快猫短视频

BLUE-green bugs could help save forests by replacing wood as a source of
paper. Researchers have shown for the first time that the photosynthetic
cyanobacteria can make cellulose.

Paper and cotton consist mainly of cellulose, a polymer made of strings of
glucose molecules that reinforces the cell walls of plants. But wood isn鈥檛 an
ideal source of cellulose because it contains impurities such as lignin, which
have to be removed. And while cotton is a purer source, it also contains
impurities that are expensive to remove.

So Malcolm Brown and David Nobles at the University of Texas in Austin have
been trying to produce cellulose for paper and textiles using bacteria
(快猫短视频, 12 October 1996, p 22).
They can already extract pure cellulose from sugar-eating bugs, but a company
Brown worked with failed to make the process commercially viable.

Now the researchers have produced what they say is the first conclusive proof
that at least nine species of freshwater cyanobacteria, or blue-green algae,
make cellulose. They found genes resembling those that code for cellulose-making
enzymes in plants. And using a cellulose-binding enzyme attached to gold
particles, they showed that some cyanobacteria seem to exude cellulose.

A pond full of specially bred or genetically altered cyanobacteria could
produce far more high-quality cellulose a year than an acre of cotton plants,
Brown thinks. Because the bugs need little besides light and water, Brown says
the process should be viable. He鈥檚 already devised a cheap way to purify
cellulose from bacterial slime using bleach and detergent. 鈥淚t works
beautifully,鈥� he says.

Grant Allen, director of the Pulp and Paper Centre at the University of
Toronto, says a source of pure cellulose would be very attractive. 鈥淲hite paper
is basically cellulose,鈥� he says. But he鈥檚 not so sure whether it will be
economical to process the cellulose into some kind of wood substitute.

He also points out that large ponds will have their own environmental impact,
even if they are more efficient than forests or cotton plantations. 鈥淭o capture
a lot of light, you may have to excavate large tracts of land,鈥� he says.