Bacteria play a significant role in odor production. Thereby, we evaluated different bacteria for their ability to reduce malodorous compounds in swine using in vitro fermentation. Fresh cultures of Lactobacillus plantarum KACC 91016 (T1), L. brevis ATCC 14869(t) (T2), Bacillus subtilis KACC 10112 (T3), Saccharomyces cerevisiae KACC 30068 were used in this study. One hundred milliliters of anaerobic salt medium containing 10% fresh swine feces was transferred to serum bottles containing 1g DM of 50:50 soluble starch to casein ratio and inoculated with or without (control) 1mL of different microbial cultures and incubated for 24h. Highest (P < 0.05) total gas production was observed in T1 and lowest in control. Opposite was observed in hydrogen sulfide (H₂S) concentration, wherein lowest (P < 0.05) H₂S was observed in T1 and highest in control with 17.80% and 22.20%, respectively. Also, lower percent methanethiol, dimethyl sulfide and trimethylamine were observed in treated compared with control. Highest (P < 0.05) concentration of total fatty acids, propionate, and butyrate were also observed in T1 and the highest (P < 0.05) acetate was observed in T3. Among the bacteria used, addition of L. plantarum is the most effective for reducing malodorous compounds