The aim of this study was to screen for lactic acid bacteria (LAB) with cholesterol-lowering capacity and to evaluate their antioxidant activity. In total, 45 strains of LAB were isolated from fecal samples of Jersey and Jersey × Wagyu calves before and after colostrum intake. By 16S rDNA sequence analysis, these strains were identified to belong to five genera, including Lactococcus taiwanensis, Lactococcus lactis, Ligilactobacillus salivarius, Weissella cibaria and Weissella confusa. Due to their strong cholesterol-lowering ability, W. confusa JCM11 and JCF7 were selected for evaluation of their safety, acid and bile salt tolerance, and antioxidant capacity. The experimental results demonstrated that W. confusa JCM11 and JCF7 removed 43.8% and 43.4% of cholesterol, respectively. Safety assessments showed that both strains were non-hemolytic, exhibited significant antibacterial activity against Escherichia coli, Staphylococcus aureus, and Listeria monocytogenes, and tested negative in nitrate reductase, indole, and gelatin liquefaction tests. W. confusa JCM11 and JCF7 were highly tolerant to low pH and high bile salt concentrations. The fermentation supernatants of both strains showed good antioxidant activity. In conclusion, W. confusa JCM11 and JCF7 possess remarkable cholesterol-lowering and antioxidant activity along with excellent safety and gastrointestinal tolerance, making them valuable microbial resources for the development of functional probiotic products.

In this study, the effect of addition of water-insoluble dietary fiber (IDF) enzymatically extracted from Auricularia auricula on the acidity and viable bacterial count of fermented milk was explored. One-factor-at-a-time method combined with orthogonal array design was used to optimize the formulation (concentrations of IDF, skim milk powder and sodium carboxymethyl cellulose) of fermented milk with added IDF based on sensory evaluation score. The nutrient composition and texture characteristics of the fermented milk prepared using optimized formulation were determined. The results showed that IDF from Auricularia auricula could promote the proliferation of lactic acid bacteria. The optimum formulation consisted of 7% IDF (converted into 0.78% freeze-dried powder) 1.5% sodium carboxymethylcellulose and 2.0% skim milk powder. The prepared fermented milk contained (3.53 ± 0.08)% protein, (3.12 ± 0.03)% fat, (0.78 ± 0.12)% ash, and (19.35 ± 0.49)% solids. Addition of IDF improved the water-holding capacity, hardness, chewiness and viscosity of fermented milk during storage and at the same time showed a protective effect on the starter culture.

Biopolymer complexes fabricated by proteins and neutral polysaccharides have some specific and innovative functionalities. A better understanding of the interactions among these biopolymers might provide new insight into the applications of the complexes. Therefore, this study aimed to investigate the structural characteristics and molecular interaction mechanisms of whey protein isolates (WPI) and Auricularia auricular polysaccharides (APs). The turbidity analysis confirmed that the pH value and mixing ratio of the two polymers had strong effects on the formation of the APs-WPI complexes. All dispersions formed soluble complexes at approximately pH = 6.0 (pH_c). APs-WPI self-assembles exhibited physically cross-linked networks under higher APs proportions, while they formed spherical complexes at higher WPI ratios. The addition of APs could alter the secondary structure of WPI, and the most noticeable changes were located in the regions of β-sheet and β-turn as confirmed by circular dichroism (CD) analysis. A molecular docking study showed that the amino acid residues of β-lactoglobulin complexed with the –COOH and –OH groups of APs. Hydrogen bonds and hydrophobic interactions, which were nonbonding contributions, played a key role in the formation of the APs-WPI complex. This study provided a basis for the development and application of APs in WPI-based beverages.