Integration of agricultural residues as biomass source to saccharification bioprocess and for the production of cellulases from filamentous fungi

Exploring the potential of a new thermotolerant xylanase from Rasamsonia composticola (XylRc): production using agro-residues, biochemical studies, and application to sugarcane bagasse saccharification

Xylanases from thermophilic fungi have a wide range of commercial applications in the bioconversion of lignocellulosic materials and biobleaching in the pulp and paper industry. In this study, an endoxylanase from the thermophilic fungus Rasamsonia composticola (XylRc) was produced using waste wheat bran and pretreated sugarcane bagasse (PSB) in solid-state fermentation. The enzyme was purified, biochemically characterized, and used for the saccharification of sugarcane bagasse. XylRc was purified 30.6-fold with a 22% yield. The analysis using sodium dodecyl sulphate-polyacrylamide gel electrophoresis revealed a molecular weight of 53 kDa, with optimal temperature and pH values of 80 °C and 5.5, respectively. Thin-layer chromatography suggests that the enzyme is an endoxylanase and belongs to the glycoside hydrolase 10 family. The enzyme was stimulated by the presence of K+, Ca2+, Mg2+, and Co2+ and remained stable in the presence of the surfactant Triton X-100. XylRc was also stimulated by organic solvents butanol (113%), ethanol (175%), isopropanol (176%), and acetone (185%). The Km and Vmax values for oat spelt and birchwood xylan were 6.7 ± 0.7 mg/mL, 2.3 ± 0.59 mg/mL, 446.7 ± 12.7 µmol/min/mg, and 173.7 ± 6.5 µmol/min/mg, respectively. XylRc was unaffected by different phenolic compounds: ferulic, tannic, cinnamic, benzoic, and coumaric acids at concentrations of 2.5-10 mg/mL. The results of saccharification of PSB showed that supplementation of a commercial enzymatic cocktail (Cellic® CTec2) with XylRc (1:1 w/v) led to an increase in the degree of synergism (DS) in total reducing sugar (1.28) and glucose released (1.05) compared to the control (Cellic® HTec2). In summary, XylRc demonstrated significant potential for applications in lignocellulosic biomass hydrolysis, making it an attractive alternative for producing xylooligosaccharides and xylose, which can serve as precursors for biofuel production.

Response surface optimization of cellulase production by Aspergillus stellatus NFCCI 5299 in shake flask submerged fermentation using wheat bran

The expense of cellulase enzymes is the main barrier to the enzymatic saccharification of biomass. Numerous tactics, such as the utilizing inexpensive lignocellulosic substrates as well as economically feasible fermentation techniques for the production of the enzyme may reduce the cost of cellulases. The present investigation was aimed to improve cellulase production employing potential cellulolytic soil fungi, Aspergillus stellatus NFCCI 5299 using wheat bran as substrate. Employing response surface methodology (RSM) with central composite design (CCD), the most efficient process parameters were determined. The ideal conditions for the synthesis of carboxy methyl cellulase (CMCase) and filter paper cellulase activity (FPase) were 6 days of incubation, inoculum size of 4 mycelial disc, 125 rpm of agitation, and 3.5% of wheat bran. The significant mycelial development and enzymatic digestion of wheat bran were discovered by scanning electron microscopy (SEM) and fourier transform infrared (FTIR) analysis. The findings suggested that it can be practicable to use wheat bran as substrate under submerged fermentation utilizing Aspergillusstellatus NFCCI 5299 for efficient cellulase production.