| 1. |
- Aevarsson, Arnthór, et al.
(författare)
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Going to extremes - a metagenomic journey into the dark matter of life
- 2021
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Ingår i: FEMS Microbiology Letters. - : Oxford University Press (OUP). - 1574-6968. ; 368:12
-
Forskningsöversikt (refereegranskat)abstract
- The Virus-X-Viral Metagenomics for Innovation Value-project was a scientific expedition to explore and exploit uncharted territory of genetic diversity in extreme natural environments such as geothermal hot springs and deep-sea ocean ecosystems. Specifically, the project was set to analyse and exploit viral metagenomes with the ultimate goal of developing new gene products with high innovation value for applications in biotechnology, pharmaceutical, medical, and the life science sectors. Viral gene pool analysis is also essential to obtain fundamental insight into ecosystem dynamics and to investigate how viruses influence the evolution of microbes and multicellular organisms. The Virus-X Consortium, established in 2016, included experts from eight European countries. The unique approach based on high throughput bioinformatics technologies combined with structural and functional studies resulted in the development of a biodiscovery pipeline of significant capacity and scale. The activities within the Virus-X consortium cover the entire range from bioprospecting and methods development in bioinformatics to protein production and characterisation, with the final goal of translating our results into new products for the bioeconomy. The significant impact the consortium made in all of these areas was possible due to the successful cooperation between expert teams that worked together to solve a complex scientific problem using state-of-the-art technologies as well as developing novel tools to explore the virosphere, widely considered as the last great frontier of life.
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| 2. |
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| 3. |
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| 4. |
- Bai Palmkron, Shuai, et al.
(författare)
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Quantification of structures in freeze-dried materials using X-ray microtomography
- 2023
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Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 658
-
Tidskriftsartikel (refereegranskat)abstract
- The structure of a freeze-dried material is essential for its ability to preserve and protect biologics such as proteins, cells and other sensitive structures. The structure of a typical freeze-dried matrix can be described as pores surrounded by thin walls where the walls are the encapsulating material (for e.g. cells). The objective of this investigation is to evaluate X-ray microtomography (µCT) as a characterization method to quantifying the matrix of a freeze dried material, and compare it to scanning electron microscopy (SEM). The material consists of maltodextrin, freeze-dried below or above the glass transition temperature of the maximal freeze concentration (Tg′) and after applying annealing. The SEM images have high resolution and provide an excellent view of the sample. However, it is challenging to perform any image analysis and to ensure that a representative section is presented. The µCT images provide a rather uniform contrast between material and void, allowing for a simple grey-level thresholding when separating structure from the background. A robust image analysis procedure allows the results extracted from a representative sample volume to be evaluated. Further image analysis has been focused on understanding the thickness of the encapsulating structures by estimations of volume-weighted averages of inscribed spheres within the walls. The results show two types of structures: A large pore structure of around 20–100 µm separated by thin walls around 2–3 µm thick, and a finer structure consisting of smaller pockets of air (< 10 µm) packed in a honeycomb like structure. The structures of the samples dried below and above Tg′ have smaller and thinner structures, while material dried after annealing has larger and thicker structures. The structures display comparably small differences between the different drying protocols despite the quite different drying conditions.
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| 5. |
- Bergenholtz, Sa Schoug, et al.
(författare)
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A case study on stress preconditioning of a Lactobacillus strain prior to freeze-drying
- 2012
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Ingår i: Cryobiology. - : Elsevier BV. - 0011-2240 .- 1090-2392. ; 64:3, s. 152-159
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Tidskriftsartikel (refereegranskat)abstract
- Freeze-drying of bacterial cells with retained viability and activity after storage requires appropriate formulation, i.e. mixing of physiologically adapted cell populations with suitable protective agents, and control of the freeze-drying process. Product manufacturing may alter the clinical effects of probiotics and it is essential to identify and understand possible factor co-dependencies during manufacturing. The physical solid-state behavior of the formulation and the freeze-drying parameters are critical for bacterial survival and thus process optimization is important, independent of strain. However, the maximum yield achievable is also strain-specific and strain survival is governed by e.g. medium, cell type, physiological state, excipients used, and process. The use of preferred compatible solutes for cross-protection of Lactobacilli during industrial manufacturing may be a natural step to introduce robustness, but knowledge is lacking on how compatible solutes, such as betaine, influence formulation properties and cell survival. This study characterized betaine formulations, with and without sucrose, and tested these with the model lactic acid bacteria Lactobacillus coryniformis Si3. Betaine alone did not act as a lyo-protectant and thus betaine import prior to freeze-drying should be avoided. Differences in protective agents were analyzed by calorimetry, which proved to be a suitable tool for evaluating the characteristics of the freeze-dried end products.
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| 6. |
- Bjerketorp, Joakim, et al.
(författare)
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Formulation and stabilization of an Arthrobacter strain with good storage stability and 4-chlorophenol-degradation activity for bioremediation
- 2018
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Ingår i: Applied Microbiology and Biotechnology. - : Springer Science and Business Media LLC. - 0175-7598 .- 1432-0614. ; 102:4, s. 2031-2040
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Tidskriftsartikel (refereegranskat)abstract
- Chlorophenols are widespread and of environmental concern due to their toxic and carcinogenic properties. Development of less costly and less technically challenging remediation methods are needed; therefore, we developed a formulation based on micronized vermiculite that, when air-dried, resulted in a granular product containing the 4-chlorophenol (4-CP)-degrading Gram-positive bacterium Arthrobacter chlorophenolicus A6. This formulation and stabilization method yielded survival rates of about 60% that remained stable in storage for at least 3 months at 4 °C. The 4-CP degradation by the formulated and desiccated A. chlorophenolicus A6 cells was compared to that of freshly grown cells in controlled-environment soil microcosms. The stabilized cells degraded 4-CP equally efficient as freshly grown cells in two different set-ups using both hygienized and non-treated soils. The desiccated microbial product was successfully employed in an outdoor pot trial showing its effectiveness under more realistic environmental conditions. No significant phytoremediation effects on 4-CP degradation were observed in the outdoor pot experiment. The 4-CP degradation kinetics from both the microcosms and the outdoor pot trial were used to generate a predictive model of 4-CP biodegradation potentially useful for larger-scale operations, enabling better bioremediation set-ups and saving of resources. This study also opens up the possibility of formulating and stabilizing also other Arthrobacter strains possessing different desirable pollutant-degrading capabilities.
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| 7. |
- Chakraborty, Amrita, et al.
(författare)
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Yeast and fruit fly mutual niche construction and antagonism against mould
- 2022
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Ingår i: Functional Ecology. - : Wiley. - 0269-8463 .- 1365-2435. ; 36:7, s. 1639-1654
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Tidskriftsartikel (refereegranskat)abstract
- A goal in insect–microbe ecology is to understand the mechanisms regulating species associations and mutualistic interactions. The spotted wing drosophila Drosophila suzukii develops in ripening fruit, unlike other drosophilids that typically feed on overripe fruit, and is associated with the yeast Hanseniaspora uvarum. We hypothesized that D. suzukii and H. uvarum engage in niche construction leading to a mutualistic relation, facilitating the exploitation of fruit and berries as larval substrate. We show that H. uvarum proliferates on both ripe and on unripe raspberries, mediates attraction of D. suzukii larvae and adult flies, enhances egg-laying in mated females and is a sufficient food substrate to support larval development. Moreover, H. uvarum suppresses the antagonistic grey mould, Botrytis cinerea in collaboration with D. suzukii larvae, and produces less ethanol than baker's yeast. H. uvarum thus creates favourable conditions for D. suzukii larval development, which is susceptible to ethanol and grey mould. D. suzukii, on the other hand, vectors H. uvarum to suitable substrates such as raspberries, where larval feeding activity enhances growth of H. uvarum. Larval feeding also helps to suppress B. cinerea, which otherwise outcompetes H. uvarum on raspberry, in the absence of fly larvae. In conclusion, H. uvarum enhances D. suzukii larval development on unripe berries, and D. suzukii promotes H. uvarum dispersal and growth on berries. Yeast and fly modify their shared habitat in reciprocal niche construction and mutual interaction. Read the free Plain Language Summary for this article on the Journal blog.
