Optimization of upstream and downstream process parameters for cellulase-poor-thermo-solvent-stable xylanase production and extraction by Aspergillus tubingensis FDHN1

Abstract

Background Xylanases are important members of the hemicellulolytic enzyme system. Xylanase plays a vital role in the hydrolysis of major hemicellulosic component xylan and converts it into xylooligosaccharides and ultimately yields xylose. Cellulase-lacking or cellulase-poor xylanase with high temperature and pH stability has gained special attention, especially in paper and pulp industries. Most of the available literature highlighted the fungal xylanase production by optimizing environmental and cultural parameters. However, the importance of enzyme recovery from fermented biomass still needs attention. In this study, upstream and downstream process parameters were studied for enhancing xylanase production and extraction by a newly isolated Aspergillus tubingensis FDHN1 under solid-state fermentation using low-cost agro-residues. Results In the present study, A. tubingensis FDHN1 was used for the xylanase, with very low level of cellulase, production under solid-state fermentation (SSF). Among various agro-residues, sorghum straw enhanced the xylanase production. Under optimized upstream conditions, the highest xylanase production 2,449 ± 23 U/g was observed. Upon characterization, crude xylanase showed stability over a broad range of pH 3.0 to 8.0 up to 24 h. The temperature stability revealed the nature of the xylanase to be thermostable. Native polyacrylamide gel electrophoresis (native PAGE) and zymogram analysis revealed the multiple forms of the xylanase. Due to the many industrially important characteristics of the xylanases, the study was elaborated for optimizing the downstream process parameters such as volume of extractant, extraction time, temperature and agitation speed to recover maximum xylanase from fermented sorghum straw. The highest amount of xylanase (4,105 ± 22 U/g) was recovered using 0.05 M sodium citrate buffer (pH 6.5) at 12:1 (v/w) extractant/solid ratio, 90-min extraction time, 150-rpm agitation speed and 40°C. Finally, detailed bioprocess optimization shows an overall 6.66-fold enhancement in the xylanase yield. Conclusions The present study consolidates the importance of upstream and downstream process optimization for the overall enhancement in the xylanase production. The xylanase from A. tubingensis FDHN1 shows the stability at different pH and temperature, and it was also active in the presence of organic solvents. These properties of xylanase are very much important from an industrial application point of view.

Development of novel economical methodologies for zymographic analysis of purified xylano–pectinolytic enzymes using agrowaste‐based substrates

“…PAGE gel containing 0.5% commercial xylan substrate and protein bands of xylanase enzyme was treated with Congo red after electrophoresis for zymogram analysis. Xylanase active bands appeared as three and six clear regions against red background from enzyme preparations of Aspergillus tubingenesis and Aspergillus fumigatus Z5, respectively. Similarly, zymogram of sodium dodecyl sulfate (SDS) polyacrylamide gels containing 0.1% soluble xylan, displayed 12 proteins possessing xylanase activity from the enzyme preparation of Paenibacillus curdlanolyticus B‐6 .…”

Xylanase production from a new strain of Aspergillus terreus S9 and its application for saccharification of rice straw using combinatorial approach

“…Fusarium verticillioides exhibited maximum xylanase production (13.4 U/mL) on corn straw and corn cobs as the carbon sources [7]. Very complex nitrogen sources experience slow release and support poor growth and enzyme production while fast metabolizable nitrogen sources also suppress enzyme production [5,26]. Thus, agroindustrial residues may be exploited as cheap substrates for xylanase production, and may pave the way for eco-friendly technology development for bulk industrial enzyme production.…”

“…Lignocellulosic biomass (LB) represented mainly by agricultural/forestry residues are the most plenteous feed stock that can be exploited for production of energy and high value specialty chemicals [3]. Xylan constitutes one of the major hemicellulosic component of LB, and consists primarily of a backbone of b-1,4-linked-Dxylopyranosyl residues and side chains with varying substituent groups [4,5]. Being an heteropolysaccharide xylan requires several enzymes for its complete breakdown but endo b-(1,4)-xylanase or simply xylanase (EC 3.2.1.8), is the main enzyme which cleaves the internal b-(1,4)-linked Dxylosyl glycosidic bonds in heteroxylan [6,7].…”

“…Furthermore, valorization of agroindustrial residues may have economic, environmental, and strategic significance especially for countries like India where agriculture is the major basis of economy [1,5]. Exploitation of agroindustrial wastes as substrates for enzyme production may help reducing production cost.…”

“…Exploitation of agroindustrial wastes as substrates for enzyme production may help reducing production cost. Furthermore, valorization of agroindustrial residues may have economic, environmental, and strategic significance especially for countries like India where agriculture is the major basis of economy [1,5]. Process optimization has always been critical in any production/manufacturing units.…”