scholarly journals Summer and winter variations of dicarboxylic acids, fatty acids and benzoic acid in PM<sub>2.5</sub> in Pearl Delta River Region, China

2010 ◽  
Vol 10 (11) ◽  
pp. 26677-26703 ◽  
Author(s):  
K. F. Ho ◽  
S. S. H. Ho ◽  
S. C. Lee ◽  
K. Kawamura ◽  
S. C. Zou ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Benzoic Acid ◽  
Carbon Number ◽  
Dicarboxylic Acids ◽  
Abundant Species ◽  
Water Soluble ◽  
Photochemical Degradation ◽  
Hexadecanoic Acid ◽  
Pollutant Concentrations ◽  
River Region

Abstract. Ground-based PM2.5 samples collected in Pearl River Delta (PRD) region during winter and summer (from 14 December 2006 to 28 January 2007 in winter and from 4 July 2007 to 9 August 2007 in summer) were analyzed for 30 water-soluble organic species, including dicarboxylic acids, ketocarboxylic acids and dicarbonyls, nine fatty acids, and benzoic acid. Molecular distributions of dicarboxylic acids demonstrated that oxalic acid (C2) was the most abundant species followed by phthalic acid (Ph) in PRD region. The concentrations of total dicarboxylic acids ranged from 99 to 1340 ng m−3, with an average of 438 ± 267 ng m−3 in PRD. The concentrations of total ketocarboxylic acids ranged from 0.6 to 207 ng m−3 (43 ± 48 ng m−3 on average) while the concentrations of total α-dicarbonyls, including glyoxal and methylglyoxal, ranged from 0.2 to 89 ng m−3, with an average of 11 ± 18 ng m−3 in PRD. The total quantified water-soluble organic carbon (TQWOC) accounted for 3.4 ± 2.2% of OC and 14.3 ± 10.3% of water-soluble OC (WSOC). Hexadecanoic acid (C16:0), octadecanoic acid (C18:0) and oleic acid (C18:1) are the three most abundant fatty acids in PRD. The distributions of fatty acids are characterized by a strong even carbon number predominance with a maximum (Cmax) at hexadecanoic acid (C16:0). Ratio of C18:1 to C18:0 acts as an indicator for aerosol aging. In PRD, an average of C18:1/C18:0 ratio was 0.53 ± 0.39, suggesting an enhanced photochemical degradation of unsaturated fatty acid. Seasonal variations of the pollutant concentrations were found in the four sampling cities. Higher concentrations of TQWOC were observed in winter (544 ng m−3) than in summer (318 ng m−3). However, the abundances of TQWOC in OC mass were higher in summer (1.8–12.4%, 5.4% on average) than in winter (1.1–5.7, 2.6% on average), being consistent with enhanced secondary production of dicarboxylic acids in warmer weather. Spatial variations of water-soluble dicarboxylic acids were characterized by higher concentrations in Hong Kong and lower concentrations Guangzhou (GZ)/Zhaoqing (ZQ) during winter whereas highest concentrations were observed in GZ/ZQ during summer. These spatial and seasonal distributions are consistent with photochemical production and the subsequent accumulation under different meteorological conditions.

scholarly journals Summer and winter variations of dicarboxylic acids, fatty acids and benzoic acid in PM<sub>2.5</sub> in Pearl Delta River Region, China

2011 ◽  
Vol 11 (5) ◽  
pp. 2197-2208 ◽  
Author(s):  
K. F. Ho ◽  
S. S. H. Ho ◽  
S. C. Lee ◽  
K. Kawamura ◽  
S. C. Zou ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Benzoic Acid ◽  
Carbon Number ◽  
Dicarboxylic Acids ◽  
Water Soluble ◽  
Motor Vehicles ◽  
Photochemical Degradation ◽  
Pearl River Delta Region ◽  
Hexadecanoic Acid ◽  
River Region

