 Sample size We would present the outcome in log 10 scale compared to day 0 in community DNA extracted from fecal samples. From the previous study 15, we anticipate the standard deviation as 1.25 units. By the sample size determination with the use of software GPower version 3.1.9.2 Franz Faul, Universitat Kiel, Germany, we would need at least 8 per group to have a power of 0.8 to detect the 1.25 unit difference at the 0.05 significance level. Therefore, in this research, we collect total sample size as 16 8 per group in the initial stage. 