Platelet Metabolism during Room Temperature Storage Contributes to Bacterial Growth: Effect Mitigated By Refrigeration

Abstract Introduction: Transfusion related sepsis is a serious concern limiting platelet storage time to 5 days at room temperature. While most units are screened for bacterial contamination when collected, most bacterial monitoring methods can take up to 7 days to detect potential contamination. Thus, cold storage of platelets represents an attractive alternative for improving platelet safety. In this study, we assessed bacterial growth in platelets stored either at room temperature (22oC) or refrigerated (4oC). Methods: Apheresis platelets in plasma (PLT) were obtained from healthy donors using the Terumo Trima Accel Automated Blood Collection System (Terumo BCT). Fresh plasma (FP) was collected similarly. Aliquots of PLT or FP were transferred to pH SAFE minibags (Blood Cell Storage, Inc) and inoculated with Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis, or PBS (uninfected control). Minibag aliquots stored at RT were agitated using an orbital shaker set to 60 rpm while refrigerated aliquots were stored under static conditions. Bacterial growth was monitored daily through dilution plating. Lactate levels in PLT aliquots were assessed by iSTAT (Abbott) using CG4+ test cartridges while plasma glucose levels were assessed using blood glucose testing strips (Germaine Laboratories). Platelet activation and aggregation were assessed on days 0, 1, 3, and 5 by flow cytometry and Multiplate platelet aggregometry, respectively. Results: Bacterial growth progressed rapidly over the first 3-4 days post-collection in all PLT aliquots stored at RT except those challenged with S. epidermidis. Significant growth of S. epidermidis was not detected until day 4. No change in bacterial numbers were detected in any refrigerated aliquots through day 5. While refrigeration appeared to preserve PLT function throughout with low levels of activation irrespective of bacterial contamination, RT storage resulted in significantly (p < 0.05) decreased platelet aggregation over time which was exacerbated by bacterial contamination. In the absence of metabolically active PLTs, bacterial growth was significantly reduced, or at least delayed, in all test groups. FP aliquots challenged with Gram-negative pathogens exhibited a significant (p < 0.05) delay in bacterial growth at day 1. While growth of E. coli and P. aeruginosa recovered by day 2, growth was significantly (p < 0.05) inhibited in aliquots challenged with A. baumannii throughout the observation period. Conversely, no differences in bacteria growth were observed in aliquots challenged with Gram-positive pathogens until day 3, at which point growth appeared to be significantly (p< 0.05) stunted in FP relative to PLT aliquots. Bacterial growth appeared to correlate with PLT lactate production. However, only E. coli showed clear signs of lactate utilization as lactate levels diminished significantly after day 3. Despite this, A. baumannii, E. coli, and S. epidermidis, exhibited increased bacterial growth in FP aliquots supplemented with concentrations of lactic acid in excess of 15 mM. Conclusions: Bacterial growth, platelet activation and platelet lactate production appeared largely static throughout in refrigerated aliquots. Conversely, bacterial growth was significantly increased in all RT stored aliquots, as was lactate production suggesting platelet metabolism may contribute to bacterial growth. Illustrating this, lactic acid concentrations in excess of 15 mM modulated growth of A. baumannii, E. coli, S. epidermidis in FP. These data demonstrate that bacterial growth can be controlled through refrigeration without loss of function and RT storage may potentiate growth of certain bacterial strains through accelerated PLT metabolism. Disclosures No relevant conflicts of interest to declare.

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Platelet Lactate Production during Room Temperature Storage Promotes Bacterial Growth

Blood ◽

10.1182/blood.v128.22.2634.2634 ◽

2016 ◽

Vol 128 (22) ◽

pp. 2634-2634

Author(s):

Patrick Ketter ◽

Bernard Arulanandam ◽

Andrew P Cap

Keyword(s):

