Search

This study aimed to investigate the impact of Monascus on bioactive peptides, particularly angiotensin-converting enzyme (ACE) inhibitory peptides, during cheese maturation. The content of soluble nitrogen, α-glucosidase and ACE inhibitory activities during the ripening process were investigated. Cheese not inoculated with Monascus as a control group. The peptide profile of Monascus cheese was identified. The potential bioactive peptides were screened by bioinformatics and molecular docking, and the selected peptides were synthesized and evaluated. The results showed that compared with the control group, the pH 4.6 soluble nitrogen content (pH 4.6-SN) and trichloroacetic acid soluble nitrogen (TCA-SN) of Monascus cheese were increased by 57.98% and 38.34%, and the α-glucosidase and ACE inhibitory activities were increased by 32.21% and 73.98%, respectively. A total of 1 796 peptides were identified in the extract of Monascus cheese, including 51 ACE inhibitory peptides, 28 antioxidant peptides and 7 glucose-lowering peptides. Two ACE inhibitory peptides YPFPGPI and FPEVFGK were selected, whose half-maximal inhibitory concentration values were 207.31 and 410.61 μmol/L, respectively. The inhibition type was non-competitive. This study has provided a rapid screening method for ACE inhibitory peptides, and has proved that the addition of Monascus in cheese can effectively improve the ACE inhibitory activity, which provides a reference for exploring the potential functional properties of Monascus cheese.

The addition of adjunct culture has a significant impact on the quality of cheese. To screen adjunct culture with high protein hydrolysis and antioxidant capacity, this study evaluated 12 strains of lactic acid bacteria based on the acid production, protease activity, proteolysis, and antioxidant capacity. The potentially beneficial strain was used as adjunct culture to make quark cheese. The effect of adjunct culture on cheese quality was assessed by examining physicochemical indices, titration acidity changes, lactic acid bacteria count, texture alterations, and antioxidant activity during storage. Results showed that Lactobacillus kefiranofaciens XZ-54, which had a weak acid-producing capacity, high protease activity, protein hydrolysis, and antioxidant capacity, had the potential to be used as an adjunct fermenter for quark cheese. The addition of XZ-54 had no significant effect on the physicochemical parameters, hardness, and spread ability of quark cheese (P > 0. 05), and the viable counts of XZ-54 in the cheese were maintained above 107 CFU/ g during the 21-day storage period. Additionally, it significantly enhanced the DPPH free radical, ABTS cationic radical, and hydroxyl radical scavenging activities of the cheese. Therefore, Lactobacillus kefiranofaciens XZ-54 could be effectively employed as an adjunct culture in quark cheese, improving its antioxidant qualities and demonstrating significant potential for development and application. [ABSTRACT FROM AUTHOR]

In this study, three‐dimensional numerical simulation of gas–liquid flow in bubble columns was realized by using the computation fluid dynamics (CFD)–population balance model (PBM). The new drag model improves the stability‐constrained multi‐fluid (SCMF‐C) model because of the consideration of the wake accelerating and the hindering effects for calculating the drag correction factor. The gas holdup, axial liquid velocity, and bubble size distribution (BSD) predicted by four drag models at 0.02 and 0.1 m/s were compared. The results revealed that the proposed drag model can provide excellent predictions for both bubbly and heterogeneous flows. Because the wake accelerating and the hindering effects were considered, reliable predictions were achieved for the gas holdup, and the problem of uniform gas holdup distribution was mitigated. Therefore, the SCMF‐C model can be extended for nonuniform BSD. The gas holdup and liquid velocity increased, and the nonuniformity of radial results became pronounced at 0.1 m/s. The profiles of four drag models were similar at a low height, whereas the difference between the simulations of the four models became obvious with the variation of heights. The results of the four models were accurate, and the BSD was wide at 0.1 m/s. Subsequently, the feasibility of the four drag models was evaluated at 0.2 and 0.4 m/s. The results of the comparison revealed that the proposed drag model exhibited excellent feasibility at higher gas velocities and was powerful for the simulation of bubble columns. [ABSTRACT FROM AUTHOR]

In this study, a β‐galactosidase gene (btgal42) was first cloned from Bifidobacterium thermophilum and successfully expressed in Escherichia coli. The molecular weight of the purified BtGal42 was estimated to be 78 kDa by the sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and 225 kDa by the size‐exclusion chromatography, indicating that the native BtGal42 was a homotrimer. BtGal42 belonged to the glycosidase hydrolase family 42, exhibiting the maximum activity at pH of 7 and at temperature of 50°C. The enzyme displayed a strictly specific activity toward substrates with β‐galactosyl linkages at the nonreducing ends, of which the activity on 4‐nitrophenyl‐β‐d‐galactopyranoside was the highest, followed by 2‐nitrophenyl‐β‐d‐galactopyranoside and lactose. Among the tested metals and reagents, BtGal42 showed tolerance in the presence of various organic solvents. Importantly, BtGal42 exhibited a high reverse hydrolysis activity when using galactose as the donor and the di‐alcohol ethylene glycol and the trialcohol glycerol as the acceptors. Under unoptimized reaction conditions, the galactosyl glycerol yield reached 62.2 g/L (galactose conversion rate, 41.2%). This study might provide a feasible method for the biosynthesis of galactosyl glycerol from low‐cost glycerol and galactose, which was associated with high conversion efficiency and few byproducts. [ABSTRACT FROM AUTHOR]