1,721,410 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
Intensified processes for methane production from olive mill wastewaters
No full textAnaerobic digestion is one of the most promising technologies for treating olive mill wastewaters (OMWs). However, low methane productivities are generally achieved with dispersed-growth bioreactors, which are usually employed in OMW digestion. The
methanogenic activity seems adversely affected by phenolic compounds, which are typically present in the OMWs and generally only slightly biodegraded in conventional anaerobic processes. In order to enhance the methane productivity, more efficient digester configurations were proposed: UASB and up-flow biofilm reactors resulted to be the most promising technologies applied to such an aim in the OMW anaerobic digestion.
In particular, a significant improvement of the performances of the OMW conventional anaerobic digestion was recently documented by performing it in a passively immobilized biomass loop reactor packed with Granular Activated Carbon (GAC). Under continuous conditions, the GAC-reactor exerted COD and phenols removal productivities higher than those averagely displayed by most of the
conventional and packed-bed laboratory-scale reactors previously proposed for the OMW digestion.
Thus, to investigate the reproducibility and the stability of the GAC-biofilm process, an identically configured reactor was developed and fed with a wide variety of higher organic loads. It appeared to be a reproducible and stable process whose performances were significantly higher than those displayed by most of the bench-scale
conventional and fixed-bed bioreactors proposed so far in the literature.
Finally, an aerobic post-treatment, constituted by a second up-flow biofilm reactor packed with SB, was developed and integrated to the GAC-anaerobic digester so to implement the GAC-digester decontamination potential
Biorefineries: the case study of olive mill wastewaters (OMWs)
No full textAgroindustrial wastes handling represents a serious economical and environmental concern. In some cases, large volumes of a toxic waste, such as olive mill wastewaters (OMWs), are produced within a short time in a limited area. In literature, a number of successful biotechnological approaches were attempted to reduce their toxic content while producing secondary metabolites of a certain industrial interest or biogas (CH4). However, to date the development of several biotechnological integrated processes aimed to fully recover or bioconvert the organic components naturally present in such wastes is a feasible option, and would allow their complete low-cost exploitation as renewable feedstocks in biorefineries.
In the present communication, a case study related to the exploitation of OMWs is presented. Firstly, solid phase extraction of the polyphenolic fraction occurring in OMWs was conducted. Phenols (PHEs) are natural antioxidant compounds of high commercial value. Selective removal almost completely abated PHEs concentration in OMWs, their subsequent recovery being carried out with biocompatible solvents (i.e., ethanol). Thereafter, dephenolized OMWs were fed to a packed-bed-biofilm reactor (PBBR) for the acidogenic digestion of its organic content by means of microbial consortia. The removal of antimicrobial compounds such as PHEs was found to significantly enhance volatile fatty acids (VFAs) production respect to non-pretreated OMWs. In the following step, electrodyalisis of the VFA enriched effluent was performed in order to further increase VFAs concentration. This process also produces a secondary effluent with a reduced VFA content, which was yet sufficient to allow (1) CH4 production in PBBRs loaded with microbial consortia, (2) biohydrogen production with photosynthetic bacteria or algae, or (3) photoheterotrophic growth of algal biomass.
The effluent further enriched in VFAs was fed to a second aerobic reactor loaded with microbial consortia for sustaining polyhydroxyalkanoates (PHAs) production and storage. PHAs are biodegradable and biocompatible microbial polymers which represent a renewable alternative to actual oil-derived plastics. Preliminary experiments showed that PHAs can be succesfully loaded with specific drugs, e.g., chlorexidine, which was then released leading to bacterial growth inhibition when in vitro tests with 3 strains of Streptococcus were carried out. This feature could be exploited in medical applications to deliver selected drugs in particular regions. Furthermore, it was observed that changes of the VFAs mixture fed for PHAs storage led to the synthesis of polymers with different chemico-physical properties. Therefore, culture conditions during acidogenic digestion could be adjusted in order to address the synthesis of desired biopolymers for following applications
Degradazione di microinquinanti organici nel processo di digestione anaerobica di fanghi contaminati
No full textA multi-step physicochemical-biotechnological approach for the valorization of olive mill wastewaters
