Field of Science


Part of my course this year involves writing a Long Essay (3000 words, not really that long, but longer than most of the other ones we write). We had a choice of three, and luckily one was about bacteria, so I sort of jumped on it.

"To what extent could microbes be used as "biorefineries" that is, in biological processes for producing chemicals, fuels and polymers?"

I've been writing it for a while now, so I've come to know quite a bit about potential biorefineries and how they could work. The basic principle is that you get bacteria that you've engineered in various ways to produce a range of exciting chemicals, stick them in a fermentor, remove the chemicals at the end and sell them.

They're basically meant to work a bit like oil refineries, except using microbes and easily accessible raw materials rather than chemical processes and oil. Currently the most exciting idea at the moment is to use lignocellulose materials, that is all the bits of plants that don't get eaten (corn husks, rice stalks, bits of tree etc) in order to produce ethanol, to be used for fuel.

The closest thing that exists to biorefineries at the moment are the big ethanol refineries in the USA and Brazil. These produce ethanol from sugary substrates, sugar cane lees and maize at the moment. The major disadvantage of these is that they compete with available food stuffs, which is why there is presently the emphasis on using non-edible materials.

Lignocellulose contains two main chemicals; lignin and cellulose (biologists are not that imaginative sometimes). Lignin can't really be broken down by bacteria as yet, although there are some fungi that will do it. Cellulose can be, but needs specialist enzymes. To remove the lignin, and start breaking down the cellulose, some pretreatment is needed, mostly acids and steam.

The ideal microbe to use therefore, would be one that can break down cellulose and withstand the at least a certain degree of pretreatment, in order to reduce the cost of cooling and neutralising everything. The best one so far is Clostridium thermocellum which works best at 60 degrees C and has very efficient cellulose-digesting enzymes all held together in a complex, the cellulosome.

But when you look for current research on C. thermocellum, the very first thing that hits you is that, well, there isn't very much of it. In fact, there's hardly any of it, especially not heavy-duty 'what would this be like in a biorefinery situation' research. There's a couple of token papers about various aspects of it, and then just nothing. A spookily large amount of nothing.

There is, of course, a standard reason for this (and it doesn't involve conspiracy theories). The people who want to potentially build a biorefinery will want to make money out of it. They want to market the technology, or build a biorefinery with their own special bacteria, not tell every other competitor out there what they're doing.

From the point of view of an economist or a businessman it's a perfectly sensible thing to do. From the point of view of a researcher it's all slightly frustrating because it meant that there's a high probability that several people are all doing exactly the same experiments, and not telling each other. *sigh*

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