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

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.

Valorization of Brewer’s Spent Grain Using Biological Treatments and its Application in Feeds for European Seabass (Dicentrarchus labrax)

“…Cellulase activity was maximum at 50°C, but good activity levels were observed between 35°C and 65°C. Similarly, optimum cellulase activity was also observed at 50°C when fermenting raw oil palm leaves with Rhizopus oryzae ( Ezeilo et al, 2020 ), at 55°C for the cellulase produced by Trichoderma reesei ( Astolfi et al, 2019 ), and at 60°C for the cellulase produced by A. niger during the SSF of BSG ( Liguori et al, 2021 ).…”

“…In the present study, the optimum temperature that maximizes xylanase activity was determined to range between 45°C and 65°C, with maximum activity at 55°C. Similarly, maximum activity of xylanase produced by Aspergillus flavus was attained at 55°C ( Chen et al, 2019 ), that of xylanase produced by Simplicilium obclavatum during the wheat bran SSF was attained at 50°C ( Roy et al, 2013 ), that of xylanase produced by Rhyzopus oryzae during the SSF of raw oil palm frond leaves was attained at 60°C ( Ezeilo et al, 2020 ), and that of xylanase produced by A. niger after 10 days of the SSF of BSG was attained at 50°C ( Liguori et al, 2021 ). However, other authors reported lower optimal temperatures for xylanase activity, such as that produced from Pediococcus acidilactici , showing maximum activity at 40°C ( Adiguzel et al, 2019 ).…”

“…In addition, A. terreus showed optimum cellulase activity in the pH range of 4–5 ( Narra et al, 2014 ). Contrarily, the highest xylanase and cellulase activities obtained by the SSF of BSG with A. niger were found at neutral pH ( Liguori et al, 2021 ).…”

“…The characterization of optimal temperature and pH of xylanase and cellulase in the crude enzymatic extract anticipates that these enzymes are suitable for converting different agro-industrial materials with different industrial applications. For example, these enzymes can be used in pulp, paper, food, and beverage industries as well to produce second-generation biofuels ( Manisha & Yadav, 2017 ; Astolfi et al, 2019 ; Liguori et al, 2021 ), given their suitability to work at increasing temperatures and challenging pH levels.…”

Changes in bioactive compounds during solid‐state fermentation of Sphenarium purpurascens with Aspergillus oryzae

“…Liguori et al . (2021) reported a value of 60 U mL −1 for xylanase activity in SSF from filamentous fungi strains of Penicillium occitanis SM6. Therefore, FG presented a highly effective enzymatic degradation of hemicelluloses through xylanase, which can improve food properties.…”