Developments in solid-state fermentation for the production of biomass-degrading enzymes for the bioenergy sector

Solid-state fermentation (SSF) processes have enormous potential for many new applications using the bioconversion of agro-industrial residues into biofuels and other high value-added products. The agricultural sector is currently undergoing global expansion, especially in relation to crops used for energy production as a strategy to reduce dependence on petroleum and mitigate the effects of climate change. Consequently, a similar expansion is expected in the amounts of agricultural and forestry residues generated. The conversion of these lignocellulosic biomasses using enzymes is likely to be a key technology in future biorefineries. However, in order to make the enzymatic conversion of biomass commercially viable, it is necessary to improve the efficiency of (hemi)cellulolytic enzymes production and reduce the costs of the enzymatic cocktails employed. The focus of this review is on recent developments in SSF processes for enzymes production, and the application of such techniques in the bioenergy sector. An overview of the enzymes required for the conversion of biomass, important SSF process variables related to the production of (hemi)cellulolytic enzymes, the bioreactors that have been used for this purpose, and novel SSF configurations is provided. It is hoped that the information gathered together here will assist in the development of SSF processes that enable efficient future production of the enzymes required for the conversion of biomass.