1,720,958 research outputs found
Biodegrading biofilms on biopolymeric sorbent scaffolds
No full textAbstract
Immobilization of hydrocarbon-degrading microorganisms on biodegradable adsorbing scaffolds significantly promotes bioremediation processes in fresh and sea water . Recently low cost, ecofriendly bioremediation devices based on polycaprolactone and polylactic acid membranes hosting a biodegrading bacterial biofilm were obtained [1]. The resulting biosorbent biodegrading biofilms simultaneously adsorbed 100 % of spilled oil and biodegraded more than 66% of it over 10 days; biodegradation was 23% higher than that obtained using free living bacteria [1]. In this work, adhesion, survival and HC-biodegradation ability of these biodegrading biofilms was tested in long term experiments and under dry conditions mimicking smog-contaminated air. The HC-degrading Actinobacteria Nocardia cyriacigeorgica strain SoB, Gordonia amicalis strain SoCg [2], and
the marine hydrocarbonoclastic Alcanivorax borkumensis strain AU3-AA-7 [3] were immobilized on polylactic acid (PLA) and polycaprolactone (PCL) membranes prepared by electrospinning [1]. The capacity of adhesion and proliferation of bacterial cells into the biopolymers were evaluated using scanning electron microscopy (SEM) after 5, 10, 15 and 30 days. PLA and PCL nanofibers appear almost completely covered by
a complex three dimensional bacterial film for all the strains. Total biomass (estimated as total dsDNA) confirmed biofilm growth up to 30 days incubation. Viable plate counts and Gas Chromatography-FID analysis revealed that the biofilm was vital and functional after 30 days. Exposing a 15-day liquid incubated
biofilms to further 15 days in a hexadecane-saturated air chamber reduced by 100fold plate count yeld.
Bibliography: [1] Catania V., Lopresti F., Cappello S., Scaffaro R. and Quatrini P. (2020). N Biotechnol, 58, 25-31. [2] Quatrini P., Scaglione G., De Pasquale C., Riela S. and Puglia A.M. (2008). J. Appl. Microbiol.,104(1),251-259. [3] Catania V., Santisi S., Signa G., Vizzini S., Mazzola A., Cappello S.,. Yakimov M.M. and Quatrini P. (2015). Mar. Pollut. Bull., 99(1-2), 138-149.
Acknowledgments: Elisa Maria Petta’s PhD grant is financed by PON "Research and Innovation" 2014-2020, Axis IV "Education and
research for recovery" Action IV.5 "PhDs on green issues
BIODEGRADING BIOFILMS ON INNOVATIVE BIOPOLYMERIC SUPPORTS
No full textABSTRACT
Water bioremediation is traditionally carried out using ‘ free ’ bacterial cells, however, in recent years, utilization of ‘immobilized’ bacterial cells on adsorbing matrices, has gained attention as a promising technique due to biotechnological and economic benefits (Sonawane et al., 2022). Bacterial biofilms show greater resilience, survival and degradative activity for longer periods than cells in the planktonic state (Alessandrello et al., 2017); moreover immobilization reduces bioremediation costs, eliminate cell dilution and dispersion in the environment (Bayat et al., 2015). Possible applications of immobilized biodegrading bacteria require long-term survival and maintenance of biodegrading performances. In this study, combinations of polylactic acid (PLA) and polycaprolactone (PCL) biodegradable membrane carriers hosting selected HC-biodegrading marine and soil bacterial biofilms were tested after different incubation periods and their survival was monitored over time, simulating storage effects.
Results
Soil hydrocarbon (HC) degrading actinobacteria and marine hydrocarbonoclastic bacteria were immobilized on absorbent biodegradable biopolymeric polylactic acid (PLA) and polycaprolactone (PCL) membranes (Scaffaro et al., 2017, Catania et al., 2020). Combinations of HC-degrading bacteria and biopolymers were obtained and tested on hexadecane. After 5, 10 and 15 days incubation, the capacity of adhesion and proliferation of bacterial cells into the biopolymers was verified by scanning electron microscopy (SEM); PLA and PCL nanofibers were covered by bacterial cells already after 5 days incubation; Total biomass (estimated as total dsDNA) extracted from biofilms confirmed the colonization up to 15 days incubation. Viable plate counts showed that survival of the bacterial strains was high for the entire experimental period. HC biodegradation ability of biofilms was assessed by high resolution GC-FID analysis, after extraction of total residual HC from the liquid medium and from biopolymers, incubated for different times. HC degradation was observed during the whole experiment and resulted higher in respect to the free-living bacterial cultures. Survival tests of bacterial biofilms adsorbed on biopolymers for up to 30 days are in progress.
Conclusions
The synergistic exploitation of the high absorbent capacity of biodegradable nanofiber membranes and the catabolic capacity of HC-degrading bacteria allow to obtain biodegrading biofilms endowed with higher removal capacity of hexadecane in respect to free-living bacterial cultures. The survival and biodegrading performances of the biofilm-carrier systems is maintained after 30 days incubation. A green, low-cost, biodegradable and reusable bioremediation tool is obtained without negative impacts on the environment.