Abstract. Ground-based PM2.5 samples collected at four different sites in Pearl River Delta region (PRD) during winter and summer (from 14 December 2006 to 28 January 2007 in winter and from 4 July to 9 August 2007 in summer) were analyzed for 30 water-soluble organic species, including dicarboxylic acids, ketocarboxylic acids and dicarbonyls, nine fatty acids, and benzoic acid. Molecular distributions of dicarboxylic acids demonstrated that oxalic acid (C2) was the most abundant species followed by phthalic acid (Ph) in PRD region. The concentrations of total dicarboxylic acids ranged from 99 to 1340 ng m−3, with an average of 438 ± 267 ng m−3 in PRD. The concentrations of total ketocarboxylic acids ranged from 0.6 to 207 ng m−3 (43 ± 48 ng m−3 on average) while the concentrations of total α-dicarbonyls, including glyoxal and methylglyoxal, ranged from 0.2 to 89 ng m−3, with an average of 11 ± 18 ng m−3 in PRD. The total quantified water-soluble compounds (TQWOC) (organic carbon) accounted for 3.4 ± 2.2% of OC and 14.3 ± 10.3% of water-soluble OC (WSOC). Hexadecanoic acid (C16:0), octadecanoic acid (C18:0) and oleic acid (C18:1) were the three most abundant fatty acids in PRD. The distributions of fatty acids were characterized by a strong even carbon number predominance with a maximum (Cmax) at hexadecanoic acid (C16:0). Ratio of C18:1 to C18:0 acts as an indicator for aerosol aging. In PRD, an average of C18:1/C18:0 ratio was 0.53 ± 0.39, suggesting an enhanced photochemical degradation of unsaturated fatty acid. Moreover, the concentrations of benzoic acid ranged from 84 to 306 ng m−3, (165 ± 48 ng m−3 on average), which can be emitted as primary pollutant from motor vehicles exhaust, or formed from photochemical degradation of aromatic hydrocarbons. Seasonal variations of the organic specie concentrations were found in the four sampling cities. Higher concentrations of TQWOC were observed in winter (598 ± 321 ng m−3) than in summer (372 ± 215 ng m−3). However, the abundances of TQWOC in OC mass were higher in summer (0.9–12.4%, 4.5 ± 2.7% on average) than in winter (1.1–5.7, 2.5 ± 1.2% on average), being consistent with enhanced secondary production of dicarboxylic acids in warmer weather. Spatial variations of water-soluble dicarboxylic acids were characterized by higher concentrations in Hong Kong and lower concentrations in Guangzhou (GZ)/Zhaoqing (ZQ) during winter whereas the highest concentrations were observed in GZ/ZQ during summer. These spatial and seasonal distributions are consistent with photochemical production and the subsequent accumulation under different meteorological conditions.

scholarly journals Dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls, fatty acids and benzoic acid in PM<sub>2.5</sub> aerosol collected during CAREBeijing-2007: an effect of traffic restriction on air quality

2015 ◽  
Vol 15 (6) ◽  
pp. 3111-3123 ◽  
Author(s):  
K. F. Ho ◽  
R.-J. Huang ◽  
K. Kawamura ◽  
E. Tachibana ◽  
S. C. Lee ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Air Pollution ◽  
Air Quality ◽  
Organic Carbon ◽  
Benzoic Acid ◽  
Carbon Number ◽  
Dicarboxylic Acids ◽  
Water Soluble ◽  
Organic Species ◽  
Pollution Events

Abstract. Thirty water-soluble organic species, including dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls, fatty acids and benzoic acid were determined as well as organic carbon (OC), elemental carbon (EC) and water-soluble organic carbon (WSOC) in PM2.5 samples collected during the Campaign of Air Quality Research in Beijing 2007 (CAREBeijing-2007) in the urban and suburban areas of Beijing. The objective of this study is to identify the influence of traffic emissions and regional transport to the atmosphere in Beijing during summer. PM2.5 samples collected with or without traffic restriction in Beijing are selected to evaluate the effectiveness of local traffic restriction measures on air pollution reduction. The average concentrations of the total quantified bifunctional organic compounds (TQBOCs), total fatty acids and benzoic acid during the entire sampling period were 1184±241, 597±159 and 1496±511 ng m−3 in Peking University (PKU), and 1050±303, 475±114 and 1278±372 ng m−3 in Yufa, Beijing. Oxalic acid (C2) was found as the most abundant dicarboxylic acid at PKU and Yufa followed by phthalic acid (Ph). A strong even carbon number predominance with the highest level at stearic acid (C18:0), followed by palmitic acid (C16:0) was found for fatty acids. According to the back trajectories modeling results, the air masses were found to originate mainly from the northeast, passing over the southeast or south of Beijing (heavily populated, urbanized and industrialized areas), during heavier pollution events, whereas they are mainly from the north or northwest sector (mountain areas without serious anthropogenic pollution sources) during less pollution events. The data with wind only from the same sector (minimizing the difference from regional contribution) but with and without traffic restriction in Beijing were analyzed to evaluate the effectiveness of local traffic restriction measures on the reduction of local air pollution in Beijing. The results suggested that the traffic restriction measures can reduce the air pollutants, but the decrease of pollutants is generally smaller in Yufa compared to that in PKU. Moreover, an enhancement of EC value indicates more elevated primary emissions in Yufa during restriction periods than in non-restriction periods. This study demonstrates that even when primary exhaust was controlled by traffic restriction, the contribution of secondary organic species formed from photochemical processes was critical with long-range atmospheric transport of pollutants.

