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Frontiers in Microbiology 2022Fatty acid ethyl esters are important flavor chemicals in strong-flavor Baijiu. YJX-8 is recognized as an important microorganism for ester synthesis in the...
Fatty acid ethyl esters are important flavor chemicals in strong-flavor Baijiu. YJX-8 is recognized as an important microorganism for ester synthesis in the fermentation process. Enzyme LIP05 from YJX-8 can efficiently catalyze the synthesis of fatty acid ethyl esters under aqueous phase, but the key catalytic sites affecting esterification were unclear. The present work combined homology modeling, molecular dynamics simulation, molecular docking and site-directed mutation to analyze the catalytic mechanism of LIP05. Protein structure modeling indicated LIP05 belonged to α/β fold hydrolase, contained a lid domain and a core catalytic pocket with conserved catalytic triad Ser150-His215-Asp202, and the oxyanion hole composed of Gly73 and Thr74. Ile30 and Leu37 of the lid domain were found to affect substrate specificity. The π-bond stacking between Tyr116 and Tyr149 played an important role in stabilizing the catalytic active center of LIP05. Tyr116 and Ile204 determined the substrate spectrum by composing the substrate-entrance channel. Residues Leu83, Ile204, Ile211 and Leu216 were involved in forming the hydrophobic substrate-binding pocket through steric hindrance and hydrophobic interaction. The catalytic mechanism for esterification in aqueous phase of LIP05 was proposed and provided a reference for clarifying the synthesis of fatty acid ethyl esters during the fermentation process of strong-flavor Baijiu.
PubMed: 36713181
DOI: 10.3389/fmicb.2022.1107104 -
Foods (Basel, Switzerland) Jan 2023In this study, the microbial diversity in Tibetan flavor was analyzed based on single molecule real-time sequencing (SMRT). The volatile flavor compounds in were...
In this study, the microbial diversity in Tibetan flavor was analyzed based on single molecule real-time sequencing (SMRT). The volatile flavor compounds in were detected using the headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). In addition, the correlation between various microbes and volatile flavor compounds was explored. Our studies indicated that the dominant bacterial genera in Tibetan flavor were , , , , , , , , and . The dominant fungal genera were , , and . 101 volatile compounds were detected in the samples, including alcohols, acids, esters, aldehydes, hydrocarbons, ketones, ethers, aromatics and pyrazines, and 10 key flavor compounds were identified using the relative odor activity value (ROAV). The results of our correlation analysis showed that was mainly associated with the synthesis of aldehydes such as trans-2-octenal, and was associated with the synthesis of most aldehydes. This paper has systematically investigated the physicochemical indices, microbial community structure and flavor compounds of Tibetan flavor , which is helpful in gaining a deeper understanding of the characteristics of Tibetan flavor .
PubMed: 36673416
DOI: 10.3390/foods12020324 -
Foods (Basel, Switzerland) Dec 2022Monascus-fermented cheese (MC) is a new type of mold-ripened cheese that combines a traditional Chinese fermentation fungus, Monascus purpureus M1, with Western cheese...
Monascus-fermented cheese (MC) is a new type of mold-ripened cheese that combines a traditional Chinese fermentation fungus, Monascus purpureus M1, with Western cheese fermentation techniques. In this study, the compositions of the volatile aroma compounds in MC were analyzed during a 30-day ripening period using SPME-Arrow and GC-O-MS. The activity of esterase in MC, which is a key enzyme catalyzing esterification reaction, was determined and compared with the control group (CC). Next, sensory analysis was conducted via quantitative descriptive analysis followed by Pearson correlation analysis between esterase activity and the key flavor compounds. A total of 76 compounds were detected. Thirty-three of these compounds could be smelled at the sniffing port and were identified as the key aroma compounds. The esterase activity in MC was found to be 1.24~1.33 times that of the CC. Moreover, the key odor features of ripened MC were alcohol and fruity flavors, considerably deviating from the sour and cheesy features found for the ripened CC. Furthermore, correlation analysis showed that esterase activity was strongly correlated (|r|> 0.75, p < 0.05) with various acids such as pentanoic and nonanoic acids and several aromatic esters, namely, octanoic acid ethyl ester and decanoic acid ethyl ester, revealing the key role that esterases play in developing the typical aroma of ripened MC.
PubMed: 36553768
DOI: 10.3390/foods11244026 -
Frontiers in Microbiology 2022The presence of undesirable microorganisms in silage always leads to poor fermentation quality and low aerobic stability. Pyroligneous acid (PA), a by-product of biochar...
