Formation mechanisms of ethyl acetate and organic acids in Kluyveromyces marxianus L1-1 in Chinese acid rice soup

This study aims to explore the formation mechanism of ethyl acetate and organic acids in acid rice soup(rice-acid soup)inoculated with Kluyveromyces marxianus L1-1 through the complementary analysis of transcriptome and proteome.The quantity of K.marxianus L1-1 varied significantly in the fermentation process of rice-acid soup and the first and third days were the two key turning points in the growth phase of K.marxianus L1-1.Importantly,the concentrations of ethyl acetate,ethanol,acetic acid,and L-lactic acid increased from day 1 to day 3.At least 4231 genes and 2937 proteins were identified and 610 differentially expressed proteins were annotated to 30 Kyoto Encyclopedia of Genes and Genomes(KEGG)pathways based on the analysis results of transcriptome and proteome.The key genes and proteins including up-regulated alcohol dehydrogenase family,alcohol O-acetyltransferase,acetyl-CoA C-acetyltransferase,acyl-coenzyme A thioester hydrolase,and down-regulated aldehyde dehydrogenase family were involved in glycolysis/gluconeogenesis pathways,starch and sucrose metabolism pathways,amino sugar and nucleotide sugar metabolism pathways,tricarboxylic acid(TCA)cycle,and pyruvate metabolism pathways,thus promoting the formation of ethyl acetate,organic acids,alcohols,and other esters.Our results revealed the formation mechanisms of ethyl acetate and organic acids in rice-acid soup inoculated with K.marxianus L1-1.

Anti-lipid-oxidation effects and edible safety evaluation of the oil extracted by a supercritical CO_(2) process from coix seed fermented by Monascus purpureus

The physicochemical properties and composition of coix seed oil produced by Monascus purpureus fermentation and supercritical CO_(2)extraction were determined.Anti-lipid-oxidation and edible safety were evaluated using a cholesterol-fish oil model,acute oral toxicity assay,and genetic toxicity assay in vitro and in vivo,respectively.The results show that the extraction oil from fermented coix seed(FCS-O)had good physicochemical quality and abundant active components with physiological function.In particular,γ-tocotrienol,γ-oryzanol,coixenolide and oleic acid concentrations reached 72.83μg/g,745.96μg/g,9.65 mg/g and 316.58 mg/100 g DW,respectively.The FCS-O exhibited higher antioxidant capability in inhibiting lipid oxidation and peroxidation.Compared to the blank control,the concentrations of 7-ketocholestreol and peroxide only were 8.42μg/mL and 16.16 mmol/kg at 168 h of oxidation(P<0.01).In addition,the FCS-O has been confirmed to be a very safe edible oil,with no acute toxicity(LD50>10 g/kg bw,considered actually non-toxic)and no induced mutagenicity,cytotoxicity or genotoxicity.These results serve as a good safety reference for future application of the oil from fermented coix seed.The development and utilization of this kind of oil will be beneficial as a food,food ingredient,nutritional supplement,or natural food antioxidant to promote good health function.

Heteroatom dopant strategy triggered high-potential plateau to non-graphitized carbon with highly disordered microstructure for high-performance sodium ion storage

Non-graphitized carbon(NGC)has been extensively utilized as carbonaceous anode in sodium-ion batteries(SIBs).However,more optimization to achieve competitive capacity and stability is still challenging for SIBs.In the study,the dopant strategy is utilized to construct nitrogen/sulfur-doped non-graphitized carbon(N-NGC or S-NGC)shell decorated on three-dimensional graphene foam(GF)as a self-support electrode.The highly disordered microstructures of heteroatom doped carbons are produced by applying a low-temperature pyrolysis treatment to precursors containing nitrogen and sulfur.The DFT calculations of Na-ion adsorption energies at diverse heteroatom sites show marginal-S,pyrrolic N and pyridinic N with more intensive Na-ion adsorption ability than middle-S,C=O and pristine carbon.The N-NGC with dominant small graphitic regions delivers adsorption ability to Na-ion,while the S-NGC with significant single carbon lattice stripes demonstrates redox reaction with Na-ion.Evidently,in comparison with only adsorption-driven slope regions at high potential for N-NGC,the redox reaction-generated potentialplateau enables non-graphitized S-NGC superior discharge/charge capacity and cycle-stability in the slope region.This work could provide deep insight into the rational design of non-graphitized carbon with rich microstructure and composition.

