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

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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.