The present invention is a method of enriching at least one bacterial species from a target bacterial system, including: culturing the target bacterial ecosystem in a culture media in a single-stage chemostat under the following conditions: (i) a system retention time of about 5 to about 290 hours, (ii) a temperature of about 37° C., (iii) a pH of about 6.8 to 7, and (iv) maintenance of Establish anaerobic conditions to the chemostat for a time sufficient to enrich the at least one bacterial species； where the culture media comprises a prepared starch substrate, and where the target bacterial system is a fecal derived sample obtained from a patient that has not been treated with an antibiotic for at least 6 months.
