Title : Xylaria karsticola NBIMCC 9097: Insights into controlled in vitro cultivation and the synthesis of antimicrobial bioactive metabolites
Abstract:
Xylaria karsticola was isolated from the basidiocarp of Macrolepiota procera (Basidiomycota), from Stara Planina Mountain, Bulgaria and it was the second report for such species found in Europe. The isolate was deposited in the GenBank database under accession number MW996752 and in the National Bank of Industrial Microorganisms and Cell Cultures of Bulgaria under accession number NBIMCC 9097. Phylogenetic analysis grouped this isolate with other X. karsticola strains. Xylaria karsticola is a species within the Xylaria genus, known for its diverse bioactive metabolites. Specific methodologies for controlled submerged cultivation for mycelium growth stimulation could influence nutraceutical compounds production. Based on the in vitro cultivation this X. karsticola NBIMCC 9097 presents an interesting source for future screening of natural secondary metabolites with antimicrobial properties. This research aimed to evaluate key bioprocess parameters through mathematical modeling of the growth kinetics of X. karsticola and to assess the antimicrobial activity of the resulting biomass. The cultivation process was modeled and the mathematical modeling accurately described the cultivation kinetics, with experimental data aligning well with the applied models. Antimicrobial activity was determined through the disk diffusion and broth microdilution methods. The disk diffusion method produces fast and reliable results regarding the presence or absence of antimicrobial activity, which makes it suitable for screening. Sixteen test-microorganisms, eight of which were pathogens or conditional pathogens, associated with food and cosmetic products were screened. The mycelium biomass extracts of X. karsticola obtained with methylene chloride demonstrated antibacterial activity towards E. coIi ATCC 8739 with a clear inhibition zone of 9,5 mm, Pseudomonas aeruginosa ATCC 9027 (d=8 mm), Candida albicans ATCC 10231 (d=8 mm) and Bacillus subtilis ATCC 6633 (d=9 mm).
For the determination of the minimal inhibitory concentration (MIC), only the extracts, which demonstrated significant antimicrobial activity were selected. The hexane and ethyl acetate extracts demonstrated the highest antimicrobial activity towards Pseudomonas aeruginosa ATCC 9027 and the MIC was respectively 0.067 mg/mL and 0.059 mg/mL. The MIC of the methylene chloride extract towards E. coIi ATCC 8739 was 2.12 mg/mL, and a concentration of 3,22 mg/ml was sufficient to suppress the growth of Candida albicans ATCC 10231.
The findings of this study suggest that the newly identified Xylaria karsticola holds significant potential. With further research and additional investigations, it could be developed into a promising source of nutraceuticals with antimicrobial properties.
This research was funded by THE NATIONAL SCIENCE FUND OF BULGARIA under contract № КП-06-Н87/9, from 06.12.2024, “Xylaria karsticola (Ascomycota) - cell-based cultivation and MULTI-OMICS approach for bioprospecting and revealing the potential for obtaining new bioactive metabolites with therapeutic properties”
