Enzymatic profiles of hydrolysis of lignocellulosic materials from Aspergillus terreus strains isolated from the rumen of beef cattle from Brazil

Abstract

Degradation of lignocellulosic materials by Aspergillus terreus isolated from rumen fluid, fungal biomass, in vitro substrate degradation, pH at end of incubation, concentrations of total protein (TP) and total cellulase (TC) were performed.In prior assay, submerged fermentations of sugarcane bagasse (SB) or Urochloa decumbens (UD) by five A.terreus isolates were performed.Subsequently, submerged fermentation using the two most promising isolates were evaluated comparing two nitrogen sources for cellulases, CMCases, avicelase and xylanases productions at 0, 72, 144, 216 and up to 288 h, in a factorial (2 × 2 × 5). During fermentation with UD and SB, showing lignin values 7.50 and 6.15%, respectively, the enzymatic activities at 50 °C were higher than those observed in the pH and temperature simulating the rumen (39 °C), allowing us to determine the optimal conditions under which the enzymes of interest may function in the animal model.The interaction between substrates and the evaluated periods was significant. Specifically for UD, the isolates V15 and V22 produced 226.14 and 210.72 nmol/L.s, respectively, which concentrations did not differ from each other.The isolates of this fungus showed growth ranging from 669 mg/L for the V79 isolate, using UD , and o 19,695 mg/L for the V22 isolate using SB after 216 h in medium supplemented with ammonium sulfate.Total protein levels were influenced by the substrates evaluated and by fermentation periods. The activity carboxymethylcellulases (CMCases) and xylanases presented values between 15.42 and 92.51 nmol/L.s for SB and from 5.14 to 226.14 nmol/L.s for UD fermentations. Using urea or ammonium sulfate, the V79 isolate in SB fermentation and the V49 isolate in UD fermentation, at 288 h, presented the highest rates of TP. The quantifications of TC in pH 4.5 at 50 °C were higher presenting 12,380.97 nmol/L.s and PT 347.575,0 nmol/mg.s, respectively by biomass, than those produced at pH 6.8 and 39 °C. The two selected A. terreus isolates from bovine rumen showed potential to use in the industrial microbiology and as additives to diets of ruminants. • Total protein contents showed significant differences for substrate interactions as a function of nitrogen source • Urea treatment resulted in higher pH values for both isolates and substrates, unlike fermentation containing ammonium sulfate, which showed acidic pH values • Additionally, only when analyzed as a function of substrate (sugarcane bagasse and U. decumbens ) for the following parameters: dry matter degradation, total proteins, total cellulase, total protein by total cellulase, xylanase, total protein by xylanase, xylanase by biomass, similarly significant differences were observed (P < 0.05). • The substrates influenced only the degradation rate and the isolates did not influence the evaluated parameters. However, nitrogen source influenced degradation and enzyme production