The presence of undesirable microorganisms in silage always leads to poor fermentation quality and low aerobic stability. Pyroligneous acid (PA), a by-product of biochar production, is known to have strong antimicrobial and antioxidant activities. To investigate the effects of PA on fermentation characteristics, aerobic stability, and microbial communities, Napier grass was ensiled with or without 1 and 2% PA for 30 days and then aerobically stored for 5 days. The results showed that PA application decreased ( < 0.01) the pH value, ammonia nitrogen content, and number of undesirable microorganisms (coliform bacteria, yeasts, and molds) after 30 days of ensiling and 5 days of exposure to air. The temperature of the PA-treated group was stable during the 5-day aerobic test, which did not exceed room temperature more than 2°C. The addition of PA also enhanced the relative abundance of and reduced that of and . The relative abundance of was higher in PA-treated silage than in untreated silage. The addition of PA decreased the relative abundance of and increased that of after 5 days of exposure to air. The abundances of and were relatively high in 2% PA-treated NG, while these genera were note observed in the control group. These results suggested that the addition of PA could improve fermentation characteristics and aerobic stability, and alter microbial communities of silage.
PubMed: 36523820
DOI: 10.3389/fmicb.2022.1034198 -
Bioresources and Bioprocessing Dec 2022As a widely consumed fermented milk product, yogurt undergoes constant development to increase its functional properties. Monascus purpureus-fermented durian seed, which...
As a widely consumed fermented milk product, yogurt undergoes constant development to increase its functional properties. Monascus purpureus-fermented durian seed, which has been proven to possess antioxidative properties, has the potential to improve yogurt properties. This study aimed to analyze the use of Monascus-fermented durian seed (MFDS) as a functional ingredient in yogurt and its effect on physicochemical properties, lactic acid bacteria (LAB) count, antioxidative properties, and consumer acceptability of set-type yogurt during refrigeration. Changes in physicochemical properties, including color, pH, titratable acidity, syneresis, LAB count, total phenolic content (TPC), and antioxidant activity were evaluated at 7-day intervals during 14 days of refrigerated storage (4 °C). Sensory evaluations were carried out for freshly made samples after 7 days of storage. The results showed that the addition of MFDS to yogurt gave significant effects on some of the parameters measured. Yogurt with added MFDS powder produced a more red color (L = 88.55 ± 1.28, a* = 2.63 ± 0.17, b* = 11.45 ± 1.15, c = 11.75 ± 1.15, H = 77.00 ± 0.64), reached the highest TPC (2.21 ± 0.46 mg/GAE g), antioxidant activity (0.0125 ± 0.0032 mg GAE/g), and syneresis (5.24 ± 0.51%) throughout 14 days of storage. The addition of MFDS only gave a slight difference to pH and titratable acidity, while no significant difference was made for LAB count. For sensory evaluation, the addition of MFDS, particularly the ethanol extract, to yogurt was well-liked by panelists. Citrinin content in MFDS yogurt can be decreased under the limits set. Overall, the addition of MFDS has a high potential of improving yogurt properties, particularly its antioxidative properties.
PubMed: 38647786
DOI: 10.1186/s40643-022-00619-y -
Proceedings of the National Academy of... Dec 2022Sino-Tibetan is the second largest language family in the world. Recent linguistic and genetic studies have traced its origin to Neolithic millet farmers in the Yellow...
Sino-Tibetan is the second largest language family in the world. Recent linguistic and genetic studies have traced its origin to Neolithic millet farmers in the Yellow River region of China around 8,000 y ago and also suggested that initial divergence among branches of Sino-Tibetan coincided with expansion of the Neolithic Yangshao culture to the west and southwest during the sixth millennium BP. However, archaeological investigations to date have been insufficient to understand the lifeways of these migrant Proto Sino-Tibetan speakers. Here, we present the results of the interdisciplinary research on the material culture and ritual activities related to the initial southwestward migration of Yangshao populations, based on evidence from microfossil remains on ceramics at three sites in Gansu and Sichuan, regional archaeological contexts, and ethnographic accounts of modern Gyalrong Tibetans. The first Yangshao migrants may have integrated with indigenous hunter-gatherers in the NW Sichuan highlands, and adopted broad-spectrum subsistence strategies, consisting of both millet farming and foraging for local wild resources. Meanwhile, the migrants appear to have retained important ritual traditions previously established in their Yellow River homelands. They prepared starter with mold and rice for brewing alcoholic beverages, which may have been consumed in communal drinking festivals associated with the performance of ritual dancing. Such ritual activities, which to some extent have survived in the ceremonies in SW China, may have then played a central role in maintaining and reinforcing cultural identities, social values, and connections with the homelands of the Proto Sino-Tibetan migrants.
