Jicheng Wang

Fermentation characteristics and transit tolerance of probiotic Lactobacillus casei Zhang in soymilk and bovine milk during storage

Lactobacillus casei Zhang is a novel strain that was screened out of koumiss collected in Inner Mongolia, and our previous research showed that L. casei Zhang has health benefits such as cholesterol-reducing and immunomodulating effects. The fermentation characteristics of L. casei Zhang in soymilk and bovine milk and the transit tolerance of L. casei Zhang in fermented milk products during refrigerated storage for 28 d were assessed. A faster decrease in pH and faster growth of L. casei Zhang during fermentation were observed in soymilk compared with bovine milk at various inoculation rates, probably because of the low pH buffering capacity of soymilk. The fermented bovine milk samples had much higher final titratable acidity (TA) values (between 0.80 and 0.93%) than the soymilk samples (between 0.40 and 0.46%). Dramatic increases in TA values in the fermented soymilk samples during storage were observed, and the TA values of the fermented soymilk samples changed from <0.56% to values between 0.86 and 0.98%. On the other hand, only slight increases in TA were observed in the bovine milk samples during the 28 d of storage. The survival rates of freshly prepared cultures of L. casei Zhang in simulated gastric juice at pH 2.0 and 2.5 were 31 and 69%, respectively, and the delivery of L. casei Zhang through fermented soymilk and bovine milk significantly improved the viability of L. casei Zhang in simulated gastric transit. Lactobacillus casei Zhang showed good tolerance to simulated gastric juice and intestinal juice in the fermented soymilk and bovine milk samples, and maintained high viability (>10(8) cfu/g) during storage at 4 degrees C for 28 d. Our results indicated that both soymilk and bovine milk could serve as vehicles for delivery of probiotic L. casei Zhang, and further research is needed to elucidate the mechanism of the change in pH and TA of L. casei Zhang in fermented milk samples during fermentation and storage and to understand the difference between soy- and milk-based systems.

Complete Genome Sequence of Streptococcus thermophilus Strain ND03

Streptococcus thermophilus strain ND03 is a Chinese commercial dairy starter used for the manufacture of yogurt. It was isolated from naturally fermented yak milk in Qinghai, China. We present here the complete genome sequence of ND03 and compare it to three other published genomes of Streptococcus thermophilus strains.

Complete Genome Sequence of Lactobacillus helveticus H10

Lactobacillus helveticus strain H10 was isolated from traditional fermented milk in Tibet, China. We sequenced the whole genome of strain H10 and compared it to the published genome sequence of Lactobacillus helveticus DPC4571.

Complete genome sequence of Lactobacillus delbrueckii subsp. bulgaricus strain ND02.

Lactobacillus delbrueckii subsp. bulgaricus strain ND02 is a Chinese commercial dairy starter used for the manufacture of yoghurt. It was isolated from naturally fermented yak milk in Qinghai, China. Here, we report the main genome features of ND02 and several differences with two other published genomes of Lactobacillus delbrueckii subsp. bulgaricus strains.

Complete Genome Sequence of Probiotic Bifidobacterium animalis subsp. lactis Strain V9

Bifidobacterium animalis subsp. lactis strain V9 is a Chinese commercial bifidobacteria with several probiotic functions. It was isolated from a healthy Mongolian child in China. We present here the complete genome sequence of V9 and compare it to 3 other published genome sequences of B. animalis subsp. lactis strains. The result indicates the lack of polymorphism among strains of this subspecies from different continents.

Transcriptome analysis of probiotic Lactobacillus casei Zhang during fermentation in soymilk

Lactobacillus casei Zhang is a widely recognized probiotic bacterium, which is being commercially used in China. To study the gene expression dynamics of L. casei Zhang during fermentation in soymilk, a whole genome microarray was used to screen for differentially expressed genes when grown to the lag phase, the late logarithmic phase, and the stationary phase. Comparisons of different transcripts next to each other revealed 162 and 63 significantly induced genes in the late logarithmic phase and stationary phase, of which the expression was at least threefold up-regulated and down-regulated, respectively. Approximately 38.4% of the up-regulated genes were associated with amino acid transport and metabolism notably for histidine and lysine biosynthesis, followed by genes/gene clusters involved in carbohydrate transport and metabolism, lipid transport and metabolism, and inorganic ion transport and metabolism. The analysis results suggest a complex stimulatory effect of soymilk-based ecosystem on the L. casei Zhang growth. On the other hand, it provides the very first insight into the molecular mechanism of L. casei strain for how it will adapt to the protein-rich environment.

Comparative analysis of the gene expression profile of probiotic Lactobacillus casei Zhang with and without fermented milk as a vehicle during transit in a simulated gastrointestinal tract.

Studies have found that the survival of probiotics could be strongly enhanced with dairy products as delivery vehicles, but the molecular mechanism by which this might occur has seldom been mentioned. In this study, microarray technology was used to detect the gene expression profile of Lactobacillus casei Zhang with and without fermented milk used as a delivery vehicle during transit in simulated gastrointestinal juice. Numerous genes of L. casei Zhang in strain suspension were upregulated compared to those from L. casei Zhang in fermented milk. These data might indicate that L. casei Zhang is stimulated directly without the protection of fermented milk, and the high-level gene expression observed here may be a stress response at the transcriptional level. A large proportion of genes involved in translation and cell division were downregulated in the bacteria that were in strain suspension during transit in simulated intestinal juice. This may impede protein biosynthesis and cell division and partially explain the lower viability of L. casei Zhang during transit in the gastrointestinal tract without the delivery vehicle.

Comparison of nutrition and microbiological compositions between two types of fermented milk from Tibet in China

Twenty-nine traditional fermented yak milk (kurut) and 15 traditional fermented Mongolian cow milk (FMCM) samples were collected from three regions of Tibet in China, and their chemical composition and microbiological properties were analyzed. Average levels of the major composition of kurut and FMCM, respectively, were as follows: total solid, 16.91±1.30 g/100 g and 12.65±1.14 g/100 g; fat, 6.83±1.18 g/100 g and 3.92±0.92 g/100 g; total protein, 4.93±0.36 g/100 g and 3.33±0.71 g/100 g; free amino acid, 8.57±3.22 mmol/l and 2.23±0.62 mmol/l; calcamin, 117.26±9.66 mg/100 g and 86.51±7.55 mg/100 g; and phosphorus, 109.28±7.97 mg/100 g and 78.86±6.99 mg/100 g. The average bacteria count of lactic acid bacteria in kurut and FMCM were 7.66±0.71 and 8.03±0.68 log colony-forming units (cfu)/ml, respectively. Moreover, the average yeast counts of these two samples were 6.48±0.81 and 5.92±0.52 log cfu/ml, respectively. The result showed that the major nutritional composition content of kurut was significantly higher than that of FMCM, which indicated that kurut can be considered an invaluable fermentation product for human being.