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| 8. |
- Garcia, Armando Hernández, et al.
(författare)
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Isothermal microcalorimetry for rapid viability assessment of freeze-dried Lactobacillus reuteri
- 2017
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Ingår i: Process Biochemistry. - : Elsevier BV. - 1359-5113. ; 55, s. 49-54
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Tidskriftsartikel (refereegranskat)abstract
- The rapid assessment of viable cells in freeze-dried formulations of probiotic Lactobacilli is an important issue in the probiotic industry. The probiotic Lactobacillus reuteri DSM 17938 is the active ingredient of BioGaia Protectis whose viable cell concentrations are currently determined using the classical and time-consuming viable count technique. In this paper we present a rapid method based on Isothermal microcalorimetry (IMC) for viability assessment of freeze-dried DSM 17938. Fresh and rehydrated freeze-dried cells were incubated in MRS medium at different cell concentration and the thermal power (mu W) at 37 degrees C was measured over time. A linear dependence between the time to reach a certain thermal power value and the decimal logarithm of viable cells was found. This allowed rapid viability assessment of rehydrated cells, reducing the detection time from 48 h (viable count) to 10 h (microcalorimetry) in samples with 3 x 10(3) cfu/mL, and to 4 h in samples with 4 x 10(6) cfu/mL. No significant differences were found between the two methods when freeze-dried rehydrated cells were analysed (p > 0.05). Therefore, IMC is a promising tool to be used in the quality control of freeze-dried DSM 17938 as well as other bacteria-based products. (C) 2017 Elsevier Ltd. All rights reserved.
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| 9. |
- Hernández, Armando, et al.
(författare)
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Impact of the fermentation parameters pH and temperature on stress resilience of Lactobacillus reuteri DSM 17938
- 2019
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Ingår i: AMB Express. - : Springer Science and Business Media LLC. - 2191-0855. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- This study was undertaken to investigate the impact of culture pH (4.5–6.5) and temperature (32–37 °C) on the stress resilience of Lactobacillus reuteri DSM 17938 during freeze-drying and post freeze-drying exposure to low pH (pH 2)and bile salts. Response-surface methodology analysis revealed that freeze-drying survival rates Ncells after drying/Ncells before drying*100 were linearly related to pH with the highest survival rate of 80% when cells were cultured at pH 6.5 and the lowest was 40% when cells were cultured at pH 4.5. The analysis further revealed that within the chosen temperature range the culture temperature did not significantly affect the freeze-drying survival rate. However, fermentation at pH 4.5 led to better survival rates when rehydrated cells were exposed to low pH shock or bile salts. Thus, the effect of pH onfreeze-drying survival was in contrast to effects on low pH and bile salts stress tolerance. The rationale behind this irreconcilability is based on the responses being dissimilar and are not tuned to each other. Culturing strain DSM17938 at pH values higher than 5.5 could be a useful option to improve the survivability and increase viable cell numbers in the final freeze-dried product. However, the dissimilar responses for the process- and application parameterstested here suggest that an optimal compromise has to be found in order to obtain the most functional probiotic product possible.
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| 10. |
- Holmqvist, Mona, 1961-, et al.
(författare)
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Bestydelsen av slutbokstaven s i engelska ord : en studie av elevers sätt att förstå vad tillägget av -s innebär
- 2006
-
Konferensbidrag (refereegranskat)abstract
- Denna studie beskriver hur elever från skolår fem till gymnasiets första år erfar slutbokstaven s i engelska ord. Den metod som använts i studien är learning study med parallella lektioner (Holmqvist, M., Gustavsson, I. & Wernberg, A., in press). Studien genomförs med en variationsteoretisk utgångspunkt (Holmqvist, 2004), vilket innebär att ett särskilt fokus riktas på lärandeobjektets kritiska aspekter, det vill säga vad som måste urskiljas för att förståelse uppnås av ett fenomen. Dessutom studeras om och hur eleverna erbjuds att urskilja dessa, om de kan eller erbjuds urskilja flera aspekter simultant (samtidigt) samt vilken form av variation som elevernas uttryckta erfarande visar. Studien tar sin utgångspunkt i vad eleverna erfar, något som analyseras utifrån en fenomenografisk ansats. Därefter planeras en lektion grundad i analyser av dels videoobservationer efter de inspelade lektionerna och dels elevernas resultat vid de test som genomförts, vilka fokuserar på förekomst av slutbokstaven s i följande former: sammandragen form, plural, tredje person singular presens, genitiv samt självständiga possessiva pronomen. Resultaten pekar på att sammandragen form samt självständiga possessiva pronomen är kritiskt att förstå för elever i främst skolår fem, men därefter tycks det som om eleverna har god förståelse av sammandragen form (’s) medan de avseende självständiga possessiva pronomen visserligen har en känsla för vad som är korrekt men inte kan berätta varför sådana ord kan sluta på s. Avseende plural-s tycks detta vålla stora problem, bland annat på grund av ord som i svenska är singular men i engelska motsvaras av plural form. Det är enklare för eleverna att urskilja när det ska vara ett s på verbet efter tredje person singular.I varje område analyseras vilka de kritiska aspekterna är för lärandeobjektet. Vi har till exempel sett att majoriteten av eleverna tror att verbändelsen –s enbart/främst talar om vilken form verbet har (presens eller imperfekt). Resultaten visar vad som krävs för att förstå –s i olika former och vad detta innebär för undervisningen.
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| 11. |
- Holmqvist, Mona, et al.
