Effects of different storage conditions on the metabolite and microbial profiles of white rice (Oryza sativa L.)

Effects of Flammulina velutipes polysaccharides on gut microbiota composition and metabolism in vitro fermentation

Flammulina velutipes polysaccharides (FVP) exhibit many biological activities, but the effects on gut microflora and metabolism were still unclear. Here, we explored the composition of FVP, their influence on human gut microflora composition and metabolites. FVP were used to vitro fermentation through human fecal inoculums. In addition, 16S rRNA sequencing were used to assess the effects of FVP on the gut microbiota. The metabolic profiles were investigated using untargeted metabolomics approaches in the LC-MS platform. The results showed that FVP was mainly consisted of glucose, mannose, xylose, fucose and galactose. FVP is shown to increase the relative abundances of Bifidobacteriaceae, as well as Bacteroidaceae and remarkably decrease the numbers of genera Lachnospiraceae coupled with Enterococcaceae. The differential metabolites were identified and mainly involved the metabolism of glycerophospholipid, linoleic acid and synthesis of unsaturated fatty acids. FVP may exhibit biological activity function by regulating gut microflora composition and metabolites.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01192-y.

Effects of tebuconazole application at different growth stages on rice grain quality of rice-based untargeted metabolomics

Tebuconazole (TEB) is a pesticide widely used in crops and has a strong control effect on fungal pathogens. TEB abuse has caused many food safety problems. In this study, the TEB residue in rice and the effect of TEB on white rice quality were investigated. The results showed that under two spraying concentrations, the TEB residue in rice was 11.21-19.05 μg/kg and 24.45-31.12 μg/kg, and there was no food safety risk of pesticide residue. When applying TEB according to the instructions, no significant effect was found. However, when 3 times the recommended TEB concentration was used at the filling stage, the protein content of white rice decreased significantly from 106.52 mg/g to 80.72 mg/g. At the jointing，heading and filling stage, the amylose content of white rice decreased to 53.95 mg/g, 48.77 mg/g and 49.04 mg/g from the blank control group. Plant metabolic analysis using LC-QTOF/MS revealed that the amino acid-related metabolic pathways in white rice were significantly affected by TEB. This is closely related to the decrease in protein accumulation in white rice and the stress response of rice plants. The increase in pantothenic acid content in white rice indicated that the glycolysis pathway of white rice plants was affected, and the consumption of starch and sucrose increased, leading to the inhibition of amylose accumulation in white rice. The increase in soluble sugar content and decrease in phosphocholine content in white rice suggested that rice plants were affected by TEB exposure, which produced similar effects under drought stress.

Research advance in gas detection of volatile organic compounds released in rice quality deterioration process

Rice quality deterioration will cause grievous waste of stored grain and various food safety problems. Gas detection of volatile organic compounds (VOCs) produced by deterioration is a nondestructive detection method to judge rice quality and alleviate rice spoilage. This review discussed the research advance of VOCs detection in terms of nondestructive detection methods of rice quality deterioration, applications of VOCs in grain detection, inspection of characteristic gas produced during rice spoilage, rice deterioration prevention and control, and detection of VOCs released by rice mildew and insect attack. According to the main causes of rice quality deterioration and major sources of VOCs with off-odor generated during rice storage, deterioration can be divided into mold and insect infection. The results of literature manifested that researches mainly focused on the infection of Aspergillus in the mildew process and the attack of certain pests in recent years, thus the research scope was limited. In this paper, the gas detection methods combined with the chemometrics to qualitatively analyze the VOCs, as well as the correlation with the number of colonies and insects were further studied based on the common dominant strains during rice mildew, that is, Aspergillus and Penicillium fungi, and the common pests during storage, that is, Sitophilus oryzae and Rhyzopertha dominica. Furthermore, this paper pointed out that the quantitative determination of characteristic VOCs, the numeration relationship between VOCs and the degree of mildew and insect infestation, the further expansion of detection range, and the application of degraded rice should be the spotlight of future research.

