In this study,high-throughput sequencing was used to analyze the microbial diversity and relative abundance of the blueberry epidermis and found that lactic acid bacteria(LAB)represent a relatively abundant group.Puta...In this study,high-throughput sequencing was used to analyze the microbial diversity and relative abundance of the blueberry epidermis and found that lactic acid bacteria(LAB)represent a relatively abundant group.Putative LAB strains were isolated and purified from the blueberry epidermis by traditional biological methods.Thirty LAB strains were identified by genotype identification,physiological and biochemical test,and 16 S rDNA sequence analysis revealed 100% sequence identity between 8 isolated strains and the representative LAB in the blueberry epidermis.Of the 8 strains,ZYN-0417(Lactobacillus rhamnosus)and ZYN-0221(Lactobacillus plantarum)showed strong tolerance in the probiotic test.Under gastric acid conditions with a pH of 2.0,the respective survival rate reached 65.71% and 68.85%.The respective survival rate reached 96.45% and 98.37% in 1.8% bile salt.After incubation in vitro gastrointestinal fluid for 240 min,the respective survival rate reached 91.00% and 86.26%.The antioxidant capacity test showed that the DPPH scavenging rate of ZYN-0417 and ZYN-0221 reached 85.45% and 87.45%,with ABTS free radical scavenging rate of 76.03% and 66.17%,OH scavenging rate of 57.30% and 46.93%,and Fe2+chelating ability of 46.34% and 43.70%,respectively.Fermentation study showed that ZYN-0417 and ZYN-0221 were capable of strong acid production with respective pH values and total acid content of 3.64 and 3.63,14.88 mg·L^(-1) and 14.85 mg·L^(-1) after 36 h of fermentation.Moreover,ZYN-0417 and ZYN-0221 showed strong extracellular protease activity(82.99 U·mL^(-1) and 95.17 U·mL^(-1),respectively).Blueberry juice fermentation showed robust growth of ZYN-0417 and ZYN-0221 and the viable bacterial number of LAB reached 13-14 log CUF·mL^(-1) at the end of fermentation.In summary,blueberry-derived LAB have good probiotic and antioxidant properties,and strong fermentation properties in low acid environments,thus showing the potential of their use for the lactobacillus fermentation of fruit and vegetables.展开更多
A yeast strain R6 was obtained by the method of thiamine（VB1） auxotrophic negative selection from the edible oil-polluted soil in Zibo, China. Physiological and biochemical experiments revealed that strain R6 shared...A yeast strain R6 was obtained by the method of thiamine（VB1） auxotrophic negative selection from the edible oil-polluted soil in Zibo, China. Physiological and biochemical experiments revealed that strain R6 shared common feature with Rhodotorula mucilaginosa according to the API 20 C AUX yeast identification system which has been tested previously. Furthermore, the 18 S r DNA gene of strain R6 was amplified and sequenced. Phylogenetic analysis based on the 18 S r DNA sequence and the relatives indicated that R6 shared 99% homologies with the members of R. mucilaginosa, suggesting that strain R6 belonged to R. mucilaginosa.Investigation showed that strain R6 possessed the capacity of accumulating exocellular alpha-ketoglutaric acid（alpha-KG）. Finally, the fermentation conditions of R6 to accumulate alpha-KG was optimized by controlling each single fermenting variable and detected through high performance liquid chromatography（HPLC）. Results showed that both VB1 and Ca CO3 in fermentation medium were the key factors influencing the cumulant of alpha-KG. The discovery of natural auxotrophic strain R6 not only broadened the microbial resource which can achieve lots of alpha-KG production through fermentation, but also laid a foundation for further fermentation regulation to achieve excessive alpha-KG accumulation.展开更多
The indigenous starter cultures isolated from fermented food can compete with spoilage and pathogenic bacteria and improve the flavor and organoleptic properties of products.The purposes of this work were to screen an...The indigenous starter cultures isolated from fermented food can compete with spoilage and pathogenic bacteria and improve the flavor and organoleptic properties of products.The purposes of this work were to screen and assess the safety,potential probiotic,and fermentation properties of indigenous starter cultures isolated from dry-cured ducks.The properties of indigenous starter cultures were investigated by antibiotic resistance,virulence genes,in vivo toxicity,simulated gastrointestinal,adhesion capacity to Caco-2 cells,inoculation fermentation,etc.Overall,six strains were isolated and identified,including Lactobacillus sakei D15,Weissella hellenica D20,Lactobacillus curvatus D2,Staphylococcus simulans