Fungal biodegradation of genetically modified and lignin-altered quaking aspen (Populus tremuloides Michx.)

Better access to wood carbohydrates as a result of reduced, or altered, lignin is a goal of biopulping, as well as biofuel research. In the present article, woods from three transgenic trees and one wild-type quaking aspen (Populus tremuloides Michx.) were analyzed in terms of mass loss of cellulose and lignin after incubation with lignocellulolytic fungi. The transgenic trees had reduced lignin content through transfer of an antisense -4CL gene, elevated syringyl/guaiacyl (S/G) ratio through insertion of a sense CAld5H gene and low lignin content and elevated S/G ratio through simultaneous insertion of -4CL and CAld5H genes, respectively. The lignocellulolytic fungi employed were a lignin-selective white rot fungus Ceriporiopsis subvermispora, a simultaneous white rot fungus Trametes versicolor and a brown rot fungus Postia placenta. Reduced lignin degradation was observed in woods with increased S/G ratios indicating that this analytical feature influences decay resistance, regardless of the fungal decay mechanism.