scholarly journals Optimization of a Two-Species Microbial Consortium for Improved Mcl-PHA Production From Glucose–Xylose Mixtures

2022 ◽  
Vol 9 ◽  
Author(s):  
Yinzhuang Zhu ◽  
Mingmei Ai ◽  
Xiaoqiang Jia
Keyword(s):  
Acetic Acid ◽  
Microbial Consortium ◽  
Physical And Mechanical Properties ◽  
Substrate Utilization ◽  
Microbial Consortia ◽  
Mixed Substrates ◽  
Metabolic Capacity ◽  
E Coli ◽  
Pha Production ◽  
Good Substitute

Polyhydroxyalkanoates (PHAs) have attracted much attention as a good substitute for petroleum-based plastics, especially mcl-PHA due to their superior physical and mechanical properties with broader applications. Artificial microbial consortia can solve the problems of low metabolic capacity of single engineered strains and low conversion efficiency of natural consortia while expanding the scope of substrate utilization. Therefore, the use of artificial microbial consortia is considered a promising method for the production of mcl-PHA. In this work, we designed and constructed a microbial consortium composed of engineered Escherichia coli MG1655 and Pseudomonas putida KT2440 based on the “nutrition supply–detoxification” concept, which improved mcl-PHA production from glucose-xylose mixtures. An engineered E. coli that preferentially uses xylose was engineered with an enhanced ability to secrete acetic acid and free fatty acids (FFAs), producing 6.44 g/L acetic acid and 2.51 g/L FFAs with 20 g/L xylose as substrate. The mcl-PHA producing strain of P. putida in the microbial consortium has been engineered to enhance its ability to convert acetic acid and FFAs into mcl-PHA, producing 0.75 g/L mcl-PHA with mixed substrates consisting of glucose, acetic acid, and octanoate, while also reducing the growth inhibition of E. coli by acetic acid. The further developed artificial microbial consortium finally produced 1.32 g/L of mcl-PHA from 20 g/L of a glucose–xylose mixture (1:1) after substrate competition control and process optimization. The substrate utilization and product synthesis functions were successfully divided into the two strains in the constructed artificial microbial consortium, and a mutually beneficial symbiosis of “nutrition supply–detoxification” with a relatively high mcl-PHA titer was achieved, enabling the efficient accumulation of mcl-PHA. The consortium developed in this study is a potential platform for mcl-PHA production from lignocellulosic biomass.

SATP (YaaH), a succinate–acetate transporter protein in Escherichia coli

2013 ◽  
Vol 454 (3) ◽  
pp. 585-595 ◽  
Author(s):  
Joana Sá-Pessoa ◽  
Sandra Paiva ◽  
David Ribas ◽  
Inês Jesus Silva ◽  
Sandra Cristina Viegas ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Succinic Acid ◽  
Critical Role ◽  
Amino Acid Residues ◽  
E Coli ◽  
Transporter Protein ◽  
Affinity Constants ◽  
In Trans

In the present paper we describe a new carboxylic acid transporter in Escherichia coli encoded by the gene yaaH. In contrast to what had been described for other YaaH family members, the E. coli transporter is highly specific for acetic acid (a monocarboxylate) and for succinic acid (a dicarboxylate), with affinity constants at pH 6.0 of 1.24±0.13 mM for acetic acid and 1.18±0.10 mM for succinic acid. In glucose-grown cells the ΔyaaH mutant is compromised for the uptake of both labelled acetic and succinic acids. YaaH, together with ActP, described previously as an acetate transporter, affect the use of acetic acid as sole carbon and energy source. Both genes have to be deleted simultaneously to abolish acetate transport. The uptake of acetate and succinate was restored when yaaH was expressed in trans in ΔyaaH ΔactP cells. We also demonstrate the critical role of YaaH amino acid residues Leu131 and Ala164 on the enhanced ability to transport lactate. Owing to its functional role in acetate and succinate uptake we propose its assignment as SatP: the Succinate–Acetate Transporter Protein.

