1,721,051 research outputs found
Biodegradation of oil-based plastics in the environment: Existing knowledge and needs of research and innovation
No full textThe production of synthetic oil-based plastics has led to the accumulation of huge amounts of the plastic waste in the environment, especially in the marine system, very often the final sink for many types of conventional wasted plastics. In particular, (micro)plastics account for the majority of litter items in the marine environment and a high percentage of such litter is originating from land sources. Attempts to mitigate the harmful effects of conventional plastics such as the development of novel management strategies together with the gradual substitution of them with biodegradable (bio)plastics are representing future solutions. However, high amounts of conventional plastics have been accumulating in the environment since several years. Although many studies reported on their potential biodegradation by microbes in and from terrestrial environments, very little is known about the biodegradability of these plastics in freshwater systems and only recently more reports on their biodegradation by marine microorganisms/in marine environment were made available. In this review, we first provide a summary of the approaches applied for monitoring and assessing conventional plastics biodegradation under defined conditions. Then, we reviewed historical and recent findings related to biodegradation of four major plastics produced in European Union (EU), i.e. Polyethylene, Polyvinyl Chloride, Polypropylene and Polystyrene, in terrestrial and aquatic environments and by pure and mixed microbial cultures obtained from them
Mediterranean Sea bacteria as a potential source of long-chain polyunsaturated fatty acids
No full textLong-chain polyunsaturated fatty acids (LC-PUFAs), including EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are important nutritional ingredients in fish feed. So far, fish oil has been used as a main source of LC-PUFAs; however, the limited global supply of fish oil is not able to meet the demand of the growing aquaculture sector. Hence, sustainability of aquaculture industry could be supported by searching alternative sources of these compounds. Marine microorganisms represent a sustainable and stable supply source of LC-PUFAs. A collection of 209 bacterial isolates obtained from sediment samples recovered in the Mediterranean Sea was screened in order to select new LC-PUFAs producers. Among 95 putative producers selected based on colourimetric screening, 31 quickly growing were selected for further studies. The detection of LC-PUFAs was confirmed from 15 isolates belonging to the genera Marinobacter, Halomonas and Thalassospira by GC-FID analysis. Among them, the isolate Marinobacter sp. G16.20 was found to be a potentially high LC-PUFA producer exhibiting relatively high levels of DHA in particular (maximum productivity of 1.85 ± 0.371 mg/g, representing 45.89% of the total fatty acids detected and identified). Microorganisms belonging to the genera reported in this study showed biotechnological traits interesting for their potential future application in aquaculture
Characterization of polyvalent and safe Bacillus thuringiensis strains with potential use for biocontrol
No full textSixteen Bacillus thuringiensis (Bt) strains were screened for their anti-insect, antibacterial and antifungal determinants by phenotypic tests and PCR targeting major insecticidal proteins and complements, chitinases, lactonases, β-1,3-glucanases and zwittermicinA. Six strains had genes of at least two major insecticidal toxins and of insecticidal complements. With regard to fungal biocontrol, all the strains inhibited Fusarium oxysporum and Aspergillus flavus growth and four strains had all or most of the antifungal determinants examined, with strain Bt HD932 showing the widest antifungal activity spectrum. Autolysins, bacteriocin and AHL-lactonases were produced by all or most of the tested strains with different activity spectra including pathogens like Listeria monocytogenes. Safety evaluation was carried out via PCR by screening the B. cereus psychrotolerance-related genes, toxin genes and the virulence pleiotropic regulator plcR. Diarrheal enterotoxins and other toxin genes were widespread among the collection with strains Bt HD9 and H45 lacking psychrotolerance-related genes, while five strains were positive. Only three strains (BMG1.7, H172, H156) resulted positive with primer sets targeting partial or complete plcR gene. By Vero Cell Assays, Bt HD868 followed by Bt HD9 were shown to be the safest strains. These polyvalent and safe Bt strains could be very promising in field applicatio
Polyvinyl chloride biodegradation by Pseudomonas citronellolis and Bacillus flexus
Full text linkThe accumulation of high amounts of petroleum-derived plastics in the environment has raised ecological and health concerns. The aim of this work was to study the biodegradative abilities of five bacterial strains, namely Pseudomonas chlororaphis, Pseudomonas citronellolis, Bacillus subtilis, Bacillus flexus and Chelatococcus daeguensis, towards polyethylene, polypropylene, polystyrene and polyvinyl chloride films under aerobic conditions. Preliminary screening resulted in the selection of P. citronellolis and B. flexus as potential PVC film degraders. Both strains were able to form a biofilm on the plastic film surface and to cause some modifications to the FTIR spectra of biomass-free PVC films. The two strains were then used to set up a PVC film biodegradation assay in 2-liter flasks. After 45 days incubation, fragmentation of the film was observed, suggesting that PVC biodegradative activity took place. Gel permeation chromatography analysis showed a reduction in average molecular weight of 10% for PVC incubated with P. citronellolis, with PVC polymer chains apparently attacked. Based on these results, the P. citronellolis strain was selected for biodegradation assays of two waste PVC films, used either nonsterile or subjected to ethanol sterilization. Chemical analyses on the incubated films confirmed the biodegradation of waste PVC plastics as shown by a gravimetric weight loss of up to about 19% after 30 days incubation. In summary, this work reports the biodegradation of PVC films by P. citronellolis and B. flexus. Both strains were shown to act mainly against PVC additives, exhibiting a low biodegradation rate of PVC polymer
Effect of alcohols on growth and biodiesel waste glycerol fermentation to 1,3-propanediol by Citrobacter freundii DSM 15979 strain
No full textbiomolecules
Marinobacter sp. from marine sediments produce highly stable surface-active agents for combatting marine oil spills
