Abstract:

Lime is an important auxiliary material for producing edible and medicinal fungi. The aim of this study is to survey the quality of the lime auxiliary materials used in edible fungi cultivation at present, and optimize the amount of lime addition in oyster mushroom (Pleurotus ostreatus) cultivation, as a reference for production of P. ostreatus and other mushrooms. The contents of Ca(OH)₂, CaO, CaCO₃ and MgO in 8 lime samples of different sources were detected by phase-analysis of digested samples. No. 7 lime was added to the corn-cob substrate with different proportions to cultivate P. ostreatus. The mycelial growth, pH change in the substrate, and fruiting yield were compared between different treatments. The assays showed that only No. 2, No. 3 and No. 7 lime had high contents of effective constituents [Ca(OH)₂ and CaO], while the other samples had high contents of impurities in CaCO₃ or MgO. Using the No. 7 lime with an effective constituent over 96%, the optimal amount of lime addition was 2% as shown by the cultivation experiments. At this ratio, the substrate mix could reach pH 9.53, reducing to pH 7.72 after 24 h, and further to pH 6.35 after a steaming sterilization for 36 h. In this substrate, the mycelia grew the fastest and the yield was the highest. It suggests that the quality of lime could be an important factor influencing mushroom production, using low-quality lime will increase the cost of production, and even cause yield decrease in large-scale. Therefore, in the production of edible fungi, it is crucial to pay attention to the quality of lime auxiliary materials. For P. ostreatus cultivation, merely 2% addition of lime can effectively increase the pH of the culture substrate and inhibit the growth of pollutant bacteria if the effective constituent of lime reaches 96%, that makes the cultivation substrate reach the optimum pH range for P. ostreatus growth thereby obtaining high and stable yield.

Key words: Pleurotus ostreatus, lime, addition amount, pH, mycelium growth rate, yield