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New method could diversify bioplastics production, lower costs

Bacteria are capable of producing thin, transparent plastic films (polylactic acid (PLA)) and plastics commonly used for medical applications (poly-3-hydroxybutyrate (PHB)).  However, unlike some other bioplastics, coaxing bacteria to make PLA or PHB has traditional required feeding them a diet of sugar (glucose).  Thus this class of non-fossil fuel based plastics raises similar food crop issues to corn ethanol.

But Victor Irorere, a Masters student in biotechnology at the University of Warwick in the United Kingdom, has offered an alternative, showing that the bacteria can be coaxed to process waste oil (think french fries) instead of the traditional glucose carbon source.

Comments Mr. Irorere, "Our bioplastic-producing bacterium, Ralstonia eutropha H16, grew much better in oil over 48 hours and consequently produced three times more PHB than when it was grown in glucose.  Electrospinning experiments, performed in collaboration with researchers from the University of Birmingham, showed that nanofibres of the plastic produced from oils were also less crystalline, which means the plastic is more suited to medical applications."

PLA and PLB are considered promising alternatives to petroleum plastics if costs can be reduced.  One advantage -- aside from improved biocompatibility -- is that the bioplastics are biodegradable, reducing landfill waste.

PLA bioplastic
PLA makes thin films that can be used as plastic wrap or in bags (right).
[Image Source: Google Images]

The study's senior author was Iza Radecka, a senior lecturer in microbiology at U of W.  She comments, "The use of biodegradable plastics such as PHB is encouraged to help reduce environmental contamination. Unfortunately the cost of glucose as a starting material has seriously hampered the commercialization of bioplastics.  Using waste cooking oil is a double benefit for the environment as it enables the production of bioplastics but also reduces environmental contamination caused by disposal of waste oil."

Following a presentation at the Society for General Microbiology's Autumn Conference, the researchers hope to expand their work to commercial-scale tests.

Source: Eurekalert



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Glucose does not mean food crop
By Solandri on 9/3/2012 6:14:40 PM , Rating: 2
quote:
coaxing bacteria to make PLA or PHB has traditional required feeding them a diet of sugar (glucose). Thus this class of non-fossil fuel based plastics raises similar food crop issues to corn ethanol.

I've espoused before the problems with corn ethanol (it's only financially viable because the U.S. subsidizes corn to deliberately overproduce). But people on the anti-corn ethanol bandwagon have taken it too far and started to automatically apply it to any crop-based ethanol.

Plants make sugars via photosynthesis. They take the energy from sunlight, and store it in a string of carbon-hydrogen-oxygen molecules we know as sugars. The primary one is glucose.

Glucose is C6 H12 O6.
Fructose is C6 H12 O6. (slightly different arrangement of atoms)
Sucrose (table sugar) is C12 H22 O11.

Carbohydrates are starches - basically multiple glucose molecules glued together. So essentially carbs are sugars glued together to make a large molecule. Your body uses sucrose and carbs as fuel by splitting them, freeing the basic glucose and fructose.

Notice a pattern? Basically a (C1 H2 O1)n arrangement, give or take one or two H or O.

Cellulose is (C6 H10 O5)n. It's a sugar! Plants take the glucose they form via photosynthesis, and glue it together in different ways. Sometimes they glue it as starches to form meaty parts like potatoes. Sometimes they glue it as cellulose to form wood. (Only the outside of a tree, the part just under the bark, is alive. The wood core is just a sugar reservoir.) That's why wood burns so readily - it contains lots of solar energy locked up in the form of sugar molecules, combined to form wood.

To access the sugar in cellulose just involves breaking it down into its constituent sugars again. Most animals lack the enzymes to do this. Ruminants (most herbivores) get around this by doing a lot of chewing and having four stomachs to physically and chemically break the cellulose down to smaller molecular chains. They and termites then have bacteria which break down the cellulose into shorter sugar chains, which they can then use as food.

So just because the process for making ethanol (aka fermentation) requires sugar does not mean it needs a sugar crop. Certainly it's easier if the plant just stores the energy as plain sugars (sugar cane, sugar beets). But nature has ways to convert raw cellulose back into sugars. We just need to figure out a cost-effective and scalable way to do it. Once we do, all the excess plant matter we currently burn or throw away - wood, parts of plants we don't eat like corn stalks and husks, gardening and landscaping trimmings, even old furniture - can be converted into alcohol for fuel.




By Motoman on 9/4/2012 11:06:02 AM , Rating: 2
We *do* eat corn stalks and husks. After they've been fed to pigs, or plowed back under to fertilize the next crop of corn.

And it doesn't matter greatly whether your ethanol process requires a "food" crop or not...if tillable soil was used to grow a crop for any purpose other than food, then the food cycle is negatively impacted...period.

As for people who go off and say stupid things like "well [x] can be grown in soil that isn't tillable anyway, so nyah Xp !" - well, there's a reason that soil isn't tillable. And if we can't till it, we probably can't cultivate it. So exactly what good does it do to identify a plant that we can neither plant nor cultivate?


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