Naturally, all wood materials and residues contain manganese elements, which are present sometime in high concentration depending upon the type of the wood ma­terials, varying from 10mg/kg to100mg/kg of dry wood. The importance of Mn2+ can clearly be found during the fungal decay on woody materials as it accumulates in the form of MnO2 precipitates. Indeed, the insoluble Mn4+ species deposits at the tip of new fungal hyphae in the early stages of infestation and growth [125]. As men­tioned earlier, Mn2+ stimulates the production of MnP and enhances the degradation of lignin components during oxidation reaction, where Mn3+ is generated by MnP and acts as a mediator for the oxidation of various phenolic compounds. Therefore, addition of Mn2+ increases the biological oxidation rate in biological pretreatment of lignocellulose. On the other hand, addition of Mn2+ inhibits the action of LiPs and its production [98, 125]. Hence, it is very essential to optimize the concentra­tion of Mn2+ in order to achieve better biological pretreatment. Indeed, in decaying wood, naturally a manganese concentration gradient is established, allowing soluble forms of manganese (Mn(I1) and Mn(III)) to diffuse into regions of low manganese concentration [126].