scholarly journals Escherichia coli O157:H7 Strain EDL933 Harbors Multiple Functional Prophage-Associated Genes Necessary for the Utilization of 5-N-Acetyl-9-O-Acetyl Neuraminic Acid as a Growth Substrate

2016 ◽  
Vol 82 (19) ◽  
pp. 5940-5950 ◽  
Author(s):  
Nadja Saile ◽  
Anja Voigt ◽  
Sarah Kessler ◽  
Timo Stressler ◽  
Jochen Klumpp ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Large Intestine ◽  
Substrate Utilization ◽  
Neuraminic Acid ◽  
Open Reading Frames ◽  
Dose Effect ◽  
Content Type ◽  
E Coli ◽  
P Proteins ◽  
Homologous Orfs

ABSTRACTEnterohemorrhagicEscherichia coli(EHEC) O157:H7 strain EDL933 harbors multiple prophage-associated open reading frames (ORFs) in its genome which are highly homologous to the chromosomalnanSgene. The latter is part of thenanCMSoperon, which is present in mostE. colistrains and encodes an esterase which is responsible for the monodeacetylation of 5-N-acetyl-9-O-acetyl neuraminic acid (Neu5,9Ac2). Whereas one prophage-borne ORF (z1466) has been characterized in previous studies, the functions of the othernanS-homologous ORFs are unknown. In the current study, thenanS-homologous ORFs of EDL933 were initially studiedin silico. Due to their homology to the chromosomalnanSgene and their location in prophage genomes, we designated themnanS-p and numbered the differentnanS-p alleles consecutively from 1 to 10. The two allelesnanS-p2 andnanS-p4 were selected for production of recombinant proteins, their enzymatic activities were investigated, and differences in their temperature optima were found. Furthermore, a function of these enzymes in substrate utilization could be demonstrated using anE. coliC600ΔnanSmutant in a growth medium with Neu5,9Ac2as the carbon source and supplementation with the different recombinant NanS-p proteins. Moreover, generation of sequential deletions of allnanS-p alleles in strain EDL933 and subsequent growth experiments demonstrated a gene dose effect on the utilization of Neu5,9Ac2. Since Neu5,9Ac2is an important component of human and animal gut mucus and since the nutrient availability in the large intestine is limited, we hypothesize that the presence of multiple Neu5,9Ac2esterases provides them a nutrient supply under certain conditions in the large intestine, even if particular prophages are lost.IMPORTANCEIn this study, a group of homologous prophage-bornenanS-p alleles and two of the corresponding enzymes of enterohemorrhagicE. coli(EHEC) O157:H7 strain EDL933 that may be important to provide alternative genes for substrate utilization were characterized.

Metagenomics Study To Compare The Taxonomy And Metabolism of a Lignocellulolytic Microbial Consortium Cultured in Different Carbon Conditions

2021 ◽  
Author(s):  
Qinggeer BORJIGIN ◽  
Bizhou ZHANG ◽  
Xiaofang Yu ◽  
Julin Gao ◽  
Xin ZHANG ◽  
...  
Keyword(s):  
Microbial Consortium ◽  
Agricultural Waste ◽  
Taxonomic Diversity ◽  
Taxonomic Composition ◽  
Microbial Consortia ◽  
Rich Diversity ◽  
Cazy Database ◽  
Taxonomic Affiliation ◽  
In Situ Biodegradation

