Biological Pretreatment with White Rot Fungi and Their Co-Culture to Overcome Lignocellulosic Recalcitrance for Improved Enzymatic Digestion

Abstract

Three white rot fungi (Lenzites betulinus, Trametes orientalis, and Trametes velutina) as well as their respective paired cultures were used to pretreat Populus tomentosa for enhanced lignocellulosic degradation and enzymatic hydrolysis. Hemicellulose and cellulose were slightly degraded, while a maximum lignin degradation of 58% was caused by T. velutina during the 12-week cultivation. After the pretreated samples were subjected to enzymatic hydrolysis for 96 h, the reducing sugar released by T. orientalis at week 12 was as high as 41%, which was in line with the lignin loss at 2.2 times the control sample. Overall, the monocultures of white-rot fungi exhibited better degradation and saccharification of woody biomass than their co-culture. This can be attributed to the partial removal of lignin and hemicellulose, with an associated increase of cellulose accessibility to enzymes.

Techno-Economic Bottlenecks of the Fungal Pretreatment of Lignocellulosic Biomass

“…A collection of recent experimental studies on the fungal pretreatment of lignocellulosic biomass using white-rot fungi was selected as data source for the fungal pretreatment conditions and performance. These studies were classified according to the feedstock used into four categories: hardwood [21][22][23][24][25][26]51], perennial grasses (switchgrass and Miscanthus) [22,39,40,52,53], corn stover…”

“…However, fungal pretreatment has some potential disadvantages compared to traditional pretreatments, including long reaction times (several weeks compared to hours), lower sugar yields (maximum sugar yields around 75% vs. >90%), and feedstock sterilization requirements [18].The fungal pretreatment of woody and herbaceous feedstocks has been performed using a variety of white-rot fungal strains. The fungal pretreatment of hardwoods such as poplar, willow, and rubberwood has resulted in 18-30% lignin degradation and a glucose yield of 17-55%, using strains such as Ceriporiopsis subvermispora, Echinodontium taxoddi, Trametes orientalis, and Trametes velutina [21][22][23][24][25][26]. The fungal pretreatment of herbaceous agricultural wastes such as wheat, paddy, canola, barely and rice straw, and sorghum and sugarcane bagasse, has reported sugar yields between 25 and 70% with 20-52% lignin degradation, using white-rot fungi such as Pleurotus ostreatus, Trametes versicolor, and C. subvermispora [27][28][29][30][31][32][33][34][35][36][37][38].…”

Flax nanofibrils production via supercritical carbon dioxide pre‐treatment and enzymatic hydrolysis

“…During these pre‐treatments, hemicelluloses and lignin are partially decomposed and solubilized and therefore removed from lignocellulosic materials. Also, the explosive release of pressure occurring in the steam, ammonia, as well as supercritical CO 2 explosion results in an increase in the pore volume and the accessible surface area of the lignocellulosic materials; Biological processes using microorganisms or enzymes, to degrade lignin or glycosidic linkages in cellulose and hemicelluloses resulting in a release of sugars monomers; and Different combinations of processes mentioned above, such as hydrothermal pre‐treatment combined with acid pre‐treatment, to maximize or improve the digestibility of lignocellulosic biomasses.…”

Biomechanical Pulping of Poplar with Crude Enzyme Secreted from Trametes sp. lg-9

“…With the aid of white-rot fungi followed by non-chlorine bleaching, pulp brightness can be increased by up to 2% (Reid and Paice 1994;Ferraz et al 2008). However, pretreatment with whiterot fungi has some disadvantages such as long treatment time, large reaction space, and low efficiency (Zhong et al 2011;Wang et al 2014). Extracellular enzymes secreted by white-rot fungi can be extracted easily and have been applied in pulping and papermaking (Vaithanomsat et al 2010;Järvinen et al 2012).…”