| Summary: | 博士 === 國立中興大學 === 食品暨應用生物科技學系所 === 107 === Lactobacillus pentosus SLC 13 is a high exopolysaccharide (EPS)-producing strain with broad-spectrum antimicrobial activity and the ability to grow in simulated gastrointestinal conditions. Lactobacillus pentosus SLC 13 was isolated from mustard pickles in Taiwan for potential probiotic applications. To better understand the molecular base for its antimicrobial activity and high EPS production, entire genome of L. pentosus SLC 13 was determined by PacBio single molecule real time (PacBio SMRT) sequencing. The results showed that L. pentosus SLC 13 contains a genome with a 3,520,510-bp chromosome and a 62,498-bp plasmid. GC content of the complete genome was 46.5% and that of plasmid pSLC13 was 41.3%. Sequences were annotated at the RAST prokaryotic genome annotation server, and the results showed that the genome contained 3,172 coding sequences and 82 RNA genes. Seventy-six protein-coding sequences were identified on the plasmid pSLC13. A plantaricin gene cluster, which is responsible for bacteriocins biosynthesis and could be associated with its broad-spectrum antimicrobial activity, was identified based on comparative genomic analysis. Two gene clusters involved in EPS production were also identified. This genomic sequence might contribute to a future application of this strain as probiotic.
The commercial usage of fermented products by L. pentosus SLC 13 in the market, particularly serving as food substrates, is still inadequately accepted. Orange peel fiber powder (OPFP) and Tremella flava Chen fermented powder (TFP) were showed to be potential prebiotics for L. pentosus SLC 13. To further develop a new synbiotic fermented lactic acid beverage, L. pentosus SLC 13 was inoculated into different proportions of skim milk and soymilk as food substrates, and that with OPFP or TFP as prebiotics. Acidification rate (soymilk groups, 3.02‒4.37 mU min-1; soymilk/milk mixture groups, 1.33‒2.84 mU min-1) and fermentation time (soymilk groups, 7.09‒9.25 h; soymilk/milk mixture groups, 12.51‒27.34 h) indicated that soymilk represents a suitable substrate for L. pentosus SLC 13-mediated fermentation. Moreover, OPFP and TFP induced higher EPS production of L. pentosus SLC 13 and higher water holding capacity (WHC) of fermented beverages. Sensory evaluations suggested that soymilk groups fermented with 10 g kg -1 OPFP (SF-1.0P) and that with 5 g kg -1 TFP (SF-0.5T); soymilk-skim milk mixture groups fermented with 5 g kg -1 OPFP (HSMF-0.5P) and that with 10 g kg -1 TFP (HSMF-1.0T) represent highly potential for using as fermented drinks. Additionally, SF-1.0P and SF-0.5T products could be preserved for at least 21 days at 4 °C, with high viable cell counts (> 8.8 log10 CFU mL-1) and WHC. In this study, we developed SF-1.0P and SF-0.5T products as new symbiotic fermented lactic acid beverage. Although, the mean score of fermented beverage supplement with TFP or OPFP for overall acceptability were lower than 5 (neither like nor dislike). In future studies, the acceptability may be increased by properly adjusting the ratio of sugar to acid or seasoning.
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