Integrative proteomic-transcriptomic analysis revealed the lifestyles of Lactobacillus paracasei H4-11 and Kluyveromyces marxianus L1-1 under co-cultivation conditions

Compared with the rice-acid soup inoculated with single starter,the synergistically intensifi ed rice-acid soup inoculated with Lactobacillus paracasei H4-11(L.paracasei H4-11)and Kluyveromyces marxianus L1-1(K.marxianus L1-1)contained more fl avor compounds.Organic acids mainly included L-lactic acid and the main volatile fl avor component was ethyl acetate.Moreover,the signal intensity of astringency and bitterness and the total concentration of volatile sulfur compounds were reduced.The combined analysis results of RNA sequencing(RNA-seq)technology and 4D label-free quantitative(4D LFQ)proteomics explained the fl avor formation pathways in rice-acid soup inoculated with L.paracasei H4-11 and K.marxianus L1-1.In L.paracasei H4-11,L-lactate dehydrogenase,phosphoglucomutase,acetate kinase,alcohol dehydrogenase and acetyl-CoA were up-regulated and D-lactate dehydrogenase and N-Acetyltransferase were down-regulated.In K.marxianus L1-1,Acetyl-CoA,acetaldehyde dehydrogenase,acyl-coenzyme A,N-acetyltransferase,and L-lactate dehydrogenase were up-regulated and hexokinase,alcohol dehydrogenase,and alcohol O-acetyltransferase were down-regulated.The above up-regulation and down-regulation synergistically promoted the formation of characteristic fl avor compounds(mainly L-lactic acid and ethyl acetate).Enzyme-linked immunoassay(ELISA)and parallel reaction monitoring(PRM)quantitative analysis respectively verifi ed that 5 key metabolic enzymes and 27 proteins in L.paracasei H4-11 and K.marxianus L1-1 were associated with the characteristic fl avor of rice-acid soup,as confi rmed by the quantitative results of 4D LFQ.

Characteristics of traditional Chinese acidic rice soup(rice-acid)prepared with different fermentation methods

Rice-acid,a Chinese traditional acidic rice soup(rice-acid),is widely accepted by consumers due to its unique flavor and anti-oxidation,anti-aging and immunity enhancement functions.This study confirmed that L-lactic acid and malic acid were the main organic acids in rice-acid.Low-temperature rice-acid samples produced by enterprises had the highest signal intensity of sour taste.The total content of free amino acids in different fermented rice-acid samples were in the range of 0.003-0.468 mg/g.42 key volatile flavor compounds were identified in rice-acid.8 volatile compounds with a higher contribution to the aroma of rice-acid were respectively acetic acid,1-octen-3-ol,2-heptanol,ethyl acetate,propyl propionate,hexanal,nonanal,and2,3-butanedione.The interaction between lactic acid bacteria(3.00×10^(3)-7.02×10^(6) CFU/mL)and yeasts(5.04×10^(4)-2.25×10^(8) CFU/mL)affected the formation of taste and aroma components in rice-acid.The physicochemical characteristics including titratable acidity,pH,reducing sugars,amino acid nitrogen,gammaaminobutyric acid showed significant differences between low-temperature fermentation samples and hightemperature fermentation samples.In addition,relationships linking all data through Pearson coefficient correlation were also reported.In summary,the study can be used to improve the quality of rice-acid products.

The cause of germination increases the phenolic compound contents of Tartary buckwheat(Fagopyrum tataricum)

In order to study the changes and mechanism of phenolic compounds during Tartary buckwheat germination,the dynamic changes of phenolic compounds were analyzed,and the activities of enzymes that regulate phenolic compound biosynthesis and degradation were monitored.Total phenolics and total flavonoids presented an interesting dynamic trend with the extension of the germination time,and rutin,gallic acid,chlorogenic acid as well as 2,3,4-trihydroxybenzoic acid contents showed an increasing trend during germination period,the contents were up to(2663.4±61.1),(449.12±5.26),(99.953±7.800)and(50.442±1.477)mg/100 g DW,respectively.Phenylalanine ammonia lyase(PAL)and chalcone isomerase(CHI)are dominant enzymes in regulating phenolic compound biosynthesis,which showed an increasing trend.Rutin degrading enzyme(RDEs)is the key enzyme in regulating phenolic compound degradation,which showed a decreasing trend.These results suggested that germination processing increases the phenolic compound contents of Tartary buckwheat,which may be regulated by the activation of PAL,CHI and the inhibition of RDEs.