Production of xylooligosaccharides from garlic straw xylan by purified xylanase from Bacillus mojavensis UEB-FK and their in vitro evaluation as prebiotics

• Novel acido-tolerant-xylanase was purified from a newly strain B. mojavensis UEB-FK.
• The purified xylanase showed high thermal stability, even incubated in 60 °C for 90 min.
• The enzyme was stable over a broad pH range and in presence of some additives.
• Enzymatic production of xylooligosaccharides from garlic straw xylan.
• The generated XOS exhibited prebiotics efficacy under in vitro system.

A newly isolated Bacterium strain named UEB-FK was selected from Tunisian Sahara, exhibiting the highest clear zone on agar plates containing oat spelt xylan by staining with Congo red. On the basis of 16S rDNA sequence analysis, this strain was identified as Bacillus mojavensis. This strain produced extracellular xylanase. Xylanase from the strain was purified to homogeneity and had an apparent molecular weight of 14 kDa. The Km and Vmax values of the purified xylanase on oat spelt xylan were 3.85 mg/mL and 250.02 U/mg, respectively. The optimum pH and temperature for the enzyme were found to be 4.0 and 50 °C, respectively, and the enzyme exhibited significant heat stability even incubated in 60 °C for 90 min. In addition, the enzyme was found to be stable in a wide range of pH (3–9) and in presence of some detergents and organic solvents. The main hydrolysis products yielded from garlic straw extracted xylan were xylobiose and xylotriose. The resulting xylooligosaccharides (XOS) could be used as a special nutrient for lactic bacteria. Therefore, prebiotic effect of XOS was evaluated by in vitro fermentation using known probiotic strains viz. Bifidobacterium adolescentis and Lactobacillus acidophilus.