A strain with high production of exopolysaccharide(EPS) was isolated from dried milk cake(a traditional fermented food from Inner Mongolia). The strain was called N21 and later identified as Leuconostoc citreum( Leu. ...A strain with high production of exopolysaccharide(EPS) was isolated from dried milk cake(a traditional fermented food from Inner Mongolia). The strain was called N21 and later identified as Leuconostoc citreum( Leu. citreum). The strain was cultured in Man-Rogosa-Sharpe medium containing 50 g/L of sucrose for 48 h at 30 °C and the EPS purified, with a yield of 24.5 g/L. An average molecular weight of 6.07 × 10~6 g/mol was determined by high-performance size-exclusion chromatography. The structure of the purified EPS was investigated through gas chromatography, ~1H and ^(13)C nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. The results demonstrated a polysaccharide composed of D-glucopyranose units in a linear chain with consecutive α(1 → 6) linkages. No branching was found in the structure of the exopolysaccharide. The purified EPS showed high water solubility and emulsibility. Based on the thermogravimetric curve, the degradation temperature of the EPS was 308.47 °C, which suggested that the dextran in the study exhibited high thermal stability. The results indicated that Leu. citreum N21 could be widely used to produce linear EPS and that the EPS has potential applications in food science and processing as a food additive.展开更多
To study the effects of mixed starter consisted of different fermentative type of lactic acid bacteria(LAB)on the fermentation of suansun,two lactic acid bacteria(Leuconostoc citreum NM-12 and Lactobacillus plantarum ...To study the effects of mixed starter consisted of different fermentative type of lactic acid bacteria(LAB)on the fermentation of suansun,two lactic acid bacteria(Leuconostoc citreum NM-12 and Lactobacillus plantarum L01)isolated from Chinese traditional fermented vegetable were used in the preparation of suansun.The fermentation was carried out at ambient temperature(around 25℃)for 96 h by inoculating different mixing ratios of LAB(inoculated fermentation)or using natural microbes(natural fermentation).The changes of pH,titratable acid(TA),microbe communities,free sugars,organic acids,nitrite and volatile compounds during fermentation were evaluated.Suansun treated with high Leuconostoc citreum ratio inoculation exhibited a quickly change in pH and TA,resulting from the rapid increase in the number of viable cells,at the early stage of fermentation and produced more mannitol(0.12–0.46 mg/mL)and acetic acid(0.93–3.56 mg/mL).However,Suansun treated with high Lactobacillus plantarum ratio inoculation had lower pH and higher TA at the later stage of fermentation and produced more lactic acid(5.32–7.68 mg/mL).No mannitol was detected in suansun when only Lactobacillus plantarum was inoculated in fermentation.No p-cresol was produced in the inoculated fermentation with mixed starter culture,in addition to the production of ethyl acetate and 2.3-butanedione,which had a positive effect on the flavor of suansun.In summary,this study demonstrated the application value of mixed starter consisted of different fermentative type of LAB.LAB types and mixing ratios greatly affected the types and concentration of metabolites in suansun fermentation.展开更多
为探索不同发酵类型乳酸菌接种发酵的差异,将柠檬明串珠菌与植物乳杆菌分别接种发酵竹笋,测定竹笋发酵过程中总酸、pH值、乳酸菌总数、有机酸、游离糖和亚硝酸盐含量的变化。结果表明:接种柠檬明串珠菌可以快速启动发酵,在24 h乳酸菌总...为探索不同发酵类型乳酸菌接种发酵的差异,将柠檬明串珠菌与植物乳杆菌分别接种发酵竹笋,测定竹笋发酵过程中总酸、pH值、乳酸菌总数、有机酸、游离糖和亚硝酸盐含量的变化。结果表明:接种柠檬明串珠菌可以快速启动发酵,在24 h乳酸菌总数达到9.44 lg cfu/mL,迅速降低pH值,抑制腐败菌的生长,植物乳杆菌能够形成更低的pH值环境,2种乳酸菌对有机酸的代谢能力不同。此外,接种柠檬明串珠菌还能产生泡菜的特征风味物质甘露醇,相比植物乳杆菌产生的亚硝酸盐含量更低。证实不同发酵类型乳酸菌在接种发酵过程中化学成分的变化存在差异。展开更多
