The Experts below are selected from a list of 600 Experts worldwide ranked by ideXlab platform
Ali Karabulut - One of the best experts on this subject based on the ideXlab platform.
-
The effects of Propionibacterium acidipropionici and Lactobacillus plantarum, applied at ensiling, on the fermentation and aerobic stability of low dry matter corn and sorghum silages
Journal of Industrial Microbiology and Biotechnology, 2006Co-Authors: İsmail Filya, Ekin Sucu, Ali KarabulutAbstract:The aim of this work was to study the effects of applying a strain of Propionibacterium acidipropionici , with or without Lactobacillus plantarum , on the fermentation and aerobic stability characteristics of low dry matter (DM) corn ( Zea mays L.) and sorghum ( Sorghum bicolor L.) silages. Corn at the dent stage and sorghum at the flowering stage were harvested. Treatments comprised control (no additives), P. acidipropionici , L. plantarum and a combination of P. acidipropionici and L. plantarum . Fresh forages were sampled prior to ensiling. Bacterial inoculants were applied to the fresh forage at 1.0×10^6 colony-forming units per gram. After treatment, the chopped fresh materials were ensiled in 1.5-l anaerobic glass jars equipped with a lid that enabled gas release only. Three jars per treatment were sampled on days 2, 4, 8, 16 and 60 after ensiling, for chemical and microbiological analysis. At the end of the ensiling period, 60 days, the silages were subjected to an aerobic stability test. The L. plantarum inoculated silages had significantly higher levels of lactic acid than the controls, P. acidipropionici and combination of P. acidipropionici and L. plantarum inoculated silages ( P
-
the effects of Propionibacterium acidipropionici and lactobacillus plantarum applied at ensiling on the fermentation and aerobic stability of low dry matter corn and sorghum silages
Journal of Industrial Microbiology & Biotechnology, 2006Co-Authors: İsmail Filya, Ekin Sucu, Ali KarabulutAbstract:The aim of this work was to study the effects of applying a strain of Propionibacterium acidipropionici, with or without Lactobacillus plantarum, on the fermentation and aerobic stability characteristics of low dry matter (DM) corn (Zea mays L.) and sorghum (Sorghum bicolor L.) silages. Corn at the dent stage and sorghum at the flowering stage were harvested. Treatments comprised control (no additives), P. acidipropionici, L. plantarum and a combination of P. acidipropionici and L. plantarum. Fresh forages were sampled prior to ensiling. Bacterial inoculants were applied to the fresh forage at 1.0×106 colony-forming units per gram. After treatment, the chopped fresh materials were ensiled in 1.5-l anaerobic glass jars equipped with a lid that enabled gas release only. Three jars per treatment were sampled on days 2, 4, 8, 16 and 60 after ensiling, for chemical and microbiological analysis. At the end of the ensiling period, 60 days, the silages were subjected to an aerobic stability test. The L. plantarum inoculated silages had significantly higher levels of lactic acid than the controls, P. acidipropionici and combination of P. acidipropionici and L. plantarum inoculated silages (P<0.05). The P. acidipropionici did not increase propionic and acetic acid levels of the silages. After the aerobic exposure test, the L. plantarum and combination of P. acidipropionici and L. plantarum had produced more CO2 than the controls and the silages inoculated with P. acidipropionici (P<0.05). All silages had high levels of CO2 and high numbers of yeasts and molds in the experiment. Therefore, all silages were deteriorated under aerobic conditions. The P. acidipropionici and combination of P. acidipropionici and L. plantarum were not able to improve the aerobic stability of fast-fermenting silages, because they could not work well in this acidic environment. The results showed that P. acidipropionici and combination of P. acidipropionici and L. plantarum did not improve the aerobic stability of low DM corn and sorghum silages, which are prone to aerobic deterioration.