(författare)
-
Bestydelsen av slutbokstaven s i engelska ord : en studie av elevers sätt att förstå vad tillägget av -s innebär
- 2006
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Denna studie beskriver hur elever från skolår fem till gymnasiets första år erfar slutbokstaven s i engelska ord. Den metod som använts i studien är learning study med parallella lektioner (Holmqvist, M., Gustavsson, I. & Wernberg, A., in press). Studien genomförs med en variationsteoretisk utgångspunkt (Holmqvist, 2004), vilket innebär att ett särskilt fokus riktas på lärandeobjektets kritiska aspekter, det vill säga vad som måste urskiljas för att förståelse uppnås av ett fenomen. Dessutom studeras om och hur eleverna erbjuds att urskilja dessa, om de kan eller erbjuds urskilja flera aspekter simultant (samtidigt) samt vilken form av variation som elevernas uttryckta erfarande visar. Studien tar sin utgångspunkt i vad eleverna erfar, något som analyseras utifrån en fenomenografisk ansats. Därefter planeras en lektion grundad i analyser av dels videoobservationer efter de inspelade lektionerna och dels elevernas resultat vid de test som genomförts, vilka fokuserar på förekomst av slutbokstaven s i följande former: sammandragen form, plural, tredje person singular presens, genitiv samt självständiga possessiva pronomen. Resultaten pekar på att sammandragen form samt självständiga possessiva pronomen är kritiskt att förstå för elever i främst skolår fem, men därefter tycks det som om eleverna har god förståelse av sammandragen form (’s) medan de avseende självständiga possessiva pronomen visserligen har en känsla för vad som är korrekt men inte kan berätta varför sådana ord kan sluta på s. Avseende plural-s tycks detta vålla stora problem, bland annat på grund av ord som i svenska är singular men i engelska motsvaras av plural form. Det är enklare för eleverna att urskilja när det ska vara ett s på verbet efter tredje person singular. I varje område analyseras vilka de kritiska aspekterna är för lärandeobjektet. Vi har till exempel sett att majoriteten av eleverna tror att verbändelsen –s enbart/främst talar om vilken form verbet har (presens eller imperfekt). Resultaten visar vad som krävs för att förstå –s i olika former och vad detta innebär för undervisningen.
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| 12. |
- Holmström, Anna, et al.
(författare)
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YopK of Yersinia pseudotuberculosis controls translocation of Yop effectors across the eukaryotic cell membrane
- 1997
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Ingår i: Molecular Microbiology. - : Wiley. - 0950-382X .- 1365-2958. ; 24:1, s. 73-91
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Tidskriftsartikel (refereegranskat)abstract
- Introduction of anti-host factors into eukaryotic cells by extracellular bacteria is a strategy evolved by several Gram-negative pathogens. In these pathogens, the transport of virulence proteins across the bacterial membranes is governed by closely related type III secretion systems. For pathogenic Yersinia, the protein transport across the eukaryotic cell membrane occurs by a polarized mechanism requiring two secreted proteins, YopB and YopD. YopB was recently shown to induce the formation of a pore in the eukaryotic cell membrane, and through this pore, translocation of Yop effectors is believed to occur (Håkansson et al., 1996b). We have previously shown that YopK of Yersinia pseudotuberculosis is required for the development of a systemic infection in mice. Here, we have analysed the role of YopK in the virulence process in more detail. A yopK-mutant strain was found to induce a more rapid YopE-mediated cytotoxic response in HeLa cells as well as in MDCK-1 cells compared to the wild-type strain. We found that this was the result of a cell-contact-dependent increase in translocation of YopE into HeLa cells. In contrast, overexpression of YopK resulted in impaired translocation. In addition, we found that YopK also influenced the YopB-dependent lytic effect on sheep erythrocytes as well as on HeLa cells. A yopK-mutant strain showed a higher lytic activity and the induced pore was larger compared to the corresponding wild-type strain, whereas a strain overexpressing YopK reduced the lytic activity and the apparent pore size was smaller. The secreted YopK protein was found not to be translocated but, similar to YopB, localized to cell-associated bacteria during infection of HeLa cells. Based on these results, we propose a model where YopK controls the translocation of Yop effectors into eukaryotic cells.
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| 13. |
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| 14. |
- Håkansson, Sebastian, et al.
(författare)
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Domesticering av mikroorganismer
- 2011
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Ingår i: Genteknik som tar skruv. - 9789154060610 ; , s. 211-222
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Bokkapitel (populärvet., debatt m.m.)
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| 15. |
- Håkansson, Sebastian
(författare)
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Survival and phosphate solubilisation activity of desiccated formulations of Penicillium bilaiae and Aspergillus niger influenced by water activity
- 2018
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Ingår i: Journal of Microbiological Methods. - : Elsevier BV. - 0167-7012 .- 1872-8359. ; 150, s. 39-46
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Tidskriftsartikel (refereegranskat)abstract
- The impact of formulation and desiccation on the shelf life of phosphate (P)-solubilising microorganisms is often under-studied, particularly relating to their ability to recover P-solubilisation activity. Here, Penicilllium bilaiae and Aspergillus niger were formulated on vermiculite (V) alone, or with the addition of protectants (skimmed milk (V + SM) and trehalose (V + T)), and on sewage sludge ash with (A + N) and without nutrients (A), and dried in a convective air dryer. After drying, the spore viability of P. bilaiae was greater than that of A. niger. V formulations achieved the highest survival rates without being improved by the addition of protectants. P. bilaiae formulated on V was selected for desiccation in a fluidised bed dryer, in which several temperatures and final water activities (aw) were tested. The highest spore viability was achieved when the formulation was dried at 25 degrees C to a final aw > 0.3. During three months' storage, convective air dried formulations were stable for both strains, except in the presence of skimmed milk for P. bilaiae which saw a decrease in spore viability. In the fluidised bed-dried formulations, when aw > 0.3, the loss in viability was higher, especially when stored at 20 degrees C, than at aw < 0.1. P-solubilisation activity performed on ash was preserved in most of the formulations after desiccation and storage. Overall, a low drying temperature and high final aw positively affected P. bilaiae viability, however a trade-off between higher viability after desiccation and shelf life should be considered. Further research is needed to optimise viability over time and on more sustainable carriers.
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| 16. |
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| 17. |
- Kessler, Vadim, et al.
(författare)
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CaptiGel Technology for Encapsulation of Biomaterials and Medicines
- 2009
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Inorganic materials receive increasing interest as components and major constituents of encapsulation formulations for bio-molecules and microorganisms. Sol-gel technology is broadly recognized as a versatile synthetic approach to colloidal inorganic materials, perspective as potential hydrosol and hydrogel matrices for encapsulation. The industrial development in this field has been mostly focused on silica in the view of the availability of both organic and inorganic precursors of silica gels and, especially, due to their easy handling and facile control over gelation parameters. Metal oxides have been practically excluded from this application domain, because of the high chemical reactivity and apparent bio-incompatibility of the related precursor chemicals. However, the metal oxides with compositions corresponding to naturally abundant biocompatible minerals, for example titanium dioxide (registered even as the Food Additive E171), can represent an attractive alternative to silica. Stable and biocompatible hydrosols and hydrogels of titanium dioxide and other metal oxides can be successfully prepared using modification of the related metal organic precursors with hydrophilic ligands, especially if the latter can be supplied with electric charge through interaction with acids or bases [1]. The produced colloids are then naturally buffered within biocompatible pH region. An attractive feature of the thus produced colloid particles is that they possess a core-shell structure: the crystalline core contributes with attractive UV-protective properties, while the amorphous shell hinders the negative photochemical activity and permits easy aggregation of the particles into continuous films, self-assembling at any phase boundary, for example, a cell membrane of a microorganism. This permits to produce formulations able to protect the encapsulated biomaterial from both chemical and physical hazards. Another attractive feature of titanium dioxide is its specific biodegradability, offering possibility of enhanced chemically and bio-chemically triggered release [2]. Metal oxide surfaces possess even a pronounced affinity to carboxylate and phosphate/phosphonate functions present in the formula of many important medicines. Release of these drugs after their chemosorption in the oxide hydrogels is a slow and kinetically controlled process sought in many medical applications, which makes the produced materials attractive for drug delivery applications. 1. Kessler, V.G.; Seisenbaeva, G.A.; Håkansson, S.; Unell, M, Metal Oxide Hydrogels and Hydrosols, Their Preparation and Use, PCT application WO07145573. 2. Kessler, V.G.; Seisenbaeva, G.A.; Håkansson, S.; Unell, M, Chemically Triggered Biodelivery Using Metal–Organic Sol–Gel Synthesis. Angew. Chem. Int. Ed., 2008. 47(44): p. 8506-8509
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| 18. |
- Kämpfer, Peter, et al.
