Sequential Screening of Lactic Acid Bacteria from Fermented Sour Bamboo Shoots and Their Effects on Patient-Derived Fecal Microbiota In Vitro

Naturally fermented sour bamboo shoots represent a potential source of functionally active lactic acid bacteria (LAB). This study screened LAB from sour bamboo shoots and evaluated their potential to modulate patient-derived fecal microbiota in vitro. A total of 42 candidate isolates were obtained by morphological and physiological/biochemical screening. Five isolates showing intermediate antibiotic resistance were excluded, and the remaining 37 isolates were evaluated for gastrointestinal tolerance, antagonistic activity against enteric pathogens, and adhesion-related properties. Principal component analysis (PCA) identified nine strains for further evaluation. These strains were individually introduced into an in vitro colonic fermentation system prepared from pooled fecal samples of patients with bacterial diarrheal enteritis. After 48 h of fermentation, microbial community composition was assessed by 16S rRNA gene sequencing, and short-chain fatty acids (SCFAs) were quantified. LAB treatment was associated with a higher relative abundance of Firmicutes and a lower relative abundance of Proteobacteria. Compared with the mixed fecal suspension (MFS) control, the relative abundance of Escherichia–Shigella decreased to below 1% in the MRS-6, MRS-12, MRS-36, and MRS-46 groups, accompanied by increases in health-associated commensal genera including Blautia, Bifidobacterium, Faecalibacterium, and Bacteroides. Total SCFA concentrations reached 14.51, 13.55, and 12.16 mmol/L in the MRS-36, MRS-46, and MRS-6 groups, respectively, with the highest butyrate concentrations observed in the MRS-36 and MRS-46 groups. These findings establish a sequential screening framework linking in vitro functional phenotypes with validation in a complex fecal microbial community and identify candidate strains with promising microbiota- and SCFA-modulating potential.