-
the effect of Propionibacterium acidipropionici with or without lactobacillus plantarum on the fermentation and aerobic stability of wheat sorghum and maize silages
Journal of Applied Microbiology, 2004Co-Authors: İsmail Filya, Ekin Sucu, Ali KarabulutAbstract:I. FILYA, E. SUCU AND A. KARABULUT. 2004. Aims: To determine the effect of Propionibacterium acidipropionici, alone or in combination with Lactobacillus plantarum, on the fermentation and aerobic stability of wheat, sorghum and maize silages. Methods and Results: The inoculants were applied at 1AE0 · 10 6 CFU g )1 . Silages with no additives served as control. Fresh forages were sampled prior to ensiling. Three jars per treatment were sampled on days 2, 4, 8, 16 and 60 after ensiling, for chemical and microbiological analysis. At the end of the ensiling period, the silages were subjected to an aerobic stability test. The P. acidipropionici-inoculated silages had significantly higher levels of acetic and propionic acid than the L. plantarum or P. acidipropionici + L. plantarum-inoculated silages (P <0 AE05). Therefore, yeast activity was impaired in the P. acidipropionici-inoculated silages. As a result, P. acidipropionici decreased CO2 production and improved aerobic stability of wheat, sorghum and maize silages. However, the combination of P. acidipropionici + L. plantarum did not improve aerobic stability of the silages. Conclusions: The P. acidipropionici was very effective in protecting the wheat, sorghum and maize silages exposed to air under laboratory conditions, probably because the acidic environment under ensiling conditions is favourable for this micro-organism. Significance and Impact of the Study: The use of P. acidipropionici, as a silage inoculant can improve the aerobic stability of silages by inhibition of yeast activity.
-
The effect of Propionibacterium acidipropionici, with or without Lactobacillus plantarum, on the fermentation and aerobic stability of wheat, sorghum and maize silages.
Journal of applied microbiology, 2004Co-Authors: İsmail Filya, Ekin Sucu, Ali KarabulutAbstract:I. FILYA, E. SUCU AND A. KARABULUT. 2004. Aims: To determine the effect of Propionibacterium acidipropionici, alone or in combination with Lactobacillus plantarum, on the fermentation and aerobic stability of wheat, sorghum and maize silages. Methods and Results: The inoculants were applied at 1AE0 · 10 6 CFU g )1 . Silages with no additives served as control. Fresh forages were sampled prior to ensiling. Three jars per treatment were sampled on days 2, 4, 8, 16 and 60 after ensiling, for chemical and microbiological analysis. At the end of the ensiling period, the silages were subjected to an aerobic stability test. The P. acidipropionici-inoculated silages had significantly higher levels of acetic and propionic acid than the L. plantarum or P. acidipropionici + L. plantarum-inoculated silages (P
Patrick Boyaval - One of the best experts on this subject based on the ideXlab platform.
-
in vivo13c nmr study of the bidirectional reactions of the wood werkman cycle and around the pyruvate node in Propionibacterium freudenreichii subsp shermanii and Propionibacterium acidipropionici
Metabolic Engineering, 1999Co-Authors: Catherine Deborde, Dominique Rolin, Patrick BoyavalAbstract:This study used in vitro 13C NMR spectroscopy to directly examine bidirectional reactions of the Wood-Werkman cycle involved in central carbon metabolic pathways of dairy propionibacteria during pyruvate catabolism. The flow of [2-13C]pyruvate label was monitored on living cell suspensions of Propionibacterium freudenreichii subsp. shermanii and Propionibacterium acidipropionici under acidic conditions. P. shermanii and P. acidipropionici cells consumed pyruvate at apparent initial rates of 161 and 39 micromol min(-1) g(-1) (cell dry weight), respectively. The bidirectionality of reactions in the first part of the Wood-Werkman cycle was evident from the formation of intermediates such as [3-13C]pyruvate and [3-13C]malate and of products like [2-13C]acetate from [2-13C]pyruvate. For the first time alanine labeled on C2 and C3 and aspartate labeled on C2 and C3 were observed during [2-13C]pyruvate metabolism by propionibacteria. The kinetics of aspartate isotopic enrichment was evidence for its production from oxaloacetate via aspartate aminotransferase. Activities of a partial tricarboxylic acid pathway, acetate synthesis, succinate synthesis, gluconeogenesis, aspartate synthesis, and alanine synthesis pathways were evident from the experimental results.