Lactate Dehydrogenase ◽

Carbon Source ◽

Bacterial Growth ◽

Room Temperature ◽

Bacterial Contamination ◽

Pyruvate Dehydrogenase Complex ◽

Lactate Production ◽

Student’S T ◽

Lactate Levels ◽

Student’S T Test

Abstract Introduction: Transfusion related sepsis is a serious concern for both military and civilian trauma centers. The primary source of bacterial contamination associated with such events is room temperature (RT) stored platelets. Due to high risk of bacterial contamination, RT stored platelets may only be administered up to 5 days post-collection. Although approved by the FDA, cold stored platelets may only be administered 3 days post-collection under current regulations. In this study, we utilized the opportunistic pathogen Acinetobacterbaumannii - a reported cause of platelet contamination and important hospital acquired infection (HAI) - as a model organism to assess bacterial growth in platelets stored either at room temperature (22oC) or refrigerated (4oC), as well as determine contributors to bacterial growth. Methods: Apheresis platelets in plasma (PLT) were obtained from healthy donors using the Terumo Trima Accel Automated Blood Collection System (Terumo BCT). Platelet poor plasma (PPP) was obtained from PLT aliquots centrifuged twice at 2,500 x g for 5 min. Other PLT aliquots were stimulated with Phorbol 12-myristate 13-acetate (PMA) to generate activated platelets (aPLT). Following activation, aPLTs were pelleted through centrifugation at 2,500 x g for 5 min and the releasate (REL) was transferred to a separate container. Pelleted aPLTs were washed 3 times in sterile PBS and suspended in PPP. In some experiments aliquots of PPP were supplemented with 40 mM lactic acid. Aliquots of PLT, PPP, aPLT, and REL were transferred to pH SAFE minibags (Blood Cell Storage, Inc) and inoculated (a.k.a., contaminated) with A. baumannii clinical isolate Ci79. Minibag aliquots stored at RT were agitated using an orbital shaker set to 60 rpm while refrigerated aliquots were stored under static conditions. Bacterial growth was monitored daily through dilution plating. In some experiments, lactate levels in PLT aliquots were assessed by iSTAT (Abbott) using CG4+ test cartridges. Results: Bacterial growth progressed exponentially over the first 3 days post-collection in PLT aliquots stored at RT. However, growth was significantly (p < 0.05) reduced in PPP units (Fig. 1A). Neither platelet activation status nor released factors appeared to have any effect as no significant differences were observed in bacterial growth between contaminated PLT and aPLT units, nor between contaminated PPP and REL units (Fig. 1A). Growth progressed at a much faster rate and to a greater magnitude in the presence of live platelets (PLT and aPLT), suggesting the contribution of platelet metabolism. Thus, lactate levels were assessed in PLT units and found to mirror bacterial growth (Fig. 1B). Furthermore, addition of lactic acid to RT stored PPP restored bacterial growth (Fig. 1A). Growth remained static throughout under all treatment conditions stored refrigerated. Conclusions: Bacterial growth remained static over the 5 day post-collection observation period during cold storage. Additionally, bacterial growth at RT appeared to be related to increased production of lactate from pyruvate via NAD-dependent lactate dehydrogenase (nLDH) following glycolysis (Fig. 1C). To that end, many bacteria, including A. baumannii,as well as various Staphylococcus spp, and Streptococcus spp, possess genes encoding for NAD-independent lactate dehydrogenases (iLDH) which enable utilization of lactate as a carbon source (Fig. 1D). These data demonstrate that not only can bacterial growth be controlled through refrigeration, but RT stored platelets potentiate bacterial growth through their accelerated metabolism relative to cold storage. Figure 1 Lactate Promotes Bacterial Growth at Room Temperature in Stored Platelets. Bacterial growth under various conditions (PLT ●, aPLT ▼, PPP + Lactate ■, PPP ■, or REL ▲) during RT storage (A). Lactate production mirrors bacterial growth over time (B). Simplified schematic detailing platelet lactate production (NAD-dependent lactate dehydrogenase = nLDH) (C). Utilization of lactate by bacteria as a carbon source (NAD-independent lactate dehydrogenase = iLDH; pyruvate dehydrogenase complex = PDH complex) (D). Error bars represent ± SD. Statistical differences determined by student's t-test. Statistical differences between PLT and PPP; * = p < 0.05, ** = p < 0.005, *** = p < 0.0005. Statistical differences between PLT and PPP + Lac; Ψ = p < 0.05, Ψ Ψ = p < 0.005. Figure 1. Lactate Promotes Bacterial Growth at Room Temperature in Stored Platelets. Bacterial growth under various conditions (PLT ●, aPLT ▼, PPP + Lactate ■, PPP ■, or REL ▲) during RT storage (A). Lactate production mirrors bacterial growth over time (B). Simplified schematic detailing platelet lactate production (NAD-dependent lactate dehydrogenase = nLDH) (C). Utilization of lactate by bacteria as a carbon source (NAD-independent lactate dehydrogenase = iLDH; pyruvate dehydrogenase complex = PDH complex) (D). Error bars represent ± SD. Statistical differences determined by student's t-test. Statistical differences between PLT and PPP; * = p < 0.05, ** = p < 0.005, *** = p < 0.0005. Statistical differences between PLT and PPP + Lac; Ψ = p < 0.05, Ψ Ψ = p < 0.005. Disclosures No relevant conflicts of interest to declare.

