Abstract
The xylanolytic and amylolytic yeasts were qualitatively determined by Cong red xylan agar and soluble starch agar plates, respectively. The most xylanase and α-amylase inducible strain (AUN-02) was selected and identified using PCR amplification of 26S rRNA gene and sequence analysis. The comparison of the alignment results and phylogenetic analysis of the sequences of the isolated yeast to published rRNA gene sequences in GenBank, confirmed the identification of the isolate as Pichia membranifaciens. Xylanase and α-amylase production by isolated P. membranifaciens were investigated at different pH values (4-8), temperature degrees (20-45°C), incubation time (1-7 days) and various substrates.A higher production of xylanase (38.8 U/mL) and a-amylase (28.7 U/mL) was obtained after 4 days of fermentation of P. membranifaciens. Higher activity of xylanase (36.83 U/mL) and a-amylase (27.7 U/mL) was obtained in the fermentation of P. membranifaciens in a culture medium adjusted to pH 7.0. The optimum temperature showed maximum xylanase and a-amylase activity (42.6 and 32.5 units/mL, respectively) was estimated at 35 °C. The xylanase and a-amylase activities of P. membranifaciens were estimated and compared for the different substrates tested. The strain revealed 100% relative activity of xylanase and a-amylase on beechwood and potato starch, respectively. The affinity of enzymes towards substrate was estimated using Km values. The Km values of xylanase and α-amylase increased in the order of pH’s 7.0, 6.0 and 4.5 (0.85, 1.6 and 3.4 mg xylan/mL and 0.22, 0.43 and 2.8 mg starch/mL, respectively). the yeast P. membranifaciensis is suitable for produce neutral xylanase and α-amylase enzymes. So, it could be used as a promising strain for production of these enzymes in industrial field.
Highlights
Biotechnology became an alternative and conventional trend in the fields of industry and analysis
All isolated yeasts were screened for xylanase and α-amylase production and one promising isolate designated as AUN-02 was selected
The alignment of 26S rRNA gene sequences of the yeast AUN02 with the reported 26S rRNA sequences from GenBank using basic local alignment search tool (BLAST) indicates 100% with Pichia membranifaciens Phylogenetic tree was developed for AUN-02 isolate along with other GenBank sequences of the same genus
Summary
Biotechnology became an alternative and conventional trend in the fields of industry and analysis. The microbial enzymes meet the industrial demand and a large number of them are commercially available[2]. Xylanases are hydrolytic enzymes that cleave the b-1,4 glycosidic bonds of xylan. They are applied for the production of hydrolysates in food and beverage industries, bioethanol and azodye removal[3]. These are used to enhance the nutrients digestibility in animal feed[4] as well as used for biobleaching of kraft pulp in pulp and paper industry[5]. The optimum activity of fungal xylanases is neutral or slightly acidic pH’s12
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