In order to study the effect of fermentation with a mixed starter culture of lactic acid bacteria on the quality of multigrain dough and steamed bread, yellow pea flour, naked oat flour, gluten flour and oat β-glucan (OBG) were mixed together to prepare dough and steamed bread with a direct vat set (DVS) mixed starter culture of lactic acid bacteria. The acidifying capacity of lactic acid bacteria in dough was investigated, and the contents of OBG, resistant starch (RS) and free amino acids and the microstructure of dough were analyzed. Also, the quality and nutritional characteristics of steamed multigrain bread and steamed wheat bread before and after fermentation were compared. The results showed that lactic acid bacteria had strong acidifying capacity in fermented multigrain dough, and the contents of lactic acid and acetic acid were 24.85 and 8.98 mg/mL, respectively, after 24 hours of fermentation. Compared with unfermented multigrain dough, the OBG content in lactic acid bacteria fermented multigrain dough decreased by 32.56%, the RS content increased by 32.88%, the total amount of free amino acids increased by 1.46 times, the amino acid composition pattern was better, proteins and cellulose were partially degraded, and the gluten network was more compact and continuous. In terms of nutrition, the dietary fiber content of steamed multigrain bread was higher than 6% both before and after lactic acid bacteria fermentation, and the protein content was 40.35% and 38.38% in steamed unfermented and fermented multigrain bread, respectively, indicating that steamed multigrain bread is rich in dietary fiber and protein. Its dietary fiber and protein contents were higher than those of steamed wheat bread. Lactic acid bacteria fermented multigrain steamed bread had higher in vitro protein digestibility and specific volume, and the overall sensory score of steamed lactic acid bacteria fermented multigrain bread was significantly higher than that of steamed unfermented multigrain bread, and the overall acceptability was higher.

Inflammatory bowel disease (IBD) is an inflammatory disease of the gastrointestinal tract whose pathogenesis is not yet clear and it tends to recurrent. The global prevalence of IBD has reached 0.3% and is increasing as a result of changes in living environment and dietary habits. Current treatments for IBD focus on anti-inflammatory drugs and intestinal immunomodulatory therapy, and recent studies on intestinal microorganisms have shown that the occurrence of IBD is closely related to changes in the intestinal flora and some intestinal microorganisms can alleviate IBD in various ways. In this paper, we review the application and action mechanism of the probiotic intestinal bacterium Bifidobacterium and its preparations in IBD treatment, expecting to provide a reference for the treatment of IBD by probiotics.

The two-peptide (class IIb) bacteriocins are generally thermostable small-molecule (< 10 kDa) two-component antimicrobial peptides produced by Gram-positive bacteria. This class of peptides mainly rely on peptide-peptide interactions mediated by typical motifs to form active dimeric transmembrane proteins. Numerous studies have shown that two-peptide bacteriocins have reliable safety and desirable bacteriostatic effect, holding great potential in the control of drug-resistant bacteria. Therefore, the structural features and action mechanisms of two-peptide bacteriocins have received considerable research attention. From the perspectives of the structure formation of two-peptide bacteriocins, peptide-peptide interaction, and peptide-membrane interaction, this article summarizes the mechanism of action of this class of antimicrobial peptides. Meanwhile, the structural regularity of two-peptide bacteriocins and the structural features affecting their activities are elaborated by synthesizing current research. This review will provide new ideas for future research on two-peptide bacteriocins.

To investigate the structural properties and catalytic activity of α-L-fucosidases belonging to the GH29A family, the gene coding for the AlfB enzyme from Lactobacillus rhamnosus GG was obtained from the NCBI database. A bioinformatics analysis was conducted on AlfB, followed by heterologous expression of the recombinant enzyme in Escherichia coli under optimized conditions. The bioinformatics analysis revealed that AlfB was a single-domain enzyme with two conserved active sites: the nucleophilic catalytic residue Asp166 and the acid-base catalytic residue Glu32. The optimal induction conditions for the recombinant enzyme were determined to be 25 ℃ for a duration of 28 h. The optimal temperature and pH of the purified recombinant enzyme was 35 ℃ and 6.0, respectively. It was strongly inhibited by Cu²⁺ but strongly activated by Mn²⁺. Recombinant AlfB exhibited a high affinity for 2'-fucosyllactose (2'-FL) and transformed p-nitrophenyl-α-L-fucopyranoside (pNP-Fuc) and lactose into 2'-FL and its isomer 3'-FL via transglycosylation. These results set the stage for further elucidating the catalytic activity and mechanism of action of AlfB.

