Extracellular enzymes of Pleurotus ostreatus vary among the proportions of acid detergent fiber and lignin of corn stover (Zea mays L.) hybrids with similar contents of cell walls

Abstract

The objective was to analyze the effect of corn stover neutral detergent fiber (NDF) composition on endoglucanase (End), exoglucanase (Exo), xylanase (Xyl), β-glucosidase (β-glu), and laccase (Lac), enzyme activities (EA) in enzyme extracts of Pleurotus ostreatus cultivated in liquid culture media were amended with residues of NDF, acid detergent fiber (ADF) and lignin (sa) + ashes of high-valleys and subtropical corn stover hybrids. The EA were followed 24 d. The EA peaks of End, Exo, β-glu, Xyl, and Lac of P. ostreatus in corn stover and their NDF, ADF, lignin (sa) + ashes fractions showed that CM with less hemicellulose and more ADF could promote the highest End:Xyl ratios (average, 0.58:1). In complete corn stover culture media, Xyl apported around 45 % to the R² of a multiple regression linear model where Y = reducing sugars (RS), and positively correlated with β-glu and End (r = 0.95 and 0.77; P < 0.0001). Conversely, in the culture media supplemented with NDF, ADF, and lignin (sa), β-glucosidase was primarily related RS (R²=0.36; P < 0.0001), while Lac negatively correlated with Exo and β-glu (r = -0.30 and −0.49, P < 0.05). Lac peaked before Cel and Xyl, and its action contributed 5.1–7.5 % to RS (R², P < 0.0001). Inhibitors of corn stover reduced EA of commercial fibrolytic and Lac enzyme extracts (P < 0.0001). Differences of hemicellulose and ADF proportions in culture media can enhance the cellulases EA profiles of P. ostreatus, useful to obtain specific enzyme extracts for ruminant feed applications; however, further in vivo tests with ruminants are necessary to validate present results.