-
In Vivo13C NMR Study of the Bidirectional Reactions of the Wood–Werkman Cycle and around the Pyruvate Node in Propionibacterium freudenreichii subsp. shermanii and Propionibacterium acidipropionici
Metabolic engineering, 1999Co-Authors: Catherine Deborde, Dominique Rolin, Patrick BoyavalAbstract:This study used in vitro 13C NMR spectroscopy to directly examine bidirectional reactions of the Wood-Werkman cycle involved in central carbon metabolic pathways of dairy propionibacteria during pyruvate catabolism. The flow of [2-13C]pyruvate label was monitored on living cell suspensions of Propionibacterium freudenreichii subsp. shermanii and Propionibacterium acidipropionici under acidic conditions. P. shermanii and P. acidipropionici cells consumed pyruvate at apparent initial rates of 161 and 39 micromol min(-1) g(-1) (cell dry weight), respectively. The bidirectionality of reactions in the first part of the Wood-Werkman cycle was evident from the formation of intermediates such as [3-13C]pyruvate and [3-13C]malate and of products like [2-13C]acetate from [2-13C]pyruvate. For the first time alanine labeled on C2 and C3 and aspartate labeled on C2 and C3 were observed during [2-13C]pyruvate metabolism by propionibacteria. The kinetics of aspartate isotopic enrichment was evidence for its production from oxaloacetate via aspartate aminotransferase. Activities of a partial tricarboxylic acid pathway, acetate synthesis, succinate synthesis, gluconeogenesis, aspartate synthesis, and alanine synthesis pathways were evident from the experimental results.
İsmail Filya - One of the best experts on this subject based on the ideXlab platform.
-
The effects of Propionibacterium acidipropionici and Lactobacillus plantarum, applied at ensiling, on the fermentation and aerobic stability of low dry matter corn and sorghum silages
Journal of Industrial Microbiology and Biotechnology, 2006Co-Authors: İsmail Filya, Ekin Sucu, Ali KarabulutAbstract:The aim of this work was to study the effects of applying a strain of Propionibacterium acidipropionici , with or without Lactobacillus plantarum , on the fermentation and aerobic stability characteristics of low dry matter (DM) corn ( Zea mays L.) and sorghum ( Sorghum bicolor L.) silages. Corn at the dent stage and sorghum at the flowering stage were harvested. Treatments comprised control (no additives), P. acidipropionici , L. plantarum and a combination of P. acidipropionici and L. plantarum . Fresh forages were sampled prior to ensiling. Bacterial inoculants were applied to the fresh forage at 1.0×10^6 colony-forming units per gram. After treatment, the chopped fresh materials were ensiled in 1.5-l anaerobic glass jars equipped with a lid that enabled gas release only. Three jars per treatment were sampled on days 2, 4, 8, 16 and 60 after ensiling, for chemical and microbiological analysis. At the end of the ensiling period, 60 days, the silages were subjected to an aerobic stability test. The L. plantarum inoculated silages had significantly higher levels of lactic acid than the controls, P. acidipropionici and combination of P. acidipropionici and L. plantarum inoculated silages ( P
-
the effects of Propionibacterium acidipropionici and lactobacillus plantarum applied at ensiling on the fermentation and aerobic stability of low dry matter corn and sorghum silages
