## 1 Introduction
This degradation occurs extracellularly through enzymes such as lactose, versatile peroxidase and manganese peroxidase (MnP) for ligninolytic fungi and intracellularly [13] or by the cytochrome P450 intracellular enzyme system [14]. In both cases, more polar substances are obtained because of the degradation of these toxic compounds. The use of filamentous fungi in this procedure is essential due to the fact that the networks formed by hyphae and mycelium favor soil colonization and the establishment of a synergic relation between fungi and bacteria [15; 16]. The great disadvantage of this technique is the time it takes for the degradation of the contaminants, which is greater when compared to the physico-chemical techniques mentioned above. In addition, it must be considered that the colonization of the fungus could be limited or impaired due to the interaction with the microbial population of the soil or even by high concentrations of contaminants [17]. Currently, mushroom cultivation is carried out worldwide. After mushroom production, the substrate plus the cultivated mycelium generates the spent mushroom substrate (SMS) waste. Every 1 kg of fresh mushroom generates between 2.5 and 5 kg of fresh SMS [18]. The disposal of these residues is an environmental problem, being the most frequent those from the crop of _Agaricus bisporus_ and _Pleurotus_ spp. [19]. Some alternatives to disposal are described or implemented, for example: [20] amendment and fertilizer for agricultural soils, plant biostimulant, as animal feed or in aquaculture, in pest and disease management, as energy feedstock (alternative fuel, production of biogas), in vermiculture or as a component of casing material or ingredient of new growth substrates for further mushroom growing cycles [18; 20; 21; 22]. All these possibilities promote the circular economy concept and are in line with the Green Deal of the European Union in contrast to the traditional disposal of SMS [19]. SMS wastes are based on lignocellulosic materials [23]and contain viable mycelium and specific microbiota able to colonize polluted soils and degrade a wide variety of soil contaminants [24; 25; 26]. The re-use of SMSs in environmental remediation is a promising way to covert this agricultural waste into a sustainable bioreactor promoting the green development of the global mushroom industry [20]. Different SMSs were used to adsorb organic and inorganic contaminants or to degrade organic contaminants from water [21; 23; 27]. The compost SMS is an effective adsorbent to minimize the availability of metals in soil and enhanced the phytoremediation of mining soil [28], reduced the leaching of pesticides from soil [29] and minimized the impact of herbicides in soil microbial community [30]. The ability of SMS to remove a wide variety of organic contaminants from soils was reported in different publications [20; 25; 31]. Hence, we hypothesize that the use of SMS to remediate polluted soils with petroleum hydrocarbons is a valuable strategy to re-use this agricultural waste. The main objective of this work is to assess the capability of four SMS, _Pleurotus ergvili_ (king mushroom), _Lentinula edodes_ (shiitake), _Pleurotus ostreatus_ (oyster mushroom) and _Agaricus bisporus_ (champignon) to enhance biodegradation of petroleum hydrocarbons from a soil highly contaminated with crude oil.