Identification, optimization of culture conditions and activity analysis of fermentation products of Xylaria escharoidea

Objective  Xylaria has valuable medicinal value and high economic value. Xylaria species collected from abandoned nest of termites were identified, and its liquid fermentation and solid culture conditions were optimized. The antibacterial and antioxidant activities of liquid fermentation product were determined. The study aimed at providing reference for exploitation and application of Xylaria escharoidea.

Method  The morphology observation and ITS sequencing were used to identify Xylaria species. The effects of adding different carbon sources, nitrogen sources and metal ions in liquid fermentation on mycelial growth were investigated. The effects of adding amino acids in solid medium on stromata growth were also analyzed. Furthermore, the antibacterial and antioxidant activities of liquid fermentation product were determined through plate bacteriostatic method and DPPH method.

Result  The collected strains were identified as X. escharoidea based on morphology and molecular data. The optimum carbon source in liquid fermentation was soluble starch, the optimum nitrogen source was silkworm pupa powder, and the optimum inorganic salt was MgSO₄. The optimum liquid medium component screened by orthogonal test was soluble starch 4% (w), silkworm pupa powder 0.6% (w) and MgSO₄ 0.06% (w). All valine, isoleucine and threonine could significantly promote the growth of stromata in solid medium. The antibacterial effect of liquid fermentation product was significantly better than that of potassium sorbate, and the antioxidant activity to DPPH was (75.19±2.08)%, significantly superior than that of vitamin E.

Conclusion  The optimized liquid fermentation and solid culture conditions can increase mycelial yield and promote stromata growth. The liquid fermentation product of X. escharoidea has excellent antibacterial and antioxidant activities, and possesses high exploitation and utilization value.