(författare)
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Proposal of Coetzeea brasiliensis gen. nov. sp. nov. isolated from larvae of Anopheles darlingi
- 2016
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Ingår i: International Journal of Systematic and Evolutionary Microbiology. - : Microbiology Society. - 1466-5026 .- 1466-5034. ; 66, s. 5211-5217
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Tidskriftsartikel (refereegranskat)abstract
- A Gram-stain-negative, rod-shaped strain, Braz8T, isolated from larvae ofAnopheles darlingiwas investigatedusing a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequences showed that strainBraz8Twas related most closely to species of the genusThorsellia, with 95.6, 96.5 and 96.6% similarity to thetype strains ofThorsellia anophelis,Thorsellia kandunguensisandThorsellia kenyensis, respectively, andformed a separate branch in the phylogenetic tree next to the monophyletic cluster of the genusThorsellia.Chemotaxonomic data supported the allocation of the strain to the familyThorselliaceae. The major fatty acidswere C18:1!7c, C16:0and C14:0. The quinone system was composed of ubiquinones Q-8 and Q-7 (1:0.3),the predominant polar lipids were diphosphatidylglycerol and phosphatidylglycerol, and the polyamine patternshowed the major compound putrescine. However, qualitative and quantitative differences in the majorpolyamine, polar lipid profile and fatty acid patterns distinguished strain Braz8Tfrom species of the genusThorsellia. Phylogenetic analysis based on 16S rRNA gene sequences, average nucleotide identity, DNA–DNAhybridization, multilocus sequence analysis as well as physiological and biochemical tests distinguished strainBraz8Tboth genotypically and phenotypically from the threeThorselliaspecies but also showed its placementin the familyThorselliaceae. Thus, strain Braz8Tis considered to represent a novel species of a new genus mostclosely related to the genusThorsellia, for which the nameCoetzeea brasiliensisgen. nov., sp. nov. is proposed.The type strain ofCoetzeea brasiliensisis Braz8T(=LMG 29552T=CIP 111088T)
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| 19. |
- Kämpfer, Peter, et al.
(författare)
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Proposal of Thorsellia kenyensis sp. nov. and Thorsellia kandunguensis sp. nov., isolated from the larvae of Anopheles arabiensis as members of the family Thorselliaceae fam. nov.
- 2015
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Ingår i: International Journal of Systematic and Evolutionary Microbiology. - : Microbiology Society. - 1466-5026 .- 1466-5034. ; 65, s. 444-451
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Tidskriftsartikel (refereegranskat)abstract
- Two Gram-negative, rod-shaped strains, T2.1T and W5.1.1T, isolated from larvae of the mosquito Anopheles arabiensis, were investigated using a polyphasic approach. On the basis of 16S rRNA gene sequence similarity studies, strains T2.1T and W5.1.1T were shown to belong to the genus Thorsellia, both showing 97.8 % similarity to the type strain of Thorsellia anophelis, with 98.1 % similarity to each other. Chemotaxonomic data supported the allocation of the strains to the genus Thorsellia: their major fatty acids were C18 : 1ω7c, C16 : 0 and C14 : 0 and they harboured a ubiquinone Q-8 quinone system and a polyamine pattern with the major compound 1,3-diaminopropane. Qualitative and quantitative differences in their polar lipid profiles distinguished strains T2.1T and W5.1.1T from each other and from T. anophelis. Average nucleotide identity (ANI), DNA–DNA hybridization, multilocus sequence analysis (MLSA) as well as physiological and biochemical tests allowed T2.1T and W5.1.1T to be distinguished both genotypically and phenotypically from each other and from the type strain of T. anophelis. Thus, we propose that these isolates represent two novel species of the genus Thorsellia, named Thorsellia kenyensis sp. nov. (type strain T2.1T = CCM 8545T = LMG 28483T = CIP 110829T) and Thorsellia kandunguensis sp. nov. (type strain W5.1.1T = LMG 28213T = CIP 110794T). Furthermore, phylogenetic analysis based on nearly full-length 16S rRNA gene sequences showed that the genus Thorsellia forms a separate branch, distinct from the families Enterobacteriaceae, Pasteurellaceae and Orbaceae. As a consequence, a new family Thorselliaceae fam. nov. is proposed. An emended description of Thorsellia anophelis is also provided.
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| 20. |
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| 21. |
- Melin, Petter, et al.
(författare)
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Biological preservation of plant derived animal feed with antifungal microorganisms : safety and formulation aspects
- 2007
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Ingår i: Biotechnology letters. - Dordrecht, Netherlands : Springer. - 0141-5492 .- 1573-6776. ; 29:8, s. 1147-1154
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Forskningsöversikt (refereegranskat)abstract
- During storage of moist animal feed, growth of detrimental fungi causing spoilage, or being mycotoxigenic or pathogenic, is a severe problem. Addition of biopreservative yeasts or lactic acid bacteria can significantly reduce this problem. However, their use requires several careful considerations. One is the safety to the animal, humans and the environment, tightly connected to legal aspects and the need for pre-market authorisation when supplementing feed with microorganisms. Although both yeasts and lactic acid bacteria are considered comparatively safe organisms due to low production of toxic metabolites, it is of great importance to understand the mechanisms behind the biopreservative abilities. Another important issue concerns practical aspects, such as the economic production of large amounts of the organisms and the development of a suitable formulation giving the organisms a long shelf life. These aspects are discussed and a recommendation of this review is that both safety and formulation aspects of a specific microbe should be considered at an early stage in the selection of new organisms with biopreservation potential.
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| 22. |
- Melin, Petter, et al.
(författare)
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Formulation and stabilisation of the biocontrol yeast Pichia anomala
- 2011
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Ingår i: Antonie van Leeuwenhoek. International Journal of General and Molecular Microbiology. - Dordrecht, Netherlands : Springer Netherlands. - 0003-6072 .- 1572-9699. ; 99:1, s. 107-112
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Tidskriftsartikel (refereegranskat)abstract
- The yeast Pichia anomala has antifungal activities and its potential in biocontrol and biopreservation has previously been demonstrated. To practically use an organism in such applications on a larger scale the microbe has to be formulated and stabilised. In this review we give an overview of our experience of formulating and stabilising P. anomala strain J121 in a wider perspective. The stabilisation techniques we have evaluated were liquid formulations, fluidised bed drying, lyophilisation (freeze-drying) and vacuum drying. With all methods tested it was possible to obtain yeast cells with shelf lives of at least a few months and in all cases the biocontrol activity was retained. Fluidised bed drying was dependent on the addition of cottonseed flour as a carrier during the drying process. In liquid formulations a sugar, preferentially trehalose, was a required additive. These two kinds of microbial stabilisation are easily performed and relatively inexpensive but in order to keep the cells viable the biomaterial has to be stored at cool temperatures. However, there is room for optimization, such as improving the growth conditions, or include preconditioning steps to enable the cells to produce more compatible solutes necessary to survive formulation, desiccation and storage. In contrast, lyophilisation and vacuum drying require a lot of energy and are thus expensive. On the other hand, the dried cells were mostly intact after one year of storage at 30A degrees C. Inevitably, the choice of formulation and stabilisation techniques will be dependent also on the intended use.