Journal of Industrial Microbiology & Biotechnology, 2006Co-Authors: İsmail Filya, Ekin Sucu, Ali KarabulutAbstract:The aim of this work was to study the effects of applying a strain of Propionibacterium acidipropionici, with or without Lactobacillus plantarum, on the fermentation and aerobic stability characteristics of low dry matter (DM) corn (Zea mays L.) and sorghum (Sorghum bicolor L.) silages. Corn at the dent stage and sorghum at the flowering stage were harvested. Treatments comprised control (no additives), P. acidipropionici, L. plantarum and a combination of P. acidipropionici and L. plantarum. Fresh forages were sampled prior to ensiling. Bacterial inoculants were applied to the fresh forage at 1.0×106 colony-forming units per gram. After treatment, the chopped fresh materials were ensiled in 1.5-l anaerobic glass jars equipped with a lid that enabled gas release only. Three jars per treatment were sampled on days 2, 4, 8, 16 and 60 after ensiling, for chemical and microbiological analysis. At the end of the ensiling period, 60 days, the silages were subjected to an aerobic stability test. The L. plantarum inoculated silages had significantly higher levels of lactic acid than the controls, P. acidipropionici and combination of P. acidipropionici and L. plantarum inoculated silages (P<0.05). The P. acidipropionici did not increase propionic and acetic acid levels of the silages. After the aerobic exposure test, the L. plantarum and combination of P. acidipropionici and L. plantarum had produced more CO2 than the controls and the silages inoculated with P. acidipropionici (P<0.05). All silages had high levels of CO2 and high numbers of yeasts and molds in the experiment. Therefore, all silages were deteriorated under aerobic conditions. The P. acidipropionici and combination of P. acidipropionici and L. plantarum were not able to improve the aerobic stability of fast-fermenting silages, because they could not work well in this acidic environment. The results showed that P. acidipropionici and combination of P. acidipropionici and L. plantarum did not improve the aerobic stability of low DM corn and sorghum silages, which are prone to aerobic deterioration.
-
the effect of Propionibacterium acidipropionici with or without lactobacillus plantarum on the fermentation and aerobic stability of wheat sorghum and maize silages
Journal of Applied Microbiology, 2004Co-Authors: İsmail Filya, Ekin Sucu, Ali KarabulutAbstract:I. FILYA, E. SUCU AND A. KARABULUT. 2004. Aims: To determine the effect of Propionibacterium acidipropionici, alone or in combination with Lactobacillus plantarum, on the fermentation and aerobic stability of wheat, sorghum and maize silages. Methods and Results: The inoculants were applied at 1AE0 · 10 6 CFU g )1 . Silages with no additives served as control. Fresh forages were sampled prior to ensiling. Three jars per treatment were sampled on days 2, 4, 8, 16 and 60 after ensiling, for chemical and microbiological analysis. At the end of the ensiling period, the silages were subjected to an aerobic stability test. The P. acidipropionici-inoculated silages had significantly higher levels of acetic and propionic acid than the L. plantarum or P. acidipropionici + L. plantarum-inoculated silages (P <0 AE05). Therefore, yeast activity was impaired in the P. acidipropionici-inoculated silages. As a result, P. acidipropionici decreased CO2 production and improved aerobic stability of wheat, sorghum and maize silages. However, the combination of P. acidipropionici + L. plantarum did not improve aerobic stability of the silages. Conclusions: The P. acidipropionici was very effective in protecting the wheat, sorghum and maize silages exposed to air under laboratory conditions, probably because the acidic environment under ensiling conditions is favourable for this micro-organism. Significance and Impact of the Study: The use of P. acidipropionici, as a silage inoculant can improve the aerobic stability of silages by inhibition of yeast activity.
-
The effect of Propionibacterium acidipropionici, with or without Lactobacillus plantarum, on the fermentation and aerobic stability of wheat, sorghum and maize silages.
