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Li HK, Zhi X, Vieira A, Whitwell HJ, Schricker A, Jauneikaite E, Li H, Yosef A, Andrew I, Game L, Turner CE, Lamagni T, Coelho J, Sriskandan S. Characterization of emergent toxigenic M1 UK Streptococcus pyogenes and associated sublineages. Microb Genom 2023; 9:mgen000994. [PMID: 37093716 PMCID: PMC10210942 DOI: 10.1099/mgen.0.000994] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 02/23/2023] [Indexed: 04/25/2023] Open
Abstract
Streptococcus pyogenes genotype emm1 is a successful, globally distributed epidemic clone that is regarded as inherently virulent. An emm1 sublineage, M1UK, that produces increased levels of SpeA toxin was associated with increased scarlet fever and invasive infections in England in 2015/2016. Defined by 27 SNPs in the core genome, M1UK is now dominant in England. To more fully characterize M1UK, we undertook comparative transcriptomic and proteomic analyses of M1UK and contemporary non-M1UK emm1 strains (M1global). Just seven genes were differentially expressed by M1UK compared with contemporary M1global strains. In addition to speA, five genes in the operon that includes glycerol dehydrogenase were upregulated in M1UK (gldA, mipB/talC, pflD, and phosphotransferase system IIC and IIB components), while aquaporin (glpF2) was downregulated. M1UK strains have a stop codon in gldA. Deletion of gldA in M1global abrogated glycerol dehydrogenase activity, and recapitulated upregulation of gene expression within the operon that includes gldA, consistent with a feedback effect. Phylogenetic analysis identified two intermediate emm1 sublineages in England comprising 13/27 (M113SNPs) and 23/27 SNPs (M123SNPs), respectively, that had failed to expand in the population. Proteomic analysis of invasive strains from the four phylogenetic emm1 groups highlighted sublineage-specific changes in carbohydrate metabolism, protein synthesis and protein processing; upregulation of SpeA was not observed in chemically defined medium. In rich broth, however, expression of SpeA was upregulated ~10-fold in both M123SNPs and M1UK sublineages, compared with M113SNPs and M1global. We conclude that stepwise accumulation of SNPs led to the emergence of M1UK. While increased expression of SpeA is a key indicator of M1UK and undoubtedly important, M1UK strains have outcompeted M123SNPs and other emm types that produce similar or more superantigen toxin. We speculate that an accumulation of adaptive SNPs has contributed to a wider fitness advantage in M1UK on an inherently successful emm1 streptococcal background.
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Affiliation(s)
- Ho Kwong Li
- Department of Infectious Disease, Imperial College London, London, UK
- MRC Centre for Molecular Bacteriology & Infection (CMBI), Imperial College London, London, UK
| | - Xiangyun Zhi
- Department of Infectious Disease, Imperial College London, London, UK
- MRC Centre for Molecular Bacteriology & Infection (CMBI), Imperial College London, London, UK
| | - Ana Vieira
- Department of Infectious Disease, Imperial College London, London, UK
- MRC Centre for Molecular Bacteriology & Infection (CMBI), Imperial College London, London, UK
| | - Harry J. Whitwell
- National Phenome Centre and Imperial Clinical Phenotyping Centre, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, UK
- Department of Metabolism, Digestion and Reproduction, Imperial College London, London, UK
| | - Amelia Schricker
- UK Dementia Research Institute, Department of Brain Sciences, Imperial College London, London, UK
| | - Elita Jauneikaite
- NIHR Health Protection Unit in Healthcare-associated Infection and Antimicrobial Resistance, Imperial College London, London, UK
- School of Public Health, Imperial College London, London, UK
| | - Hanqi Li
- Department of Infectious Disease, Imperial College London, London, UK
| | - Ahmed Yosef
- Department of Infectious Disease, Imperial College London, London, UK
| | - Ivan Andrew
- Genomics Facility, UKRI-MRC London Institute for Medical Sciences (LMS), Imperial College London, London, UK
| | - Laurence Game
- Genomics Facility, UKRI-MRC London Institute for Medical Sciences (LMS), Imperial College London, London, UK
| | - Claire E. Turner
- The Florey Institute, School of Biosciences, University of Sheffield, South Yorkshire, UK
| | - Theresa Lamagni
- NIHR Health Protection Unit in Healthcare-associated Infection and Antimicrobial Resistance, Imperial College London, London, UK
- Centre for Infections, UK Health Security Agency, London, UK
| | - Juliana Coelho
- NIHR Health Protection Unit in Healthcare-associated Infection and Antimicrobial Resistance, Imperial College London, London, UK
- Centre for Infections, UK Health Security Agency, London, UK
| | - Shiranee Sriskandan
- Department of Infectious Disease, Imperial College London, London, UK
- MRC Centre for Molecular Bacteriology & Infection (CMBI), Imperial College London, London, UK
- NIHR Health Protection Unit in Healthcare-associated Infection and Antimicrobial Resistance, Imperial College London, London, UK
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2
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Okoye CO, Dong K, Wang Y, Gao L, Li X, Wu Y, Jiang J. Comparative genomics reveals the organic acid biosynthesis metabolic pathways among five lactic acid bacterial species isolated from fermented vegetables. N Biotechnol 2022; 70:73-83. [PMID: 35525431 DOI: 10.1016/j.nbt.2022.05.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Revised: 02/28/2022] [Accepted: 05/02/2022] [Indexed: 10/18/2022]