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| 23. |
- Mosquera, Katherine D., et al.
(författare)
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Comparative assessment of the bacterial communities associated with Anopheles darlingi immature stages and their breeding sites in the Brazilian Amazon
- 2023
-
Ingår i: Parasites and Vectors. - : Springer Nature. - 1756-3305. ; 16:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: The neotropical anopheline mosquito Anopheles darlingi is a major malaria vector in the Americas. Studies on mosquito-associated microbiota have shown that symbiotic bacteria play a major role in host biology. Mosquitoes acquire and transmit microorganisms over their life cycle. Specifically, the microbiota of immature forms is largely acquired from their aquatic environment. Therefore, our study aimed to describe the microbial communities associated with An. darlingi immature forms and their breeding sites in the Coari municipality, Brazilian Amazon. Methods: Larvae, pupae, and breeding water were collected in two different geographical locations. Samples were submitted for DNA extraction and high-throughput 16S rRNA gene sequencing was conducted. Microbial ecology analyses were performed to explore and compare the bacterial profiles of An. darlingi and their aquatic habitats. Results: We found lower richness and diversity in An. darlingi microbiota than in water samples, which suggests that larvae are colonized by a subset of the bacterial community present in their breeding sites. Moreover, the bacterial community composition of the immature mosquitoes and their breeding water differed according to their collection sites, i.e., the microbiota associated with An. darlingi reflected that in the aquatic habitats where they developed. The three most abundant bacterial classes across the An. darlingi samples were Betaproteobacteria, Clostridia, and Gammaproteobacteria, while across the water samples they were Gammaproteobacteria, Bacilli, and Alphaproteobacteria. Conclusions: Our findings reinforce the current evidence that the environment strongly shapes the composition and diversity of mosquito microbiota. A better understanding of mosquito–microbe interactions will contribute to identifying microbial candidates impacting host fitness and disease transmission. Graphical Abstract: [Figure not available: see fulltext.].
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| 24. |
- Mårtensson, Gustav, et al.
(författare)
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Medial temporal atrophy in preclinical dementia : Visual and automated assessment during six year follow-up
- 2020
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Ingår i: NeuroImage: Clinical. - : Elsevier BV. - 2213-1582. ; 27
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Tidskriftsartikel (refereegranskat)abstract
- Medial temporal lobe (MTL) atrophy is an important morphological marker of many dementias and is closely related to cognitive decline. In this study we aimed to characterize longitudinal progression of MTL atrophy in 93 individuals with subjective cognitive decline and mild cognitive impairment followed up over six years, and to assess if clinical rating scales are able to detect these changes. All MRI images were visually rated according to Scheltens’ scale of medial temporal atrophy (MTA) by two neuroradiologists and AVRA, a software for automated MTA ratings. The images were also segmented using FreeSurfer's longitudinal pipeline in order to compare the MTA ratings to volumes of the hippocampi and inferior lateral ventricles. We found that MTL atrophy rates increased with CSF biomarker abnormality, used to define preclinical stages of Alzheimer's Disease. Both AVRA's and the radiologists’ MTA ratings showed similar longitudinal trends as the subcortical volumes, suggesting that visual rating scales provide a valid alternative to automatic segmentations. Our results further showed that it took more than 8 years on average for individuals with mild cognitive impairment, and an Alzheimer's disease biomarker profile, to increase the MTA score by one. This suggests that discrete MTA ratings are too coarse for tracking individual MTL atrophy in short time spans. While the MTA scores from each radiologist showed strong correlations to subcortical volumes, the inter-rater agreement was low. We conclude that the main limitation of quantifying MTL atrophy with visual ratings in clinics is the subjectiveness of the assessment.
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| 25. |
- Nilsson, Louise K. J., et al.
(författare)
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Characterization of Bacterial Communities in Breeding Waters of Anopheles darlingi in Manaus in the Amazon Basin Malaria-Endemic Area
- 2019
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Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 0095-3628 .- 1432-184X. ; 78:4, s. 781-791
-
Tidskriftsartikel (refereegranskat)abstract
- The microbiota in mosquito breeding waters can affect ovipositing mosquitoes, have effects on larval development, and can modify adult mosquito-gut bacterial composition. This, in turn, can affect transmission of human pathogens such as malaria parasites. Here, we explore the microbiota of four breeding sites for Anopheles darlingi, the most important malaria vector in Latin America. The sites are located in Manaus in the Amazon basin in Brazil, an area of active malaria transmission. Using 16S rRNA gene sequencing by MiSeq, we found that all sites were dominated by Proteobacteria and Firmicutes and that 94% of the total number of reads belonged to 36 operational taxonomic units (OTUs) identified in all sites. Of these, the most common OTUs belonged to Escherichia/Shigella, Staphylococcus, and Pseudomonas. Of the remaining 6% of the reads, the OTUs found to differentiate between the four sites belonged to the orders Burkholderiales, Actinomycetales, and Clostridiales. We conclude that An. darlingi can develop in breeding waters with different surface-water bacteria, but that the common microbiota found in all breeding sites might indicate or contribute to a suitable habitat for this important malaria vector.
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| 26. |
- Nilsson, Louise K. J.
(författare)
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Exploration of bacteria associated with Anopheles mosquitoes around the world : For the prevention of transmission of malaria
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Every year, hundreds of thousands of people die from malaria. Malaria is a disease caused by parasites, which are spread by female vector mosquitoes of the genus Anopheles. Current control measures against malaria are based on drugs against the parasites and vector control using insecticides. A problem with these measures is the development of resistance, both in the parasites against the drugs and the mosquitoes against the insecticides. Therefore, additional areas of malaria control must be explored. One such area involves the bacteria associated with the vector mosquitoes. Bacteria have been shown to affect mosquitoes at all life stages, e.g. by affecting choice of oviposition site by female mosquitoes, development of larvae and susceptibility to parasite infection in adults. Furthermore, genetic modification of symbiotic bacteria has been suggested as a mean of killing the parasites in the mosquitoes. This thesis is based on four field studies and one laboratory study and aims to investigate the naturally occurring bacteria associated with different life stages of malaria mosquitoes and how they are acquired. All studies are based on amplicon sequencing of the 16S rRNA gene. We found that overall mosquitoes contain different bacterial communities. However, bacteria associated with adults reflect their life history and can predict the origin of mosquitoes. Bacteria in larvae are similar during the developmental stages but vary with breeding site. Also in larvae, the bacteria could be used to predict the origin of breeding site. Some bacteria could be related to the presence or absence of Anopheles around human habitations and the diversity of aquatic bacteria in breeding sites is large, though some taxa are common. Overall, both environmental and host-genetic factors affect the gut bacterial composition in adult females. In conclusion, this thesis contributes to increasing the knowledge of bacterial diversity associated with Anopheles mosquitoes and to provide insight into how the bacteria are acquired, which can be useful in malaria control.
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| 27. |
- Nykyri, Johanna, et al.