Journal of applied microbiology, 2004Co-Authors: İsmail Filya, Ekin Sucu, Ali KarabulutAbstract:I. FILYA, E. SUCU AND A. KARABULUT. 2004. Aims: To determine the effect of Propionibacterium acidipropionici, alone or in combination with Lactobacillus plantarum, on the fermentation and aerobic stability of wheat, sorghum and maize silages. Methods and Results: The inoculants were applied at 1AE0 · 10 6 CFU g )1 . Silages with no additives served as control. Fresh forages were sampled prior to ensiling. Three jars per treatment were sampled on days 2, 4, 8, 16 and 60 after ensiling, for chemical and microbiological analysis. At the end of the ensiling period, the silages were subjected to an aerobic stability test. The P. acidipropionici-inoculated silages had significantly higher levels of acetic and propionic acid than the L. plantarum or P. acidipropionici + L. plantarum-inoculated silages (P
Jian Chen - One of the best experts on this subject based on the ideXlab platform.
-
Comparative genomics and transcriptomics analysis-guided metabolic engineering of Propionibacterium acidipropionici for improved propionic acid production.
Biotechnology and bioengineering, 2017Co-Authors: Ningzi Guan, Jian Chen, Hyun-dong Shin, Rachel R. Chen, Long LiuAbstract:Acid stress induced by the accumulation of organic acids during the fermentation of propionibacteria is a severe limitation in the microbial production of propionic acid (PA). To enhance the acid resistance of strains, the tolerance mechanisms of cells must first be understood. In this study, comparative genomic and transcriptomic analyses were conducted on wild-type and acid-tolerant Propionibacterium acidipropionici to reveal the microbial response of cells to acid stress during fermentation. Combined with the results of previous proteomic and metabolomic studies, several potential acid-resistance mechanisms of P. acidipropionici were analyzed. Energy metabolism and transporter activity of cells were regulated to maintain pH homeostasis by balancing transmembrane transport of protons and ions; redundant protons were eliminated by enhancing the metabolism of certain amino acids for a relatively stable intracellular microenvironment; and protective mechanism of macromolecules were also induced to repair damage to proteins and DNA by acids. Transcriptomic data indicated that the synthesis of acetate and lactate were undesirable in the acid-resistant mutant, the expression of which was 2.21-fold downregulated. In addition, metabolomic data suggested that the accumulation of lactic acid and acetic acid reduced the carbon flow to PA and led to a decrease in pH. On this basis, we propose a metabolic engineering strategy to regulate the synthesis of lactic acid and acetic acid that will reduce by-products significantly and increase the PA yield by 12.2% to 10.31 ± 0.84 g/g DCW. Results of this study provide valuable guidance to understand the response of bacteria to acid stress and to construct microbial cell factories to produce organic acids by combining systems biology technologies with synthetic biology tools. This article is protected by copyright. All rights reserved
-
Comparative metabolomics analysis of the key metabolic nodes in propionic acid synthesis in Propionibacterium acidipropionici
Metabolomics, 2014Co-Authors: Ningzi Guan, Long Liu, Hyun-dong Shin, Zhongping Shi, Jian ChenAbstract:Propionic acid (PA) is an important platform chemical used in the agriculture, food, and pharmaceutical industries. The biosynthesis of PA by propionibacteria has become an attractive alternative to traditional petrochemical processes owing to the environmentally friendly features of biorefinery. In a previous study, we significantly increased PA production in Propionibacterium acidipropionici by improving acid tolerance via genome shuffling. In this study, we undertook metabolomics analysis of parental P. acidipropionici and its genome-shuffled mutant to find the key metabolic nodes influencing PA production. In total, 142 intracellular metabolites were identified, of which those produced in amounts of greater than twofold difference between the two strains were further investigated with principal components analysis. The regulatory functions of key metabolites involved in the PA biosynthetic pathway were also forecast and analyzed according to their potential impact on metabolism. The results indicated that the amounts of metabolic intermediates of glycolysis, the Wood–Werkman cycle, and amino acid metabolism differed markedly between parental P. acidipropionici and its mutants. Based on the results of comparative metabolomics analysis, exogenous addition of key metabolites (precursors and amino acids) was performed to improve PA production. Under optimized conditions, 105 mM lactate, 20 mM fumarate, and 30 mM succinate were added to the culture of P. acidipropionici CGMCC 1.2230 in a 3-L anaerobic fermenter, and the PA titer increased from 23.1 ± 12 to 35.8 ± 1.0 g/L. This study revealed the key metabolic nodes of PA synthesis in P. acidipropionici through comparative metabolomics analysis, which may be helpful for the metabolic engineering of P. acidipropionici for improved PA production.
