Characteristics of Aspergillus niger xylanases produced on rice husk and wheat bran in submerged culture and solid‐state fermentation for an applicability proposal

Abstract

Summary Xylanolytic rich filtrates were obtained by A. niger sp in both submerged and solid‐state culture using rice husk or wheat bran as the only carbon source. Filtrates obtained on rice husk showed the highest activities (~6500 and 5200 U g−1, respectively). Independent of carbon source, these filtrates were very stable in an acidic pH range (4–7) and mild temperatures, with high half‐life time values (more than 7 h at 50 °C) in the corresponding inactivation kinetic models. Also the effect of different metallic ions and denaturing substances was verified finding that these enzymes are not metaloproteins, and metals as Hg2+ and Pb2+ caused the greatest loss of xylanolytic activity (not higher than 30%). Xylanases produced by this A. niger strain showed important features that make them potential candidates for applications on human and livestock food industries.

Conditioning of agro-industrial residues for producing enzymes, additives and chemical precursors

“…Each bottle was inoculated with a spore suspension of Aspergillus niger (1×10 7 spores per gram of dry substrate). The initial moisture of the substrate after inoculation was 80% [19]. All experimental cultures were maintained at 37 °C for ten days, with sampling every 24 hours.…”

Conditioning and use of prickly pear peels for the production of lignocellulosic enzymes by Aspergillus niger sp. on solid-state cultures

“…After the strain was activated, the inoculums were prepared on potato dextrose agar medium, and the resulting spores were harvested from 5-days cultures at 27 °C. Conidia were dispersed in a sterile 0.9% (w/v) NaCl solution, and the spores contained in the resulting suspension were counted in a Neubauer chamber (Membrillo-Venegas et al, 2013).…”

“…Total soluble sugars in the supernatant and hydrolyzed centrifuge cake were measured using the phenol-sulfuric method (Dubois et al, 1956;López-Legarda et al, 2017). For estimation of xylanase activity, samples were incubated with a 1.0 % (w/v) solution of Birchwood xylan dissolved in sodium acetate buffer (50 mM, pH 5), and released reducing sugars were then quantified (Membrillo-Venegas et al, 2013). For laccase activity, the oxidation level of guaiacol 10 mM in an acetate buffer (0.5 mM, pH 5) was registered at 470 nm every 20 s for 3 min, after adding the samples to the reaction mixture (Durán-Hinojosa et al, 2017).…”

Solid-State Culture for Lignocellulases Production

“…The optical density obtained was compared with a 1 g/L xylose standard curve. One unit of xylanolytic activity was deined as the enzyme necessary for the release of 1 μmol of xylose under the described conditions [12].…”