Escherichia coli hydrogenase activity and H2 production under glycerol fermentation at a low pH

2011 ◽  
Vol 36 (7) ◽  
pp. 4323-4331 ◽  
Author(s):  
Karen Trchounian ◽  
Viviana Sanchez-Torres ◽  
Thomas K. Wood ◽  
Armen Trchounian
Keyword(s):  
Escherichia Coli ◽  
H2 Production ◽  
Low Ph ◽  
Hydrogenase Activity ◽  
Glycerol Fermentation

ETHANOL SUPPLEMENTATION AS A NEW APPROACH TO REGULATE GROWTH AND HYDROGEN PRODUCTION OF $ \textit{ESCHERICHIA COLI} $ UPON GLYCEROL FERMENTATION

2020 ◽  
Vol 54 (2 (252)) ◽  
pp. 138-146
Author(s):  
A.A. Poladyan
Keyword(s):  
Escherichia Coli ◽  
Redox Potential ◽  
Bacterial Growth ◽  
H2 Production ◽  
Glycerol Fermentation ◽  
Medium Ph ◽  
New Approach ◽  
E Coli ◽  
Peptone Medium ◽  
By Products

Molecular hydrogen (H2) and ethanol are the main by-products of glycerol fermentation by Escherichia coli. In this study, the growth of E. coli BW25113 was investigated with the addition of small amounts (0.05 to 2 %) of ethanol alone and in a combination with glycerol The bacterial growth, the kinetic of the redox potential, and the H2 production in peptone medium, pH 7.5, were investigated upon various amounts of ethanol supplementation. In the presence of any amount of ethanol, but upon the absence of other sources of carbon, no H2 production was observed. Whereas ethanol (0.3 to 1 %) with a combination of glycerol stimulated both bacterial growth and H2 production, pH 7.5. A correlation was observed between the redox potential and stimulated by ethanol bacterial growth. The obtained results can be applied to regulate fermentation processes in biotechnology.

Microbial Quality of Hoummos (Chickpea Dip) Commercially Produced in Jordan

1994 ◽  
Vol 57 (5) ◽  
pp. 431-435 ◽  
Author(s):  
MOHAMMED I. YAMANI ◽  
BASIM A. AL-DABABSEH
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Low Ph ◽  
Plate Count ◽  
Microbial Quality ◽  
Aerobic Plate Count ◽  
And Staphylococcus Aureus ◽  
Reference Samples ◽  
Hygienic Conditions

Sixty samples of fresh hoummos (chickpea dip) from 15 restaurants were examined in winter and summer to find out numbers and types of microorganisms present. Five reference samples, produced by the investigators under hygienic conditions, were examined for comparison. The microbial load of commercial hoummos was high, and spherical lactic acid bacteria (LAB) belonging to Lactococcus, Enterococcus and Leuconostoc were the predominant microorganisms. The means of the aerobic plate count (APC) and the counts of LAB and coliforms (1.9 × 108, 1.6 × 108 and 2.9 × 105/g, respectively) in summer samples were significantly higher (p < 0.05) than the averages of the same counts in winter samples (2.7 × 107, 1.6 × 107 and 2.2 × 103/g). The average summer and winter yeast counts were 4.2 × 104 and 1.5 × 104g, respectively. In reference samples of hoummos, APC and LAB counts were < 103/g, while the coliform and yeast counts were < 10/g and 102/g, respectively, indicating lack of hygienic practices during the production of commercial hoummos. Salmonella was not detected in any sample, and Escherichia coli and Staphylococcus aureus counts of all samples were < 10/g. The relatively low pH of hoummos (the average pH of all samples was 5.1) and the rapid growth of LAB, possibly accompanied by production of inhibitory substances, may explain the predominance of these bacteria, and could have contributed to the absence of the pathogens examined.

scholarly journals Characterization and antimicrobial activity of vaginal lactobacillus isolate

2011 ◽  
Vol 63 (1) ◽  
pp. 29-35 ◽  
Author(s):  
Gordana Zavisic ◽  
Zeljka Radulovic ◽  
Valentina Vranic ◽  
Jelena Begovic ◽  
L. Topisirovic ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Staphylococcus Aureus ◽  
Pseudomonas Aeruginosa ◽  
Antimicrobial Activity ◽  
Survival Rate ◽  
Bile Salts ◽  
Antimicrobial Effect ◽  
Low Ph ◽  
Probiotic Potential ◽  
Pathogenic Escherichia Coli

The aim of this study was to investigate the probiotic potential of bacteriocin-producing lactobacilli strain Lactobacillus plantarum G2 isolated from the vaginal mucus of healthy women. The antimicrobial effect of G2 was confirmed in the mixed culture with pathogenic Escherichia coli, Staphylococcus aureus, Salmonella abony and Pseudomonas aeruginosa, while bacteriocine activity was detected against S. aureus and S. abony only. The strain showed an excellent survival rate in low pH and in the presence of bile salts. The percentage of adhered cells of L. plantarum G2 to hexadecane was 63.85?2.0 indicating the intermediate hydrophobicity.

scholarly journals Fermentative Utilization of Glycerol by Escherichia coli and Its Implications for the Production of Fuels and Chemicals

2007 ◽  
Vol 74 (4) ◽  
pp. 1124-1135 ◽  
Author(s):  
Abhishek Murarka ◽  
Yandi Dharmadi ◽  
Syed Shams Yazdani ◽  
Ramon Gonzalez
Keyword(s):  
Escherichia Coli ◽  
Anaerobic Fermentation ◽  
Glycerol Metabolism ◽  
Nuclear Magnetic Resonance Analysis ◽  
Glycerol Fermentation ◽  
Glycerol Utilization ◽  
Negative Effect ◽  
Balance Analysis ◽  
Fuels And Chemicals ◽  
High Degree

ABSTRACT Availability, low prices, and a high degree of reduction make glycerol an ideal feedstock to produce reduced chemicals and fuels via anaerobic fermentation. Although glycerol metabolism in Escherichia coli had been thought to be restricted to respiratory conditions, we report here the utilization of this carbon source in the absence of electron acceptors. Cells grew fermentatively on glycerol and exhibited exponential growth at a maximum specific growth rate of 0.040 ± 0.003 h−1. The fermentative nature of glycerol metabolism was demonstrated through studies in which cell growth and glycerol utilization were observed despite blocking several respiratory processes. The incorporation of glycerol in cellular biomass was also investigated via nuclear magnetic resonance analysis of cultures in which either 50% U-13C-labeled or 100% unlabeled glycerol was used. These studies demonstrated that about 20% of the carbon incorporated into the protein fraction of biomass originated from glycerol. The use of U-13C-labeled glycerol also allowed the unambiguous identification of ethanol and succinic, acetic, and formic acids as the products of glycerol fermentation. The synthesis of ethanol was identified as a metabolic determinant of glycerol fermentation; this pathway fulfills energy requirements by generating, in a redox-balanced manner, 1 mol of ATP per mol of glycerol converted to ethanol. A fermentation balance analysis revealed an excellent closure of both carbon (∼95%) and redox (∼96%) balances. On the other hand, cultivation conditions that prevent H2 accumulation were shown to be an environmental determinant of glycerol fermentation. The negative effect of H2 is related to its metabolic recycling, which in turn generates an unfavorable internal redox state. The implications of our findings for the production of reduced chemicals and fuels were illustrated by coproducing ethanol plus formic acid and ethanol plus hydrogen from glycerol at yields approaching their theoretical maximum.

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