-
Understanding of how Propionibacterium acidipropionici respond to propionic acid stress at the level of proteomics.
Scientific reports, 2014Co-Authors: Ningzi Guan, Long Liu, Hyun-dong Shin, Rachel R. Chen, Jian ChenAbstract:Propionic acid (PA) is an important platform chemical in the food, agriculture, and pharmaceutical industries and is mainly biosynthesized by propionibacteria. Acid tolerance in PA-producing strains is crucial. In previous work, we investigated the acid tolerance mechanism of Propionibacterium acidipropionici at microenvironmental levels by analyzing physiological changes in the parental strain and three PA-tolerant mutants obtained by genome shuffling. However, the molecular mechanism of PA tolerance in P. acidipropionici remained unclear. Here, we performed a comparative proteomics study of P. acidipropionici CGMCC 1.2230 and the acid-tolerant mutant P. acidipropionici WSH1105; MALDI-TOF/MS identified 24 proteins that significantly differed between the parental and shuffled strains. The differentially expressed proteins were mainly categorized as key components of crucial biological processes and the acid stress response. Quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) was used to confirm differential expression of nine key proteins. Overexpression of the secretory protein glyceraldehyde-3-phosphate dehydrogenase and ATP synthase subunit α in Escherichia coli BL21 improved PA and acetic acid tolerance; overexpression of NADH dehydrogenase and methylmalonyl-CoA epimerase improved PA tolerance. These results provide new insights into the acid tolerance of P. acidipropionici and will facilitate the development of PA production through fermentation by propionibacteria.
-
Systems-level understanding of how Propionibacterium acidipropionici respond to propionic acid stress at the microenvironment levels: Mechanism and application
Journal of biotechnology, 2013Co-Authors: Ningzi Guan, Long Liu, Hyun-dong Shin, Rachel R. Chen, Juan Zhang, Zhongping Shi, Jian ChenAbstract:Abstract In previous work, three evolved Propionibacterium acidipropionici mutants with higher tolerant capacity of propionic acid (PA) were obtained by genome shuffling. Here, we attempted to unravel the acid-tolerant mechanism of P. acidipropionici by comparing the physiological changes between P. acidipropionici and three mutants. The parameters used for comparison included intracellular pH (pH i ), NAD + /NADH ratio, H + -ATPase activity, and the intracellular amino acids concentrations. It was indicated that the acid tolerance of P. acidipropionici was systematically regulated. Specifically, low pH i promoted the P. acidipropionici to biosynthesize more H + -ATPase to pump the protons out of the cells, and as a result, the NAD + /NADH ratio increased due to the decreased protons concentration. The increased arginine, aspartic acid, and glutamic acid concentrations helped to resist the acidic environment by consuming more H + and generating more ATP and NH 3 . Based on what was analyzed above, 20 mM arginine and aspartic acid were added during the shaker culture of P. acidipropionici , and the maximal PA titer reached 14.38 g/L, which was increased by 39.9% compared with the control.
