Screening of Fungal Strains for Cellulolytic and Xylanolytic Activities Production and Evaluation of Brewers’ Spent Grain as Substrate for Enzyme Production by Selected Fungi

Addolorata De Chiaro,Luciana Porto de Souza Vandenberghe,Vincenza Faraco,Rossana Liguori,Anna Pennacchio,Leila Birolo,Carlos Ricardo Soccol

doi:10.3390/en14154443

Addolorata De Chiaro, Luciana Porto de Souza Vandenberghe + Show 5 more

Open Access

https://doi.org/10.3390/en14154443

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Abstract

Brewer’s spent grain (BSG), the solid residue of beer production, is attracting significant attention as raw material for the production of added value substances, since until recently it was mainly used as animal feed or deposited in landfills, causing serious environmental problems. Therefore, this work aimed at developing a bioprocess using BSG as a substrate for the production of cellulases and xylanases for waste saccharification and bioenergy production. Different fungi were analyzed for their cellulolytic and xylanolytic abilities, through a first screening on solid media by assessment of fungal growth and enzyme production on agar containing carboxylmethylcellulose or xylan as the sole carbon source, respectively. The best cellulase and xylanase producers were subjected to quantitative evaluation of enzyme production in liquid cultures. Aspergillus niger LPB-334 was selected for its ability to produce cellulase and xylanase at high levels and it was cultivated on BSG by solid state fermentation. The cellulase production reached a maximum of 118.04 ± 8.4 U/g of dry substrate after 10 days of fermentation, while a maximum xylanase production of 1315.15 ± 37.5 U/g of dry substrate was reached after 4 days. Preliminary characterization of cellulase and xylanase activities and identification of the enzymes responsible were carried out.

Highlights

The actualization of a circular economy through the use of lignocellulosic wastes as renewable resources can lead to reducing the dependence on fossil-based resources and contribute to sustainable waste management, limiting greenhouse gas emissions and environmental impacts [1]
The fungus producing both higher levels of cellulase and xylanase activities was selected for the experiment of solid state fermentation on brewer’s spent grain (BSG) and cellulase and xylanase activities produced at maximum time of production were subjected to enzyme characterization and protein identification
Thirty-two fungal strains from the DEBB Collection, belonging to the genera Lentinus, Pleurotus, Trametes and Aspergillus spp., were analyzed for their cellulolytic and xylanolytic abilities by assessment of fungal growth and enzyme production on agar plates containing carboxylmethylcellulose (CMC) or xylan as the sole carbon source, respectively (Table 1)

Summary

Introduction

The actualization of a circular economy through the use of lignocellulosic wastes as renewable resources can lead to reducing the dependence on fossil-based resources and contribute to sustainable waste management, limiting greenhouse gas emissions and environmental impacts [1]. A full recycling and re-use of agro-industrial lignocellulosic wastes take place in second generation biorefinery platforms, where bio-based products (food, feed, chemicals) and bioenergy (biofuels, power and heat) are generated through integrated and sustainable processes [2]. The enzymatic hydrolysis of the (hemi)cellulose after lignin removal presents environmental advantages in comparison to the chemical method, but poses economical drawbacks due to the high production costs of the involved enzymes [9]. This leads to a search for alternative low-cost substrates based on wastes for enzyme production

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