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Real-Time Bioluminescence Analysis of Escherichia coli O157:H7 Survival on Livestock Meats Stored Fresh, Cold, or Frozen

Journal of Food Protection ◽

10.4315/0362-028x.jfp-18-207 ◽

2018 ◽

Vol 81 (11) ◽

pp. 1906-1912 ◽

Cited By ~ 1

Author(s):

SEONG B. PARK ◽

SHECOYA B. WHITE ◽

CHRISTY S. STEADMAN ◽

CLAY A. CAVINDER ◽

SCOTT T. WILLARD ◽

...

Keyword(s):

Escherichia Coli ◽

Real Time ◽

Bacterial Growth ◽

Room Temperature ◽

Storage Conditions ◽

Escherichia Coli O157 ◽

Production Environment ◽

Real Time Monitoring ◽

E Coli ◽

C Storage

ABSTRACT Foodborne bacteria such as Escherichia coli O157:H7 can cause severe hemorrhagic colitis in humans following consumption of contaminated meat products. Contamination with pathogenic bacteria is frequently found in the food production environment, and adequate household storage conditions of purchased foods are vital for illness avoidance. Real-time monitoring was used to evaluate bacterial growth in ground horse, beef, and pork meats maintained under various storage conditions. Various levels of E. coli O157:H7 carrying the luxCDABE operon, which allows the cells to emit bioluminescence, were used to inoculate meat samples that were then stored at room temperature for 0.5 day, at 4°C (cold) for 7 or 9 days, or −20°C (frozen) for 9 days. Real-time bioluminescence imaging (BLI) of bacterial growth was used to assess bacterial survival or load. Ground horse meat BLI signals and E. coli levels were dose and time dependent, increasing during room temperature and −20°C storage, but stayed at low levels during 4°C storage. No bacteria survived in the lower level inoculum groups (101 and 103 CFU/g). With an inoculum of 107 CFU/g, pork meats had higher BLI signals than did their beef counterparts, displaying decreased BLI signals during 7 days storage at 4°C. Both meat types had higher BLI signals in the fat area, which was confirmed with isolated fat tissues in the beef meat. Beef lean and fat tissues contrasted with both pork fat and lean tissues, which had significantly higher BLI signals and bacterial levels. BLI appears to be a useful research tool for real-time monitoring of bacterial growth and survival in various stored livestock meats. The dependence of E. coli O157:H7 growth on meat substrate (fat or lean) and storage conditions may be used as part of an effective antibacterial approach for the production of safe ground horse, beef, and pork meats.

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The Physiological Responses of Escherichia coli Triggered by Phosphoribulokinase (PrkA) and Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase (Rubisco)

Microorganisms ◽

10.3390/microorganisms8081187 ◽

2020 ◽

Vol 8 (8) ◽

pp. 1187

Author(s):

En-Jung Liu ◽

I-Ting Tseng ◽

Yi-Ling Chen ◽

Ju-Jiun Pang ◽

Zhi-Xuan Shen ◽

...

