Fungi can replace chemical pretreatment of wood

Fungi can make chemical treatment of wood for the production of second-generation biofuels unnecessary. The same fungi are also converting indigestible rice straw into tasty animal feed. This was discovered by researchers of Plant Research International.

Rice straw samples have been inoculated with various types of fungi. After colonisation the digestibility of the rice straw is tested.
Rice straw samples have been inoculated with various types of fungi. After colonisation the digestibility of the rice straw is tested.

Waste flows and woody plants can easily be upgraded into second-generation biofuels, fine chemicals, or animal feed. The plant waste flows are then first subjected to chemical pre-treatment before enzymatic decomposition of the cellulose and hemicellulose. The released sugars are then fermented into bioethanol or are converted into fine chemicals.

Chemical pretreatment is necessary because plants contain lignin. Degradability of lignin is very poor and the substance is protecting cellulose and hemicellulose. Disadvantage is that chemical pretreatment is costly because the chemicals need to be removed in a follow-up step. Another problem is the frequent formation of byproducts inhibiting a next step in the production process.

Biological pretreatment

Pretreatment can also be carried out in a biological, natural way. A special group of fungi, basidiomycetes, is continually decomposing lignin in the wild, thus improving the availability of cellulose and hemicellulose. In a next step they are using enzymes to convert this cellulose and hemicellulose into sugars. The fungi use these sugars for mycelium growth but in particular for the rapid production of mushrooms as soon as conditions are right.

The fact that fungi can indeed be used in manufacturing processes was discovered by our scientists together with scientists of the Animal Science Group of Wageningen UR when studying rice straw, a material poorly digested by cattle. A pilot study with rumen flora showed an improved digestibility of rice straw after treatment with the oyster mushroom fungus. The capability to decompose cellulose and hemicellulose of the rumen flora is strongly improved after the preliminary work of the oyster mushroom fungus.

The scientists wish to take another step. They are attempting to isolate genes that are decomposing the plant cell wall for insertion into production crops for biofuels. The idea is that these genes are ‘triggered’ after harvest resulting in the crop already being pretreated immediately after harvest, even before it enters the factory.

To

  • Project Upgrading poorly digestible feed and organic waste with fungi