(författare)
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Isothermal microcalorimetry for thermal viable count of microorganisms in pure cultures and stabilized formulations
- 2019
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Ingår i: Journal of Applied Toxicology. - : Springer Science and Business Media LLC. - 0260-437X .- 1099-1263. ; 19
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundQuantification of viable microorganisms is an important step in microbiological research as well as in microbial product formulation to develop biological control products or probiotics. Often, the efficiency of the resulting product is dependent on the microbial cell density and their viability, which may decrease over time. Commonly, the number of viable cells is determined by serial dilution and plating techniques or flow cytometry. In 2017, we developed a mathematical model for isothermal microcalorimetry (IMC) data analysis and showed that the new method allows for a more rapid quantification of viable fresh and freeze-dried anaerobic Lactobacillus reuteri cells than traditional viable count methods.ResultsThis study developed the new method further by applying it to well-known aerophilic plant-beneficial microbial species (Pseudomonas brassicacearum, Bacillus amyloliquefaciens subsp. plantarum and Clonostachys rosea) used in biological control products. We utilized IMC to quantify viable cells in microbial pure cultures as well as when coated onto wheat seeds. The results from this study confirmed that thermal viable count methods are more rapid and sensitive than traditional viable count techniques. Most interestingly, a thermal viable count method was able to quantify microbes coated on seeds despite the presence of the natural microbiota of the seeds. Our results also showed that, in contrast to plating techniques for which clustered cells skew the results, IMC does not require single cells for accurate viable counts.ConclusionsThermal viable count methods are novel methods for the rapid quantification of divergent bacterial and fungal species and enhance the speed, sensitivity, and accuracy of routine viable counts of pure cultures and controlled microbiomes such as plant seed coatings.
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| 28. |
- Pazik, Robert, et al.
(författare)
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Precursor and Solvent Effects in the Nonhydrolytic Synthesis of Complex Oxide Nanoparticles for Bioimaging Applications by the Ether Elimination (Bradley) Reaction
- 2009
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 15, s. 6820-6826
-
Tidskriftsartikel (refereegranskat)abstract
- Investigation of the solvent and alkoxide precursor effect on the nonhydrolytic sol–gel synthesis of oxide nanoparticles by means of an ether elimination (Bradley) reaction indicates that the best crystallinity of the resulting oxide particles is achieved on application of aprotic ketone solvents, such as acetophenone, and of smallest possible alkoxide groups. The size of the produced primary particles is always about 5 nm caused by intrinsic mechanisms of their formation. The produced particles, possessing the composition of natural highly insoluble minerals, are biocompatible. Optical characteristics of the perovskite complex oxide nanoparticles can easily be controlled through doping with rare earth cations; for example, by Eu3+. They can be targeted through surface modification by anchoring the directing biomolecules through a phosphate or phosphonate moiety. Testing of the distribution of Eu-doped BaTiO3 particles, modified with ethylphosphonic acid, demonstrates their facile uptake by the plants with active fluid transport, resulting finally in their enhanced concentration within the cell membranes
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| 29. |
- Persson, Cathrine, et al.
(författare)
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Cell-surface-bound Yersinia translocate the protein tyrosine phosphatase YopH by a polarized mechanism into the target cell
- 1995
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Ingår i: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 18:1, s. 135-150
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Tidskriftsartikel (refereegranskat)abstract
- YopH is translocated by cell-surface-bound bacteria through the plasma membrane to the cytosol of the HeLa cell. The transfer mechanism is contact dependent and polarizes the translocation to only occur at the contact zone between the bacterium and the target cell. More than 99% of the PTPase activity is associated with the HeLa cells. In contrast to the wild-type strain, the yopBD mutant cannot deliver YopH to the cytosol. Instead YopH is deposited in localized areas in the proximity of cell-associated bacteria. A yopN mutant secretes 40% of the total amount of YopH to the culture medium, suggesting a critical role of YopN in regulation of the polarized translocation. Evidence for a region in YopH important for its translocation through the plasma membrane of the target cell but not for secretion from the pathogen is provided.
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| 30. |
- Schoug, Åsa, et al.
(författare)
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Differential effects of polymers PVP90 and Ficoll400 on storage stability and viability of Lactobacillus coryniformis Si3 freeze-dried in sucrose
- 2010
-
Ingår i: Journal of Applied Microbiology. - : Oxford University Press (OUP). - 1364-5072 .- 1365-2672. ; 108:3, s. 1032-1040
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Tidskriftsartikel (refereegranskat)abstract
- AIMS: To investigate the effect of freeze-dried Lactobacillus coryniformis Si3 on storage stability by adding polymers to sucrose-based formulations and to examine the relationship between amorphous matrix stability and cell viability. METHODS AND RESULTS: The resistance to moisture-induced sucrose crystallization and effects on the glass transition temperature (Tg) by the addition of polymers to the formulation were determined by different calorimetric techniques. Both polymers increased the amorphous matrix stability compared to the control, and poly(vinyl)pyrrolidone K90 was more effective in increasing amorphous stability than Ficoll 400. The viability of Lact. coryniformis Si3 after storage was investigated by plate counts following exposure to different moisture levels and temperatures for up to 3 months. The polymers enhanced the cellular viability to different degrees, dependent upon polymer and storage condition. CONCLUSIONS: Polymers can be used to enhance the stability of freeze-dried Lact. coryniformis Si3 products, but cell viability and matrix stability do not always correlate. The general rule of thumb to keep a highly amorphous product 50 degrees below its Tg for overall stability seemed to apply for this type of bacterial products. We showed that by combining thermal analysis with plate counts, it was possible to determine storage conditions where cell viability and matrix stability were kept high. SIGNIFICANCE AND IMPACT OF THE STUDY: The results will aid in the rational formulation design and proper determination of storage conditions for freeze-dried and highly amorphous lactic acid bacteria formulations. We propose a hypothesis of reason for different stabilizing effects on the cells by the different polymers based on our findings and previous findings.
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| 31. |
- Schoug, Åsa, et al.
(författare)
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Freeze-drying of Lactobacillus coryniformis Si3--effects of sucrose concentration, cell density, and freezing rate on cell survival and thermophysical properties
- 2006
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Ingår i: Cryobiology. - Maryland Heights, USA : Elsevier BV. - 0011-2240 .- 1090-2392. ; 53:1, s. 119-127
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Tidskriftsartikel (refereegranskat)abstract
- Freeze-drying is commonly used to stabilize lactic acid bacteria. Many factors have been reported to influence freeze-drying survival, including bacterial species, cell density, lyoprotectant, freezing rate, and other process parameters. Lactobacillus coryniformis Si3 has broad antifungal activity and a potential use as a food and feed biopreservative. This strain is considered more stress sensitive, with a low freeze-drying survival, compared to other commercialized antifungal lactic acid bacterial strains. We used a response surface methodology to evaluate the effects of varying sucrose concentration, cell density and freezing rate on Lb. coryniformis Si3 freeze-drying survival. The water activity of the dry product, as well as selected thermophysical properties of importance for freeze-drying; degree of water crystallization and the glass transition temperature of the maximally freeze concentrated amorphous phase (Tg') were determined. The survival of Lb. coryniformis Si3 varied from less than 6% to over 70% between the different conditions. All the factors studied influenced freeze-drying survival and the most important factor for survival is the freezing rate, with an optimum at 2.8 degrees C/min. We found a co-dependency between freezing rate and formulation ingredients, indicating a complex system and the need to use statistical tools to detect important interactions. The degree of water crystallization decreased and the final water activity increased as a function of sucrose concentration. The degree of water crystallization and Tg' was not affected by the addition of 10(8)-10(10) CFU/mI. At 10(11) CFU/ml, these thermophysical values decreased possibly due to increased amounts of cell-associated unfrozen water.
