To obtain the optimization formulation of pure cultures in Tibetan kefir, the influence of the different mixtures of five strains in the pure cultures in Tibetan kefir on the flavor components in fermented milk was st...To obtain the optimization formulation of pure cultures in Tibetan kefir, the influence of the different mixtures of five strains in the pure cultures in Tibetan kefir on the flavor components in fermented milk was studied using the mixture design. The regression model on microorganism composition and main metabolites was established. The results suggested that the predictable production of lactate reached the maximum of 8.16 g L-1, while the most predictable production of diacetyl, ethanol, and CO2 were 77.23 mg L-1, 4259 mg L-1, and 2.12 g L-1, respectively. Based on these, the response values that satisfied all expectations were optimized, and the most excellent combination was Lactococcus lactis 27%, Leuconostoc mesenteroides 37%, Lactobacillus kefiri 11%, Lactobacillus casei 10%, and Kluyveromyces rnarxianus 15%. With the aid of analysis software （Design-expert 6.0.5）, the formulation of pure cultures in Tibetan kefir can be optimized for several responses and the best formulation can be obtained.展开更多
This study describes the changes in the microbial growth,physicochemical properties,phenolics,enzyme activity,and antioxidant activity of Goji berry juice during fermentation with Tibetan kefir grains(TKG).The results...This study describes the changes in the microbial growth,physicochemical properties,phenolics,enzyme activity,and antioxidant activity of Goji berry juice during fermentation with Tibetan kefir grains(TKG).The results showed that TKG grew well in Goji berry juice,and yeasts were dominant in the later period of fermentation(5.20×10^(8) CFU/mL).The main fungal genus of TKG and fermented Goji berry juice(24,48,and 72 h)was Kazachstania stably.The relative abundance of Lactobacillus in Goji berry juice decreased from 92.05%to 33.11%after 72 h-fermentation,while that of Acetobacter increased to 66.81%.In addition,72 h-fermentation led to the consumption of 82.55%of total sugar and 93.90%of reducing sugar,as well as dramatic changes in organic acids.The main volatile substances changed from aldehydes(61.98%)to alcohols(55.24%)and esters(38.54%).The content of total soluble flavonoids(STFC)in Goji berry juice was significantly increased from 42.28 mg RE/100 mL to 85.69 mg RE/100 mL after complete fermentation(p<0.01).Furthermore,16 flavonoids,eight phenolic acids,one phenolic acid derivative,and two coumarins were identified by HRLC-ESI-MS/MS.α-Amylase and xylanase were primarily responsible for the release of flavonoids(mangiferin,rutin,hyperoside,isoquercitrin,and quercetin)during fermentation,thus significantly enhancing the reducing power and OH⋅scavenging activity of Goji berry juice.展开更多
Tibetan kefir grains (TKGs) and their products are multi-functional health supplements. This study aimed to explore the diversity of microorganisms in Tibetan kefir grains (TKGs) and the protective effect of isolates ...Tibetan kefir grains (TKGs) and their products are multi-functional health supplements. This study aimed to explore the diversity of microorganisms in Tibetan kefir grains (TKGs) and the protective effect of isolates on ethanol-treated HepG2 cells. Metagenomic sequencing showed that Lactobacillus Kefiranofaciens was the most abundant bacterial taxon, while Kluyveromyces marxianus was the most abundant fungal taxum in TKGs. Thirteen isolates belonging to the genera Lactobacillus (3), Fructobacillus (1), Lactococcus (1), Pediococcus (1), Acetobacter (3), and Kluyveromyces (4), were obtained by cultivation methods. KEGG pathway analysis revealed that K. marxianus contributed four KEGG pathways related to hepatic disease. LC-MS analysis revealed CFEs are rich sources of peptides amino acids, lipids and amino acids. Cell-free extracts (CFEs) prepared from K. marxianus protected HepG2 cells from ethanol-induced injury. Treatment with CFEs from isolates YG-4 and YK-6 significantly increased cell viability and reduced ethanol cytotoxicity. Also, YG-4 and YK-6 decreased reactive oxygen species, malondialdehyde and alanine aminotransferase, increased superoxide dismutase and catalase, and reduced apoptosis and loss of potential in mitochondria. In addition, CFEs, especially YG-4-derived CFEs, decreased ethanol-induced inflammatory cytokines (IL-6, IL-17 and TNF-α), while YG-4 and YK-6 CFEs upregulated the regulatory cytokine IL-4. Thus, YG-4 had the most significant anti-inflammatory effects by reducing ethanol-induced oxidative stress. These isolates’ properties may provide new avenues to use K. maxianus in alcoholic liver disease.展开更多
文摘To obtain the optimization formulation of pure cultures in Tibetan kefir, the influence of the different mixtures of five strains in the pure cultures in Tibetan kefir on the flavor components in fermented milk was studied using the mixture design. The regression model on microorganism composition and main metabolites was established. The results suggested that the predictable production of lactate reached the maximum of 8.16 g L-1, while the most predictable production of diacetyl, ethanol, and CO2 were 77.23 mg L-1, 4259 mg L-1, and 2.12 g L-1, respectively. Based on these, the response values that satisfied all expectations were optimized, and the most excellent combination was Lactococcus lactis 27%, Leuconostoc mesenteroides 37%, Lactobacillus kefiri 11%, Lactobacillus casei 10%, and Kluyveromyces rnarxianus 15%. With the aid of analysis software （Design-expert 6.0.5）, the formulation of pure cultures in Tibetan kefir can be optimized for several responses and the best formulation can be obtained.