基金supported by the National Science and Technology Support Plan Project(No.2015BAD16B01)
文摘A strain with high production of exopolysaccharide(EPS) was isolated from dried milk cake(a traditional fermented food from Inner Mongolia). The strain was called N21 and later identified as Leuconostoc citreum( Leu. citreum). The strain was cultured in Man-Rogosa-Sharpe medium containing 50 g/L of sucrose for 48 h at 30 °C and the EPS purified, with a yield of 24.5 g/L. An average molecular weight of 6.07 × 10~6 g/mol was determined by high-performance size-exclusion chromatography. The structure of the purified EPS was investigated through gas chromatography, ~1H and ^(13)C nuclear magnetic resonance spectroscopy, and Fourier transform infrared spectroscopy. The results demonstrated a polysaccharide composed of D-glucopyranose units in a linear chain with consecutive α(1 → 6) linkages. No branching was found in the structure of the exopolysaccharide. The purified EPS showed high water solubility and emulsibility. Based on the thermogravimetric curve, the degradation temperature of the EPS was 308.47 °C, which suggested that the dextran in the study exhibited high thermal stability. The results indicated that Leu. citreum N21 could be widely used to produce linear EPS and that the EPS has potential applications in food science and processing as a food additive.
基金supported by the Guangxi colledge students’innovation and entrepreneurship training projects,China(S202110594095).
文摘To study the effects of mixed starter consisted of different fermentative type of lactic acid bacteria(LAB)on the fermentation of suansun,two lactic acid bacteria(Leuconostoc citreum NM-12 and Lactobacillus plantarum L01)isolated from Chinese traditional fermented vegetable were used in the preparation of suansun.The fermentation was carried out at ambient temperature(around 25℃)for 96 h by inoculating different mixing ratios of LAB(inoculated fermentation)or using natural microbes(natural fermentation).The changes of pH,titratable acid(TA),microbe communities,free sugars,organic acids,nitrite and volatile compounds during fermentation were evaluated.Suansun treated with high Leuconostoc citreum ratio inoculation exhibited a quickly change in pH and TA,resulting from the rapid increase in the number of viable cells,at the early stage of fermentation and produced more mannitol(0.12–0.46 mg/mL)and acetic acid(0.93–3.56 mg/mL).However,Suansun treated with high Lactobacillus plantarum ratio inoculation had lower pH and higher TA at the later stage of fermentation and produced more lactic acid(5.32–7.68 mg/mL).No mannitol was detected in suansun when only Lactobacillus plantarum was inoculated in fermentation.No p-cresol was produced in the inoculated fermentation with mixed starter culture,in addition to the production of ethyl acetate and 2.3-butanedione,which had a positive effect on the flavor of suansun.In summary,this study demonstrated the application value of mixed starter consisted of different fermentative type of LAB.LAB types and mixing ratios greatly affected the types and concentration of metabolites in suansun fermentation.
文摘为探索不同发酵类型乳酸菌接种发酵的差异,将柠檬明串珠菌与植物乳杆菌分别接种发酵竹笋,测定竹笋发酵过程中总酸、pH值、乳酸菌总数、有机酸、游离糖和亚硝酸盐含量的变化。结果表明:接种柠檬明串珠菌可以快速启动发酵,在24 h乳酸菌总数达到9.44 lg cfu/mL,迅速降低pH值,抑制腐败菌的生长,植物乳杆菌能够形成更低的pH值环境,2种乳酸菌对有机酸的代谢能力不同。此外,接种柠檬明串珠菌还能产生泡菜的特征风味物质甘露醇,相比植物乳杆菌产生的亚硝酸盐含量更低。证实不同发酵类型乳酸菌在接种发酵过程中化学成分的变化存在差异。
