Explore the vast range of titles available.

The probiotic efficacy and fermentative ability of Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus), a widely used probiotic, is majorly affected by its acid tolerance. Here, we conducted whole-genome sequencing of the high acid-tolerant L. bulgaricus LJJ stored in the laboratory. Compared with the whole genome of low acid-tolerant strain L. bulgaricus ATCC11842, the results show that 16 candidate acid-tolerant genes may be involved in the regulation of the acid tolerance of L. bulgaricus LJJ. Association analysis of candidate acid-tolerant genes and acid-tolerant traits of different L. bulgaricus strains revealed that the three genes dapA, dapH, and lysC are the main reasons for the strong acid tolerance of L. bulgaricus LJJ. The results of real-time quantitative PCR (RT-qPCR) supported this conclusion. KEGG pathway analysis showed that these three acid-tolerant genes are involved in the synthesis of lysine; the synthesis of lysine may confer L. bulgaricus LJJ strong acid tolerance. This study successfully revealed the acid tolerance mechanism of L. bulgaricus LJJ and provides a theoretical basis for the subsequent selection of strains with high acid tolerance for improved probiotic functions.Key points• Three genes are identified as acid-tolerant genes, respectively, lysC, dapA, and dapH.• LysC and dapA are the major key genes in the synthesis of lysine.• The synthesis of lysine may confer L. bulgaricus LJJ strong acid tolerance.

Lipases play an important dual role in the dairy industry. Lipases improve quality but cause deterioration and changes in quality during the processing and storage of dairy products. Therefore, a rapid and sensitive method for determining lipase activity is needed. A new reagent, called a ‘Clarifying Buffer’, was developed for the clarification of opaque milk and the direct detection of lipase activity in milk using spectrophotometry. The present study successfully used a microplate-based method to analyze lipase activity in milk products. The lipase activities of raw milk samples subjected to different heat treatments were evaluated using the new method. The new method was sensitive to the activity of trace lipase in milk samples treated at 135 °C for 5, 10, and 30 s.

We aimed to obtain the optimal formula for human milk fat substitute (HMFS) through a combination of software and an evaluation model and further verify its practicability through an animal experiment. The results showed that a total of 33 fatty acid (FA) and 63 triglyceride (TAG) molecular species were detected in vegetable oils. Palmitic acid, oleic acid, linoleic acid, 18:1/16:0/18:1, 18:2/16:0/18:2, 18:1/18:1/18:1 and 18:1/18:2/18:1, were the main molecular species among the FAs and TAGs in the vegetable oils. Based on the HMFS evaluation model, the optimal mixed vegetable oil formula was blended with 21.3% palm oil, 2.8% linseed oil, 2.6% soybean oil, 29.9% rapeseed oil and 43.4% maize oil, with the highest score of 83.146. Moreover, there was no difference in the weight, blood routine indices or calcium and magnesium concentrations in the feces of the mice between the homemade mixed vegetable oil (HMVO) group and the commercial mixed vegetable oil (CMVO) group, while nervonic acid (C24:1) and octanoic acid (C8:0) were absorbed easily in the HMVO group. Therefore, these results demonstrate that the mixing of the different vegetable oils was feasible via a combination of computer software and an evaluation model and provided a new way to produce HMFS.

