Production and Characterization of Xylanolytic Enzyme from White Rot Fungi Isolated from Decayed Woods
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Date
2021-02-22
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Addis Ababa University
Abstract
Utilization of enzymes like xylanase, in different industrial processes across the globe gained more attention than the chemical catalyst because they are highly selective, easy to control and have a negligible environmental impact since they produce very small amount of byproducts. Therefore, this study was undertaken with the objective of production, purification and characterization of xylanase from white rot fungi. In the present investigation, 68 white rot fungi (WRF) isolates were screened for xylanolytic potential using qualitative (plate assay) and quantitative (ferementation) methods. The optimum growth conditions for xylanase production were determined by growing fungal isolates at different: - pH values, incubation temprature and carbon and nitrogen sources. The feremetation was conducted under SSF and SmF condition using wheat straw as sole carbon source. The enzyme was assayed using 3, 5-dinitrosalysalic acid (DNS) method by measuring the amount of xylose released in μmol/ml/min at 540nm. Partial purification of the enzyme was conducted by ammonium sulfate precipitation method and protein concentration determined. Partial purified xylanas was characteriazed under different physico-chemical condtions to determine the optimum pH, temperature and the effect of metal ions. Among 68 WRF qualitatively screened, 17 isolates with ≥4.55 cm hydrolysis zone on mineral salt medium (MSM) or basal medium were selected and subjected to qualitative screenng. Out of quantitatively screened isolates, five WRF isolates with high xylanase yield (73.63±0.0283–63.6±0.01247 U/ml) were selected and used for further study. It was found that, the optimum xylanse production was at pH 5.0 and 28 oC temperature. Among carbon and nitrogen sources, xylan and yeast extract respectively, enhanced xylanase production. Solid state fermentation (SSF) favored xylanase production than that of submerged fermentation (SmF). The partial purified xylanase showed higher specific activity than the crude extract. Highest xylanase activity (80.9–61.274 U/ml) was recorded in the pH range of 5.0–6.5 and at 50 oC. Among the metal ions tested, Mg2+, Ca2+ and Mn2+ enhanced relative activity of xylanse (127.28–110.06%) while Cu2+, Fe2+ and K+ showed inhibitive effect with 43.4–17% loss of relative activity. In this study, kinetics parameters (Km and Vmax) were determined from Lineweaver-Burk plot. Xylanase from the isolates showed 0.32–0.545 mg/ml Km and 86.95–113.63 μmol min-1mg-1 Vmax. Xylanase from white rote fungal isolates exhibited properties suitable for applications in animal feed and different food industries like bakery, fruit juice and wine industries.
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Decaying Woods, Enzyme Assay, Kinetics, Lineweaver-Burk Plot