The quality of fermented milk can be improved by the exopolysaccharides (EPSs) produced by probiotics. Bifidobacterium breve H4-2 and H9-3 with different EPS production were used as co-fermented probiotics to ferment goat milk in the present study. The physicochemical properties of fermented goat milk and the interaction between goat milk casein and CEPS (EPSs separated from starter culture and B. breve H4-2 fermented goat milk) were investigated. Results indicated that both B. breve H4-2 and H9-3 have similar gene clusters for EPS synthesis, but B. breve H4-2 exhibits a higher ability in EPS productions. Compared to the starter culture group, combining B. breve H4-2 or H9-3 with a starter culture significantly increased the levels of EPSs ((724.16 ± 1.54) and (607.15 ± 4.55) mg/L) and lactic acid ((14.62 ± 0.02) and (16.87 ± 0.01) mg/mL) at the late storage period. Co-fermentation also enhanced the water holding capacity, firmness, consistency, cohesion, and viscosity index, reduced dehydration in fermented goat milk. Moreover, the interaction study revealed that CEPS reduced the particle size and increased the ζ-potential absolute value of the CEPS and casein mixture system. Additionally, CEPS effectively mitigated casein aggregation, thereby enhancing the stability of fermented goat milk. These findings present a novel perspective for the development of a natural starter.

This study aimed to comparatively analyze the common and unique glycoside hydrolase (GH) family genes in Bifidobacterium. On this basis, a rapid method for isolating target Bifidobacterium strains from infant fecal samples was developed. The GH family genes of four bifidobacterial taxa, including B. breve, B. longum subsp. longum, B. bifidum and B. longum subsp. infantis, were compared, revealing that there were common and unique patterns in the GH family genes among these species, which could serve as molecular markers for the isolation and identification of Bifidobacterium strains. Based on colony polymerase chain reaction (PCR) and nucleic acid electrophoresis, a rapid method for the isolation and identification of the aforementioned bifidobacterial strains were successfully developed and applied to the isolation of B. bifidum. This method is characterized by not only high efficiency of isolation but also low costs. The results of this study contribute to a better understanding of the diversity of Bifidobacterium, thereby laying a foundation for future probiotic research and development.

Human milk is the most important source of nutrition in early infancy, which can meet all the nutritional needs in the first 6 months after birth. It contains many bioactive substances that can regulate the intestinal flora, promote the development of the immune system, and enhance the intestinal barrier. Human milk oligosaccharides (HMOs) are one of the active substances in human milk. They cannot be directly digested and absorbed by infants, but can be used as a prebiotic to stimulate the establishment and evolution of the gut microbiota. Bifidobacterium longum subsp. infantis is a dominant microorganism in the gut of breastfed infants, which has almost all gene clusters required for metabolizing the major HMOs, and its interaction with HMOs plays a key role in the early intestinal health of infants. This review summarizes the composition and structure of HMOs, describes the utilization of HMOs by B. longum subsp. infantis and summarizes the beneficial effects B. longum subsp. infantis exerts in infants by metabolizing HMOs, which will lay the foundation for exploring the interaction mechanism between HMOs and the gut microbiota, as well as its role in infant intestinal development and maturation.

In recent years, antibiotic-resistant pathogens have placed tremendous pressure on pathogen control within the livestock industry. Consequently, we have turned our attention to phages, a unique type of virus that has co-evolved with bacteria for an extended period. PE-1 is a bacteriophage strain capable of effectively controlling target pathogens and was isolated from samples collected from dead piglets suffering from intestinal disease and their living environment. Enterotoxigenic Escherichia coli (ETEC) K88 was employed as an inhibitory target to characterize the growth characteristics and in vitro antibacterial effects of bacteriophage PE-1. Morphological analysis tentatively classified phage PE-1 as belonging to the Podoviridae family. The one-step growth curve revealed that phage PE-1 had a short latent period of 10 min, a rise period of 20 min, and a burst size of 13 PFU/cell. The optimal multiplicity of infection (MOI) for phage PE-1 is 10, and the phage maintained normal activity at pH levels between 4−11 and temperatures no higher than 55 °C. Through two in vitro simulated test experiments, we evaluated the antibacterial efficacy of the bacteriophage. Our findings indicated that bacteriophage PE-1 delayed the growth activity of ETEC K88 by more than 2 h and reduced the proliferation rate of the host bacteria under infection conditions. Moreover, the bacteriophage decreased the concentration of host bacteria that reached the stationary phase. After inoculating the host bacteria with the optimal MOI, the host bacteria concentration dropped by nearly three orders of magnitude after 4 h. In conclusion, bacteriophage PE-1 demonstrates potential as an antibacterial agent for ETEC K88.