Obtaining Cellulose-Available Raw Materials by Pretreatment of Common Agro-Forestry Residues With Pleurotus spp.

Milica Galić,Mirjana Stajić,Jelena Vukojević,Jasmina Ćilerdžić

doi:10.3389/fbioe.2021.720473

Milica Galić, Mirjana Stajić + Show 2 more

Open Access

https://doi.org/10.3389/fbioe.2021.720473

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Abstract

The goals of the present study were to characterize the profile of ligninolytic enzymes in five Pleurotus species and determine their ability to delignify eight common agro-forestry residues. Generally, corn stalks were the optimal inducer of Mn-dependent peroxidase activity, but the activity peak was noted after wheat straw fermentation by P. eryngii (3066.92 U/L). P. florida was the best producer of versatile peroxidase, especially on wheat straw (3028.41 U/L), while apple sawdust induced the highest level of laccase activity in P. ostreatus (49601.82 U/L). Efficiency of the studied enzymes was expressed in terms of substrate dry matter loss, which was more substrate-than species-dependent. Reduction of substrate dry mass ranged between 24.83% in wheat straw and 8.83% in plum sawdust as a result of fermentation with P. florida and P. pulmonarius, respectively. The extent of delignification of the studied substrates was different, ranging from 51.97% after wheat straw fermentation by P. pulmonarius to 4.18% in grapevine sawdust fermented by P. ostreatus. P. pulmonarius was also characterized by the highest cellulose enrichment (6.54) and P. ostreatus by very low one (1.55). The tested biomass is a highly abundant but underutilized source of numerous value-added products, and a cocktail of ligninolytic enzymes of Pleurotus spp. could be useful for its environmentally and economically friendly transformation.

Highlights

Lignocellulose accounts for about 60% of the total biomass on Earth and presents promising raw material for various industrial processes, such as production of bioethanol, paper, feed, food and numerous other value-added products (Stajić et al, 2009; Rastogi and Shrivastava, 2017)
P. eryngii HAI 193 was the best producer of highly active forms of MnP on most substrates except plum and apple sawdusts, while P. ostreatus HAI 1105 and P. salignus HAI 326 were the weakest MnP producers on almost all residues (Figure 1)
As for the effect of substrate type, maximal MnP activity in P. eryngii was measured after fermentation of wheat straw (3066.92 U/L), while this activity was slightly lower on corn stalks (2848.48 U/L) and lowest on apple sawdust (308.71 U/ L)

Summary

Introduction

Lignocellulose accounts for about 60% of the total biomass on Earth and presents promising raw material for various industrial processes, such as production of bioethanol, paper, feed, food and numerous other value-added products (Stajić et al, 2009; Rastogi and Shrivastava, 2017). Its complex chemical structure makes its utilization extremely demanding (Bilal et al, 2017). The most challenging phase in its transformation is removal of lignin, i.e., release of cellulose and hemicellulose for subsequent enzymatic hydrolysis. Lignin is a most recalcitrant natural compound, whose physical and chemical mineralization is neither ecologically nor economically justified. The development of biological pretreatment systems represents the current trend in biotechnology (Meehnian et al, 2017). Owing to their well developed enzymatic system, fungi are a highly effective biofactory for lignocellulose conversion to cellulose-available resources. An enzyme cocktail composed of laccases, peroxidases and numerous auxiliary enzymes, makes white-rot mushrooms the most efficient delignifiers and potential participants in numerous biotechnological

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