Review of solid state fermentation for lignocellulolytic enzyme production: challenges for environmental applications

Abstract

Within the context of increasing environmental concern, energy production from lignocellulosic substrates is gaining great interest. Enzymes have proven their efficiency in the degradation of the lignocellulosic complex but their use remains limited in environmental applications such as anaerobic digestion mainly due to their prohibitive cost. Therefore, solid state fermentation (SSF) emerges as an interesting alternative for the in situ production of lignocellulolytic enzymes. Various research efforts on the lab scale optimization of SSF are discussed. They are presented according to the type of inoculum used in the process: bacterial species and fungal species under both mesophilic and thermophilic conditions. In general, parameters that impact the SSF process include: substrate type and particle size, substrate pretreatment, inoculum, nutrient supplementation, moisture content, pH, aeration, temperature and mixing. Using different substrates, authors aim at maximizing enzyme production taking into account one to several of the indicated operational parameters. The reviewed research puts forward the adaptation of the operational parameters, enzyme production cost and loading, enzyme mixture quality and efficiency and finally reactor design as the main challenges for environmental large-scale application.