In order to confirm the efficacy of the carbonate precipitation method based on an enzyme catalyst and microbial functions in increasing peat strength, we performed laboratory tests with the urease enzyme and a urease-producing bacterium from peat and measured ammonia-nitrogen and nitrate-nitrogen concentration, unconfined compressive strength, and diversity of the microbial community by using next generation DNA sequencing. We then investigated the influence of the conditions used during the

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... dition of the urease enzyme and the subsequent increase in the population of the urease-producing bacterium during the test term. From the results obtained, it was found that the addition of the urease enzyme increased calcite precipitation and also increased the unconfined compressive strength(over 50kN/m 2 ) and the production of ammonium ions; this increase in the concentration of ammonium ions increased the pH of the peat. We also found a change in the composition of the microbial community under the carbonate precipitation conditions.