Researchers at the Vienna University of Technology have developed what they say is a new cheap method to produce erythritol from straw with the help of mould fungi. They say that the experiments have been a big success, and now the procedure will be optimised for industry.
Their study is published in AMB Express.
Erythritol has many great advantages, note the researchers: it does not make you fat, it does not cause tooth decay, it has no effect on the blood sugar and, unlike other sweeteners, it does not have a laxative effect. In Asia it is already widely used and it is becoming more and more common in other parts of the world too. Up until now, erythritol could only be produced with the help of special kinds of yeast in highly concentrated molasses. At the TU Vienna, a method has now been developed to produce the sweetener from ordinary straw with the help of a mould fungus.
Straw is often considered to be worthless and is therefore burnt, but it can be a precious resource, the research team said. Some of its chemical components can be made into valuable products. First, the finely chopped straw has to be “opened up”: with the help of solvents, the cell walls are broken, the lignin is dissolved away. The remaining xylan and cellulose are then processed further.
“Usually the straw has to be treated with expensive enzymes to break it down into sugar”, said Professor Robert Mach (Vienna University of Technology). “In highly concentrated molasses, special strains of yeast can then turn the sugar into erythritol, if they are placed under extreme osmotic stress.”
The enzymes opening up the straw can be obtained with the help of the mould fungus Trichoderma reesei. This kind of mould also plays the leading role in the new production process developed at the Vienna University of Technology.
Two big advantages have been achieved by genetically modifying the fungus: the process of obtaining the enzymes from mould cultures and chemically cleaning them used to be cumbersome – now the improved strain can be directly applied to the straw. Secondly, the mould can now produce erythritol directly from the straw. The intermediate step of producing molasses is not necessary any more and no yeast has to be used.
“We knew that the mould fungus Trichoderma reesei is in principle capable of producing erythritol, but usually only in tiny quantities”, said Mach. “By genetically modifying it, we managed to stimulate the production of an enzyme, which enables the large-scale production of the sweetener.”
Erythritol is about 70 to 80 percent as sweet as sugar. Today, 23,000 tons of erythritol are produced every year. This quantity could increase considerably if the trend of switching to erythritol spreads from Asia to Europe and the US, the researchers believe.
The researchers have patented the new production process, and assigned to Austrian company ANNIKKI which creates chemicals from straw.
“We have proven that the new production method works”, said Mach. “Now we want to improve it together with our industry partners so that it can be used for large-scale production.”
