Carbohydrate-hydrolyzing enzyme ratios during fungal degradation of woody and non-woody lignocellulose substrates

Abstract

Understanding the order that enzymes are secreted during lignocellulosic degradation is relevant both to better understanding basic fungal degradation mechanisms and to industrial attempts to control reactions for biofuels production and other bioprocessing technology. Much is known about the enzymes that are produced and their effect on individual substrates, but little is known about temporal variation and relative enzyme activity on different lignocellulosics substrates. Wood decay fungi Trametes versicolor and Postia placenta were grown in liquid culture with different substrates (aspen, pine, corn stover, prairie grass and alfalfa) over a 16-week period. Samples of liquid media were taken every 2 weeks for endoglucanase, β-glucosidase and xylanase activity measurement. Endoglucanase:β-glucosidase:xylanase ratios varied for both fungi over the sampling period. T. versicolor showed large differences in cellulase enzyme (total cellulase:endoglucanase:β-glucosidase) composition when grown on woody substrates compared with non-woody substrates; there were also difference between the two wood types. This research presents evidence that the ratio of carbohydrate-hydrolyzing enzymes secreted by fungi is not influenced solely by lignin:carbohydrate content of the substrate and other factors including cell anatomy and constituent composition have some control on enzyme production. This provides a useful and broad survey of natural adaptations to various plant tissues relevant to bioenergy and general bioprospecting.