scholarly journals Dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls, fatty acids and benzoic acid in PM<sub>2.5</sub> aerosol collected during CAREBeijing-2007: an effect of traffic restriction on air quality

2014 ◽  
Vol 14 (10) ◽  
pp. 14855-14887 ◽  
Author(s):  
K. F. Ho ◽  
R.-J. Huang ◽  
K. Kawamura ◽  
E. Tachibana ◽  
S. C. Lee ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Air Pollution ◽  
Air Quality ◽  
Organic Carbon ◽  
Benzoic Acid ◽  
Elemental Carbon ◽  
Carbon Number ◽  
Dicarboxylic Acids ◽  
Water Soluble ◽  
Organic Species

Abstract. Thirty water-soluble organic species, including dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls, fatty acids, and benzoic acid were determined as well as organic carbon (OC), elemental carbon (EC) and water-soluble organic carbon (WSOC) in PM2.5 samples collected during the Campaign of Air Quality Research in Beijing 2007 (CAREBeijing-2007) in the urban and suburban areas of Beijing. The objective of this study is to identify the influence of traffic emissions and regional transport to the atmosphere in Beijing during summer. PM2.5 samples collected with or without traffic restriction in Beijing are selected to evaluate the effectiveness of local traffic restriction measure on air pollution reduction. The average concentrations of the total quantified bifunctional organic compounds (TQBOC), total fatty acids and benzoic acid during the entire sampling period were 1184 ± 241 ng m−3, 597 ± 159 ng m−3 and 1496 ± 511ng m−3 in PKU, and 1050 ± 303 ng m−3, 475 ± 114 ng m−3 and 1278 ± 372 ng m−3 in Yufa. Oxalic acid (C2) was found as the most abundant dicarboxylic acid at PKU and Yufa, followed by phthalic acid (Ph). A strong even carbon number predominance with the highest level at palmitic acid (C16:0), followed by stearic acid (C18:0) was found for fatty acids. According to the back trajectories modeling results, the air masses were found to originate mainly from northeast, passing over southeast or south of Beijing (heavily populated, urbanized and industrialized areas), during heavier pollution events, whereas they are mainly from north or northwest sector (mountain areas without serious anthropogenic pollution sources) during cleaner events. The data with wind only from the same sector (minimizing the difference from regional contribution) but with and without traffic restriction in Beijing were analyzed to evaluate the effectiveness of local traffic restriction measure on the reduction of local air pollution in Beijing. The results suggested that the "traffic restriction" measure can reduce the air pollutants, but the decrease of pollutants is generally smaller in Yufa compared to that in PKU. Moreover, an enhancement of elemental carbon (EC) value indicates elevated primary emissions in Yufa during restriction period than non-restriction period. This study demonstrates that even when primary exhaust was controlled by traffic restriction, the contribution of secondary organic species formed from photochemical processes was critical with long-range atmospheric transport of pollutants.

scholarly journals Molecular composition of dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls and fatty acids in atmospheric aerosols from Tanzania, East Africa during wet and dry seasons

2013 ◽  
Vol 13 (4) ◽  
pp. 2235-2251 ◽  
Author(s):  
S. L. Mkoma ◽  
K. Kawamura
Keyword(s):  
Fatty Acids ◽  
Dicarboxylic Acids ◽  
Dry Season ◽  
Water Soluble ◽  
Molecular Composition ◽  
Wet Season ◽  
Dry Seasons ◽  
Pm2.5 And Pm10 ◽  
Related Compounds ◽  
Wet And Dry Seasons

