Efficiency of Lignocellulolytic Extracts from Thermotolerant Strain Fomes sp. EUM1: Stability and Digestibility of Agricultural Wastes

Abstract

Production of lignocellulolytic enzymes by the thermotolerant Fomes sp. EUM1 was determined in solid cultures using corn stover (CS) as a sole substrate or supplemented with 20 % wheat bran (CS+WB). This supplementation increased (P< 0.05) enzymatic activity per gram of initial dry matter (gdm) for xylanases and cellulases: 160 IU g dm -1 and 37 IU g dm -1 , respectively; while laccases reached a similar yield (3.3 IU g dm -1 ) for both cultures. Nevertheless, laccases showed different stability patterns at 39°C and pH 6: half-life time ( t½) was doubled in extracts from CS+WB (23.5 h); whereas t½ for the other enzymes from both cultures showed no difference. Both extracts by Fomes sp. EUM1 and a commercial enzymatic product were used on forages: corn stover, (CS), sugarcane bagasse (SCB), and alfalfa hay (AH). The fractional rate of gas production (FR; ml g -1 h -1 ) increased (P< 0.05) at 9 hours in CS compared to the sample without enzymes. The use of any enzymes favoured higher maximum gas volume ( Vm ; h -1 ) on SCB. The in vitro digestibility (IVD) of CS after using the commercial product was 12% higher, while our extracts from CS and CS+WB showed 16 and 21% improvements (P< 0.05), respectively, suggesting a higher specificity of these enzymes produced on the same substrate (CS). In addition to the proven stability, the versatility of extracts from CS and CS+WB was confirmed by the increase in IVD values for SCB (up to 100%) in relation to the control without enzymes.