Integrated chemo-enzymatic strategy for production of functional xylooligosaccharides from sunflower stalk biomass.

Sunflower stalk biomass (SSB), a xylan rich agro-residue may serve as an efficient substrate for prebiotics-xylooligosaccharides (XOS) production, offering significant application potential for food/pharmaceutical industries. Current study optimized a chemo-enzymatic bioprocess for XOS production from SSB using Design of Experiments, and the XOS were characterized for various biofunctional attributes. Optimization of delignification (1:1 acetic acid 8.74 M : hydrogen peroxide 21.6 M, at 2.07% w/v biomass loading, 44.16 °C, 3.98 h), followed by xylan extraction with NaOH (10.18% biomass loading, 59 °C, and 6.50% NaOH), enhanced the xylan yield (2.44-fold). Purity and thermal stability of xylan were confirmed by FTIR and TGA, respectively. Xylan was hydrolyzed (2%, w/v xylan, 100 IU endoxylanase, 24 h) using an in-house β-xylosidase-free endoxylanase from Aspergillus flavus MG-7 to produce XOS. A high XOS yield (91.37%, w/w) with varying degree of polymerization i.e. xylotetrose (66.53%, w/w), xylotriose (12.96%, w/w), and xylobiose (11.87%, w/w) was obtained. The XOS exhibited strong growth-promoting activity for the probiotic Lactobacillus plantarum M-13, LPM-13 (18.76 log CFU/ml), a positive prebiotic activity score (1.57 relative to E. coli), and significant antioxidant activity (DPPH free radical scavenging activity 88.47% at 5.0 mg/ml). A varying antibacterial activity of cultural filtrate of LPM-13-grown modified MRS (glucose replaced with XOS, 1% w/v) was observed against E. coli 73.62%, Klebsiella sp. 68.24%, P. aeruginosa 64.29%, E. faecalis 57.42%, B. cereus 53.21%, M. luteus 51.73%, S. pneumoniae 47.53%, and P. alcaligenes 34.27%. Results suggest that XOS from SSB may have promising applications in the food, pharmaceutical, and nutraceutical industries.