Optimization of Xylanase Production by Bacillus sp. K1 Using Lignocellulo-sic Residues

Abstract

The xylanases are enzymes that hydrolyze xylan, producing fermentable sugars such as xylose and xylobiose. These enzymes have several industrial applications, among which its use in biobleaching and second-generation bioethanol stands out. The main objective in the present study is the optimization of the bacterial xylanase production by the strain Bacillus sp. K1, which has been previously isolated from rotting wood samples collected at Lakehead University's premises for its Biology Department. The variables investigated for optimization were physical such as pH, temperature and inoculum volume; and composition of the fermentation medium such as carbon source, organic and inorganic nitrogen source and percentage ratio between these components. Additionally, the effect of metal ions (sodium, potassium, magnesium, calcium, ferrous, nickelous, cupric, cobaltous and manganous) and surfactants (Tween-20, dodecyl sodium sulfate and Triton X-100) in the xylanase enzyme activity was determined. The highest production of xylanase was obtained after 36h fermentation and the optimal physical conditions associated with the xylanase production were pH 6, temperature 35 ºC and inoculum volume 1%. The optimum composition of the fermentation medium consists of: wheat bran 4%, glucose 0,5%, NH₄NO₃ 0,5%, K₂HPO₄ 0,1%, KCl 0,1%, MgSO₄ 0,05%, peptone 0,5%, SDS 0,1%. The enzyme activity generated is 264,96±7,89 IU/L, with a 248,79% increase from the initial conditions. The most important inhibitors were cupric and manganous ions with 32,00% and 49,16% inhibition compared to the control experiment.