References:
Alessandrello, M. J., Tomás, M. S. J., Raimondo, E. E., Vullo, D. L. and Ferrero, M. A. “Petroleum oil removal by immobilized bacterial cells on polyurethane foam under different temperature conditions”, Marine pollution bulletin, 122(1-2), 156-160 (2017).
Bayat, Z., Hassanshahian, M. and Cappello, S. “Immobilization of microbes for bioremediation of crude oil polluted environments: a mini review”, The open microbiology journal, 9, 48 (2015).
Catania, V., Lopresti, F., Cappello, S., Scaffaro, R. and Quatrini, P. “Innovative, ecofriendly biosorbent-biodegrading biofilms for bioremediation of oil-contaminated water”, New Biotechnology, 58, 25-31 (2020).
Scaffaro, R., Lopresti, F., Catania, V., Santisi, S., Cappello, S., Botta, L. and Quatrini, P. “Polycaprolactone-based scaffold for oil-selective sorption and improvement of bacteria activity for bioremediation of polluted water: Porous PCL system obtained by leaching melt mixed PCL/PEG/NaCl composites: Oil uptake performance and bioremediation efficiency”, European Polymer Journal, 91, 260-273 (2017).
Sonawane, J. M., Rai, A. K., Sharma, M., Tripathi, M. and Prasad, R. “Microbial biofilms: Recent advances and progress in environmental bioremediation”, Science of The Total Environment, 153843 (2022).
Catania, V., Santisi, S., Signa, G., Vizzini, S., Mazzola, A., Cappello, S., ... & Quatrini, P. (2015). Intrinsic bioremediation potential of a chronically polluted marine coastal area. Marine Pollution Bulletin, 99(1-2), 138-149.
Lo Piccolo, L., De Pasquale, C., Fodale, R., Puglia, A. M., & Quatrini, P. (2011). Involvement of an alkane hydroxylase system of Gordonia sp. strain SoCg in degradation of solid n-alkanes. Applied and environmental microbiology, 77(4), 1204-1213.
Quatrini, P., Scaglione, G., De Pasquale, C., Riela, S., & Puglia, A. M. (2008). Isolation of Gram‐positive n‐alkane degraders from a hydrocarbon‐contaminated Mediterranean shoreline. Journal of applied microbiology, 104(1), 251-259
1,2-DICHLOROETHANE CONTAMINATED AQUIFER: MICROBIAL COMMUNITY RESPONSE TO BIOSTIMULATION IN MICROCOSM
No full textBacterial biofilms for environmental bioremediation
Full text linkBioremediation is a promising technology for the treatment of polluted environments based on the
biodegradation capacities of native or introduced microbial populations. Bioremediation is
traditionally carried out using free bacterial cells, though utilization of immobilized bacterial cells on
adsorbing matrices is a promising technique due to biotechnological and economic benefits.
Bacterial biofilms show greater resilience, survival and degradative activity for longer periods than
cells in the planktonic state. A bioremediation system was developed immobilizing highly performant
hydrocarbon (HC)-degrading bacteria on biodegradable oil-absorbing biopolimeric carriers. Soil HC
degrading Actinobacteria Nocardia cyriacigeorgica SoB, Gordonia amicalis SoCg [1], and marine
hydrocarbonoclastic Gammaproteobacteria Alcanivorax borkumensis AU3-AA-7 [2] were
immobilized on polylactic acid (PLA) and polycaprolactone (PCL) membranes prepared by
electrospinning [3]. The capacity of adhesion and proliferation of bacterial cells into the biopolymers
were evaluated using scanning electron microscopy (SEM) after 5, 10 and 15 days, and their survival
was monitored over time simulating storage effects. PLA and PCL nanofibers were covered by
bacterial cells already after 5 days incubation. Total biomass (estimated as total dsDNA) extracted
from biofilms confirmed the colonization up to 15 days incubation. Viable plate counts showed that
survival of the bacterial strains was high for the entire experimental period, and bacterial biofilms
adsorbed on biopolymers were still viable after 30 days. HC biodegradation ability of biofilms,
assessed by GC-FID analysis, resulted higher in respect to the corresponding free-living bacterial
cultures. Expression of the biodegradative genes in biofilms are in progress. References
[1] P. Quatrini, G. Scaglione, C. De Pasquale, S. Riela and A.M. Puglia, Isolation of Gram-positive n-alkane
degraders from a hydrocarbon-contaminated Mediterranean shoreline, Journal of applied microbiology, 2008,
104(1), 251-259. https://doi.org/10.1111/j.1365-2672.2007.03544.x
[2] V. Catania, S. Santisi, G. Signa, S. Vizzini, A. Mazzola, S Cappello, M. M. Yakimov and P. Quatrini, Intrinsic
bioremediation potential of a chronically polluted marine coastal area, Marine Pollution Bulletin, 2015, 99(1-2),
138-149. https://doi.org/10.1016/j.marpolbul.2015.07.042
[3] V. Catania, F. Lopresti, S. Cappello, R. Scaffaro and P. Quatrini, Innovative, ecofriendly biosorbent
biodegrading biofilms for bioremediation of oil-contaminated water, New Biotechnology, 2020, 58, 25-31.
https://doi.org/10.1016/j.nbt.2020.04.00
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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