Optimization of culture conditions for Lentinula edodes based on Box-Behnken design

Abstract:

[Background] The conservation and development of wild Lentinula edodes germplasm resources is a crucial measure to ensure China’s food security. [Objective] To clarify the culture conditions for different states of L. edodes and lay a foundation for the development and application. [Methods] We optimized the parameters of solid culture and liquid fermentation by single factor tests, orthogonal design, and response surface methodology based on the biological characteristics of the strain. [Results] The wild strain Le.Msy collected was identified as L. edodes. It exhibited good growth at 24 ℃, with mycelial growth favoring a weakly acidic environment of pH 5.0–6.0. The strain showed no strong preference to carbon sources among the nutrients in the culture medium and could grow with other nitrogen sources except urea. The optimal carbon to nitrogen ratio for mycelial growth was within the range of 20:1 to 30:1, and the strain preferred magnesium ions among inorganic salts. The orthogonal experiment results indicated that the combination of maltose, wheat bran, and magnesium sulfate was most suitable for the strain growth. The medium formula optimized by the response surface methodology was composed of 23.05 g/L carbon source, 6.14 g/L nitrogen source, and 5.48 g/L inorganic salt, in which the colony diameter reached (50.10±1.02) mm after 7 days. Based on the optimized culture medium formula, liquid fermentation conditions were further optimized with biomass as the indicator. The optimal fermentation conditions were a temperature of 26.71 ℃, a shaking speed of 127.21 r/min, and an inoculum amount of 9.69 pieces per 100 mL, under which the dry biomass reached (5 505.67±93.22) mg/L. [Conclusion] Le.Msy exhibits broad adaptability to nutrients. In solid culture, colony diameter can serve as an accurate indicator of growth and development. In liquid fermentation, the density, average diameter, and effective contact area of the mycelial pellets can only reflect the strains status within a non-extreme temperature range. The dry mycelial biomass can accurately reflect the growth and development status under any parameter changes.

Key words:Lentinula edodes;wild strain;culture condition optimization;liquid fermentation;Box-Behnken design;modeling