Abstract. Atmospheric aerosol samples of PM2.5 and PM10 were collected during the wet and dry seasons in 2011 from a rural site in Tanzania and analysed for water-soluble dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls, and fatty acids using a gas chromatography/flame ionization detector (GC/FID) and GC/mass spectrometry. Here we report the molecular composition and sources of diacids and related compounds for wet and dry seasons. Oxalic acid (C2) was found as the most abundant diacid species followed by succinic and/or malonic acids whereas glyoxylic acid and glyoxal were the dominant ketoacid and α-dicarbonyl, respectively in both seasons in PM2.5 and PM10. Mean concentration of C2 in PM2.5 (121 ± 47 ng m−3) was lower in wet season than dry season (258 ± 69 ng m−3). Similarly, PM10 samples showed lower concentration of C2 (169 ± 42 ng m−3) in wet season than dry season (292 ± 165 ng m−3). Relative abundances of C2 in total diacids were 65% and 67% in PM2.5 and 65% and 64% in PM10 in the wet and dry seasons, respectively. Total concentrations of diacids (289–362 ng m−3), ketoacids (37.8–53.7 ng m−3), and α-dicarbonyls (5.7–7.8 ng m−3) in Tanzania are higher than those reported at a rural background site in Nylsvley (South Africa) but comparable or lower than those reported from sites in Asia and Europe. Diacids and ketoacids were found to be present mainly in PM2.5 in both seasons (total α-dicarbonyls in the dry season), suggesting a production of organic acids from pyrogenic sources and photochemical oxidations. Averaged contributions of total diacids to aerosol total carbon were 1.4% in PM2.5 and 2.1% in PM10 during wet season and 3.3% in PM2.5 and 3.9% in PM10 during dry season whereas those to water-soluble organic carbon were 2.2% and 4.7% in PM2.5 during wet season and 3.1% and 5.8% in PM10 during dry season. The higher ratios in dry season suggest an enhanced photochemical oxidation of organic precursors probably via heterogeneous reactions on aerosols under strong solar radiation. Strong positive correlations were found among diacids and related compounds as well as good relations to source tracers in both seasons, suggesting a mixed source from natural biogenic emissions, biomass burning, biofuel combustion, and photochemical production.

Seasonal distributions and sources of low molecular weight dicarboxylic acids, ω-oxocarboxylic acids, pyruvic acid, α-dicarbonyls and fatty acids in ambient aerosols from subtropical Okinawa in the western Pacific Rim

2014 ◽  
Vol 11 (6) ◽  
pp. 673 ◽  
Author(s):  
Bhagawati Kunwar ◽  
Kimitaka Kawamura
Keyword(s):  
Fatty Acids ◽  
Organic Aerosols ◽  
Dicarboxylic Acids ◽  
Water Soluble ◽  
Anthropogenic Sources ◽  
Asian Continent ◽  
Ambient Aerosols ◽  
Okinawa Island ◽  
Photochemical Aging ◽  
Related Compounds

Environmental context Water-soluble dicarboxylic acids and related compounds are ubiquitous in atmospheric aerosols. They are abundantly emitted from Asian countries and transported to the Pacific Ocean. During the long-range transport, photochemical processing modifies organic aerosols. We conducted a 1-year observation of diacids and related compounds at Okinawa Island, an outflow region of the Asian Continent, to clarify their sources and photochemical aging. Abstract Ambient aerosol samples were collected for 1 year at Okinawa Island, Japan, and were analysed for water-soluble dicarboxylic acids, oxoacids, α-dicarbonyls and fatty acids to better understand biogenic v. anthropogenic sources and the formation–transformation of organic aerosols during long-range atmospheric transport. Here, we report seasonal variations of diacids and related compounds in Okinawa. We found a predominance of oxalic acid (C2) followed by malonic (C3) and succinic (C4) acid. Total diacids and oxoacids maximised in spring when air masses originated from the Asian Continent with westerly winds. In contrast, phthalic acid (Ph), a tracer of anthropogenic sources, peaked in winter. We found an increased C3/C4 ratio in summer, suggesting an enhanced photochemical aging of organic aerosols. The average ratio of total diacid-C/total carbon (TC) (5.4%) is higher than that (3.1%) from the East China Sea, suggesting that Okinawa aerosols are more aged than East Asian aerosols but less aged compared to those from the remote Pacific including tropics (8.8%). Biogenic short-chain fatty acids and azelaic acid (C9), the latter is a specific oxidation product of unsaturated fatty acids, maximised in summer, whereas higher plant-derived long-chain fatty acids maximised in spring. This study demonstrates that the ambient aerosols in Okinawa are strongly influenced by the Asian outflow in winter and spring and by biogenic organic matter in summer and spring. Enhanced contribution of oxalic acid to aerosol TC in spring suggests that Okinawa organic aerosols are mainly produced in East Asia and photochemically transformed during the transport.

