PRODUCTION OF XYLOOLIGOSACCHARIDES FROM CORN COB XYLANS USING XYLANASES PRODUCED BY Fusarium sp. EA 1.3.1 IN FREE AND IMMOBILIZED FORM

Xylo-oligosaccharides (XOS) has aroused interest due to their applicability in food due to their recognized prebiotic effect. However, the high cost of obtaining XOS is one of the main challenges for commercialization on an industrial scale. Thus, alternative sources of xylans, such as corn cob, and the application of protein catalysts, such as low-cost fungal xylanolytic enzymes, are feasible and promising alternatives for obtaining XOS. This work aimed to optimize and validate the xylan extraction conditions through a Central Composite Design with two independent variables (NaOH concentration: 0.5 – 2.0 M and extraction temperature: 26 – 60 °C). After extraction, the xylans were neutralized (pH 7.0), precipitated with 90 % ethanol, and dried in an oven at 45 °C (overnight). Then, the xylans were hydrolyzed by a xylanolytic cocktail produced by the fungus Fusarium sp. EA 1.3.1 or commercial xylanase, both in free form (388.18 and 803.20 U.mL-1, 120 minutes, pH 5.5) and immobilized in alginate spheres (194.12 and 186.84 U.µg-1, 20 minutes, pH 6.5), respectively. The extracted xylan content ranged from 24.83 ± 1.63 to 88.27 ± 1.38 g.100 g-1 of initial weight, where the linear term of NaOH concentration (β1 = 22.44) was more critical than the extraction temperature (β2 = 4.27). The optimum extraction point was obtained with 2 M NaOH at 60 °C, with a desirability of 89.9 %, confirmed by the validation of the mathematical model (relative deviation <10 %). The xylans extracted under optimal conditions did not show xylose (within the limit detection of the method) nor expressive glucose levels (0.028 ± 0.21 g.100 g-1). Enzymatic hydrolysis of the optimal point of xylans by commercial xylanase and fungal xylanolytic cocktail in free forms resulted in 191.09 ± 0.5 and 116.37 ± 0.8 µmol of XOS.mL-1 of xylan extract, respectively. Regarding the immobilized derivatives, it was observed that the commercial xylanase and the xylanolytic cocktail immobilized in alginate spheres presented 5.06 and 7.52 µmol of XOS.mL-1 of xylan extract, respectively. The xylanolytic cocktail produced by the fungus Fusarium sp. EA 1.3.1 showed yields very close to the commercial enzyme, despite not being submitted to any previous purification process. However, due to the larger contact surface, both fungal and commercial xylanase in the free form presented a higher yield in the production of XOS, being more commercially advantageous. On the other hand, the immobilized derivatives of the fungal xylanolytic extract maintained 70 % of the activity even after ten cycles of reuse. Thus, the extraction of xylans from agro-industrial co-products and the application of fungal xylanases produced from low-cost carbon sources are viable alternatives for producing XOS on an industrial scale.