Combination of fungal and physicochemical processes for lignocellulosic biomass pretreatment – A review

Biofuel production from lignocellulose has recently been gaining much more attention as a result. One major problem of using lignocellulosic materials for the production of biofuel is the low accessibility of cellulose to enzymes and microorganisms. Therefore, pretreatment of lignocellulose is a critical step in biofuel production from such materials. Of the pretreatments, fungal treatment has become an important process due to its low energy demands and selective degradation of lignin and hemicellulose. This capability comes from the unique enzymatic systems, cellulolytic and ligninolytic enzymes, especially in white rot fungi. The low energy demand of fungal pretreatment has generated interest in studying the applicability of fungal pretreatment for biofuel production from woody materials. The most significant drawback of fungal pretreatment is the lengthy time required for the process. Combining fungal pretreatment with other pretreatment methods might reduce the time necessary for the whole process to operate. It can also introduce cost-effectiveness. Thus combining fungal pretreatment with other physical and chemical methods has been recently contemplated. This paper provides a comprehensive review of current fungal pretreatments and feasibility for biofuel production, with a focus on combining fungal pretreatment with other methods. The advantages and disadvantages of all physical and chemical methods were also briefly reviewed. The applicability of the combination of fungal with other pretreatment methods has been considered in a number of recent publications. To be commercially attractive, both energy demand and processing time should be reduced. In terms of energy demand reduction, combined fungal physico-chemical pretreatment has been effective. However, the lengthy time taken for the whole process has not been significantly improved upon. A great deal of work is still required to be done regarding time reduction for the process (combined fungal-physico chemical pretreatment). Therefore, it seems to remain an open field for research and process development.