Abstract
Lactic acid bacteria (LAB) comprise a widespread bacterial group, inhabiting the niches of fermented vegetables and capable of producing beneficial organic acids. In the present study, several bioinformatics approaches were used to perform whole-genome sequencing and comparative genomics of five LAB species, Lactobacillus plantarum PC1-1, Pediococcus pentosaceus PC2-1(F2), Weissella hellenica PC1A, Lactobacillus buchneri PC-C1, and Enterococcus sp. YC2-6, to enhance understanding of their different genetic functionalities and organic acid biosynthesis. The results revealed major carbohydrate-active enzymes, putative operons and unique mobile genetic elements, including plasmids, resistance genes, insertion sequences and composite transposons involved in organic acid biosynthesis. The metabolic pathways of organic acid biosynthesis emphasize the key genes encoding specific enzymes required for organic acid metabolism. The five genomes were found to contain various regions of secondary metabolite biosynthetic gene clusters, including the type III polyketide synthases (T3PKS) enriched with unique genes encoding a hydroxymethylglutaryl-CoA synthase, capable of exhibiting specific antimicrobial activity with biopreservative potential, and a cyclic AMP receptor protein (CPR) transcription factor acting as a glucose sensor in organic acid biosynthesis. This could enable the organisms to prevail in the fermentation process, suggesting potential industrial applications.
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Affiliation(s)
- Charles Obinwanne Okoye
- Biofuels Institute, Jiangsu University, Zhenjiang 212013, China; School of Environment & Safety Engineering, Jiangsu University, Zhenjiang 212013, China; Department of Zoology & Environmental Biology, University of Nigeria, Nsukka 410001, Nigeria
| | - Ke Dong
- Biofuels Institute, Jiangsu University, Zhenjiang 212013, China; School of Environment & Safety Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Yongli Wang
- Biofuels Institute, Jiangsu University, Zhenjiang 212013, China; School of Environment & Safety Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Lu Gao
- Biofuels Institute, Jiangsu University, Zhenjiang 212013, China; School of Environment & Safety Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Xia Li
- Biofuels Institute, Jiangsu University, Zhenjiang 212013, China; School of Environment & Safety Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Yanfang Wu
- Biofuels Institute, Jiangsu University, Zhenjiang 212013, China; School of Environment & Safety Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Jianxiong Jiang
- Biofuels Institute, Jiangsu University, Zhenjiang 212013, China; School of Environment & Safety Engineering, Jiangsu University, Zhenjiang 212013, China.
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Ceron-Chafla P, Chang YT, Rabaey K, van Lier JB, Lindeboom REF. Directional Selection of Microbial Community Reduces Propionate Accumulation in Glycerol and Glucose Anaerobic Bioconversion Under Elevated pCO 2. Front Microbiol 2021; 12:675763. [PMID: 34220760 PMCID: PMC8242345 DOI: 10.3389/fmicb.2021.675763] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 05/24/2021] [Indexed: 11/30/2022] Open
Abstract
Volatile fatty acid accumulation is a sign of digester perturbation. Previous work showed the thermodynamic limitations of hydrogen and CO2 in syntrophic propionate oxidation under elevated partial pressure of CO2 (pCO2). Here we study the effect of directional selection under increasing substrate load as a strategy to restructure the microbial community and induce cross-protection mechanisms to improve glucose and glycerol conversion performance under elevated pCO2. After an adaptive laboratory evolution (ALE) process, viable cell density increased and predominant microbial groups were modified: an increase in Methanosaeta and syntrophic propionate oxidizing bacteria (SPOB) associated with the Smithella genus was found with glycerol as the substrate. A modest increase in SPOB along with a shift in the predominance of Methanobacterium toward Methanosaeta was observed with glucose as the substrate. The evolved inoculum showed affected diversity within archaeal spp. under 5 bar initial pCO2; however, higher CH4 yield resulted from enhanced propionate conversion linked to the community shifts and biomass adaptation during the ALE process. Moreover, the evolved inoculum attained increased cell viability with glucose and a marginal decrease with glycerol as the substrate. Results showed differences in terms of carbon flux distribution using the evolved inoculum under elevated pCO2: glucose conversion resulted in a higher cell density and viability, whereas glycerol conversion led to higher propionate production whose enabled conversion reflected in increased CH4 yield. Our results highlight that limited propionate conversion at elevated pCO2 resulted from decreased cell viability and low abundance of syntrophic partners. This limitation can be mitigated by promoting alternative and more resilient SPOB and building up biomass adaptation to environmental conditions via directional selection of microbial community.
