| Spent bleaching clay (SBC), the by-product of edible oil refining industry, has been widely used as organic solid waste resource overseas. In recent years, developed countries'technology in extracting, separating and refining of SBC bioactive substances has been increasingly perfected. However, the research and development of SBC utilization in China is still in the beginning stage with primitive processing production, simple technology, and lower-purity product. The production process is accompanied by large energy consumption, heavy pollution, and low yield and poor performance of products. In some technically backward areas, SBC is used as fertilizer, or even abandoned as waste. On the one hand, the SBC has been accumulated in large quantities for no use in a long term polluting the environment, and no technically and economically effective methods have been found to use it. On the other hand, with the rapid development and increasing market competition of the edible mushroom industry, it is quite urgent to find low-cost alternatives for mushroom substrate. Hence, how to use SBC as resource in the edible mushroom industry is of significant realistic significance.This paper aimed to transform the industrial waste-SBC into a valuable material, use it as a resource to replace cottonseed hull, wheat bran and other costly traditional cultural materials for the cultivation of several mushroom species greatly promoted and applied in production, and select the substrate formulae suitable for the growth of various edible mushrooms in order to lower the production cost of edible mushrooms, reduce environmental pollution and improve economic benefits.Therefore, by designing comparative experiment of culture media with different varieties and treatments, the author conducted a feasible study on the utilization of SBC as resource in edible mushrooms and discussed its technological and economic feasibility.The main research methods were as follows.1. Analyzed the feasibility of SBC in the production of edible mushroom based on the measurement and results of the nutrients of SBC, secondary and micro-nutrients by nutritional composition test method; 2. Analyzed the safety of SBC in the production of edible mushrooms based on the measurement and results of heavy metal content in SBC by heavy metal element test method:3. Conducted a productively comparative experiment on 5 mushroom varieties-pleurotus ostreatus, shimeji, flammulina mushroom, auriailaria polytricha and shiitake mushroom by adding different proportions of SBC into the edible mushroom medium by microorganism processing technology; 4. Compared the growth rate, growth potential, contamination rate of mycelium in each medium, as well as the yield, biological conversion and other aspect of fruiting body by measuring and recording methods; 5. Evaluated statistical significance of test data with SPSS software by statistical method and adopted One-way Analysis of Variance to analyze the difference of the same variety subject to different treatments; 6. Analyzed the resource application effect of SBC as edible mushroom medium and selected the suitable substrate formulae containing SBC by the method of comparison.The following three factors were considered in the design of medium screening test.1. The experiment adopted 5 edible mushroom varieties and set 6 Formulae:1 CK and 5 SBC of 5%,10%,15%,20% and 40% to replace some of the cottonseed hull and wheat bran in the CK as nutrient source, and conducted a visual screening comparison of mycelial growth in the culture media with different proportions of SBC.2. The experiment investigated the efficiency of SBC as the nitrogen substitution of wheat bran. In the experiment, SBC gradually replaced bran, with the add content of SBC increasing from zero to 10%, and that of wheat bran correspondingly decreasing from 10% to zero.3. The experiment investigated the efficiency of SBC as the carbon substitution of cottonseed hull. The proportion of SBC addition in medium had a gradient increase from 10% to 40% while the content of the cottonseed hull correspondingly decreased from 69% to 39%.Through productive experiment, the major research results were as follows.1. SBC contained rich nutrients including 31.25% organic substance,19.48% humic acid,1.32% protein,0.40% amino acid,59mg/kg effective phosphorus, and 601mg/kg effective potassium, weakly acidic with the pH value of 3.52, which was quite suitable as nutrient for edible mushroom.2. The application of SBC in edible mushroom was safe, and there was no risk of heavy metal contamination. It was determined that SBC contained trace amounts of heavy metals such as mercury (Hg),lead(Pb),cadmium(Cd),arsenic(As),chromium(Cr), the concentrations of which were respectively 5 mg/kg,100 mg/kg,3 mg/kg,30 mg/kg and 300 mg/kg, much lower than the heavy metal limitation concentrations stipulated in the normative references in organic agriculture industry's standard in China. Therefore, it could be concluded that the application of SBC in mushroom production was safe and would not cause any heavy metal contamination.3. From the analysis of mycelial growth rate, it could be found that culture medium with SBC had different effects on mycelial growth of all treatments. The growth rate and full-bottled time of both pleurotus ostreatus and shimeji added with SBC appeared to be slightly disadvantageous compared with the CK. For flammulina mushroom, auriailaria polytricha and shiitake mushroom, the growth rate and full-bottled time were obviously advantageous compared with the CK within a certain range of SBC addition. SBC within the range of 5%-20% would effectively promote the mycelial growth and shorten the seeding period.4. From the analysis of the yield and biological conversion of fruiting body of edible mushroom, it could be found that culture medium containing 5% SBC was the most suitable for the growth and development of fruiting body of pleurotus ostreatus and shimeji; 15% SBC for flammulina mushroom,40% SBC for auriailaria polytricha and 10% SBC for shiitake mushroom.5. From the comparative analysis of mushroom efficiency with different culture medium formulae, it could be found that all varieties with different treatments added with SBC enjoyed a higher net production value and unit cost compensation of economic indicators than the CK, and culture medium containing 40% SBC enjoyed the maximum economic benefit in particular.6. From comprehensive considerations, the most appropriate culture fomula for the growth of pleurotus ostreatus, shimeji, flammulina mushroom and auriailaria polytricha was 40% SBC,39% cottonseed hull,20% thick wood shavings.0% wheat bran and 1% lime. The most appropriate culture formula for the growth of shiitake mushroom was 40% SBC,53% thick wood shavings,5% wheat bran.1% magnesium sulfate and 1% gypsum.The following conclusions can be drawn from the experimental results. 1.SBC contains comprehensive nutrients and appropriate C/N ration and can provide abundant carbon and nitrogen source materials for edible mushroom growth. All treatments containing SBC had normal spawn run and could successfully cultivate fruiting body of edible mushroom. It can see that SBC is a new material resource that can substitute part of cottonseed hull, wheat bran and other traditional cultivation materials of edible mushroom.2. SBC can shorten the seeding period of medium strains. Phosphor, potassium and other mineral elements contained in SBC play an important role in promoting the growth of edible mushroom.3. SBC can reduce the contamination rate of medium strains. The large amounts of organic matters and humic acid contained in SBC can stimulate the growth of edible mushrooms.4. Although the yield of edible mushroom cultivated by SBC in some treatments is not prominent, its low cost, relatively high net production value and unit cost compensation of economic indicators can produce relatively great economic benefit and reduce environmental pollution, endowing SBC with great market potential for application in the production of edible mushrooms.
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