Abstract A lignocellulolytic microbial consortium holds promise for the in situ biodegradation of crop straw and the comprehensive and effective utilization of agricultural waste. In this study, we applied metagenomics technology to comprehensively explore the metabolic functional potential and taxonomic diversity of the microbial consortia CS (cultured on corn stover) and FP (cultured on filter paper).Analyses of the metagenomics taxonomic affiliation data showed considerable differences in the taxonomic composition and functional profile of the microbial consortia CS and FP. The microbial consortia CS primarily contained members from the genera Pseudomonas, Stenotrophomonas, Achromobacter, Dysgonomonas, Flavobacterium and Sphingobacterium, as well as Cellvibrio, Azospirillum, Pseudomonas, Dysgonomonas and Cellulomonas in FP. The COG and KEGG annotation analyses revealed considerable levels of diversity. Further analysis determined that the CS consortium had an increase in the acid and ester metabolism pathways, while carbohydrate metabolism was enriched in the FP consortium. Furthermore, a comparison against the CAZy database showed that the microbial consortia CS and FP contain a rich diversity of lignocellulose degrading families, in which GH5, GH6, GH9, GH10, GH11, GH26, GH42, and GH43 were enriched in the FP consortium, and GH44, GH28, GH2, and GH29 increased in the CS consortium. The degradative mechanism of lignocellulose metabolism by the two microbial consortia is similar, but the annotation of quantity of genes indicated that they are diverse and vary greatly. The lignocellulolytic microbial consortia cultured under different carbon conditions (CS and FP) differed substantially in their composition of the microbial community at the genus level. The changes in functional diversity were accompanied with variation in the composition of microorganisms, many of which are related to the degradation of lignocellulolytic materials. The genera Pseudomonas, Dysgonomonas and Sphingobacterium in CS and the genera Cellvibrio and Pseudomonas in FP exhibited a much wider distribution of lignocellulose degradative ability.

Viability of Acid-Adapted Escherichia coli O157:H7 in Ground Beef Treated with Acidic Calcium Sulfate

2004 ◽  
Vol 67 (3) ◽  
pp. 591-595 ◽  
Author(s):  
LARRY R. BEUCHAT ◽  
ALAN J. SCOUTEN
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Calcium Sulfate ◽  
Ground Beef ◽  
Storage Period ◽  
Acid Tolerance ◽  
Escherichia Coli O157 ◽  
E Coli ◽  
Acidic Environments ◽  
Subsequent Acid

The effects of lactic acid, acetic acid, and acidic calcium sulfate (ACS) on viability and subsequent acid tolerance of three strains of Escherichia coli O157:H7 were determined. Differences in tolerance to acidic environments were observed among strains, but the level of tolerance was not affected by the acidulant to which cells had been exposed. Cells of E. coli O157:H7 adapted to grow on tryptic soy agar acidified to pH 4.5 with ACS were compared to cells grown at pH 7.2 in the absence of ACS for their ability to survive after inoculation into ground beef treated with ACS, as well as untreated beef. The number of ACS-adapted cells recovered from ACS-treated beef was significantly (α = 0.05) higher than the number of control cells recovered from ACS-treated beef during the first 3 days of a 10-day storage period at 4°C, suggesting that ACS-adapted cells might be initially more tolerant than unadapted cells to reduced pH in ACS-treated beef. Regardless of treatment of ground beef with ACS or adaptation of E. coli O157:H7 to ACS before inoculating ground beef, the pathogen survived in high numbers.

scholarly journals Current Advances in the Biodegradation and Bioconversion of Polyethylene Terephthalate

2021 ◽  
Vol 10 (1) ◽  
pp. 39
Author(s):  
Xinhua Qi ◽  
Wenlong Yan ◽  
Zhibei Cao ◽  
Mingzhu Ding ◽  
Yingjin Yuan
Keyword(s):  
Polyethylene Terephthalate ◽  
Microbial Consortium ◽  
Tricarboxylic Acid Cycle ◽  
Tca Cycle ◽  
Tricarboxylic Acid ◽  
Microbial Consortia ◽  
Plastic Pollution ◽  
One Step ◽  
Complex Polymers ◽  
The One

Polyethylene terephthalate (PET) is a widely used plastic that is polymerized by terephthalic acid (TPA) and ethylene glycol (EG). In recent years, PET biodegradation and bioconversion have become important in solving environmental plastic pollution. More and more PET hydrolases have been discovered and modified, which mainly act on and degrade the ester bond of PET. The monomers, TPA and EG, can be further utilized by microorganisms, entering the tricarboxylic acid cycle (TCA cycle) or being converted into high value chemicals, and finally realizing the biodegradation and bioconversion of PET. Based on synthetic biology and metabolic engineering strategies, this review summarizes the current advances in the modified PET hydrolases, engineered microbial chassis in degrading PET, bioconversion pathways of PET monomers, and artificial microbial consortia in PET biodegradation and bioconversion. Artificial microbial consortium provides novel ideas for the biodegradation and bioconversion of PET or other complex polymers. It is helpful to realize the one-step bioconversion of PET into high value chemicals.