Keyword(s):

Escherichia Coli ◽

Bacterial Growth ◽

Physiological Responses ◽

Lactate Production ◽

Reducing Power ◽

Glucose Consumption ◽

Redox Balance ◽

Bisphosphate Carboxylase ◽

E Coli ◽

Co2 Recycling

Phosphoribulokinase (PrkA) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) have been proposed to create a heterologous Rubisco-based engineered pathway in Escherichia coli for in situ CO2 recycling. While the feasibility of a Rubisco-based engineered pathway has been shown, heterologous expressions of PrkA and Rubisco also induced physiological responses in E. coli that may compete with CO2 recycling. In this study, the metabolic shifts caused by PrkA and Rubisco were investigated in recombinant strains where ppc and pta genes (encodes phosphoenolpyruvate carboxylase and phosphate acetyltransferase, respectively) were deleted from E. coli MZLF (E. coli BL21(DE3) Δzwf, ΔldhA, Δfrd). It has been shown that the demand for ATP created by the expression of PrkA significantly enhanced the glucose consumptions of E. coli CC (MZLF Δppc) and E. coli CA (MZLF Δppc, Δpta). The accompanying metabolic shift is suggested to be the mgsA route (the methylglyoxal pathway) which results in the lactate production for reaching the redox balance. The overexpression of Rubisco not only enhanced glucose consumption but also bacterial growth. Instead of the mgsA route, the overproduction of the reducing power was balanced by the ethanol production. It is suggested that Rubisco induces a high demand for acetyl-CoA which is subsequently used by the glyoxylate shunt. Therefore, Rubisco can enhance bacterial growth. This study suggests that responses induced by the expression of PrkA and Rubisco will reach a new energy balance profile inside the cell. The new profile results in a new distribution of the carbon flow and thus carbons cannot be majorly directed to the Rubisco-based engineered pathway.

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Escherichia coli Strains Engineered for Homofermentative Production of d-Lactic Acid from Glycerol

Applied and Environmental Microbiology ◽

10.1128/aem.00664-10 ◽

2010 ◽

Vol 76 (13) ◽

pp. 4327-4336 ◽

Cited By ~ 103

Author(s):

Suman Mazumdar ◽

James M. Clomburg ◽

Ramon Gonzalez

Keyword(s):

Escherichia Coli ◽

Lactic Acid ◽

Lactate Dehydrogenase ◽

Cell Mass ◽

Lactate Production ◽

Fumarate Reductase ◽

Glycerol Metabolism ◽

E Coli ◽

Fuels And Chemicals ◽

Microaerobic Conditions

ABSTRACT Given its availability and low price, glycerol has become an ideal feedstock for the production of fuels and chemicals. We recently reported the pathways mediating the metabolism of glycerol in Escherichia coli under anaerobic and microaerobic conditions. In this work, we engineer E. coli for the efficient conversion of glycerol to d-lactic acid (d-lactate), a negligible product of glycerol metabolism in wild-type strains. A homofermentative route for d-lactate production was engineered by overexpressing pathways involved in the conversion of glycerol to this product and blocking those leading to the synthesis of competing by-products. The former included the overexpression of the enzymes involved in the conversion of glycerol to glycolytic intermediates (GlpK-GlpD and GldA-DHAK pathways) and the synthesis of d-lactate from pyruvate (d-lactate dehydrogenase). On the other hand, the synthesis of succinate, acetate, and ethanol was minimized through two strategies: (i) inactivation of pyruvate-formate lyase (ΔpflB) and fumarate reductase (ΔfrdA) (strain LA01) and (ii) inactivation of fumarate reductase (ΔfrdA), phosphate acetyltransferase (Δpta), and alcohol/acetaldehyde dehydrogenase (ΔadhE) (strain LA02). A mutation that blocked the aerobic d-lactate dehydrogenase (Δdld) also was introduced in both LA01 and LA02 to prevent the utilization of d-lactate. The most efficient strain (LA02Δdld, with GlpK-GlpD overexpressed) produced 32 g/liter of d-lactate from 40 g/liter of glycerol at a yield of 85% of the theoretical maximum and with a chiral purity higher than 99.9%. This strain exhibited maximum volumetric and specific productivities for d-lactate production of 1.5 g/liter/h and 1.25 g/g cell mass/h, respectively. The engineered homolactic route generates 1 to 2 mol of ATP per mol of d-lactate and is redox balanced, thus representing a viable metabolic pathway.