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Affiliation(s)
- Pamela Ceron-Chafla
- Sanitary Engineering Section, Department of Water Management, Delft University of Technology, Delft, Netherlands
| | - Yu-Ting Chang
- Sanitary Engineering Section, Department of Water Management, Delft University of Technology, Delft, Netherlands
| | - Korneel Rabaey
- Center for Microbial Ecology and Technology, Ghent University, Ghent, Belgium.,Center for Advanced Process Technology for Urban Resource Recovery, Ghent, Belgium
| | - Jules B van Lier
- Sanitary Engineering Section, Department of Water Management, Delft University of Technology, Delft, Netherlands
| | - Ralph E F Lindeboom
- Sanitary Engineering Section, Department of Water Management, Delft University of Technology, Delft, Netherlands
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Evidence for auxiliary anaerobic metabolism in obligately aerobic Zetaproteobacteria. ISME JOURNAL 2020; 14:1057-1062. [PMID: 31969684 DOI: 10.1038/s41396-020-0586-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 01/06/2020] [Accepted: 01/13/2020] [Indexed: 11/08/2022]
Abstract
Zetaproteobacteria are obligate chemolithoautotrophs that oxidize Fe(II) as an electron and energy source, and play significant roles in nutrient cycling and primary production in the marine biosphere. Zetaproteobacteria thrive under microoxic conditions near oxic-anoxic interfaces, where they catalyze Fe(II) oxidation faster than the abiotic reaction with oxygen. Neutrophilic Fe(II) oxidizing bacteria produce copious amounts of insoluble iron oxyhydroxides as a by-product of their metabolism. Oxygen consumption by aerobic respiration and formation of iron oxyhydroxides at oxic-anoxic interfaces can result in periods of oxygen limitation for bacterial cells. Under laboratory conditions, all Zetaproteobacteria isolates have been shown to strictly require oxygen as an electron acceptor for growth, and anaerobic metabolism has not been observed. However, genomic analyses indicate a range of potential anaerobic pathways present in Zetaproteobacteria. Heterologous expression of proteins from Mariprofundus ferrooxydans PV-1, including pyruvate formate lyase and acetate kinase, further support a capacity for anaerobic metabolism. Here we define auxiliary anaerobic metabolism as a mechanism to provide maintenance energy to cells and suggest that it provides a survival advantage to Zetaproteobacteria in environments with fluctuating oxygen availability.
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Glycerol metabolism and its regulation in lactic acid bacteria. Appl Microbiol Biotechnol 2019; 103:5079-5093. [DOI: 10.1007/s00253-019-09830-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 04/02/2019] [Accepted: 04/04/2019] [Indexed: 01/09/2023]
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6
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Doi Y. Lactic acid fermentation is the main aerobic metabolic pathway in Enterococcus faecalis metabolizing a high concentration of glycerol. Appl Microbiol Biotechnol 2018; 102:10183-10192. [DOI: 10.1007/s00253-018-9351-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 08/18/2018] [Accepted: 08/27/2018] [Indexed: 10/28/2022]
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Jang HJ, Lee JD, Jeon HS, Kim AR, Kim S, Lee HS, Kim KB. Metabolic Profiling of Eccentric Exercise-Induced Muscle Damage in Human Urine. Toxicol Res 2018; 34:199-210. [PMID: 30057694 PMCID: PMC6057290 DOI: 10.5487/tr.2018.34.3.199] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 04/29/2018] [Accepted: 05/14/2018] [Indexed: 12/12/2022] Open
Abstract
Skeletal muscle can be ultrastructurally damaged by eccentric exercise, and the damage causes metabolic disruption in muscle. This study aimed to determine changes in the metabolomic patterns in urine and metabolomic markers in muscle damage after eccentric exercise. Five men and 6 women aged 19~23 years performed 30 min of the bench step exercise at 70 steps per min at a determined step height of 110% of the lower leg length, and stepping frequency at 15 cycles per min. 1H NMR spectral analysis was performed in urine collected from all participants before and after eccentric exercise-induced muscle damage conventionally determined using a visual analogue scale (VAS) and maximal voluntary contraction (MVC). Urinary metabolic profiles were built by multivariate analysis of principal component analysis (PCA) and orthogonal partial least square-discriminant analysis (OPLS-DA) using SIMCA-P. From the OPLS-DA, men and women were separated 2 hr after the eccentric exercise and the separated patterns were maintained or clarified until 96 hr after the eccentric exercise. Subsequently, urinary metabolic profiles showed distinct trajectory patterns between men and women. Finally, we found increased urinary metabolites (men: alanine, asparagine, citrate, creatine phosphate, ethanol, formate, glucose, glycine, histidine, and lactate; women: adenine) after the eccentric exercise. These results could contribute to understanding metabolic responses following eccentric exercise-induced muscle damage in humans.
