Spent mushroom substrate of Pleurotus pulmonarius: a source of easily hydrolyzable lignocellulose

Abstract

Pleurotus pulmonarius was cultivated on a corncob-based substrate for producing of mushrooms and for assessing the transformation of the lignocellulosics during the development of fungal biomass. Associated events, such as the release of relevant enzymes and the H2O2 generation, were also monitored. The peaks of laccase and catalase activities occurred at the 5th day and that of Mn peroxidase at the 30th day, simultaneously with a high activity of superoxide dismutase. Increase in the endocellulase and xylanase activities was observed after 10 days, with maximal activities achieved during the 20-30-day period. Maximal values of H2O2 were found after 10 days of cultivation. Electron microscopy and Fourier transform infrared (FTIR) spectroscopy showed strong alterations in the lignocellulosic fibers. The uncultivated and the cultivated substrates at different times were hydrolyzed with commercial cellulase and β-glucosidase. The highest values of reducing sugars (110.5 ± 5.6 μmol/mL), being 65 % glucose, were obtained using the 20-day cultivated substrate. After the fruiting stage (first flush), enzymatic hydrolysis of the spent mushroom substrate (SMS) yielded 53.0 ± 2.8 and 77.5 ± 4.0 μmol/mL of glucose and total reducing sugars, respectively. Although the release of reducing sugars of the P. pulmonarius SMS was lower than that obtained after 20 days of cultivation, it was still 50 % higher than that obtained using the uncultured substrate. This observation, combined with the fact that SMS constitutes a residue generated as a by-product of the depletion of an agro-industrial residue, allows to conclude that this material offers an interesting economic perspective for the obtainment of cellulosic ethanol.

Lignocellulose hydrolytic enzymes production byAspergillus flavusKUB2 using submerged fermentation of sugarcane bagasse waste

“…The decreases in the peak intensities at 1515 cm −1 , 1457 cm −1 and 1266 cm −1 suggested substantial degradation of lignin. Similar FTIR results have been reported by Xu et al (2017) for wheat straw, rice straw and corn stover degradations by Inonotus obliguus under submerged fermentation and by Corrêa et al (2016) for corncob after Pleurotus pulmonarius cultivation.…”

“…FTIR, a simple and rapid technique, is well known for qualitative and quantitative determination of lignocellulosic components. Characteristic peaks associated with cellulose, hemicellulose and lignin could be observed at 1730 cm -1 (unconjugated C=O in xylan), 1515 cm -1 (aromatic skeleton vibrations in lignin), 1457 cm -1 (CH 2 deformation stretching in lignin and xylan), 1266 cm -1 (syringyl ring breathing and C-O stretching in lignin and xylan), 1098 cm -1 (crystalline cellulose), and 898 cm -1 (β-glycosidic linkage) (Herrera-Franco and Valadez-Gonzalez 2005;Shi and Li 2012;Castoldi et al 2014;Corrêa et al 2016;Xu et al 2017).Table 3 shows the results of the analysis of the spectra corresponding to cellulose, hemicellulose and lignin, in terms of the percentage modifications of substrate after fungal cultivation relative to the substrate without fungal inoculation and Figure 4 shows the FTIR spectral analysis. The diminutions of the peak intensities at 1098 cm −1 and 898 cm −1 indicated cellulose degradation.…”

Adsorption Thermodynamics and Dynamics of Three Typical Dyes onto Bio-adsorbent Spent Substrate of Pleurotus eryngii

“…SMS had thus become one of the major agriculture wastes. Except for a few examples of SMS being used for returning to the field [14], feedstuffs [15], cultivation [16], fuel and energy materials [17], the vast majority of SMS was abandoned and caused environmental pollution. Because of the abundant surface hydroxyl, carbonyl, and carboxyl groups in SMS [12], SMS could be considered as a potentially useful low-cost bio-adsorbent for dyeing wastewater treatment.…”

Recent advances on environmentally sustainable valorization of spent mushroom substrate: A review

“…It has a high amount of carbohydrates, lipids, proteins and enzymes 61 . It is also effective in the restoration of hydrolytic proteins, 62 and the generation of biogas 63 . Biogas is an environmentally sustainable fuel generated from waste by the anaerobic digestion (AD) process, and it is recognized as the most efficient bioenergy generation method 64 .…”