Characterization, Formation Mechanism, and Curcumin Delivery of Buckwheat Peptide-Based Emulsion Gels.

This study aimed to construct a natural peptide-based emulsion gel (PG) using small peptides (∼2.2 kDa) by mild enzymatic hydrolysis of buckwheat proteins. The obtained PG presented a porous and tight texture and solid-gel viscoelasticity compared with its parent protein-based emulsion gel. Meanwhile, it exhibited good resistance against heating and freeze-thawing. Furthermore, peptide-oil interaction analysis revealed that the gel matrix was enhanced by the hydrophobic aggregation between peptides and oil molecules, H-bonding interaction of peptide molecules, and peptide-oil aggregate repulsion force. Finally, in vitro intestinal digestion experiments demonstrated that PG could embed and pH-responsively release curcumin in the gastrointestinal tract at a release rate of 53.9%. The findings unfold promising opportunities for using natural PG in a range of applications relying on large proteins or other synthesized molecules.

A new strategy to strongly release sweet-enhancing volatiles from goji pomace using trivalent iron salts.

Efforts to fully utilize pomace volatiles have been obstructed by the lack of high-performance technologies to release free and bound volatiles. This study first established that ferric chloride (FeCl3) could strongly release the sweet-enhancing volatiles (SVs) from goji pomace, thus increasing the main aroma compounds [MACs; odor activity value (OAV) > 1] from 9 to 27. The underlying mechanism included the special hydrolysis to glycosides by ferric ions acting as Brønsted and Lewis acids, and the oxidation of ß-carotene and ß-ionone by electrophilic ferrite. The sweet fragrance could be reconstituted and simulated by the 27 MACs. Subsequent extraction and concentration increased MACs on average by 2.28-fold, and the extracted essence could be used as a green and safe sweet-enhancing sugar substitute for specific consumers. These study findings laid a foundation for understanding the relationship between metal salts and flavor chemistry, further providing an opportunity for the full utilization of resources.

Inhibitory Effects of Cu2O/SiO2 on the Growth of Microcystis aeruginosa and Its Mechanism.

In this study, a novel nanomaterial Cu2O/SiO2 was synthesized based on nano-SiO2, and the inhibitory effects of different concentrations of Cu2O/SiO2 on the growth of Microcystis aeruginosa (M. aeruginosa) were studied. At the same time, the mechanism of Cu2O/SiO2 inhibiting the growth of M. aeruginosa was discussed from the aspects of Cu2+ release, chlorophyll a destruction, oxidative damage, total protein, and the phycobiliprotein of algae cells. The results showed that low doses of Cu2O/SiO2 could promote the growth of M. aeruginosa. When the concentration of Cu2O/SiO2 reached 10 mg/L, it exhibited the best inhibitory effect on M. aeruginosa, and the relative inhibition rate reached 294% at 120 h. In terms of the algae inhibition mechanism, Cu2O/SiO2 will release Cu2+ in the solution and induce metal toxicity to algae cells. At the same time, M. aeruginosa might suffer oxidative damage by the free radicals, such as hydroxyl radicals released from Cu2O/SiO2, affecting the physiological characteristics of algae cells. Moreover, after the addition of Cu2O/SiO2, a decrease in the content of chlorophyll a, total soluble protein, and phycobiliprotein was found, which eventually led to the death of M. aeruginosa. Therefore, Cu2O/SiO2 can be used as an algaecide inhibitor for controlling harmful cyanobacteria blooms.

Induction and resuscitation of the viable but nonculturable state in a cyanobacteria-lysing bacterium isolated from cyanobacterial bloom.

The viable but nonculturable (VBNC) state has been found to be a growth strategy used by many aquatic pathogens; however, few studies have focused on VBNC state on other aquatic bacterial groups. The purpose of this study was to explore the VBNC state of cyanobacteria-lysing bacteria and the conditions that regulate their VBNC state transformation. Three cyanobacteria-lysing heterotrophic bacterial strains (F1, F2 and F3) were isolated with liquid infection method from a lake that has experienced a cyanobacterial bloom. According to their morphological, physiological and biochemical characteristics and results of 16SrDNA sequence analysis, F1, F2 and F3 were identified as strains of Staphylococcus sp., Stappia sp. and Microbacterium sp., respectively. After being co-cultured with the axenic cyanobacterium, Microcystis aeruginosa 905, for 7 days, strains F1, F2 and F3 exhibited an inhibition effect on cyanobacterial growth, which was expressed as a reduction in chlorophyll concentration of 96.0%, 94.9% and 84.8%, respectively. Both autoclaved and filtered bacterial cultures still showed lytic effects on cyanobacterial cells while centrifuged pellets were less efficient than other fractions. This indicated that lytic factors were extracelluar and heat-resistant. The environmental conditions that could induce the VBNC state of strain F1 were also studied. Under low temperature (4°C), distilled deionized water (DDW) induced almost 100% of F1 cells to the VBNC state after 6 days while different salinities (1%, 3% and 5% of NaCl solution) and lake water required 18 days. A solution of the cyanobacterial toxin microcystin-LR (MC-LR) crude extract also induced F1 to the VBNC state, and the effect was stronger than DDW. Even the lowest MC-LR concentration (10 µg L(-1)) could induce 69.7% of F1 cells into VBNC state after 24 h. On the other hand, addition of Microcystis aeruginosa cells caused resuscitation of VBNC state F1 cells within 1 day, expressed as an increase of viable cell number and a decrease of VBNC ratio. Both VBNC state and culturable state F1 cells showed lytic effects on cyanobacteria, with their VBNC ratio varying during co-culturing with cyanobacteria. The findings indicated that VBNC state transformation of cyanobacteria-lysing bacteria could be regulated by cyanobacterial cells or their toxin, and the transformation may play an important role in cyanobacterial termination.