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Control of Escherichia coli O157:H7 with Sodium Metasilicate

Journal of Food Protection ◽

10.4315/0362-028x-67.7.1501 ◽

2004 ◽

Vol 67 (7) ◽

pp. 1501-1506 ◽

Cited By ~ 20

Author(s):

GEORGE H. WEBER ◽

JUDY K. O'BRIEN ◽

FREDRIC G. BENDER

Keyword(s):

Escherichia Coli ◽

Lactic Acid ◽

Room Temperature ◽

Sodium Metasilicate ◽

Antimicrobial Activities ◽

Intervention Strategies ◽

Trisodium Phosphate ◽

Escherichia Coli O157 ◽

E Coli

Three intervention strategies—trisodium phosphate, lactic acid, and sodium metasilicate—were examined for their in vitro antimicrobial activities in water at room temperature against a three-strain cocktail of Escherichia coli O157:H7 and a three-strain cocktail of “generic” E. coli. Both initial inhibition and recovery of injured cells were monitored. When 3.0% (wt/wt) lactic acid, pH 2.4, was inoculated with E. coli O157:H7 (approximately 6 log CFU/ml), viable microorganisms were recovered after a 20-min exposure to the acid. After 20 min in 1.0% (wt/wt) trisodium phosphate, pH 12.0, no viable E. coli O157:H7 microorganisms were detected. Exposure of E. coli O157:H7 to sodium metasilicate (5 to 10 s) at concentrations as low as 0.6%, pH 12.1, resulted in 100% inhibition with no recoverable E. coli O157:H7. No difference in inhibition profiles was detected between the E. coli O157:H7 and generic strains, suggesting that nonpathogenic strains may be used for in-plant sodium metasilicate studies.

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Can genetically modified Escherichia coli with neutral buoyancy induced by gas vesicles be used as an alternative method to clinorotation for microgravity studies?

Microbiology ◽

10.1099/mic.0.27062-0 ◽

2005 ◽

Vol 151 (1) ◽

pp. 69-74 ◽

Cited By ~ 11

Author(s):

Michael Benoit ◽

David Klaus

Keyword(s):

Escherichia Coli ◽

Population Density ◽

Bacterial Growth ◽

Space Flight ◽

Genetically Modified ◽

Gas Vesicles ◽

E Coli ◽

Final Population ◽

Significant Difference ◽

Static Conditions

Space flight has been shown to affect various bacterial growth parameters. It is proposed that weightlessness allows the cells to remain evenly distributed, consequently altering the chemical makeup of their surrounding fluid, and hence indirectly affecting their physiological behaviour. In support of this argument, ground-based studies using clinostats to partially simulate the quiescent environment attained in microgravity have generally been successful in producing bacterial growth characteristics that mimic responses reported under actual space conditions. A novel approach for evaluating the effects of reduced cell sedimentation is presented here through use of Escherichia coli cultures genetically modified to be neutrally buoyant. Since clinorotation would not (or would only minimally) affect cell distribution of this already near-colloidal cell system, it was hypothesized that the effects on final population density would be eliminated relative to a static control. Gas-vesicle-producing E. coli cultures were grown under clinostat and static conditions and the culture densities at 60 h were compared. As a control, E. coli that do not produce gas vesicles, but were otherwise identical to the experimental strain, were also grown under clinostat and static conditions. As hypothesized, no significant difference was observed in cell populations at 60 h between the clinorotated and static gas-vesicle-producing E. coli cultures, while the cells that did not produce gas vesicles showed a mean increase in population density of 10·5 % (P=0·001). These results further suggest that the lack of cumulative cell sedimentation is the dominant effect of space flight on non-stirred, in vitro E. coli cultures.