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| 32. |
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| 33. |
- Schoug, Åsa, et al.
(författare)
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Impact of fermentation pH and temperature on freeze-drying survival and membrane lipid composition of Lactobacillus coryniformis Si3
- 2008
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Ingår i: Journal of Industrial Microbiology & Biotechnology. - Heidelberg, Germany : Springer. - 1367-5435 .- 1476-5535. ; 35:3, s. 175-181
-
Tidskriftsartikel (refereegranskat)abstract
- During the industrial stabilization process, lactic acid bacteria are subjected to several stressful conditions. Tolerance to dehydration differs among lactic acid bacteria and the determining factors remain largely unknown. Lactobacillus coryniformis Si3 prevents spoilage by mold due to production of acids and specific antifungal compounds. This strain could be added as a biopreservative in feed systems, e.g. silage. We studied the survival of Lb. coryniformis Si3 after freeze-drying in a 10% skim milk and 5% sucrose formulation following different fermentation pH values and temperatures. Initially, a response surface methodology was employed to optimize final cell density and growth rate. At optimal pH and temperature (pH 5.5 and 34 degrees C, the freeze-drying survival of Lb. coryniformis Si3 was 67% (+/- 6%). The influence of temperature or pH stress in late logarithmic phase was dependent upon the nature of the stress applied. Heat stress (42 degrees C) did not influence freeze-drying survival, whereas mild cold- (26 degrees C), base(pH 6.5), and acid- (pH 4.5) stress significantly reduced survival. Freeze-drying survival rates varied fourfold, with the lowest survival following mild cold stress (26 degrees C) prior to freeze-drying and the highest survival after optimal growth or after mild heat (42 degrees C) stress. Levels of different membrane fatty acids were analyzed to determine the adaptive response in this strain. Fatty acids changed with altered fermentation conditions and the degree of membrane lipid saturation decreased when the cells were subjected to stress. This study shows the importance of selecting appropriate fermentation conditions to maximize freeze-drying viability of Lb. coryniformis as well as the effects of various unfavorable conditions during growth on freeze-drying survival.
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| 34. |
- Seisenbaeva, Gulaim, et al.
(författare)
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A new concept for titanium oxo-alkoxo-carboxylates' encapsulated biocompatible time temperature food indicators based on arising, not fading color
- 2010
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Ingår i: Journal of Sol-Gel Science and Technology. - : Springer Science and Business Media LLC. - 0928-0707 .- 1573-4846. ; 55, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- New insight into the factors determining formation and stability of oxo-alkoxide carboxylates of titanium permits to design biocompatible systems for encapsulation of binary food quality inorganic dyes, such as Preussian blue, in a temperature-sensitive shell. The shells are formed spontaneously on hydrolysis of carboxylic acid-modified titanium alkoxides on the surface of water droplets containing the dye components. The complete dye is then prepared through mixing of pre-frozen encapsulated droplets which can be activated by heating to room temperature and also influenced by the storage time. The stable shells are obtained from longer chain carboxylates providing the micellar self-assembly derived constructions with increased colloid stability. The factors influencing the formation of individual crystalline oxo-alkoxide carboxylates-a process competing with the micellar self-assembly and decreasing the stability of the oxo-alkoxide carboxylate shells are discussed with the starting point in the molecular structures of the known compounds and also the new complexes Ti(6)O(6)(OAc)(6)(O(i)Pr)(6) center dot A C(6)H(14) (1) and Ti(12)O(12)(OAc)(6)(O(n)Pr)(18) (2).
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| 35. |
- Seisenbaeva, Gulaim, et al.
(författare)
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Self-Assembled Titania Micelles for Drug Delivery and Bio-Control Applications
- 2009
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Konferensbidrag (refereegranskat)abstract
- The modification of titanium alkoxides with hydrophylic and easily protonated ligands proposed in this work permits preparation of highly biocompatible and photochemically inactive titania sols and gels, capable of encapsulating living microorganisms and pharmaceuticals with the release mechanism controllable in a chemical and possibly even biochemical way via addition of chelating carboxylate ligands in solutions buffered at neutral pH
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| 36. |
- Seshagiri Rao, Nikhil, et al.
(författare)
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Flow cytometric analysis reveals culture condition dependent variations in phenotypic heterogeneity of Limosilactobacillus reuteri
- 2021
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 11
-
Tidskriftsartikel (refereegranskat)abstract
- Optimisation of cultivation conditions in the industrial production of probiotics is crucial to reach a high-quality product with retained probiotic functionality. Flow cytometry-based descriptors of bacterial morphology may be used as markers to estimate physiological fitness during cultivation, and can be applied for online monitoring to avoid suboptimal growth. In the current study, the effects of temperature, initial pH and oxygen levels on cell growth and cell size distributions of Limosilactobacillus reuteri DSM 17938 were measured using multivariate flow cytometry. A pleomorphic behaviour was evident from the measurements of light scatter and pulse width distributions. A pattern of high growth yielding smaller cells and less heterogeneous populations could be observed. Analysis of pulse width distributions revealed significant morphological heterogeneities within the bacterial cell population under non-optimal growth conditions, and pointed towards low temperature, high initial pH, and high oxygen levels all being triggers for changes in morphology towards cell chain formation. However, cell size did not correlate to survivability after freeze-thaw or freeze-drying stress, indicating that it is not a key determinant for physical stress tolerance. The fact that L. reuteri morphology varies depending on cultivation conditions suggests that it can be used as marker for estimating physiological fitness and responses to its environment.
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| 37. |
- Seshagiri Rao, Nikhil, et al.
(författare)
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Non-inhibitory levels of oxygen during cultivation increase freeze-drying stress tolerance in Limosilactobacillus reuteri DSM 17938
- 2023
-
Ingår i: Frontiers in Microbiology. - 1664-302X. ; 14
-
Tidskriftsartikel (refereegranskat)abstract
- The physiological effects of oxygen on Limosilactobacillus reuteri DSM 17938 during cultivation and the ensuing properties of the freeze-dried probiotic product was investigated. On-line flow cytometry and k-means clustering gating was used to follow growth and viability in real time during cultivation. The bacterium tolerated aeration at 500 ml/min, with a growth rate of 0.74 ± 0.13 h-1 which demonstrated that low levels of oxygen did not influence the growth kinetics of the bacterium. Modulation of the redox metabolism was, however, seen already at non-inhibitory oxygen levels by 1.5-fold higher production of acetate and 1.5-fold lower ethanol production. A significantly higher survival rate in the freeze-dried product was observed for cells cultivated in presence of oxygen compared to absence of oxygen (61.8 ± 2.4 % vs 11.5 ± 4.3 %), coinciding with a higher degree of unsaturated fatty acids (UFA:SFA ratio of 10 for air sparged vs 3.59 for N2 sparged conditions.). Oxygen also resulted in improved bile tolerance and boosted 5’nucleotidase activity (370 U/L vs 240 U/L in N2 sparged conditions) but lower tolerance to acidic conditions compared bacteria grown under complete anaerobic conditions which survived up to 90 min of exposure at pH 2. Overall, our results indicate the controlled supply of oxygen during production may be used as means for probiotic activity optimisation of L. reuteri DSM 17938.