scholarly journals New Pathway for Long-Chain n-Alkane Synthesis via 1-Alcohol in Vibrio furnissii M1

2005 ◽  
Vol 187 (4) ◽  
pp. 1426-1429 ◽  
Author(s):  
Myong-Ok Park
Keyword(s):  
Fatty Acids ◽  
Carbon Number ◽  
Hexadecanoic Acid ◽  
Carbon Structure ◽  
Alkane Biosynthesis ◽  
Vibrio Furnissii ◽  
Long Chain ◽  
Tracer Experiments

ABSTRACT Alkane biosynthesis in the bacterium Vibrio furnissii M1 involves the synthesis of long-chain alkanes via 1-alcohol. Evidence for this novel pathway are the following. (i) Both even- and odd-carbon-number n-alkanes were produced from glucose, while only even-carbon-number fatty acids were produced in V. furnissii M1. This result cannot be explained by the decarbonylation pathway. (ii) Pentadecane and hexadecane were produced from 1-hexadecanoic acid by membrane fractions of V. furnissii M1, and radioisotope precursor-tracer experiments, in which 1-[1-14C]hexadecanoic acid was fed, identified the corresponding alcohol, aldehyde, and alkane derivatives. Since all metabolites maintained the radioisotope label at 1-C, they were produced by a pathway in which the carbon structure was retained, i.e., a reduction pathway. (iii) n-Hexadecane was produced when 1-hexadecanol was fed to membrane preparations.

Characterization of Organic Acids with Different Atmospheric Particle Sizes

2012 ◽  
Vol 599 ◽  
pp. 14-22
Author(s):  
Xiang He ◽  
Feng Qian ◽  
Yao Li
Keyword(s):  
Fatty Acids ◽  
Human Activities ◽  
Dicarboxylic Acids ◽  
Photochemical Reactions ◽  
Particle Sizes ◽  
Octadecanoic Acid ◽  
Hexadecanoic Acid ◽  
Average Mass ◽  
Atmospheric Particle

Atmospheric particulate samples were collected during January, February, April and May 2012, separately. Twenty-one fatty acids and seven dicarboxylic acids were measured by GC-MS. The results show that average mass concentrations of fatty acids are 809.24ng/m³, 545.34ng/m³, 386.96ng/m³ and dicarboxylic acids are 215.14 ng/m³, 156.45 ng/m³, 111.43 ng/m³ in PM10, PM2.5, PM1, respectively. Fatty acids and dicarboxylic acids concentrate mainly in the PM1. C11-C24 of fatty acids exhibit a significant even carbon predominances, but dicarboxylic acids present no parity preponderance. In the fatty acids, the concentration of hexadecanoic acid is the highest with that of octadecanoic acid followed; Nonandioic acid is the highest in dicarboxylic acids. The results of source apportionments indicate that the fatty acids are mainly related with human activities. Coal burning for heating is the most important source in January and February, but its contribution decreases sharply in April and May for fatty acids; The main source of dicarboxylic acids is photochemical reactions.

scholarly journals Size distributions of dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls and fatty acids in atmospheric aerosols from Tanzania, East Africa during wet and dry seasons

2012 ◽  
Vol 12 (9) ◽  
pp. 25657-25701
Author(s):  
S. L. Mkoma ◽  
K. Kawamura
Keyword(s):  
Fatty Acids ◽  
Dicarboxylic Acids ◽  
Dry Season ◽  
Water Soluble ◽  
Rural Site ◽  
Wet Season ◽  
Dry Seasons ◽  
Pm2.5 And Pm10 ◽  
Related Compounds ◽  
Wet And Dry Seasons