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Milk quality and its suitability for technological processing in cows with metritis

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/845/1/012101 ◽

2021 ◽

Vol 845 (1) ◽

pp. 012101

Author(s):

A S Ryhlov ◽

G M Firsov ◽

S O Loschinin ◽

A V Filatova ◽

V S Avdeenko ◽

...

Keyword(s):

Lactic Acid ◽

Cell Viability ◽

Bacterial Contamination ◽

Acid Product ◽

E Coli ◽

The Third ◽

Order Of Magnitude ◽

Technological Processing ◽

High Degree ◽

Control Samples

Abstract It has been established that the development of metritis in cows after providing obstetric aid as a result of abortion, eversion of the uterus or retention of the placenta is accompanied by an increased microbial and fungal background of the uterus. Without obstetric aid during delivery, only from 5… 9 days after birth, 35.37% of cows had genitals contaminated with various pathogenic microflora. Already on the third day of puerperia, 14 species of bacteria were isolated from cows that were assisted in delivery, which in 74.5% of cases were contaminated with pathogenic microflora: S. aureus (in 15.5% of cases), E. coli (37%), K. pneumonia (12%), and S. pyogenes (10% of cases). The results of mycological studies revealed that A. fumigatus, C. albicans and C. crusei were isolated from cows after obstetrics. It was found out that the content of somatic cells (SC) r = 0.63, the activity of muramidase (AM) r = 0.84, lactoperoxidase (LPO) r = 0.65 and lactoferrin (LF) r = 0.66 change with a high degree of correlation. Milk from cows with metritis showed 2 times higher total bacterial contamination than milk from clinically healthy animals. Milk from sick cows has a reduced number of lactic acid organisms after the first day of storage. At the same time, acid formation occurred faster by 5.0–15.0% than that in control samples of milk prepared for production of lactic acid products. The acidity in milk fermented with Lactobacillus bulgarus was 12.0-13.3% higher than that in the control sourdough samples, and the cell viability of the symbiotic combination was an order of magnitude lower (2.5×106 versus 2.5×107) compared to the control samples of the lactic acid product.

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Lactic Acid and Trisodium Phosphate Treatment of Lamb Breast To Reduce Bacterial Contamination

Journal of Food Protection ◽

10.4315/0362-028x-64.9.1439 ◽

2001 ◽

Vol 64 (9) ◽

pp. 1439-1441 ◽

Cited By ~ 13

Author(s):

A. J. RAMIREZ ◽

G. R. ACUFF ◽

L. M. LUCIA ◽

J. W. SAVELL

Keyword(s):

Escherichia Coli ◽

Lactic Acid ◽

Bacterial Contamination ◽

Combined Treatment ◽

Trisodium Phosphate ◽

E Coli ◽

Plate Counts ◽

Phosphate Treatment ◽

Water Rinse

Lactic acid and trisodium phosphate (TSP) were evaluated for the ability to reduce Escherichia coli and aerobic plate counts (APCs) on lamb breasts that were inoculated with a lamb fecal paste. A 90-s water rinse was applied followed by either a 9-s (55°C) 2% lactic acid spray, a 60-s (55°C) 12% TSP dip, or a combined treatment of both lactic acid and TSP treatments. Lactic acid reduced E. coli and APCs by 1.6 log10/cm2, and TSP caused a 1.8-log10/cm2 reduction in E. coli and a 0.7-log10/cm2 reduction in APCs. Combined reductions by the lactic acid spray followed by the TSP dip were 1.8 and 1.5 log10/cm2 for E. coli and APCs, respectively. Lactic acid and trisodium phosphate, used alone or in combination, were effective in reducing numbers of E. coli and could be useful as pathogen intervention steps in lamb slaughter processing.

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Influence of nutrient availability on in vitro growth of major bovine mastitis pathogens

Journal of Dairy Research ◽

10.1017/s0022029921000133 ◽

2021 ◽

Vol 88 (1) ◽

pp. 80-88

Author(s):

Remo Stürmlin ◽

Josef J. Gross ◽

Olga Wellnitz ◽

Lea A. Wagner ◽

Camille Monney ◽

...

