Search Results (4)

Research in metagenomics and metaproteomics can reveal how microbiological interactions in fermented foods contribute to their health benefits. This study examined three types of fermented vegetables: a standard formulation, a probiotic formulation with Lacticaseibacillus rhamnosus GG, and a polyphenol formulation with vitexin from Mung bean seed coat. Measurements were taken at day 0 (after 36 h of fermentation at room temperature) and after 15 days. We applied 16S rRNA sequencing to evaluate microbial diversity and utilized LC-MS/MS to investigate the proteomic profiles of specific genera (Lactobacillus and Weissella) and species (Lacticaseibacillus rhamnosus and Levilactobacillus brevis) of lactic acid bacteria (LAB). All of these taxa demonstrated significant relative abundance between 0 and 15 days of fermentation in our metagenomic analysis. Our findings from principal component analysis and clustering analysis categorically distinguished protein expression patterns at various stages of fermentation. By comparing samples from day 0 to day 15, we identified proteins associated with DNA replication and repair mechanisms, including transcription elongation factor GreA, tRNA pseudouridine synthase B, and helicases. We also observed their roles in protein synthesis, which encompasses oxidoreductases and aspartokinase. Furthermore, we identified strong correlations of specific proteins across the three formulations with antioxidant markers. In conclusion, the results of this study decisively enhance our understanding of the role of the proteins related to specific LAB in fermented foods, highlighting their potential to improve texture, flavor, nutritional quality, and health benefits. Full article

Rice, as a major food crop, provides necessary energy and nutrition for humans and livestock. However, its nutritional value is affected by lysine. Using point mutation, we previously obtained AK2 (aspartokinase) and DHDPS1 (dihydrodipicolinate synthase) genes insensitive to lysine feedback inhibition and constructed transgenic lines AK2-52 and DHDPS1-22, which show increased lysine synthesis, as well as Ri-12, which shows decreased lysine degradation by inhibiting rice lysine ketoglutarate reductase/saccharopine dehydrogenase (LKR/SDH) activity. In this study, further transgenic lines were hybridized and evaluated. The lysine content of mature seeds from pyramid lines PRD and PRA increased 32.5- and 29.8-fold, respectively, compared with the wild-type, while the three-gene pyramiding line PRDA had a moderate lysine content. The total lysine, total free lysine, and total protein contents of PRD and PRA also increased and had no obvious impact on the physical and chemical quality, seed appearance, and main agronomic traits. Meanwhile, comparative analysis with polygenic polymeric lines GR containing bacterial AK (lysC) and DHDPS (dapA) genes revealed differences in the way bacterial and endogenous rice AK and DHDPS regulate lysine biosynthesis. These results provide a reference for further evaluation and commercialization of high-lysine transgenic rice. Full article

The physiology of fruit ripening is defined as either ‘climacteric’ or ‘non-climacteric’. In climacteric fruit respiration during ripening increases until it reaches a peak, which is accompanied by an increase in autocatalytic ethylene production, whereas the respiration of non-climacteric fruit does not increase and they have no requirement for ethylene to complete their ripening. In an attempt to gain further insight into the involvement of autocatalytic ethylene production with the climacteric rise in respiration, tomato fruit were harvested at three defined stages of maturity prior to the climacteric peak (mature green, breaker, and early orange) and immediately exposed to the gaseous molecule 1-methylcyclopropene (1-MCP). The gene expression profile at each of these stages was monitored after 24 h, using an Affymetrix tomato microarray chip. This approach enabled us to identify ethylene responsive genes that are commonly regulated at early stages of ripening, as well as new candidate genes. In addition, 1-MCP treatment affected the levels of metabolites related to methionine biosynthesis. Methionine feeds climacteric ethylene production and we found that promotors of the genes of enzymes that catalyze the production of homoserine and homocysteine (aspartokinase/homoserine dehydrogenases and cystathionine beta lyase, respectively), precursors in the methionine pathway, contain the AtSR1 binding motif. This binding motif is recognized by ethylene activated transcription factors, hence indicating a role for ethylene in methionine synthesis during early ripening, explaining the autocatalytic ethylene production during subsequent ripening stages. Full article

In this study, a novel monomer aspartokinase (AK) from Corynebacterium pekinense was identified, and its monomer model was constructed. Site 380 was identified by homologous sequencing and monomer model comparison as the key site which was conserved and located around the binding site of the inhibitor Lys. Furthermore, the mutant A380I with enzyme activity 11.32-fold higher than wild type AK (WT-AK), was obtained by site-directed mutagenesis and high throughput screening. In the mutant A380I, the optimal temperature was raised from 26 °C (WT-AK) to 28 °C, the optimal pH remained unchanged at 8.0, and the half-life was prolonged from 4.5 h (WT-AK) to 6.0 h, indicating enhanced thermal stability. The inhibition of A380I was weakened at various inhibitor concentrations and even activated at certain inhibitor concentrations (10 mM of Lys, 5 mM or 10 mM of Lys + Thr, 10 mM of Lys + Met, 5 mM of Lys + Thr + Met). Molecular dynamics simulation results indicated that the occupancy rate of hydrogen bond between A380I and ATP was enhanced, the effect of Lys (inhibitor) on the protein was weakened, and the angle between Ser281-Tyre358 and Asp359-Gly427 was increased after mutation, leading to an open conformation (R-state) that favored the binding of substrate. Full article