product (ρ < 0.05). 10% gelatin chocolate was observed to not be significantly different in colour and sweetness, although did have significantly poorer taste and decreased smoothness when compared to conventional milk chocolate.

Not only are there taste issues with the products some countries do not permit any amount of oat flour, cornstarch or gelatin to be present in chocolate, limiting the potential applications of these methods.

High fat melting point addition

Several different high melting point fats have been tested as a component of chocolate. Two that have had the most research conducted into them are mahua (Madhuca latifolia) and kokum (Garcinia indica). These are both found in trees in India. The blending of these fats fats, was observed to improve the solidification and melting characteristics of the product. However, there would need to be a compromise reached between heat resistance and taste. A sensory evaluation found that 5% kokum chocolate was not significantly worse than normal chocolate, although this low level of the fat only raises the melting point to 34.8 °C. Also, there was no data for the taste of kokum chocolate at greater than 5%.

Heat resistant chocolate has been an idea that people have tried to perfect for a long time. During WW2 the American Military tried to make a Hershey Field Ration “D” with oat flower. As the above research shows it is possible to make heat resistant chocolate. However, the products currently are neither simple, inexpensive nor of sufficient quality compared to regular chocolate. So, nice try science…but you’ve still got a way to go!

ResearchBlogging.org

Terri A. Stortz & Alejandro G. Marangoni (2011). Heat resistant chocolate Trends in Food Science & Technology : 10.1016/j.tifs.2011.02.001

Maheshwari, B., & Yella Reddy, S. (2005). Application of kokum (Garcinia indica) fat as cocoa butter improver in chocolate Journal of the Science of Food and Agriculture, 85 (1), 135-140 DOI: 10.1002/jsfa.1967

Ogunwolu, S., & Jayeola, C. (2006). Development of non-conventional thermo-resistant chocolate for the tropics British Food Journal, 108 (6), 451-455 DOI: 10.1108/00070700610668423

Body for sale: How much are your chemical components worth?

Body for sale: How much are your chemical components worth?


Are we made of money?

You always hear stories about students selling their bodies to finance their studies. But, how much could you make from the raw materials that makes up your body? This was an idea that came to me the other day and I decided I had to find out just how much we are worth in raw chemical elements!

To work this out I first needed to find out what the make-up of my body is. Unsurpringly, the internet already had this data assembled for me. The average human is made up of 54 different elements, ranging from carbon (the most prevalent) to radium (the least prevalent). Then find the cost for the pure element, this was done with a variety of sites (but mainly chemicool.com). All the following calculations and data are relevant for an adult of approximately 70Kg, the data offers no distinction between men and women. But, due to the natural differences in body tissue composition it is likely that there will be some variation. Here are the 15 most abundant elements in the body and their real world cost values:

Element Mass in body (kg) Value per kg ($) Total value ($)
Oxygen 43 3 129
Carbon 16 24 384
Hydrogen 7 100 700
Nitrogen 1.8 4 7.2
Calcium 1.0 200 200
Phosphorus 0.780 300 234
Potassium 0.140 1000 140
Sulphur 0.140 500 70
Sodium 0.100 250 25
Chlorine 0.095 1.5 0.14
Magnesium 0.019 37 0.7
Iron 0.0042 72 0.3

This comes up to the total of $1890.34. But, what about the remaining 39 elements? The body contains a remarkable range of elements from gold to uranium. However, with their quantities so low it only works out as only $95.41.

Giving the grand total cost of the human body as $1985.77.

According to current conversion rates is about £1224.72. What could you buy for this though? Well, you could get a lower end Macbook Pro, 2722 Mars bars or you and 7 friends could all chip in to buy the latest Fiat 500…I know which I would pick!

To check out all the calculations you can download my excel workings from here