Multi-component thermostable cellulolytic enzyme production by Aspergillus niger HN-1 using pea pod waste: Appraisal of hydrolytic potential with lignocellulosic biomass

• Pea pod waste (PPW) can act as an ideal substrate for production of cellulases.
• Statistical optimization significantly improved enzyme production by Aspergillus niger HN-1.
• Crude enzyme exhibited thermostability by retaining >95% activity at 55 °C for 6 h.
• Hydrolysis of SSB with crude enzyme led to production of 700 mg sugars/g biomass.
• Value addition to PPW and SSB can help in their effective management.

Solid state fermentation with pea pod waste and Aspergillus niger HN-1 resulted in filter paper cellulase (FP) and β-glucosidase (BGL) activity of 30 FPU/gds and 270 U/gds, respectively. Validation with the response surface optimized parameters (moisture content: 65%, pH 6.0, temperature: 33 °C, time: 84 h) in a solid-state tray fermentation enhanced FP and BGL activity by about 40 and 28%, respectively. Multi-component enzyme from A. niger HN-1 produced FP, BGL, endoglucanase (EG), cellobiohydrolase (CBHI), xylanase, α-l-arabinofuranosidase, β-xylosidase and xylan esterase with activities of 41.07 ± 2.11 FPU/gds, 345.69 ± 17.1, 480.3 ± 21.5, 52.1 ± 1.5, 2800.5 ± 88.4, 88.1 ± 9.3, 280.8 ± 11.4 and 3321.7 ± 14.8 U/gds, respectively. Enzyme was optimally active at temperature and pH of 55 °C and 5.0, respectively and demonstrated thermostability by retaining >95% activity for 6 h at 55 °C. SDS-PAGE showed the presence of 11 protein bands with molecular mass ranging between 20 and 200 kDa, while zymogram revealed the presence of multiple forms of EG, CBH and BGL with varying molecular mass. Hydrolysis of sweet sorghum bagasse at relatively high substrate loading (15%, w/v) with crude enzyme at 20 FPU/gds in thermostatically controlled glass reactor led to conversion of 82–91% of holocellulose to fermentable sugars in just 24 h as evident from HPLC analysis, showing promise for the reported enzyme in bioprocessing applications.

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