基金supported by the national 13th Five-Year key Research and Development Plan project(grant number 2019YFC1606703).
文摘This study describes the changes in the microbial growth,physicochemical properties,phenolics,enzyme activity,and antioxidant activity of Goji berry juice during fermentation with Tibetan kefir grains(TKG).The results showed that TKG grew well in Goji berry juice,and yeasts were dominant in the later period of fermentation(5.20×10^(8) CFU/mL).The main fungal genus of TKG and fermented Goji berry juice(24,48,and 72 h)was Kazachstania stably.The relative abundance of Lactobacillus in Goji berry juice decreased from 92.05%to 33.11%after 72 h-fermentation,while that of Acetobacter increased to 66.81%.In addition,72 h-fermentation led to the consumption of 82.55%of total sugar and 93.90%of reducing sugar,as well as dramatic changes in organic acids.The main volatile substances changed from aldehydes(61.98%)to alcohols(55.24%)and esters(38.54%).The content of total soluble flavonoids(STFC)in Goji berry juice was significantly increased from 42.28 mg RE/100 mL to 85.69 mg RE/100 mL after complete fermentation(p<0.01).Furthermore,16 flavonoids,eight phenolic acids,one phenolic acid derivative,and two coumarins were identified by HRLC-ESI-MS/MS.α-Amylase and xylanase were primarily responsible for the release of flavonoids(mangiferin,rutin,hyperoside,isoquercitrin,and quercetin)during fermentation,thus significantly enhancing the reducing power and OH⋅scavenging activity of Goji berry juice.
基金supported by the National 13th Five-Year Key Research and Development Program(2019YFC1606703).
文摘Tibetan kefir grains (TKGs) and their products are multi-functional health supplements. This study aimed to explore the diversity of microorganisms in Tibetan kefir grains (TKGs) and the protective effect of isolates on ethanol-treated HepG2 cells. Metagenomic sequencing showed that Lactobacillus Kefiranofaciens was the most abundant bacterial taxon, while Kluyveromyces marxianus was the most abundant fungal taxum in TKGs. Thirteen isolates belonging to the genera Lactobacillus (3), Fructobacillus (1), Lactococcus (1), Pediococcus (1), Acetobacter (3), and Kluyveromyces (4), were obtained by cultivation methods. KEGG pathway analysis revealed that K. marxianus contributed four KEGG pathways related to hepatic disease. LC-MS analysis revealed CFEs are rich sources of peptides amino acids, lipids and amino acids. Cell-free extracts (CFEs) prepared from K. marxianus protected HepG2 cells from ethanol-induced injury. Treatment with CFEs from isolates YG-4 and YK-6 significantly increased cell viability and reduced ethanol cytotoxicity. Also, YG-4 and YK-6 decreased reactive oxygen species, malondialdehyde and alanine aminotransferase, increased superoxide dismutase and catalase, and reduced apoptosis and loss of potential in mitochondria. In addition, CFEs, especially YG-4-derived CFEs, decreased ethanol-induced inflammatory cytokines (IL-6, IL-17 and TNF-α), while YG-4 and YK-6 CFEs upregulated the regulatory cytokine IL-4. Thus, YG-4 had the most significant anti-inflammatory effects by reducing ethanol-induced oxidative stress. These isolates’ properties may provide new avenues to use K. maxianus in alcoholic liver disease.