No full textWaste valorization processes carried out through integrated multi-step biorefinery approaches can allow a massive exploitation of the waste organic matter. Olive mill wastewaters (OMWs) are agro-industrial wastes of a high environmental concern. A relevant part of their high COD is typically due to polyphenolic compounds, which are known to be toxic if concentrated to such extents. On the other hands, polyphenols are natural antioxidants of special relevance for several industrial sectors. Therefore, their recovery from OMWs provides the double opportunity to obtain high-added value biomolecules and to reduce the phytotoxicity of the effluent. To such an aim, an effective solid phase extraction process was recently developed [1]. The first aim of the present work was to define a protocol for the recovery and reuse of both the adsorbent (Amberlite XAD16 non-polar resin) and extraction solvent (ethanol), in order to verify the feasibility of a possible process scale-up. Very encouraging results were obtained: ethanol was recovered by means of a rotary evaporator, thus obtaining a concentrated phenolic mixture, whose antioxidant properties were demonstrated via ORAC and DPPH assays; furthermore, after its employment, the resin was washed with a sulphuric acid solution and regenerated: no significant losses of the resin adsorption capabilities were observed after 10 operation cycles. The exploitation of the OMW organic matter was further addressed toward the biotechnological production of biobased chemicals, such as H2 and volatile fatty acids (VFAs), which represent a feasible substrate for aerobic bacteria able to produce and store biopolymers such as polyhydroxyalkanoates (PHAs) [3]. A non conventional anaerobic digestion process carried out under acidogenic conditions for the obtainment of VFAs from dephenolized OMWs was recently developed [4]. The second aim of the present study was a further assessment of that process, with the aim of minimizing the process HRT. At a HRT = 5 days, a stable process capable of an effective bioconversion of the OMW organic matter into VFAs was obtained, with a VFA final concentration of about 19.7 gCOD/L, representing about 83% of the overall effluent COD.
References
[1] Bertin, L., Ferri, F., Scoma, A., Marchetti, L., Fava, F.: Recovery of high added value natural polyphenols from actual olive mill wastewater through solid phase extraction. Chem. Eng. J. 171, 1287-1293 (2011)
[2] Beccari, M., Bertin, L., Dionisi, D., Fava, F., Lampis, S., Majone, M., Valentino, F., Vallini, G., Villano, M.,: Exploiting olive oil mill effluents as a renewable resource for production of biodegradable polymers through a combined anaerobiceaerobic process. J. Chem. Technol. Biotechnol. 84, 901-908 (2009)
[3] Scoma, A., Bertin, L., Zanaroli, G., Fraraccio, S., Fava, F.: A physicochemical–biotechnological approach for an integrated valorization of olive mill wastewater. Biores. Technol. 102, 10273-10279 (2011
Anaerobic digestion of the mechanically sorted organic fraction of a municipal solid waste and its co-digestion with manure in packed-bed biofilm systems under batch conditions
No full textPacked-bed systems, consisting of 0.5 L-flask filled with tire chips or ceramic cubes, were employed in the wet batch mesophilic anaerobic digestion of a mechanically sorted organic fraction of a municipal solid waste and in its co-digestion with manure. High methane production only occurred in the latter case. Successive batch experiments demonstrated the advantages of packed-bed biofilm systems, which displayed significantly higher methane production yields with no lag-phases. Tire chips, i.e. a non-cost recyclable non-biodegradable material, provide results similar to those of ceramic cubes. The highest methane yields were achieved in the bioreactors packed with tire chips in the presence of a mixture in which the VS provided by the municipal waste represented 48% of the total waste VS. Under such conditions, the methane yield was about 70 ml/g volatile solids, representing about the 42% of the biochemical methane potential, and the 41% of the initial VS were removed
Acclimatization of methanogen consortium capable to digest relevant percentages of municipal solid waste in codigestion with cattle manure
No full textThe acclimatization of an anaerobic consortium capable of producing methane through the co-digestion of municipal solid waste (MSW) and cattle manure was achieved through a fed batch procedure1. Anaerobic microcosms consisting of 46 mL of pre-treated MSW were set up under strictly anaerobic conditions and statically incubated at 35°C. MSW volatile solids (VS) were from 60 to 100% of the mixture applied. Four successive 1-month batch experiments were performed by leaving 10% (v/v) of the digested sludge in the bottles and refilling them with the corresponding fresh cattle manure amended MSW. Biogas production and composition as well as VS, volatile fatty acids and electron acceptors occurring in the microcosms were investigated together with the structure and composition (via DGGE analysis) of microbial population responsible for the MSW digestion. Biogas and CH4 production increased significantly from the 1st to 4th batch experiment, especially where higher amounts of cattle manure were applied (i.e., about 160 mlCH4/gVS, representing the 41% of the total biogas produced, by digesting MSW with 60% of total VS).
1. Bertin, L.; Todaro, D.; Bettini, C.; Fava, F. Wat. Sci. Technol. 2008, 58(9), 1735-1742
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
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