Background Thermostable lipases from microbial sources have been substantially overexpressed in E. coli , however, these enzymes are often produced with low-level enzymatic activity and mainly in the form of inclusion bodies. Several studies have reported that the secretory production of recombinant proteins fused their N-terminus to a signal peptide has been employed to resolve the problem. In general, the feasibility of this approach largely depends on the secretory pathway of signal peptide and the type of target protein to be secreted. This study was performed to compare and optimize signal peptides for efficient secretion of thermostable lipase lipBJ10 from Pseudomonas fluorescens BJ-10. Meanwhile, a comparative study between this method and cytoplasmic secretion was implemented in secreting soluble and active lipases. Results Fusion expression using six signal peptides, i.e., PelB and five native E. coli signal peptides, as fusion partners produced more soluble and functional recombinant lipBJ10 than non-fusion expression. Recombinant lipBJ10, fused to these six diverse signal peptides, was secreted into the periplasm in E. coli . The total lipase activity in all cases of fusion expression was higher than those in non-fusion expression. The relative activity peaked when lipBJ10 was fused to DsbA, yielding a value 73.3 times greater than that of the non-fusion protein. When DsbA was used as the fusion partner, the highest activity (265.41 U/ml) was achieved with the least formation of inclusion bodies; the other four E. coli signal peptides, to some extent, led to low activity and insoluble inclusion bodies. Therefore, DsbA is the optimal signal peptide partner to fuse with lipBJ10 to efficiently produce soluble and functional protein. Conclusion We found that fusing to these signal peptides, especially that of DsbA, can significantly decrease the formation of inclusion bodies and enhance the function and solubility of lipBJ10 compared to non-fusion lipBJ10. Our results reported here can provide a reference for the high-level expression of other lipases with respect to a possible industrial application.

Background/Objectives: This study characterized the endogenous peptide profile of human milk from a Chinese multicenter cohort (n = 200 mothers) using the Orbitrap Fusion Lumos LC-MS/MS. Methods: Samples were collected across different lactation stages (2 and 6 months postpartum) and seven geographic regions (Beijing, Chengdu, Guangzhou, Jinhua, Lanzhou, Weihai, and Zhengzhou). Results: In total, 6960 peptides derived from 621 proteins were identified. Peptides from the polymeric immunoglobulin receptor (PIGR) were more abundant in the 2nd month than the 6th month, providing a high antimicrobial activity and immune functions for the infants. Moreover, region-specific variations were observed, with milk from Lanzhou exhibiting significantly higher levels of β-casein (CASB) and butyrophilin subfamily 1 member A1 (BTN1A1) peptides compared to other cities. Conclusions: Furthermore, maternal dietary intake of oils and total fat correlated positively with the intensity of specific antimicrobial peptides, including CASB_199–216, CASB_200–226, and CASB_201–226. Infant growth parameters were inversely correlated with several antimicrobial peptides, although CASB_200–225 demonstrated positive associations. These findings offer novel insights into the dynamics of endogenous peptides in human milk and may guide breastfeeding recommendations and infant formula design.

Equol is the most potent soy isoflavone metabolite and is produced by specific intestinal microorganisms of mammals. It has promising application possibilities for preventing chronic diseases such as cardiovascular disease, breast cancer, and prostate cancer due to its high antioxidant activity and hormone-like activity. Thus, it is of great significance to systematically study the efficient preparation method of equol and its functional activity. This paper elaborates on the metabolic mechanism of equol in humans; focuses on the biological characteristics, synthesis methods, and the currently isolated equol-producing bacteria; and looks forward to its future development and application direction, aiming to provide guidance for the application and promotion of equol in the field of food and health products.

In order to improve the flavor and taste of Camembert cheese, the use of Monascus as an adjunct starter for the production of Camembert-type cheese was studied to investigate its effect on the proteolysis, lipolysis, and volatile compounds during ripening for 40 days. The Camembert cheese without Monascus was used as a control. The results showed that proteolytic and lipolytic activities increased to a certain extent. The addition of Monascus promoted primary and secondary proteolysis, due to the release of some proteases by Monascus. Aspartic, Threonine, Glutamic, Glycine, Methione, Isoleucine, Phenyalanine, and Lysine contents in experimental group (R) cheese were significantly higher than those in control group (W) cheeses. In addition, the free amino acid and fatty acid contents were also affected. The identification of flavor components using gas-mass spectrometry (GC-MS) showed that 2-undecone, 2-tridecanone, phenylethyl alcohol, butanediol (responsible for the production of flowery and honey-like aroma), ethyl hexanoate, ethyl octanoate, and ethyl citrate (fruit-like aroma) were significantly higher (p < 0.05) in the experimental cheeses than in the control. The contents of 2-nonanone, 2-octanone and 2-decanone (showing milky flavor), and 1-octene-3 alcohol with typical mushroom-like flavor were lower than the control.

