## 1 Introduction
To our best knowledge, this study represents the first attempt to use _B. adusta_ for bio-delignification of GW destined for biogas production in co-digestion with OFMSW. Bio-delignification is an attractive approach because of its cost-effectiveness, low-energy requirement, low environment impact, and low formation of toxic materials such as furfural, hydroxymethylfurfural, etc., which could negatively affect anaerobic digestion [41]. However, long pretreatment times (from 13 up to 50 days) to obtain high yields of delignification have been reported, limiting the use of these processes in commercial applications [42]. In addition, there could be competition for carbohydrates between pretreatment and downstream biogas production, because certain levels of carbohydrates are required by microbes during biological pretreatment. On the other hand, the accessibility of cellulose is increased after pretreatment, which can improve biogas production [43]. Therefore, one major objective of biological pretreatment is to minimize the loss of carbohydrates and maximize the lignin removal for AD feedstocks with high digestibility [44]. Until now, bio-delignification has followed two main approaches: treatments with fungal lignolytic enzymes as free mixtures or immobilized [31; 32] and submerged or solid-state fermentations with fungal cells [45]. The microbial treatment includes fungi, such as white-rot fungi, brown-rot fungi, and soft-rot fungi, and bacteria. Both brown-rot and soft-rot fungi principally degrade the plant polysaccharides with minimal lignin degradation, while white-rot fungi are capable of complete mineralization of both the lignin and the polysaccharide components [46]. Limited research related to the improvement of biogas yield by using white-rot fungi has been done, even though data regarding the bio-delignification and hydrolysis yields are available that are vital parameters for biogas production [47]. Previous experiments of fungal pretreatments of woody and herbaceous feedstocks have been performed using a variety of white-rot fungal strains, and several studies have been carried out on different biomass, such as _Polyporus brumalis_ on wheat straw [48], _Trametes versicolor_ on corn silage [49], _Ceriporiopsis subvermispora_ on yard trimmings [50], _Pleurotus eryngii_ on corn stover [51], and _Trichoderma reesei_ on rice straw [52], reporting sugar yields between 25 and 70% with 20-52% lignin degradation. In fact, white-rot fungi are the most abundant degraders of wood in nature. Under optimal conditions, the rates at which they mineralize lignin is exploitable for industrial applications [53]. Their strategy is to decompose the lignin in wood so that they can gain access to the digestible polysaccharides (cellulose and hemicellulose) embedded in the lignin matrix. Given the chemical recalcitrance of lignin, it is evident that white-rot fungi must employ unusual mechanisms to degrade it, based on the generation of lignin-free radicals that, due to their chemical instability, subsequently undergo a variety of spontaneous cleavage reactions [54]. The white-rot fungi have been found to produce extracellular peroxididases and lacases, which usually appear in response to nutrient depletion [55]. The best characterized white-rot fungus is _Phanerohete chrysosporium_, since the discovery of the lignin peroxidase from this fungus by [PERSON] and [PERSON] [56] and [PERSON] et al. [57]. Recently, some information has become available in the literature on _Bjerkandera adusta_, which is now considered a promising candidate for further studies on bio-delignification, because it can produce a large amount of lignin peroxididases, similar to _P. chrysosporium_, but also manganese peroxidase, versatile peroxidase, and lacase, all highly effective at decomposing lignocellulosic substrates [58; 59].