Lignin degradation by co-cultured fungi: current status and future perspectives

The lignocellulosic biomass is a highly abundant and renewable resource. However, its exploitation is limited by the recalcitrance of the lignin present in the plant cellwall. In the last three decades, fungal co-cultures have increasingly been applied to overcome lignin recalcitrance by enhancing the production of ligninolytic enzymes through microbial interactions. In this paper, we systematically compile studies on fungal co-cultures used in the degradation of lignin-containing substrates to clarify the advantages and limitations of this type of culture. Based on their different delignification rate potentials, co-cultures can be classified into synergistic, antagonistic, and neutral. Co-cultivation results are generally related to the balance or imbalance of antagonistic and synergistic effects arising from the specific compatibility between the species during the interaction. It is well known that the paired species and the microenvironmental system conditions are responsible for the reported degradations,however, the mechanisms underlying these interactions remain poorly understood. In conclusion, literature results demonstrate the promising application of fungalco-cultures in biotechnological sectors to improve the degradation of lignin and its derivatives, through their better understanding of the efficient exploitation ofbiological resources on ecological and industrial scales.