What are the limitations of peroxide use in mushroom growing?

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Enzymes in raw sawdust will destroy peroxide in short order. Therefore, something has to be done to eliminate these enzymes before peroxide can be usefully added to sawdust. With current technology, this means pressure sterilizing. However, wood pellet fuel, paper fiber pellets (e.g. Crown™ Animal Bedding or Good Mews™ cat litter, etc.), and some kinds of kiln-dried sawdust can accept peroxide without pressure sterilizing, baking, or prolonged steaming. Wood pellet fuel is sawdust that has been made into hard dry pellets that can be burned in special pellet stoves.The heat and pressure used to create such pellets destroys the peroxide-decomposing enzymes. Clean newsprint, cardboard, and paper pulp can also accept peroxide as can the woody material in composite logs, and probably also the sawdust derived from milling of kiln-dried lumber. Finally, a number of "drainable" materials can be prepared readily with peroxide despite the enzymes. These materials include straw and similar plant remains, seed and nut hulls, and wood chips (see Volume II of the manual for details).

Because of their enzyme content, most soft-textured raw nitrogen supplements (such as bran, cornmeal, cottonseed meal, etc.) still need to be baked or pressure sterilized before adding them to peroxide-treated bulk substrate. However, certain processed supplements, which lack the peroxide-decomposing enzymes found in traditional supplements, do not have to be baked or pressure sterilized (see Volume I of the manual for details). Instead, they can be mixed with the substrate and treated with it. Also, my recent research has shown that steel cut oats can be used without sterilization despite their enzyme content, to enrich substrate for oyster mushrooms following the "Add-and-stir" procedure in Volume II of the peroxide manual.

In some circumstances, using the peroxide method prevents use of commercial spawn. For mushroom mycelium to grow in the presence of peroxide, it must be adapted to peroxide at a low concentration, usually by incubation of a sample of mycelium on peroxide-treated nutrient agar for a period of roughly two weeks. Without this adaptation process, peroxide will strongly inhibit or even kill mycelium at the concentrations used to prepared bulk substrate. But when properly adapted, the mycelium grows freely in peroxide-treated bulk substrate. Spawn sold commercially has generally not been adapted to peroxide, so it will normally fail to thrive when inoculated into peroxide-treated substrate. There are, however, certain exceptions to this rule. For instance, those materials which contain active peroxide-decomposing enzymes, such as straw and similar drainable "raw" substrates, can be pasteurized with a peroxide soak and then inoculated with commercial spawn. In these substrates, the peroxide will disappear by decomposition sometime after the grower drains off the soaking solution, allowing growth of the non-adapted mycelium in the peroxide-treated substrate..

If you want to germinate mushroom spores, it is best to start them first on non-peroxide medium and then transfer the mycelium to peroxide agar. Procedures for doing this are now included in Volume II of the peroxide manual.

There are two drawbacks of peroxide for liquid culture. One is that blenderized mycelium has to be used to inoculate liquid cultures. Blenderizing releases peroxide-decomposing enzymes previously encapsulated in the mycelial cells, causing peroxide to decompose in the medium. The other drawback is that, assuming one could overcome the first problem, the peroxide concentration will steadily fall as mushroom tissue circulates through the medium during the course of ordinary growth, decomposing peroxide as it goes.

The procedures described in Volume I of the peroxide manual are scaled to hobby use, and some may prove awkward to use on larger scales, or they may not work at all at those scales. Nevertheless, for growers interested in the commercial applications of the peroxide method, Volume II of the manual contains substrate-preparation procedures designed for any scale of use.

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    This document is Copyright: ©2000 by Randall R. Wayne, Ph.D. All commercial rights are reserved. No part of this work may be reproduced or used for sale in any form or by any means without permission of the author.