Reducing Pathogens by Using Zinc Oxide Nanoparticles and Acetic Acid in Sheep Meat

2014 ◽  
Vol 77 (9) ◽  
pp. 1599-1604 ◽  
Author(s):  
MAHBOUBEH MIRHOSSEINI ◽  
VAHID ARJMAND
Keyword(s):  
Zinc Oxide ◽  
Antibacterial Activity ◽  
Acetic Acid ◽  
Zno Nanoparticles ◽  
Pathogenic Bacteria ◽  
Inhibitory Effect ◽  
Initial Growth ◽  
Practical Applications ◽  
E Coli ◽  
Sheep Meat

Practical applications of different concentrations (0, 1, 2, 4, 6, and 8 mM) of zinc oxide (ZnO) suspensions containing 1% acetic acid were investigated against the pathogenic bacteria Listeria monocytogenes, Escherichia coli, Staphylococcus aureus, and Bacillus cereus. ZnO suspensions (0, 1, 3, 6, and 8 mM) containing acetic acid had a significant inhibitory effect on the growth of L. monocytogenes, E. coli, and S. aureus during 12 h of incubation, and the 8 mM suspensions of ZnO were the most effective against all the strains. These data suggested that the antibacterial activity of ZnO was concentration dependent. Thus, 6 and 8 mM ZnO were selected for further studies in meat. ZnO nanoparticles reduced initial growth of all inoculated strains in meat. To our knowledge, this is the first report describing the antibacterial activity of ZnO nanoparticles in meat and indicates the potential of these nanoparticles as an antibacterial agent in the food industry.

Efficacy of Selected Acidulants in Pureed Green Beans Inoculated with Pathogens (Escherichia coli O157:H7 and Listeria monocytogenes)

2006 ◽  
Vol 69 (8) ◽  
pp. 1865-1869 ◽  
Author(s):  
AAKASH KHURANA ◽  
GEORGE B. AWUAH ◽  
BRADLEY TAYLOR ◽  
ELENA ENACHE
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Listeria Monocytogenes ◽  
Titratable Acidity ◽  
Combined Effect ◽  
Escherichia Coli O157 ◽  
Green Beans ◽  
E Coli ◽  
Acid Ph ◽  
D Values

Studies were conducted to evaluate the combined effect of selected acidulants (acetic, citric, malic, and phosphoric acid) and heat on foodborne pathogens (Escherichia coli O157:H7 and Listeria monocytogenes) in pureed green beans. To establish a consistent reference point for comparison, the molar concentrations of the acids remained constant while the acid-to-puree ratio, titratable acidity, and undissociated acid were either measured or calculated for a target acidified green beans at a pH of 3.8, 4.2, and 4.6. The D-values at 149°F were used as the criteria for acid efficacy. Generally, acetic acid (puree, pH 3.8 and 4.2) represented the most effective acid with comparatively low D-values irrespective of the target microorganism. A 10-s heating at 149°F inactivated approximately 106 CFU/ml of E. coli O157:H7 in pureed beans at pH 3.8. The efficacy of acetic acid is likely related to the elevated percent titratable acidity, undissociated acid, and acid-to-puree ratio. The effectiveness (which in this study represents the combined effect of acid and heat) of the remaining acids (citric, malic, and phosphoric) at puree pH values of 3.8 and 4.2 were statistically insignificant (α = 0.05). Surprisingly, acetic acid (puree, pH 4.6) appeared to be the least effective as compared to the other acids tested (citric, malic, and phosphoric) especially on E. coli O157:H7 cells, while L. monocytogenes had a similar resistance to all acids at puree pH 4.6. With the exception of citric acid (pH 3.8), acetic acid (pH 4.6), and malic acid (pH 3.8 and 4.6), which were statistically insignificant (P > 0.05), the D-values for L. monocytogenes were statistically different (P ≤ 0.05) and higher than the D-values for E. coli under similar experimental conditions. A conservative process recommendation (referred to as the “safe harbor” process) was found sufficient and applicable to pureed green beans for the pH range studied.

