This is a two-part, randomized, double-blind, placebo-controlled, single center study to investigate the safety and tolerability of XBI-302 administered orally in healthy volunteers. The hypothesis of this study is that XBI-302 is safe and well tolerated with the proposed dosing regimens.

Inclusion Criteria:

1. Willing to participate and sign the ICF.

2. Healthy adults 18-55 years of age, male and female.

3. For women of childbearing age, negative serum pregnancy test at Screening and negative serum pregnancy test confirmed at the admission to the Phase 1 unit.

4. Female participants must not be pregnant, lactating, or actively trying to become pregnant. Participants who are premenopausal and of childbearing potential must have two negative pregnancy tests (serum) and both female and male participants must use medically acceptable and effective contraceptive methods during the study period, including:

   1. Having a male partner who is sterile prior to the female participant's entry into the study and is the sole sexual partner for that female participant
   2. Use of double-barrier methods of contraception; condoms with the use of caps (with spermicide) and intra-uterine devices are acceptable
   3. True abstinence, when this is in line with the preferred and usual lifestyle of the participant (Note: period abstinence [e.g., calendar, ovulation, symptothermal, post-ovulation methods] and withdrawal are not acceptable methods of contraception)

5. Clinical laboratory test values (hematology, blood chemistry, routine stool test, urinalysis, etc.) are in the normal ranges or although it was outside the normal limits, the researchers determined that the participant will still be eligible within the screening period.

6. Participants have a body mass index (BMI) between 18 and 30 kilogram per meter square (kg/m2) inclusive, and a body weight of at least 45 kilograms (kg).

Exclusion Criteria:

1. History of cardiovascular disease, immune system disease, malignant disease such as cancer, nervous system disease, hematological disease, endocrinological disease, and/or any other diseases that in the opinion of the investigator could impact assessments of safety or the gut microbiome.
2. Significant past medical history of GI conditions including inflammatory bowel disease, irritable bowel syndrome, celiac disease, history of GI malignancy or polyposis, C. difficile infection in past year.
3. GI symptoms that occur more than four times a month including acid reflux, nausea, vomiting, diarrhea, abdominal pain or cramps, abdominal distension, bloating, constipation.
4. Used oral antibiotics within 4 weeks prior to the first FMT dosing.
5. HIV infection and/or HBV/HCV infection.
6. Active tuberculosis and undergoing treatment.
7. History of mental illness, drug or alcohol abuse and/or any other behavioral issues that may impact study compliance.
8. Lactating women or participants who plan to become pregnant or conceive within half a year.
9. History of severe hypersensitivity (may cause difficulty in breathing).
10. Alcohol breathalyzer test positive, urine drug screening test positive, and/or smoker.
11. Participated in any other clinical trials within 3 months of first dose.
12. Participants with history of bowel or gastrointestinal surgery.
13. Participants who are immunosuppressed or immunocompromised, either by genetic, acquired or secondary to medication.
14. Participants who are experiencing symptoms associated with COVID-19 (including but not limited to cough, fever, shortness of breath, nausea, diarrhea, anhedonia, anosmia, ageusia or severe fatigue).