A proteinaceous surface layer (known as an S-layer) of numerous lactic acid bacteria has been shown to confer tissue adherence, specifically to epithelial cells, and protection against environmental stress. To investigate the potential of recombinant S-layer proteins to assemble on Bifidobacterium, we co-incubated S-layer proteins with Bifidobacterium adolescentis Bf 15703. This process resulted in a significant increase in fluorescence intensity at 533 nm compared to the control group, alongside a notable shift in zeta potential from −45.36 ± 4.05 mV to −24.31 ± 2.35 mV, confirming successful protein assembly. Morphological characterization of the armored bacteria supported these findings. In vitro digestion assays demonstrated significantly enhanced gastrointestinal tolerance in the modified bacterial cells. Furthermore, adhesion to HT-29 cells (a human colorectal adenocarcinoma cell line) was increased by approximately fivefold, with an adhesion rate of 1.05%. In vivo studies revealed a significantly prolonged retention time, as supported by ex vivo optical imaging and cryosection analysis. qPCR analysis confirmed sustained colonization for > 27 days. These results demonstrate that heterologously expressed S-layer proteins can successfully assemble on B. adolescentis Bf 15703, thereby enhancing its gastrointestinal resilience, adhesion, and long-term colonization capabilities in vivo.

The objective of this study was to examine the impact of ultrasonic treatment on the solubility of oyster myofibrillar protein. Oyster myofibrillar protein was subjected to ultrasonic treatment at 200 W and 20–22 kHz for different durations (0, 10, 20, 30, 40 and 50 min) and evaluated for sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) patterns, endogenous fluorescence intensity, surface hydrophobicity, total sulfhydryl content, free sulfhydryl content, and disulfide bond content. SDS-PAGE results demonstrated a noticeable increase in the intensity of myosin heavy chain bands but no changes in the intensity of protein bands after ultrasonic treatment for a certain period. In addition, the intrinsic fluorescence intensity of myofibrillar protein decreased, which was accompanied by the exposure and conversion into disulfide bonds of hydrophobic groups buried inside myofibrillar protein. These changes significantly improved the solubility of oyster myofibrillar protein. Nevertheless, excessive ultrasonic treatment led to excessive modification of the protein, resulting in a decline in its functional properties. The findings of this study provide a theoretical foundation for the application of ultrasonic treatment to oyster myofibrillar protein and for expanding its potential applications in improving the solubility of food products.

The main purpose of this study was to investigate the effect of different lactic acid bacteria and yeast strains on the volatile composition of fermented sweet melon juice. Headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) coupled with chemometrics was performed to identify the potential volatiles for the discrimination of different fermented sweet melon juice. In total, 70 volatile compounds were found in the fermented sweet melon juices. Of them, 45 compounds were annotated according to the GC-IMS database and classified into esters, alcohols, aldehydes, ketones and furans. Results from the multivariate analysis reveal that sweet melon juice fermented by different combinations of microbial strains could be distinctly separated from each other. A total of 15 volatiles with both variable importance in projection value > 1 and P < 0.05 were determined as potential markers for the discrimination of fermented sweet melon juice. This study confirms the effect of microorganisms on the flavor of the fermented sweet melon juice and shows the potential of HS-GC-IMS combined with chemometrics as a powerful strategy to obtain volatile fingerprints of different fermented sweet melon juice.