-
optimization and scale up of propionic acid production by propionic acid tolerant Propionibacterium acidipropionici with glycerol as the carbon source
Bioresource Technology, 2010Co-Authors: Yunfeng Zhu, Ming Tan, Long Liu, Lili Jiang, Jun Sun, Pengsoon Lee, Jian ChenAbstract:Abstract Propionic acid production by Propionibacterium acidipropionici with glycerol as sole carbon source was studied in 7-L batch and 10 m 3 bioreactor cultures. In batch cultures, propionic acid production increased and specific cell growth rate decreased with increasing glycerol concentrations. Maximum propionic acid production and productivity reached 44.62 ± 1.12 g/L and 0.20 ± 0.0075 g L −1 h −1 at 220 h, respectively, when glycerol was fed at a constant rate of 0.01 L/h from 72 to 120 h with an initial glycerol concentration of 30 g/L. In the 10 m 3 bioreactor, maximum propionic acid production reached 47.28 ± 0.12 g/L at 240 h. This glycerol feeding approach may be useful for propionic acid production on an industrial scale.
Catherine Deborde - One of the best experts on this subject based on the ideXlab platform.
-
in vivo13c nmr study of the bidirectional reactions of the wood werkman cycle and around the pyruvate node in Propionibacterium freudenreichii subsp shermanii and Propionibacterium acidipropionici
Metabolic Engineering, 1999Co-Authors: Catherine Deborde, Dominique Rolin, Patrick BoyavalAbstract:This study used in vitro 13C NMR spectroscopy to directly examine bidirectional reactions of the Wood-Werkman cycle involved in central carbon metabolic pathways of dairy propionibacteria during pyruvate catabolism. The flow of [2-13C]pyruvate label was monitored on living cell suspensions of Propionibacterium freudenreichii subsp. shermanii and Propionibacterium acidipropionici under acidic conditions. P. shermanii and P. acidipropionici cells consumed pyruvate at apparent initial rates of 161 and 39 micromol min(-1) g(-1) (cell dry weight), respectively. The bidirectionality of reactions in the first part of the Wood-Werkman cycle was evident from the formation of intermediates such as [3-13C]pyruvate and [3-13C]malate and of products like [2-13C]acetate from [2-13C]pyruvate. For the first time alanine labeled on C2 and C3 and aspartate labeled on C2 and C3 were observed during [2-13C]pyruvate metabolism by propionibacteria. The kinetics of aspartate isotopic enrichment was evidence for its production from oxaloacetate via aspartate aminotransferase. Activities of a partial tricarboxylic acid pathway, acetate synthesis, succinate synthesis, gluconeogenesis, aspartate synthesis, and alanine synthesis pathways were evident from the experimental results.
-
In Vivo13C NMR Study of the Bidirectional Reactions of the Wood–Werkman Cycle and around the Pyruvate Node in Propionibacterium freudenreichii subsp. shermanii and Propionibacterium acidipropionici
Metabolic engineering, 1999Co-Authors: Catherine Deborde, Dominique Rolin, Patrick BoyavalAbstract:This study used in vitro 13C NMR spectroscopy to directly examine bidirectional reactions of the Wood-Werkman cycle involved in central carbon metabolic pathways of dairy propionibacteria during pyruvate catabolism. The flow of [2-13C]pyruvate label was monitored on living cell suspensions of Propionibacterium freudenreichii subsp. shermanii and Propionibacterium acidipropionici under acidic conditions. P. shermanii and P. acidipropionici cells consumed pyruvate at apparent initial rates of 161 and 39 micromol min(-1) g(-1) (cell dry weight), respectively. The bidirectionality of reactions in the first part of the Wood-Werkman cycle was evident from the formation of intermediates such as [3-13C]pyruvate and [3-13C]malate and of products like [2-13C]acetate from [2-13C]pyruvate. For the first time alanine labeled on C2 and C3 and aspartate labeled on C2 and C3 were observed during [2-13C]pyruvate metabolism by propionibacteria. The kinetics of aspartate isotopic enrichment was evidence for its production from oxaloacetate via aspartate aminotransferase. Activities of a partial tricarboxylic acid pathway, acetate synthesis, succinate synthesis, gluconeogenesis, aspartate synthesis, and alanine synthesis pathways were evident from the experimental results.