scholarly journals Inactivation of Multi-Drug Resistant Non-Typhoidal Salmonella and Wild-Type Escherichia coli STEC Using Organic Acids: A Potential Alternative to the Food Industry

Pathogens ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 849
Author(s):  
Vinicius Silva Castro ◽  
Yhan da Silva Mutz ◽  
Denes Kaic Alves Rosario ◽  
Adelino Cunha-Neto ◽  
Eduardo Eustáquio de Souza Figueiredo ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Acetic Acid ◽  
Organic Acids ◽  
Sodium Hypochlorite ◽  
Bacterial Species ◽  
Disk Diffusion ◽  
Clinical Strains ◽  
Linear Pattern ◽  
E Coli ◽  
Log Reduction

Salmonella and Escherichia coli are the main bacterial species involved in food outbreaks worldwide. Recent reports showed that chemical sanitizers commonly used to control these pathogens could induce antibiotic resistance. Therefore, this study aimed to describe the efficiency of chemical sanitizers and organic acids when inactivating wild and clinical strains of Salmonella and E. coli, targeting a 4-log reduction. To achieve this goal, three methods were applied. (i) Disk-diffusion challenge for organic acids. (ii) Determination of MIC for two acids (acetic and lactic), as well as two sanitizers (quaternary compound and sodium hypochlorite). (iii) The development of inactivation models from the previously defined concentrations. In disk-diffusion, the results indicated that wild strains have higher resistance potential when compared to clinical strains. Regarding the models, quaternary ammonium and lactic acid showed a linear pattern of inactivation, while sodium hypochlorite had a linear pattern with tail dispersion, and acetic acid has Weibull dispersion to E. coli. The concentration to 4-log reduction differed from Salmonella and E. coli in acetic acid and sodium hypochlorite. The use of organic acids is an alternative method for antimicrobial control. Our study indicates the levels of organic acids and sanitizers to be used in the inactivation of emerging foodborne pathogens.

Engineering of Stable Recombinant Bacteria for Production of Chiral Medium-Chain-Length Poly-3-Hydroxyalkanoates

1999 ◽  
Vol 65 (8) ◽  
pp. 3265-3271 ◽  
Author(s):  
Maria A. Prieto ◽  
Michele B. Kellerhals ◽  
Gian B. Bozzato ◽  
Dragan Radnovic ◽  
Bernard Witholt ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Chain Length ◽  
Expression System ◽  
Average Molecular Weight ◽  
Polydispersity Index ◽  
Recombinant Bacteria ◽  
E Coli ◽  
Medium Chain ◽  
Medium Chain Length ◽  
Pha Production

ABSTRACT In order to scale up medium-chain-length polyhydroxyalkanoate (mcl-PHA) production in recombinant microorganisms, we generated and investigated different recombinant bacteria containing a stable regulated expression system for phaC1, which encodes one of the mcl-PHA polymerases of Pseudomonas oleovorans. We used the mini-Tn5 system as a tool to constructEscherichia coli 193MC1 and P. oleovoransPOMC1, which had stable antibiotic resistance and PHA production phenotypes when they were cultured in a bioreactor in the absence of antibiotic selection. The molecular weight and the polydispersity index of the polymer varied, depending on the inducer level. E. coli 193MC1 produced considerably shorter polyesters thanP. oleovorans produced; the weight average molecular weight ranged from 67,000 to 70,000, and the polydispersity index was 2.7. Lower amounts of inducer added to the media shifted the molecular weight to a higher value and resulted in a broader molecular mass distribution. In addition, we found that E. coli 193MC1 incorporated exclusively the R configuration of the 3-hydroxyoctanoate monomer into the polymer, which corroborated the enantioselectivity of the PhaC1 polymerase enzyme.

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