Microbial detection in milk is crucial for food safety and quality, as beneficial and harmful microorganisms can affect consumer health and dairy product integrity. Identifying and quantifying these microorganisms helps prevent contamination and spoilage. The study employs advanced molecular techniques to detect and quantify the genomic DNA for the target hydrolytic enzyme coding genes lipA and aprX based on the multi-align sequence conserved region, specific primer pair, and hydrolysis probes designed using the singleplex qPCR and multiplex qPCR. Cultured isolates and artificially contaminated sterilized ultra-high-temperature (UHT) milk were analyzed for their specificity, cross-reactivity, and sensitivity. The finding indicated that strains with lipA and aprX genes were amplified while the other strains were not amplified. This indicated that the designed primer pairs/probes were very specific to the target gene of interest. The specificity of each design primer pair was checked using SYBR Green qPCR using 16 different isolate strains from the milk sample. The quantification specificity of each strain target gene was deemed to be with a mean Ct value for positive pseudomonas strain > 16.98 ± 1.76 (p < 0.0001), non-pseudomonas positive strain ≥ 27.47 ± 1.25 (p < 0.0001), no Ct for the negative control and molecular grade water. The sensitivity limit of detection (LOD) analyzed based on culture broth and milk sample was >105 and >104 in PCR amplification while it was >104 and >103 in real-time qPCR, respectively. At the same time, the correlation regression coefficient of the standard curve based on the pure culture cell DNA as the DNA concentration serially diluted (20 ng/µL to 0.0002 ng/µL) was obtained in multiplex without interference and cross-reactivity, yielding R2 ≥ 0.9908 slope (−3.2591) and intercepting with a value of 37, where the efficiency reached the level of 95–102% sensitivity reached up to 0.0002 ng/µL concentration of DNA, and sensitivity of microbial load was up to 1.2 × 102 CFU/mL. Therefore, multiplex TaqMan qPCR simultaneous amplification was considered the best method developed for the detection of the lipA and aprX genes in a single tube. This will result in developing future simultaneous (three- to four-gene) detection of spoilage psychrotrophic bacteria in raw milk.

Type 2 diabetes is one of the main causes of cardiovascular diseases, kidney diseases, and visual impairments, posing a global healthcare challenge. The current treatment of this disease, involving glucagon-like peptide-1 (GLP-1), is faced with problems such as frequent injections and plasmid instability. In this study, we used the native clustered regularly interspaced short palindromic repeats-CRISPR-associated protein 9 (CRISPR-Cas9) system of Lacticaseibacillus paracasei to develop a novel, genetically stable, and orally administrable strain expressing human GLP-1. Integration and subsequent expression of glp-1 gene were confirmed by genomic sequencing, qPCR, and Nano LC-MS. The engineered strain demonstrated stable genomic integration and sustained high-level expression of GLP-1 over multiple generations. This innovative approach provides a promising strategy for the oral delivery of therapeutic peptides, potentially enhancing patient compliance and improving the treatment of diabetes and other chronic diseases requiring peptide-based therapies.

Milk is an ideal environment for the growth of microorganisms, especially psychrotrophic bacteria, which can survive under cold conditions and produce heat-resistant enzymes. Psychrotrophic bacteria create the great problem of spoiling milk quality and safety. Several ways that milk might get contaminated by psychrotrophic bacteria include animal health, cowshed hygiene, water quality, feeding strategy, as well as milk collection, processing, etc. Maintaining the quality of raw milk is critically essential in dairy processing, and the dairy sector is still affected by the premature milk deterioration of market-processed products. This review focused on the recent detection and control strategies of psychrotrophic bacteria and emphasizes the significance of advanced sensing methods for early detection. It highlights the ongoing challenges in the dairy industry caused by these microorganisms and discusses future perspectives in enhancing milk quality through innovative rapid detection methods and stringent processing controls. This review advocates for a shift towards more sophisticated on-farm detection technologies and improved control practices to prevent spoilage and economic losses in the dairy sector.