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| 38. |
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| 39. |
- Svensson, Fredric, et al.
(författare)
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Hybrid Drug Delivery Patches Based on Spherical Cellulose Nanocrystals and Colloid Titania-Synthesis and Antibacterial Properties
- 2018
-
Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- Spherical cellulose nanocrystal-based hybrids grafted with titania nanoparticles were successfully produced for topical drug delivery. The conventional analytical filter paper was used as a precursor material for cellulose nanocrystals (CNC) production. Cellulose nanocrystals were extracted via a simple and quick two-step process based on first the complexation with Cu(II) solution in aqueous ammonia followed by acid hydrolysis with diluted H2SO4. Triclosan was selected as a model drug for complexation with titania and further introduction into the nanocellulose based composite. Obtained materials were characterized by a broad variety of microscopic, spectroscopic, and thermal analysis methods. The drug release studies showed long-term release profiles of triclosan from the titania based nanocomposite that agreed with Higuchi model. The bacterial susceptibility tests demonstrated that released triclosan retained its antibacterial activity against Escherichia coli and Staphylococcus aureus. It was found that a small amount of titania significantly improved the antibacterial activity of obtained nanocomposites, even without immobilization of model drug. Thus, the developed hybrid patches are highly promising candidates for potential application as antibacterial agents.
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| 40. |
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| 41. |
- Wessman, Per, et al.
(författare)
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Formulations for freeze-drying of bacteria and their influence on cell survival
- 2013
-
Ingår i: Journal of Visualized Experiments. - : MyJove Corporation. - 1940-087X. ; :78
-
Tidskriftsartikel (refereegranskat)abstract
- Cellular water can be removed to reversibly inactivate microorganisms to facilitate storage. One such method of removal is freeze-drying, which is considered a gentle dehydration method. To facilitate cell survival during drying, the cells are often formulated beforehand. The formulation forms a matrix that embeds the cells and protects them from various harmful stresses imposed on the cells during freezing and drying. We present here a general method to evaluate the survival rate of cells after freeze-drying and we illustrate it by comparing the results obtained with four different formulations: the disaccharide sucrose, the sucrose derived polymer Ficoll PM400, and the respective polysaccharides hydroxyethyl cellulose (HEC) and hydroxypropyl methyl cellulose (HPMC), on two strains of bacteria, P. putida KT2440 and A. chlorophenolicus A6. In this work we illustrate how to prepare formulations for freeze-drying and how to investigate the mechanisms of cell survival after rehydration by characterizing the formulation using of differential scanning calorimetry (DSC), surface tension measurements, X-ray analysis, and electron microscopy and relating those data to survival rates. The polymers were chosen to get a monomeric structure of the respective polysaccharide resembling sucrose to a varying degrees. Using this method setup we showed that polymers can support cell survival as effectively as disaccharides if certain physical properties of the formulation are controlled.
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| 42. |
- Wessman, Per, et al.
(författare)
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Impact of matrix properties on survival of freeze-dried bacteria
- 2011
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Ingår i: Journal of the Science of Food and Agriculture. - : Wiley. - 0022-5142 .- 1097-0010. ; 91:14, s. 2518-2528
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Disaccharides are in general first choice as formulation compounds when freezedrying microorganisms. Although polysaccharides and other biopolymers are considered too large to stabilize and interact with cell components in the same beneficial way as disaccharides, polymers have been reported to support cell survival. In the present study we compare the efficiency of sucrose, the polymers Ficoll, hydroxyethylcellulose, hydroxypropylmethylcellulose and polyvinylalcohol to support survival of three bacterial strains during freeze-drying. The initial osmotic conditions were adjusted to be similar for all formulations. Formulation characterization was used to interpret the impact that different compound properties had on cell survival. Results: Despite differences in molecular size, both sucrose and the sucrose based polymer Ficoll supported cell survival after freeze-drying equally well. All formulations became amorphous upon dehydration. Scanning electron microscopy and X-ray diffraction data showed that the discerned differences in structure of the dry formulations had little impact on the survival rates. The capability of the polymers to support cell survival correlated with the surface activity of the polymers in a similar way for all investigated bacterial strains. Conclusion: Polymer-based formulations can support cell survival as effectively as disaccharides if formulation properties of importance for maintaining cell viability are identified and controlled.
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| 43. |
- Önneby, Karin, et al.
(författare)
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Effects of di- and polysaccharide formulations and storage conditions on survival of freeze-dried Sphingobium sp.
- 2013
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Ingår i: World Journal of Microbiology & Biotechnology. - : Springer Science and Business Media LLC. - 0959-3993 .- 1573-0972. ; 29:8, s. 1399-1408
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Tidskriftsartikel (refereegranskat)abstract
- In this study we have compared the ability of the organic polymers Ficoll and hydroxyethylcellulose (HEC) and the disaccharides sucrose and trehalose to support cell survival during freeze-drying and subsequent storage of a gram-negative Sphingobium sp. In addition to determination of viability rates, cell integrity was evaluated using lipid peroxidation and RNA quality assays for the different storage conditions and formulation compositions. All formulations resulted in high initial cell survival rates after freeze-drying. However, the disaccharide formulations were superior to the polymer-based formulations in supporting cell survival during storage with the exception of Ficoll that upon storage under vacuum yielded bacterial survival rates equal to that of sucrose. Storage in the presence of both oxygen and moisture was detrimental for bacterial survival in all formulations tested, however, lipid peroxidation or RNA damages were not the controlling mechanisms for cell death in this system. The ability of Ficoll and HEC to support cell survival during freeze-drying show that organic polymers, expected to lack the water replacing capability of e.g. disaccharides, can successfully be used as lyoprotectants. For storage under vacuum conditions we suggest that the intracellular amount of sugars (i.e. trehalose), or other protective native cell components, is sufficient for a basic protection inside the bacteria cell and that the amorphous state is the most important aspect of the formulation excipient. However, when exposed to oxygen and moisture during storage this protection is not sufficient to prevent cell degeneration.
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| 44. |
- Önneby, Karin, et al.
(författare)
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Reduced leaching of the herbicide MCPA after bioaugmentation with a formulated and stored Sphingobium sp.
- 2014
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Ingår i: Biodegradation. - : Springer Science and Business Media LLC. - 0923-9820 .- 1572-9729. ; 25, s. 291-300
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Tidskriftsartikel (refereegranskat)abstract
- The use of pesticides on sandy soils and on many non-agricultural areas entails a potentially high risk of water contamination. This study examined leaching of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) after bioaugmentation in sand with differently formulated and stored Sphingobium sp. T51 and at different soil moisture contents. Dry formulations of Sphingobium sp. T51 were achieved by either freeze drying or fluidised bed drying, with high initial cell viability of 67-85 %. Storage stability of T51 cells was related to formulation excipient/carrier and storage conditions. Bacterial viability in the fluidised bed-dried formulations stored at 25 A degrees C under non-vacuum conditions was poor, with losses of at least 97 % within a month. The freeze-dried formulations could be stored substantially longer, with cell survival rates of 50 %, after 6 months of storage at the same temperature under partial vacuum. Formulated and long-term stored Sphingobium cells maintained their MCPA degradation efficacy and reduced MCPA leaching as efficiently as freshly cultivated cells, by at least 73 % when equal amounts of viable cells were used. The importance of soil moisture for practical field bioaugmentation techniques is discussed.
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