D12,Staphylococcus equorum D19,and Staphylococcus edaphicus D17.The obtained strains showed high safety.Additionally,most strains displayed excellent probiotic properties,including tolerance to lower pH,lysozyme,bile salt,and a high survival rate of the simulated gastrointestinal phase.The adhesion ability of strain cells to Caco-2 cells was 9.22%-14.21%.And the probiotic properties of strains can be strengthened by the expression of specific enzymes.The inoculation with the isolated strains(LS-D15,LC-D2 and SS-D12)could contribute to the formation of volatile flavor compounds in samples.Overall,results demonstrated that strains possessed excellent safety and probiotic properties,and can be used as starter cultures to enhance the quality and flavor of the dry-cured duck.展开更多
This study investigated the synergistic effects of sourdough(SD)combined with cellulase(Cel-SD),and xylanase(Xyl-SD)on the quality of frozen steamed stuffed buns(FSSB)during freeze-thaw(FT)cycles.The results demonstra...This study investigated the synergistic effects of sourdough(SD)combined with cellulase(Cel-SD),and xylanase(Xyl-SD)on the quality of frozen steamed stuffed buns(FSSB)during freeze-thaw(FT)cycles.The results demonstrated that after three FT cycles,the addition of Cel-SD and Xyl-SD significantly improved the specific volume and texture of FSSB(p<0.05).The content of water-soluble polysaccharides and reducing sugars in fermented dough was also elevated by the incorporation of Cel-SD and Xyl-SD.The analysis of fermentation properties revealed that Cel-SD and Xyl-SD enhanced total gas production and retention capacity in frozen dough,contributing to the improved specific volume of FSSB.Low-field nuclear magnetic resonance(LF-NMR)analysis indicated that Cel-SD and Xyl-SD inhibited water migration,increasing the proportion of tightly bound water(A21)and reducing free water(A23).Notably,Xyl-SD exhibited a significant reduction in freezable water content from 55%to 43%in frozen dough after four FT cycles(p<0.05).Furthermore,compared to the control group,the SDS-extractable protein and free sulfhydryl(SH)group content in Cel-SD group decreased after FT cycles,indicating that the gluten stability was enhanced.These results revealed that the combination of sourdough with cellulase or xylanase exerts synergistic effects in improving the quality of frozen steamed stuffed buns and enhancing the freeze-thaw tolerance of frozen dough.This study provides a novel strategy and a theoretical foundation for the application of sourdough,cellulase,and xylanase in frozen dough products.展开更多
基金supported by grants from the Ministry of Fundamental Research Funds in Heilongjiang Provincial Universities(No.145109318).
文摘In this study,high-throughput sequencing was used to analyze the microbial diversity and relative abundance of the blueberry epidermis and found that lactic acid bacteria(LAB)represent a relatively abundant group.Putative LAB strains were isolated and purified from the blueberry epidermis by traditional biological methods.Thirty LAB strains were identified by genotype identification,physiological and biochemical test,and 16 S rDNA sequence analysis revealed 100% sequence identity between 8 isolated strains and the representative LAB in the blueberry epidermis.Of the 8 strains,ZYN-0417(Lactobacillus rhamnosus)and ZYN-0221(Lactobacillus plantarum)showed strong tolerance in the probiotic test.Under gastric acid conditions with a pH of 2.0,the respective survival rate reached 65.71% and 68.85%.The respective survival rate reached 96.45% and 98.37% in 1.8% bile salt.After incubation in vitro gastrointestinal fluid for 240 min,the respective survival rate reached 91.00% and 86.26%.The antioxidant capacity test showed that the DPPH scavenging rate of ZYN-0417 and ZYN-0221 reached 85.45% and 87.45%,with ABTS free radical scavenging rate of 76.03% and 66.17%,OH scavenging rate of 57.30% and 46.93%,and Fe2+chelating ability of 46.34% and 43.70%,respectively.Fermentation study showed that ZYN-0417 and ZYN-0221 were capable of strong acid production with respective pH values and total acid content of 3.64 and 3.63,14.88 mg·L^(-1) and 14.85 mg·L^(-1) after 36 h of fermentation.Moreover,ZYN-0417 and ZYN-0221 showed strong extracellular protease activity(82.99 U·mL^(-1) and 95.17 U·mL^(-1),respectively).Blueberry juice fermentation showed robust growth of ZYN-0417 and ZYN-0221 and the viable bacterial number of LAB reached 13-14 log CUF·mL^(-1) at the end of fermentation.In summary,blueberry-derived LAB have good probiotic and antioxidant properties,and strong fermentation properties in low acid environments,thus showing the potential of their use for the lactobacillus fermentation of fruit and vegetables.