Abstract. Atmospheric aerosol samples of PM2.5 and PM10 were collected during the wet and dry seasons in 2011 from a rural site in Tanzania and analysed for water-soluble dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls and fatty acids using a gas chromatography (GC) and GC/mass spectrometry. Here we report the size distribution and sources of diacids and related compounds for wet and dry seasons. Oxalic acid (C2) was found as the most abundant diacid species followed by succinic and/or malonic acids whereas glyoxylic acid and glyoxal were the dominant ketoacids and α-dicarbonyls, respectively in both seasons in PM2.5 and PM10. Mean concentration of C2 in PM2.5 (121.5&amp;pm; 46.6 ng m−3) was lower in wet season than dry season (258.1&amp;pm; 69.5 ng m−3). Similarly, PM10 samples showed lower concentration of C2 (168.6 &amp;pm; 42.4 ng m−3) in wet season than dry season (292.4&amp;pm; 164.8 ng m−3). Relative abundances of C2 in total diacids were 65.4% and 67.1% in PM2.5 and 64.6% and 63.9% in PM10 in the wet and dry seasons, respectively. Total concentrations of diacids (289–362 m−3), ketoacids (37.8–53.7ng m−3), and α-dicarbonyls (5.7–7.8 ng m−3) in Tanzania are higher to those reported at a rural background site in Nylsvley (South Africa) but comparable or lower to those reported from sites in Asia and Europe. Diacids and ketoacids were found to be present mainly in the fine fraction in both seasons (total α-dicarbonyls in the dry season), suggesting a production of organic aerosols from pyrogenic sources and photochemical oxidations. The averaged contributions of total diacid carbon to aerosol total carbon were 1.4% in PM2.5 and 2.1% in PM10 in wet season and 3.3% in PM2.5 and 3.9% in PM10 in dry season whereas those to water-soluble organic carbon were 2.2% and 4.7% inPM2.5 and 3.1% and 5.8% in PM10 during the wet and dry seasons, respectively. These ratios suggest an enhanced photochemical oxidation of organic precursors and heterogeneous reactions on aerosols under strong solar radiation and high humidity. Correlations among organic components and relations between source tracers with diacids and related compounds in both seasons showed influence of mixed sources from natural biogenic emissions, biomass burning, biofuel combustion, and enhanced photochemical production.

scholarly journals Identification of the Potential Role of the Rumen Microbiome in Milk Protein and Fat Synthesis in Dairy Cows Using Metagenomic Sequencing

Animals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1247
Author(s):  
Xin Wu ◽  
Shuai Huang ◽  
Jinfeng Huang ◽  
Peng Peng ◽  
Yanan Liu ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Amino Acid ◽  
Milk Fat ◽  
Milk Protein ◽  
Volatile Fatty Acids ◽  
Rumen Fluid ◽  
Abundant Species ◽  
Metagenomic Sequencing ◽  
Amino Acid Synthesis ◽  
Prevotella Species

The rumen contains abundant microorganisms that aid in the digestion of lignocellulosic feed and are associated with host phenotype traits. Cows with extremely high milk protein and fat percentages (HPF; n = 3) and low milk protein and fat percentages (LPF; n = 3) were selected from 4000 lactating Holstein cows under the same nutritional and management conditions. We found that the total concentration of volatile fatty acids, acetate, butyrate, and propionate in the rumen fluid was significantly higher in the HPF group than in the LPF group. Moreover, we identified 38 most abundant species displaying differential richness between the two groups, in which Prevotella accounted for 68.8% of the species, with the highest abundance in the HPF group. Functional annotation based on the Kyoto Encyclopedia of Gene and Genome (KEGG), evolutionary genealogy of genes: Non-supervised Orthologous Groups (eggNOG), and Carbohydrate-Active enzymes (CAZy) databases showed that the significantly more abundant species in the HPF group are enriched in carbohydrate, amino acid, pyruvate, insulin, and lipid metabolism and transportation. Furthermore, Spearman’s rank correlation analysis revealed that specific microbial taxa (mainly the Prevotella species and Neocallimastix californiae) are positively correlated with total volatile fatty acids (VFA). Collectively, we found that the HPF group was enriched with several Prevotella species related to the total VFA, acetate, and amino acid synthesis. Thereby, these fulfilled the host’s needs for energy, fat, and rumen microbial protein, which can be used for increased biosynthesis of milk fat and milk protein. Our findings provide novel information for elucidation of the regulatory mechanism of the rumen in the formation of milk composition.

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