Abstract: The apparatus according to the invention is adapted for transcutaneous treatment by gas. The apparatus (10) comprises a rigid-wall cabinet (20) and having an upper opening and at least one openable panel, wherein a seat (25) is arranged inside the cabinet (20), and the cabinet (20) comprises at least one gas concentration measurement unit (29a), and the cabinet (20) further comprises a gas inlet (30) for feeding the treatment gas and a gas outlet (31) for discharging the treatment gas; a gas supply unit (40) coupled to the gas inlet (30) of the cabinet (20) via a pipe (41) and through an interposed controllable valve (42); and a gas tank (50) connected to the gas supply unit (40).

Abstract: A cellulosic starting material, substantially devoid of nitrogen values is moistened to bring its water content to at least 50%, pasteurized by steam treatment during which the temperature is increased to a maximum of about 70.degree. C and maintained at such temperature for about 12 hours during which time a relative humidity of about 100% is likewise maintained whereby the starting material is digested. The material is cooled to about 55.degree. C to proliferate thermophilic metabolite producing microorganisms. This temperature is maintained for about 36 hours and is then lowered to about 40.degree.-45.degree. C and maintained at that level for about 24 hours whereby another group of microorganisms is proliferated. The substrate so produced is cooled to 25.degree. C or less. The process provides the substrate with metabolites that protect it against microorganisms which compete for substrate carbon sources with the macrofungi to be cultivated on the substrate.