| Summary: | 博士 === 國立中興大學 === 食品暨應用生物科技學系所 === 106 === The aim of this study was to characterize high exopolysaccharide (EPS)-producing lactic acid bacteria (LAB) isolated from mustard pickles in Taiwan for potential probiotic applications and evaluate the effect of orange peel fiber powder (OPFP) in comparison to that of Tremella flava Chen fermented powder (TFP) on Lactobacillus pentosus SLC 13 exopolysaccharide (EPS) production for future development of EPS-rich fermented drinks by botanical LAB. Among 39 collected LAB strains from mustard pickles, four most productive EPS-producing strains were selected for further analysis. Comparative analyses of 16S rDNA, rpoA, and pheS sequences demonstrated that these strains were members of Lactobacillus plantarum-group (LPG). LAB NCD 2, NLD 4, SLC 13, and NLD 16 showed survival rates of 95.83 ± 0.49%, 95.07 ± 0.64%, 105.84 ± 0.82%, and 99.65 ± 0.31%, respectively, under simulated gastrointestinal condition. No cytotoxic effects on macrophage RAW 264.7 cells were observed when they were treated with a low dose (1 μg/mL) of stimulants extracted from the tested four LAB strains(except SLC 13). The production of nitric oxide in RAW 264.7 cells incubated with various LAB stimulants showed a dose-dependent increase. Among the four strains, SLC 13 showed higher inhibitory activity on growth of Enterococcus faecalis (BCRC 12302) and Yersinia enterocolitica (BCRC 10807). NLD 4 showed strong inhibitory activity against Escherichia coli O157:H7 (ATCC 43894) as compared with the other three strains. EPS production and growth by L. pentosus SLC 13 in MRS broth supplemented with different concentrations of glucose, OPFP, and TFP were investigated. The results of this study showed that supplementation with 6% glucose, 2% OPFP, and 2% TFP significantly promoted EPS production (from 0.4322 ± 0.0145 to 2.0302 ± 0.1572, from 0.4340 ± 0.0142 to 2.4691 ± 0.0268, and from 0.4372 ± 0.0395 to 2.5582 ± 0.0873 g/ L, respectively) and bacterial viability (from 7.06 ± 0.08 to 8.88 ± 0.05, from 7.02 ± 0.01 to 7.67 ± 0.07, and 6.99 ± 0.04 to 7.96 ± 0.07 log 10 CFU/ mL, respectively). Maximum EPS production (2.6647 ± 0.0380 g/ L) of L. pentosus SLC 13 was observed when 2% OPFP pretreated with 3 N HCl was added to the culture medium. Supplementation of 2% OPFP treated with 20 U xylanase, 20 U cellulase, and 10 U cellulase/10 U xylanase increased the EPS production (from 2.4691 ± 0.0268 to 3.1488 ± 0.0410, 3.1467 ± 0.0574, and 3.2169 ± 0.0895 g/ L, respectively) by strain L. pentosus SLC 13. The antioxidant activity of EPS and antibacterial property of the MRS broth were investigated by adding 6% glucose, 2% OPFP, and 2% TFP to the L. pentosus SLC 13 culture medium. The highest reducing power and DPPH and ABTS radical scavenging activities of EPS (20 mg/ mL) were observed when the culture medium was supplemented with 6% glucose (121.1548 ± 2.1861, 73.7676 ± 3.1502, and 85.1297 ± 0.7075%, respectively). Supplementation with 6% glucose and 2% OPFP enhanced the antibacterial property of the L. pentosus SLC 13 medium against Staphylococcus aureus (BCRC 11863) and Salmonella enterica (BCRC 10746) respectively. In summary, our results suggest that L. pentosus SLC 13 may be a good candidate for probiotic applications and for development of antibacterial compounds. This study regarding culture medium by adding 2% OPFP promotes EPS production (increased to 5.6892 times), growth (EPS yield per unit cell was about 0.0528 ng/ cell), and antibacterial property of L. pentosus SLC 13 suggest that it has potential for industrial application as an economic prebiotic.
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