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Affiliation(s)
- Hyun-Jun Jang
- College of Pharmacy, Dankook University, Cheonan, Korea.,Department of Animal Biotechnology, Chonbuk National University, Jeonju, Korea
| | - Jung Dae Lee
- Division of Toxicology, College of Pharmacy, Sungkyunkwan University, Suwon, Korea
| | - Hyun-Sik Jeon
- Department of Kinesiologic Medical Science, Graduate School, Dankook University, Cheonan, Korea
| | - Ah-Ram Kim
- Department of Kinesiologic Medical Science, Graduate School, Dankook University, Cheonan, Korea.,Department of Physical Therapy, Namseoul University, Cheonan, Korea
| | - Suhkmann Kim
- Department of Chemistry and Chemistry Institute of Functional Materials, Pusan National University, Busan, Korea
| | - Ho-Seong Lee
- Department of Kinesiologic Medical Science, Graduate School, Dankook University, Cheonan, Korea
| | - Kyu-Bong Kim
- College of Pharmacy, Dankook University, Cheonan, Korea
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Alves de Oliveira R, Komesu A, Vaz Rossell CE, Maciel Filho R. Challenges and opportunities in lactic acid bioprocess design—From economic to production aspects. Biochem Eng J 2018. [DOI: 10.1016/j.bej.2018.03.003] [Citation(s) in RCA: 161] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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9
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Marzan LW, Barua R, Akter Y, Arifuzzaman M, Islam MR, Shimizu K. A single metabolite production by Escherichia coli BW25113 and its pflA.cra mutant cultivated under microaerobic conditions using glycerol or glucose as a carbon source. J Genet Eng Biotechnol 2017; 15:161-168. [PMID: 30647652 PMCID: PMC6296642 DOI: 10.1016/j.jgeb.2017.01.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 12/08/2016] [Accepted: 01/04/2017] [Indexed: 10/31/2022]
Abstract
Abundant, low prices and a highly reduced nature make glycerol to be an ideal feedstock for the production of reduced biochemicals and biofuels. Escherichia coli has been paid much attention as the platform of microbial cell factories due to its high growth rate (giving higher metabolite production rate) and the capability of utilizing a wide range of carbon sources. However, one of the drawbacks of using E. coli as a platform is its mixed metabolite formation under anaerobic conditions. In the present study, it was shown that ethanol could be exclusively produced from glycerol by the wild type E. coli, while d-lactic acid could be exclusively produced from glucose by pflA.cra mutant, where the glucose uptake rate could be increased by this mutant as compared to the wild type strain. It was also shown that the growth rate is significantly reduced in pflA.cra mutant for the case of using glycerol as a carbon source due to redox imbalance. The metabolic regulation mechanisms behind the fermentation characteristic were clarified to some extent.
