Enzymatic pre-treatment of lignocellulosic biomass for biogas production – review

Currently, due to global concerns regarding energy security and its environmental consequences, biomass has been promoted as an important resource for reducing greenhouse gas emissions through its conversion into biofuels. The main limitation in the use of lignocellulosic substrate for biofuel production is its resistant structure. Pre-treatment is a necessary step to overcome the lignocellulosic biomass rigid structure and to improve its biodegradability for energetic conversion (biomethane, biohydrogen, bioethanol, etc.). Lately, a number of pre-treatment methods have been studied and applied, such as physical, thermal, chemical and biological pre-treatment which can be used individually or in combination. Compared to physical and chemical pre-treatment techniques, biological pre-treatment usually requires much lower energy consumption and does not involve the use of chemicals, which presents economic advantages and a minimal impact on the environment. The anaerobic digestion process has proven to be an effective technology for converting organic substrate into energy in the form of biogas. Including a pre-treatment technique in anaerobic digestion processes increases lignocellulosic biomass digestibility and improves the biogas yield. The aim of this review is to give an overview on the enzymatic pre-treatment applied to lignocellulosic biomass substrate used for biogas production. There are presented different types of enzymes, namely cellulose, lipase, amylase, protease, and ligninolytic enzymes which are responsible for the degradation of lignocellulosic substrate. The article includes information related to the structure of lignocellulosic biomass, the advantages of biological pre-treatment, as well as the current state of research in the direction of enzymatic treatment to enhance the anaerobic digestion process.