Pretreatment of Canola Residue with Strains of White-Rot Fungi by Solid-State Fermentation for Lignocellulosic Conversion to Ethanol.

Post harvest crop residues from agricultural fields are valuable renewable sources of lignocellulosic materials suitable for conversion to ethanol. Corn (Zea mays) and soybean (Glycine max) are the primary crops used for ethanol and biodiesel production respectively. However, winter canola (Brassica napus) has greater potential than soybean for biodiesel production. This plant residue could be used for bioconversion to ethanol after delignification, which limits the efficiency of bioconversion lignocellulosics to ethanol. This study focused on pretreatment involving white rot fungi (WRF) and solid-state fermentation (SSF) to achieve delignification of canola biomass. Local isolates of WRF currently identified as WRF #1-#7 were screened for the production lignocellulose modifying enzymes and lignin degradation, under SSF experimental set up that was sampled after 7, 14 and 21 days of incubation. Laccase, manganese dependent and lignin peroxidases, carboxymethylcellulase and xylanase were found to be active to various extents in the isolates tested. Analyses of treated samples for lignin, hemicellulose and cellulose (LHC) contents revealed that all WRF strains tested actively reduced lignin contents in canola biomass. Among isolates tested, LHC degradation varied considerably and the most efficient was isolate #1, which in comparison to control (LHC = 15%, 17% and 45% respectively) gave LHC values of 8.6%, 16.4% and 46.5% respectively; and that amounts to 43.1%  lignin reduction after 21 days of incubation. Results also indicated that all isolates are selective white-rot degraders, except isolate #4 which degraded lignin and hemicellulose the least and  cellulose the most (LHC = 12.8%, 17.5% and 43.9%, respectively). Because of the promising results we are conducting further experiments by screening selected WRF for their ability to release biomass monomeric sugars (arabinose, xylose, fructose, glucose, mannose, and galactose) from residue of winter canola, scale up of SSF using best performing strains and DNA based identification of WRF isolates.