Topics: Archaeology; Language; Linguistics; Agriculture; China
PubMed: 36508670
DOI: 10.1073/pnas.2212006119 -
Current Research in Food Science 2022The exopolysaccharides (EPS) produced by the edible medicinal fungus (EMP) become the center of growing interest due to their techno-functional properties and their...
The exopolysaccharides (EPS) produced by the edible medicinal fungus (EMP) become the center of growing interest due to their techno-functional properties and their numerous applications in the food industries; however, the low EPS yields limit its application. In this study, the effect of genistein supplementation on the production, rheological and antioxidant properties of EPS by . and its biosynthesis mechanism were explored. The results indicated that the addition of genistein (3 g/L) generated a 110% and 59% increase in the maximum mycelial biomass and EPS yield, respectively. The genistein supplementation group (G-EMP) had higher molar percentages of Xyl and Man, and significantly decreased molecule weight and particle size of EPS, which resulted in stronger antioxidant effect and cell growth promotion. Rheological analysis showed that both EMP and G-EMP demonstrated pseudoplastic fluid behavior and G-EMP exhibited strong gel-like elastic behavior (G' > G"). Furthermore, genistein not only facilitated the production of EPS by regulating cell membrane permeability, enhancing cellular respiratory metabolism and monosaccharide precursor synthesis pathways, and enhancing antioxidant enzyme activity to reduce oxidative stress damage, but also affected the composition of the monosaccharides by increasing enzyme activity in the underlying synthesis pathways. These findings expand the application of . resources and provide a paradigm for future study of the structural and functional characteristics of EPS.
PubMed: 36425595
DOI: 10.1016/j.crfs.2022.11.011 -
Toxins Nov 2022Citrinin (CIT) is a mycotoxin found in foods and feeds and most commonly discovered in red yeast rice, a food additive made from ordinary rice by fermentation with ....
Citrinin (CIT) is a mycotoxin found in foods and feeds and most commonly discovered in red yeast rice, a food additive made from ordinary rice by fermentation with . Currently, no enzyme is known to be able to degrade CIT effectively. In this study, it was discovered that manganese peroxidase (MnP) from could degrade CIT. The degradation appeared to be fulfilled by a combination of direct and indirect actions of the MnP with the CIT. Pure CIT, at a final concentration of 10 mg/L, was completely degraded by MnP within 72 h. One degradation product was identified to be dihydrocitrinone. The toxicity of the CIT-degradation product decreased, as monitored by the increased survival rate of the Caco-2 cells incubated with MnP-treated CIT. In addition, MnP could degrade CIT (with a starting concentration of up to 4.6 mg/L) completely contaminated in red yeast rice. MnP serves as an excellent candidate enzyme for CIT detoxification.
Topics: Humans; Citrinin; Caco-2 Cells; Peroxidases
PubMed: 36422974
DOI: 10.3390/toxins14110801 -
Frontiers in Microbiology 2022
PubMed: 36406431
DOI: 10.3389/fmicb.2022.1075162 -
Brazilian Journal of Microbiology :... Mar 2023Eco-friendly natural pigment demand has ever-increasing popularity due to health and environmental concerns. In this context, the aim of this study was to evaluate the...
Eco-friendly natural pigment demand has ever-increasing popularity due to health and environmental concerns. In this context, the aim of this study was to evaluate the feasibility use of Saba banana peel as low-cost fermentable substrate for the production of pigments, xylanase and cellulase enzymes by Monascus purpureus. Among the strains tested, M. purpureus TISTR 3385 produced pigments better and had higher enzyme activities. Under the optimal pigment-producing conditions at the initial moisture content of 40% and initial pH of 6.0, the pigments comprising yellow, orange, and red produced by the fungi were achieved in the range of 0.40-0.93 UA/g/day. The maximum xylanase and cellulase activities of 8.92 ± 0.46 U/g and 4.72 ± 0.04 U/g were also obtained, respectively. More importantly, solid-state fermentation of non-sterile peel could be achieved without sacrificing the production of the pigments and both enzymes. These indicated the potential use of the peel as fermentable feedstock for pigment production by the fungi and an environmental-friendly approach for sustainable waste management and industrial pigment and enzyme application.
Topics: Fermentation; Monascus; Musa; Pigments, Biological; Cellulases
PubMed: 36348258
DOI: 10.1007/s42770-022-00866-3