Integrated genomic and transcriptomic analysis reveals unique mechanisms for high osmotolerance and halotolerance in Hyphopichia yeast

The yeast species Hyphopichia is common in nature and strongly competitive under harsh environmental conditions. Here, we characterized Hyphopichia burtonii KJJ43 and H. pseudoburtonii KJS14, which exhibit strong halotolerance, using genomic and transcriptomic analyses. The genomes of H. burtonii and H. pseudoburtonii comprised eight chromosomes with 85.17% nucleotide identity and significant divergence in synteny. Notably, both Hyphopichia genomes possessed extended gene families of amino acid permeases and ATP-binding cassette (ABC) transporters, whose dynamic expression patterns during osmotic stress were revealed using transcriptome profiling. Intriguingly, we found unique features of the HOG pathway activated by Hog1p even under non-osmotic stress conditions and the upregulation of cytosolic Gpd1 protein during osmotic stress. Associated with hyperfilamentation growth under high osmotic conditions, a set of genes in the FLO family with induced expression in response to NaCl, KCl, and sorbitol supplementation were identified. Moreover, comparative transcriptome analysis reveals the NaCl-specific induction of genes involved in amino acid biosynthesis and metabolism, particularly BAT2. This suggests the potential association between oxoacid reaction involving branched-chain amino acids and osmotolerance. The combined omics analysis of two Hyphopichia species provides insights into the novel mechanisms involved in salt and osmo-stress tolerance exploited by diverse eukaryotic organisms.

Dynamic monitoring of fatty acid value in rice storage based on a portable near-infrared spectroscopy system

The fatty acid value of rice is one of the important indexes to reflect its freshness. A portable near-infrared spectroscopy (NIRS) system was designed and assembled to dynamically monitor fatty acid values in rice storage in this study. First, the near-infrared (NIR) spectra of rice samples in different storage periods were obtained using the portable NIRS system. Then, a weighted multiplicative scatter correction with variable selection (WMSCVS) algorithm was applied to the original spectra for scattering correction, and to compress variable space for achieving characteristic wavelengths. Finally, a partial least square (PLS) regression model was established using the characteristic wavelengths to realize the rapid monitoring of fatty acid values in rice storage. The results showed that the performance of the optimal PLS model based on the features by the WMSCVS algorithm was significantly better than those of the optimal PLS models based on SNV and MSC pre-processing spectra, with the determination coefficient (R_P²) of 0.9615 and the root mean square error of prediction (RMSEP) of 0.3626 in the predictive process. The overall results demonstrate that it is feasible to use the portable NIRS system developed by our team to quickly monitor the fatty acid values in rice storage.

Comparative metabolic expressions of fermented soybeans according to different microbial starters

The quality of fermented soybeans can be determined by diverse metabolites produced by microorganisms. Mass spectrometry-based metabolomic approach was applied to investigate the differences in volatile and non-volatile metabolite profiles of fermented soybeans by different microorganisms [e.g., molds, yeasts, lactic acid bacteria (LAB), and other bacteria]. The partial least squares-discriminant analysis (PLS-DA) for volatile metabolites profiles indicated that the fungi group (mold/yeast) was clearly discriminated from the bacteria group (bacteria/LAB). The metabolic pathways related to the formation of volatile metabolites also differed according to microorganisms. In particular, the formation of branched-chain aliphatic alcohols and esters increased in the fungi group, while that of volatiles derived from fatty acids was superior in the bacteria group. In addition, we could determine the microorganism-specific metabolites using a correlation network analysis. This study can provide the fundamental knowledge on the metabolic differences according to the type of microorganisms in fermented soybeans.

Quality changes in perilla seed powder related to storage duration and temperature

Perilla seed powder (PSP) was stored at 25 °C, 35 °C, and 45 °C for 8 weeks. Changes in the metabolite profiles of the powders, including fatty acids, were monitored. Correlations between these changes and quality parameters, including lipid oxidation, color, and antioxidant activity, were analyzed to evaluate the effects of storage duration and temperature on PSP quality. Acid values increased significantly with the duration of storage, but not with temperature. Multivariate statistical analysis was performed to identify differences among the metabolite profiles. The PSP sample stored for 1 week at 45 °C and all samples stored at 25 °C and 35 °C were grouped separately from the control and samples stored at 45 °C for more than 4 weeks. Among the many metabolites associated with these differences, lysophosphatidylethanolamines, tocopherol, sitosterol, tryptophan, 12-hydroxyjasmonic acid glucoside, and maltose correlated negatively with quality parameters with the exception of L* and antioxidant activity. Luteolin, apigenin, luteolin 4'-methyl ester, citric acid, isocitric acid, 9(S)-HPODE, and 3,5-octadien-2-one correlated positively with quality. Although the quantities of some antioxidants and lipids decreased during storage, the results suggested that the quality of PSP samples stored at 25 °C, 35 °C, and 45 °C for 8 weeks was acceptable. This was because lipid oxidation promoted by the storage environment was limited by antioxidants in the samples. These metabolites could be useful for monitoring changes in PSP quality.