Optimization of pretreatment and enzymatic hydrolysis coupled with ultrasonication for the production of xylooligosaccharides from corn cob

Xylooligosaccharides (XOS) hold industrial importance owing to their prebiotic, antioxidant, antibiotic, and anti-inflammatory potential. The fungal enzyme xylanase (Talaromyces thermophilus F1208) is known for its capacity to produce XOS by hydrolytic degradation. This study aims to achieve the maximum xylan yield through experiments by optimizing corn cob pyrolysate’s parameters. The xylan in the pyrolysis solution was converted into XOS using the ultrasonic-coupled enzymolysis method and optimizing its parameters. Optimizing pyrolysis conditions employing maleic acid concentration, pyrolysis temperature, and holding time resulted in a maximum xylan yield (20.04%) at 0.2%, 180 °C, and 30 min of the three parameters, respectively. The multivariate response surface methodology (RSM) for pyrolysis statistically validated the results and suggested pyrolysis temperature and holding time to be the most crucial parameters influencing the yield. Similarly, the highest yield of XOS (21.75%) was obtained at 7.5 pH, 4-h reaction time, and 6-U/mL enzyme dosage for the enzyme hydrolysis alone by selecting these three as optimization parameters. In the case of enzyme hydrolysis coupled to ultrasonication, the maximum yield of 27% XOS was achieved at 190 °C pretreatment temperature, 30-min ultrasonication time, 55 °C ultrasonication temperature, and 0.31-W/cm2 ultrasonication frequency, which was ~25% higher than that obtained using enzymatic hydrolysis alone. Moreover, ultrasonic intervention shortened the reaction time to 12.5% of the original time. The difference in enzymatic hydrolysis of xylan components (H1–H5) after alcohol precipitation was also investigated. It was found that the H2 and H3 substrates were slow reaction xylans, which were not easy to be enzymatically hydrolyzed.