基金Supported by the Natural Science Foundation of Shandong Province,China(ZR2010CQ017)Program of Young Teachers Development of Shandong University of Technology~~
文摘A yeast strain R6 was obtained by the method of thiamine（VB1） auxotrophic negative selection from the edible oil-polluted soil in Zibo, China. Physiological and biochemical experiments revealed that strain R6 shared common feature with Rhodotorula mucilaginosa according to the API 20 C AUX yeast identification system which has been tested previously. Furthermore, the 18 S r DNA gene of strain R6 was amplified and sequenced. Phylogenetic analysis based on the 18 S r DNA sequence and the relatives indicated that R6 shared 99% homologies with the members of R. mucilaginosa, suggesting that strain R6 belonged to R. mucilaginosa.Investigation showed that strain R6 possessed the capacity of accumulating exocellular alpha-ketoglutaric acid（alpha-KG）. Finally, the fermentation conditions of R6 to accumulate alpha-KG was optimized by controlling each single fermenting variable and detected through high performance liquid chromatography（HPLC）. Results showed that both VB1 and Ca CO3 in fermentation medium were the key factors influencing the cumulant of alpha-KG. The discovery of natural auxotrophic strain R6 not only broadened the microbial resource which can achieve lots of alpha-KG production through fermentation, but also laid a foundation for further fermentation regulation to achieve excessive alpha-KG accumulation.
基金supported by the Major Science and Technology Program of Anhui,China(2021d06050001)the Anhui Provincial Natural Science Foundation of China(2108085QC148)the Fundamental Research Funds for the Central Universities of China(JZ2021HGQA0242,JZ2022HGTB0263 and JZ2021HGQB0278).
文摘The indigenous starter cultures isolated from fermented food can compete with spoilage and pathogenic bacteria and improve the flavor and organoleptic properties of products.The purposes of this work were to screen and assess the safety,potential probiotic,and fermentation properties of indigenous starter cultures isolated from dry-cured ducks.The properties of indigenous starter cultures were investigated by antibiotic resistance,virulence genes,in vivo toxicity,simulated gastrointestinal,adhesion capacity to Caco-2 cells,inoculation fermentation,etc.Overall,six strains were isolated and identified,including Lactobacillus sakei D15,Weissella hellenica D20,Lactobacillus curvatus D2,Staphylococcus simulans D12,Staphylococcus equorum D19,and Staphylococcus edaphicus D17.The obtained strains showed high safety.Additionally,most strains displayed excellent probiotic properties,including tolerance to lower pH,lysozyme,bile salt,and a high survival rate of the simulated gastrointestinal phase.The adhesion ability of strain cells to Caco-2 cells was 9.22%-14.21%.And the probiotic properties of strains can be strengthened by the expression of specific enzymes.The inoculation with the isolated strains(LS-D15,LC-D2 and SS-D12)could contribute to the formation of volatile flavor compounds in samples.Overall,results demonstrated that strains possessed excellent safety and probiotic properties,and can be used as starter cultures to enhance the quality and flavor of the dry-cured duck.
基金supported by the National Natural Science Foundation of China(Grant No.32072253)the Collaborative Innovation Center of Food Safety and Quality Control in Jiangsu Province,Jiangnan University.
文摘This study investigated the synergistic effects of sourdough(SD)combined with cellulase(Cel-SD),and xylanase(Xyl-SD)on the quality of frozen steamed stuffed buns(FSSB)during freeze-thaw(FT)cycles.The results demonstrated that after three FT cycles,the addition of Cel-SD and Xyl-SD significantly improved the specific volume and texture of FSSB(p<0.05).The content of water-soluble polysaccharides and reducing sugars in fermented dough was also elevated by the incorporation of Cel-SD and Xyl-SD.The analysis of fermentation properties revealed that Cel-SD and Xyl-SD enhanced total gas production and retention capacity in frozen dough,contributing to the improved specific volume of FSSB.Low-field nuclear magnetic resonance(LF-NMR)analysis indicated that Cel-SD and Xyl-SD inhibited water migration,increasing the proportion of tightly bound water(A21)and reducing free water(A23).Notably,Xyl-SD exhibited a significant reduction in freezable water content from 55%to 43%in frozen dough after four FT cycles(p<0.05).Furthermore,compared to the control group,the SDS-extractable protein and free sulfhydryl(SH)group content in Cel-SD group decreased after FT cycles,indicating that the gluten stability was enhanced.These results revealed that the combination of sourdough with cellulase or xylanase exerts synergistic effects in improving the quality of frozen steamed stuffed buns and enhancing the freeze-thaw tolerance of frozen dough.This study provides a novel strategy and a theoretical foundation for the application of sourdough,cellulase,and xylanase in frozen dough products.