Keyword(s):

Bacterial Growth ◽

Nutrient Availability ◽

Bovine Mastitis ◽

Milk Composition ◽

B Vitamins ◽

E Coli ◽

Streptococcus Uberis ◽

Whole Milk ◽

Mastitis Pathogens

AbstractThe aim of the present study was to investigate the effects of milk composition changes on the in vitro growth of bovine mastitis pathogens. Nutritional requirements of three major bovine mastitis pathogens Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Streptococcus uberis (S. uberis) were investigated in vitro. We used ultra-high temperature (UHT) treated milk with different contents of fat, protein, and carbohydrates to test the influence of the availability of various milk constituents on pathogen growth characteristics. Additionally, the bacterial growth was investigated under experimentally modified nutrient availability by dilution and subsequent supplementation with individual nutrients (carbohydrates, different nitrogen sources, minerals, and different types of B vitamins) either to milk or to a conventional medium (thioglycolate broth, TB). Varying contents of fat, protein or lactose did not affect bacterial growth with the exception of growth of S. uberis being promoted in protein-enriched milk. The addition of nutrients to diluted whole milk and TB partly revealed different effects, indicating that there are media-specific growth limiting factors after dilution. Supplementation of minerals to diluted milk did not affect growth rates of all studied bacteria. Bacterial growth in diluted whole milk was decreased by the addition of high concentrations of amino acids in S. aureus, and by urea and additional B vitamins in E. coli and S. aureus. The growth rate of S. uberis was increased by the addition of B vitamins to diluted whole milk. The present results demonstrate that growth-limiting nutrients differ among pathogen types. Because reduced bacterial growth was only shown in diluted milk or TB, it is unlikely that alterations in nutrient availability occurring as a consequence of physiological changes of milk composition in the cow's udder would directly affect the susceptibility or course of bovine mastitis.

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Synthesis, antibiotic structure–activity relationships, and cellulose dissolution studies of new room-temperature ionic liquids derived from lignin

Biotechnology for Biofuels ◽

10.1186/s13068-021-01898-x ◽

2021 ◽

Vol 14 (1) ◽

Cited By ~ 1

Author(s):

Shihong Liu ◽

Michael Gonzalez ◽

Celine Kong ◽

Scott Weir ◽

Aaron M. Socha

Keyword(s):

Antibacterial Activity ◽

Ionic Liquids ◽

Room Temperature ◽

Oxidation Products ◽

Cellulose Dissolution ◽

Melting Points ◽

E Coli ◽

Alkyl Chains ◽

Renewable Feedstocks ◽

Commodity Chemicals

Abstract Background Ionic liquids (ILs) are promising pretreatment solvents for lignocellulosic biomass, but are largely prepared from petroleum precursors. Benzaldehydes from depolymerized lignin, such as vanillin, syringaldehyde, and 4-methoxy benzaldehyde, represent renewable feedstocks for the synthesis of ionic liquids. We herein report syntheses of novel lignin-derived ionic liquids, with extended N-alkyl chains, and examine their melting points, cellulose dissolution capacities, and toxicity profiles against Daphnia magna and E. coli strain 1A1. The latter organism has been engineered to produce isoprenol, a drop-in biofuel and precursor for commodity chemicals. Results The new N,N-diethyl and N,N-dipropyl methyl benzylammonium ILs were liquids at room temperature, showing 75–100 °C decreased melting points as compared to their N,N,N-trimethyl benzylammonium analog. Extension of N-alkyl chains also increased antibacterial activity threefold, while ionic liquids prepared from vanillin showed 2- to 4-fold lower toxicity as compared to those prepared from syringaldehyde and 4-methoxybenzaldehyde. The trend of antibacterial activity for anions of lignin-derived ILs was found to be methanesulfonate < acetate < hydroxide. Microcrystalline cellulose dissolution, from 2 to 4 wt% after 20 min at 100 °C, was observed in all new ILs using light microscopy and IR spectroscopy. Conclusions Ionic liquids prepared from H-, S- and G-lignin oxidation products provided differential cytotoxic activity against E. coli and D. magna, suggesting these compounds could be tailored for application specificity within a biorefinery.

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