Optimization of xylanase production by Pichia kudriavzevii and Candida tropicalis isolated from the wood product workshop.

Enzymatic compounds can be found abundantly and provide numerous advantages in microbial organisms. Xylanases are used in various pharmaceutical, food, livestock, poultry, and paper industries. This study aimed to investigate xylanase-producing yeasts, xylose concentration curve and their enzymatic activity under various factors including carbon and nitrogen sources, temperature, and pH. Enzyme activity was evaluated under different conditions before, during, and after purification. The yeast strains were obtained from the wood product workshop and were subsequently cultivated on YPD (yeast extract peptone dextrose) medium. Additionally, the growth curve of the yeast and its molecular identification were conducted. The optimization and design process of xylan isolated from corn wood involved the use of Taguchi software to test different parameters like carbon and nitrogen sources, temperature, and pH, with the goal of determining the most optimal conditions for enzyme production. In addition, the Taguchi method was utilized to conduct a multifactorial optimization of xylanase enzyme activity. The isolated species were partially purified using ammonium sulfate precipitation and dialysis bag techniques. The results indicated that 3 species (8S, 18S, and 16W) after molecular identification based on 18S rRNA gene sequencing were identified as Candida tropicalis SBN-IAUF-1, Candida tropicalis SBN-IAUF-3, and Pichia kudriavzevii SBN-IAUF-2, respectively. The optimal parameters for wheat carbon source and peptone nitrogen source were found at 50 °C and pH 9.0 through single-factor optimization. By using the Taguchi approach, the best combination for highest activity was rice-derived carbon source and peptone nitrogen source at 50 °C and pH 6.0. The best conditions for xylanase enzyme production in single-factor optimization of wheat bran were 2135.6 U/mL, peptone 4475.25 U/mL, temperature 50 °C 1868 U/mL, and pH 9.0 2002.4 U/mL. Among the tested yeast, Candida tropicalis strain SBN-IAUF-1 to the access number MZ816946.1 in NCBI was found to be the best xylanase product. The highest ratio of enzyme production at the end of the delayed phase and the beginning of the logarithmic phase was concluded by comparing the growth ratio of 8S, 16W, and 18S yeasts with the level of enzymatic activity. This is the first report on the production of xylan polymer with a relative purity of 80% in Iran. The extracellular xylanases purified from the yeast species of C. tropicalis were introduced as a desirable biocatalyst due to their high enzymatic activity for the degradation of xylan polymers.

Efficacious antibacterial potency of novel bacteriophages against ESBL-producing Klebsiella pneumoniae isolated from burn wound infections.

BACKGROUND AND OBJECTIVES: Prevalence of extended spectrum ß-lactamase (ESBL) leads to the development of antibiotic resistance and mortality in burn patients. One of the alternative strategies for controlling ESBL bacterial infections is clinical trials of bacteriophage therapy. The aim of this study was to isolate and characterize specific bacteriophages against ESBL-producing Klebsiella pneumoniae in patients with burn ulcers. MATERIALS AND METHODS: Clinical samples were isolated from the hospitalized patient in burn medical centers, Iran. Biochemical screenings and 16S rRNA gene sequencing were determined. The phages were isolated from municipal sewerage treatment plants, Isfahan, Iran. TEM and FESEM, adsorption velocity, growth curve, host range, and the viability of the phage particles as well as proteomics and enzyme digestion patterns were examined. RESULTS: The results showed that Klebsiella pneumoniae Iaufa_lad2 (GenBank accession number: MW836954) was confirmed as an ESBL-producing strain using combined disk method. This bacterium showed significant sensitivity to three phages including PɸBw-Kp1, PɸBw-Kp2, and PɸBw-Kp3. Morphological characterization demonstrated that the phage PɸBw-Kp3 to the Siphoviridae family (lambda-like phages) and both phages PɸBw-Kp1 and ɸBw-Kp2 to the Podoviridae family (T1-like phages). The isolated bacteriophages had a large burst size, thermal and pH viability and efficient adsorption rate to the host cells. CONCLUSION: In present study, the efficacy of bacteriophages against ESBL pathogenic bacterium promises a remarkable achievement for phage therapy. It seems that, these isolated bacteriophages, in the form of phage cocktails, had a strong antibacterial impacts and a broad-spectrum strategy against ESBL-producing Klebsiella pneumoniae isolated from burn ulcers.