Full text linkBackground: The application of chemical dispersants as a response to marine oil spills is raising concerns related to their potential toxicity also towards microbes involved in oil biodegradation. Hence, oil spills occurring under marine environments necessitate the application of biodispersants that are highly active, stable and effective under marine environment context. Biosurfactants from marine bacteria could be good candidates for the development of biodispersant formulations effective in marine environment. This study aimed at establishing a collection of marine bacteria able to produce surface-active compounds and evaluating the activity and stability of the produced compounds under conditions mimicking those found under marine environment context.Results: A total of 43 different isolates were obtained from harbor sediments. Twenty-six of them produced mainly bioemulsifiers when glucose was used as carbon source and 16 were biosurfactant/bioemulsifiers producers after growth in the presence of soybean oil. Sequencing of 16S rRNA gene classified most isolates into the genus Marinobacter. The produced emulsions were shown to be stable up to 30 months monitoring period, in the presence of 300 g/l NaCl, at 4 °C and after high temperature treatment (120 °C for 20 min). The partially purified compounds obtained after growth on soybean oil-based media exhibited low toxicity towards V. fischeri and high capability to disperse crude oil on synthetic marine water.Conclusions: To the best of our knowledge, stability characterization of bioemulsifiers/biosurfactants from the non-pathogenic marine bacterium Marinobacter has not been previously reported. The produced compounds were shown to have potential for different applications including the environmental sector. Indeed, their high stability in the presence of high salt concentration and low temperature, conditions characterizing the marine environment, the capability to disperse crude oil and the low ecotoxicity makes them interesting for the development of biodispersants to be used in combatting marine oil spills
Microbial Exopolysaccharides as Alternative Sources of Dietary Fibers with Interesting Functional and Healthy Properties
No full textTraditional polysaccharides obtained from plants may suffer from a lack of reproducibility in their rheological properties, purity, supply and cost. Most of the used plant polysaccharides are chemically modified to improve their characteristics. Microbial exopolysaccharides (EPSs) are principally composed of carbohydrate polymers, and they are produced by many microorganisms including bacteria, yeasts and fungi. Microorganisms can synthesize EPSs and excrete them out of cell either as soluble or insoluble polymers. These EPSs are able not only to protect the microorganisms themselves against desiccation, phage attack, antibiotics or toxic compounds, but also can be applied in several biotechnological applications. In food products they increase the dietary fiber content and can be used as viscosifiers, stabilizers, emulsifiers or gelling agents to improve physical and structural properties of water and oil holding capacity, viscosity, texture, sensory characteristics and shelf-life. EPSs are used as additives in various foods, such as dairy products, jams and jellies, wine and beer, fishery and meat products, icings and glazes, frozen foods and bakery products. Over the past few decades, interest in using microbial EPSs in food processing has been increasing because of main reasons such as easy production, better rheological and stability characteristics, cost effectiveness and supply. Dextran, xanthan, pullulan, curdlan, levan and gellan and alginate are the main examples of industrially important microbial exopolysaccharides. They also play crucial role in conferring beneficial physiological effects on human health, such as the ability to lower pressure and to reduce lipid level in blood. Furthermore, these EPSs exhibit antitumor, immunomodulating, antioxidant and antibacterial properties. The utility of various biopolymers are dependent on their monosaccharide composition, type of linkages present, degree of branching and molecular weight.
In the present chapter, an attempt was taken to recapitulate the most important polysaccharides isolated from microorganisms as well as the main methods for microbial exopolysaccharide production, purification and structural characterization. In addition, the functional and healthy benefits of EPSs and their applications in food industry were described
Analysis of lactic-acid bacteria succession by length heterogeneity-PCR during maize ensiling in response to different fermentation conditions
No full textBiotechnology for a Sustainable Aquaculture: Selection of Safe Marine Bacteria Producers of LC-PUFAs and Antimicrobials
Full text linkThe contribution of aquaculture to global food production in the fishing industry is expanding. The sustainability of the sector urge aquaculture industry to develop processes aimed at improving quantity and quality of fish, containing costs, reducing environmental threats by minimizing wastes and valorizing by-products.
Several studies were carried out on the valorisation of fishing industry by-products/wastes and many of the products obtained are available in commerce. However, only very few reports are available on the selection/application of probiotics in aquaculture as well as on the use of antimicrobial compounds from microbial origin for the control of bacterial pathogens. In this context, the aim of the research activity is to select novel safe marine bacteria able to produce LC-PUFAs and/or antimicrobial compounds active against aquaculture fish pathogenic bacteria with the perspective of their application in aquaculture.
The first part of the work has been dedicated to the selection of LC-PUFAs bacterial producers. For this purpose, 209 marine bacterial isolates from the Mediterranean Sea was screened in order to select new LC-PUFAs, EPA and DHA bacterial producers. After colourimetric screening, ITS typing, GC-FID analysis and molecular identification of marine isolates, different Marinobacter sp., Thalassospira sp and Halomonas sp. isolates could produce DHA.
41 isolates was screened for the production of antimicrobial compounds exhibiting activity against farmed fish pathogens. After screening and preliminary characterization, were selected 8 marine bacterial isolates able to produce stable compounds.
In conclusion 10 strains able to produce both antimicrobial compounds active against different aquaculture fish pathogenic bacteria and LC-PUFAs were selected. These results are interesting and promising since these isolates belong to bacterial species that have never been reported to be involved in human or animal pathology and exhibited traits that give them high potential for the application in aquaculture in order to optimize fish production
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