An integrated approach to the sustainable production of xylanolytic enzymes from Aspergillus niger using agro-industrial by-products

Abstract

Xylanolytic enzymes were produced by Aspergillus niger NRRL3 grown on agro-industrial by-products obtained from the processing of wheat flour without pretreatment. Significant parameters for xylanase production were screened and optimized. The xylanolytic activity obtained in the optimized extract was 138.3 ± 2.6 U/mL, higher than the activity obtained in an unoptimized medium (14.5 ± 0.3 U/mL) in previous work. The optimized fermentation process was performed in a successful 40-fold scale-up. The optimized enzymatic extract obtained was characterized by LC-MS. Nine enzymes were identified as constituents of the xylanolytic complex. Moreover, the xylanolytic enzymes were stable until 60 °C and over a broad range of pH. Sodium, calcium, cobalt and manganese had no inhibitory effect, meanwhile 1% w/v polyvinylpyrrolidone and 1% w/v dextran increased the xylanolytic activity. The saccharification efficiency was evaluated and the surface morphology of the lignocellulosic substrate was monitored by using scanning electron microscopy (SEM). The synergistic combination of the extracted (o purified) xylanolytic enzymes permitted a higher xylan conversion beneficial for diverse applications, such as bioethanol production. Thus, these agroindustrial by-products can be used within the framework of a circular economy, rendering an added value bioproduct, which is reused in the industry.

Graphical Abstract

Keywords:

• Agroindustrial by-products
• biorefinery
• circular economy
• xylanolytic enzyme

Acknowledgments

We would like to thank the staff from the Statistical Area for the data processing and the English Department (Faculty of Biochemical and Pharmaceutical Sciences, UNR) for the language correction of the manuscript. We thank Dra. Silvia Moreno from CEQUIBIEM for performing the analysis of protein samples by LC-MS.

Disclosure statement

The authors declare that there is no potential conflict of interest with respect to the research, authorship, and/or publication of this article.

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Additional information

Funding

This work was supported by the Agencia Nacional de Promoción Científica y Tecnológica under Grant [PICT2016-1170]; Ministerio de Ciencia, Tecnología e Innovación Productiva de Santa Fe under Grant [IO2018009]; and the Consejo Nacional de Invetigaciones Científicas y Técnicas (CONICET) under Grant [PUE BD20160041CO] and Secretary of Science and Technology of National University of Rosario under Grant [80020180100033UR]