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Key Words
- ATP, adenosine triphosphate
- AcCoA, acetyl-coenzyme A
- Biofuel
- DCW, dry cell weight
- DHA, dihydroxyacetone
- Escherichia coli
- Ethanol production
- GAPDH, -glyceraldehyde-3-phosphate dehydrogenase
- GDH, glutamate dehydrogenase
- Glucose
- Glycerol
- KH2PO4, potassium dihydrogen phosphate
- KOH, potassium hydroxide
- LB, Luria Bertani
- LDH, lactate dehydrogenase
- M9, type of minimal media
- MgSO4, magnesium sulfate
- NAD+, nicotinamide adenine dinucleotide
- NADH, reduced form of nicotinamide adenine dinucleotide
- Na2HPO4, sodium phosphate
- NaCl, sodium chloride
- NaOH, sodium hydroxide
- OAA, oxaloacetic Acid
- OD, optical density
- PEP, phosphoenol pyruvate
- PEP, phosphoenolpyruvic acid
- PTS, phospho-transferase system
- PYR, pyruvate
- Pfl, pyruvate formatelyase
- TCA, tri-carboxylic acid
- UV, ultra violet
- cAMP, cyclic adenosine monophosphate
- cAMP-Crp, cAMP receptor protein
- pflA.cra mutant
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Affiliation(s)
- Lolo Wal Marzan
- Department of Genetic Engineering and Biotechnology, Faculty of Biological Sciences, University of Chittagong, Chittagong - 4331, Bangladesh
| | - Rinty Barua
- Department of Genetic Engineering and Biotechnology, Faculty of Biological Sciences, University of Chittagong, Chittagong - 4331, Bangladesh
| | - Yasmin Akter
- Department of Genetic Engineering and Biotechnology, Faculty of Biological Sciences, University of Chittagong, Chittagong - 4331, Bangladesh
| | - Md. Arifuzzaman
- Department of Biochemistry and Biotechnology, University of Science and Technology Chittagong, Bangladesh
| | - Md. Rafiqul Islam
- Department of Genetic Engineering and Biotechnology, Faculty of Biological Sciences, University of Chittagong, Chittagong - 4331, Bangladesh
| | - Kazuyuki Shimizu
- Department of Bioscience & Bioinformatics, Kyushu Institute of Technology, Iizuka, Fukuoka 820-8502, Japan
- Institute of Advanced Bioscience, Keio University, Tsuruoka, Yamagata 997-0017, Japan
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Complete Genome Sequence of Enterococcus faecalis Strain W11 Isolated from an Algal Food Product. GENOME ANNOUNCEMENTS 2016; 4:4/5/e01037-16. [PMID: 27688337 PMCID: PMC5043555 DOI: 10.1128/genomea.01037-16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
ABSTRACT
Here, we report the complete genome sequence of
Enterococcus faecalis
strain W11 isolated from an algal food product in Japan. This study should facilitate the identification of a novel mechanism of glycerol metabolic control in lactic acid bacteria.
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Murakami N, Oba M, Iwamoto M, Tashiro Y, Noguchi T, Bonkohara K, Abdel-Rahman MA, Zendo T, Shimoda M, Sakai K, Sonomoto K. l-Lactic acid production from glycerol coupled with acetic acid metabolism by Enterococcus faecalis without carbon loss. J Biosci Bioeng 2016; 121:89-95. [DOI: 10.1016/j.jbiosc.2015.05.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 04/27/2015] [Accepted: 05/17/2015] [Indexed: 11/27/2022]
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L-lactate production from biodiesel-derived crude glycerol by metabolically engineered Enterococcus faecalis: cytotoxic evaluation of biodiesel waste and development of a glycerol-inducible gene expression system. Appl Environ Microbiol 2015; 81:2082-9. [PMID: 25576618 DOI: 10.1128/aem.03418-14] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Biodiesel waste is a by-product of the biodiesel production process that contains a large amount of crude glycerol. To reuse the crude glycerol, a novel bioconversion process using Enterococcus faecalis was developed through physiological studies. The E. faecalis strain W11 could use biodiesel waste as a carbon source, although cell growth was significantly inhibited by the oil component in the biodiesel waste, which decreased the cellular NADH/NAD(+) ratio and then induced oxidative stress to cells. When W11 was cultured with glycerol, the maximum culture density (optical density at 600 nm [OD600]) under anaerobic conditions was decreased 8-fold by the oil component compared with that under aerobic conditions. Furthermore, W11 cultured with dihydroxyacetone (DHA) could show slight or no growth in the presence of the oil component with or without oxygen. These results indicated that the DHA kinase reaction in the glycerol metabolic pathway was sensitive to the oil component as an oxidant. The lactate dehydrogenase (Ldh) activity of W11 during anaerobic glycerol metabolism was 4.1-fold lower than that during aerobic glycerol metabolism, which was one of the causes of low l-lactate productivity. The E. faecalis pflB gene disruptant (Δpfl mutant) expressing the ldhL1LP gene produced 300 mM l-lactate from glycerol/crude glycerol with a yield of >99% within 48 h and reached a maximum productivity of 18 mM h(-1) (1.6 g liter(-1) h(-1)). Thus, our study demonstrates that metabolically engineered E. faecalis can convert crude glycerol to l-lactate at high conversion efficiency and provides critical information on the recycling process for biodiesel waste.
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