The path to next generation biofuels: successes and challenges in the era of synthetic biology

Volatility of oil prices along with major concerns about climate change, oil supply security and depleting reserves have sparked renewed interest in the production of fuels from renewable resources. Recent advances in synthetic biology provide new tools for metabolic engineers to direct their strategies and construct optimal biocatalysts for the sustainable production of biofuels. Metabolic engineering and synthetic biology efforts entailing the engineering of native and de novo pathways for conversion of biomass constituents to short-chain alcohols and advanced biofuels are herewith reviewed. In the foreseeable future, formal integration of functional genomics and systems biology with synthetic biology and metabolic engineering will undoubtedly support the discovery, characterization, and engineering of new metabolic routes and more efficient microbial systems for the production of biofuels

Intensification of the aerobic bioremediation of an actual site soil historically contaminated by polychlorinated biphenyls (PCBs) through bioaugmentation with a non acclimated, complex source of microorganisms

BACKGROUND: The biotreatability of actual-site polychlorinated biphenyl (PCB)-contaminated soils is often limited by their poor content of autochthonous pollutant-degrading microorganisms. In such cases, inoculation might be the solution for a successful bioremediation. Some pure and mixed cultures of characterized PCB degrading bacteria have been tested to this purpose. However, several failures have been recorded mostly due to the inability of inoculated microbes to compete with autochthonous microflora and to face the toxicity and the scarcity of nutrients occurring in the contaminated biotope. Complex microbial systems, such as compost or sludge, normally consisting of a large variety of robust microorganisms and essential nutrients, would have better chances to succeed in colonizing degraded contaminated soils. However, such sources of microorganisms have been poorly applied in soil bioremediation and in particular in the biotreatment of soil with PCBs. Thus, in this study the effects of Enzyveba, i.e. a consortium of non-adapted microorganisms developed from composted material, on the slurry- and solid-phase aerobic bioremediation of an actual-site, aged PCB-contaminated soil were studied. RESULTS: A slow and only partial biodegradation of low-chlorinated biphenyls, along with a moderate depletion of initial soil ecotoxicity, were observed in the not-inoculated reactors. Enzyveba significantly increased the availability and the persistence of aerobic PCB- and chlorobenzoic acid-degrading cultivable bacteria in the bioreactors, in particular during the earlier phase of treatment. It also markedly enhanced PCB-biodegradation rate and extent (from 50 to 100%) as well as the final soil detoxification, in particular under slurry-phase conditions. Taken together, data obtained suggest that Enzyveba enhanced the biotreatability of the selected soil by providing exogenous bacteria and fungi able to remove inhibitory or toxic intermediates of PCB biodegradation and/or exogenous nutrients able to sustain microorganisms in charge for PCB mineralization. CONCLUSION: Enzyveba appears a promising agent for bioaugmenting actual-site PCB-polluted soils with a native low content of indigenous specialized microflora. This not only for its positive effects on the soil biotreatability but also for its availability on the market at a relatively low cost

Properties of poly(vinyl alcohol) films as determined by thermal curing and addition of polyfunctional organic acids

The aim of the study was to assess the effect of the addition of citric and malic acid and heat curing on the mechanical, physical and optical properties of poly(vinyl alcohol) (PVOH) films. The addition of the organic acids without successive thermal treatments has a mere plasticising effect, while their application with heat curing has a combined crosslinking and plasticising effect. While conventional plasticizers and crosslinkers improve either extensibility or tensile strength of films, respectively, the addition of citric and malic acid coupled with heat curing determined good tensile strength and extensibility. Hydrophilicity was significantly reduced by thermal curing and even further reduced with the organic acids addition. The high transparency of the PVOH films was not affected either by heat-curing, acid addition and their combination, while the use of high curing temperature coupled with acid addition caused a slight yellowing of the films. The use of citric and malic acid in combination with thermal curing is a viable strategy for tailoring the performances of PVOH films thus broadening their spectrum of application

Improvement of Paper Resistance against Moisture and Oil by Coatings with Poly(-3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and Polycaprolactone (PCL)

Surface hydrophobicity and grease resistance of paper may be achieved by the application of coatings usually derived from fossil-oil resources. However, poor recyclability and environmental concerns on generated waste has increased interest in the study of alternative paper coatings. This work focuses on the study of the performances offered by two different biopolymers, poly(3hydroxybutyrate-co-3hydroxyvalerate) (PHBV) and polycaprolactone (PCL), also assessing the effect of a plasticizer (PEG) when used as paper coatings. The coated samples were characterized for the structural (by scanning electron microscopy, SEM), diffusive (water vapor and grease barrier properties), and surface properties (affinity for water and oil, by contact angle measurements). Samples of polyethylene-coated and fluorinated paper were used as commercial reference. WVTR of coated samples generally decreased and PHBV and PCL coatings with PEG at 20% showed interesting low wettability, as inferred from the water contact angles. Samples coated with PCL also showed increased grease resistance in comparison with plain paper. This work, within the limits of its lab-scale, offers interesting insights for future research lines toward the development of cellulose-based food contact materials that are fully recyclable and compostable

Vanillin production using metabolically engineered Escherichia coli under non-growing conditions

BACKGROUND: Vanillin is one of the most important aromatic flavour compounds used in the food and cosmetic industries. Natural vanillin is extracted from vanilla beans and is relatively expensive. Moreover, the consumer demand for natural vanillin highly exceeds the amount of vanillin extracted by plant sources. This has led to the investigation of other routes to obtain this flavour such as the biotechnological production from ferulic acid. Studies concerning the use of engineered recombinant Escherichia coli cells as biocatalysts for vanillin production are described in the literature, but yield optimization and biotransformation conditions have not been investigated in details. RESULTS: Effect of plasmid copy number in metabolic engineering of E. coli for the synthesis of vanillin has been evaluated by the use of genes encoding feruloyl-CoA synthetase and feruloyl hydratase/aldolase from Pseudomonas fluorescens BF13. The higher vanillin production yield was obtained using resting cells of E. coli strain JM109 harbouring a low-copy number vector and a promoter exhibiting a low activity to drive the expression of the catabolic genes. Optimization of the bioconversion of ferulic acid to vanillin was accomplished by a response surface methodology. The experimental conditions that allowed us to obtain high values for response functions were 3.3 mM ferulic acid and 4.5 g/L of biomass, with a yield of 70.6% and specific productivity of 5.9 μmoles/g × min after 3 hours of incubation. The final concentration of vanillin in the medium was increased up to 3.5 mM after a 6-hour incubation by sequential spiking of 1.1 mM ferulic acid. The resting cells could be reused up to four times maintaining the production yield levels over 50%, thus increasing three times the vanillin obtained per gram of biomass. CONCLUSION: Ferulic acid can be efficiently converted to vanillin, without accumulation of undesirable vanillin reduction/oxidation products, using E. coli JM109 cells expressing genes from the ferulic acid-degrader Pseudomonas fluorescens BF13. Optimization of culture conditions and bioconversion parameters, together with the reuse of the biomass, leaded to a final production of 2.52 g of vanillin per liter of culture, which is the highest found in the literature for recombinant strains and the highest achieved so far applying such strains under resting cells conditions

A review on slurry bioreactors for bioremediation of soils and sediments

The aim of this work is to present a critical review on slurry bioreactors (SB) and their application to bioremediation of soils and sediments polluted with recalcitrant and toxic compounds. The scope of the review encompasses the following subjects: (i) process fundamentals of SB and analysis of advantages and disadvantages; (ii) the most recent applications of SB to laboratory scale and commercial scale soil bioremediation, with a focus on pesticides, explosives, polynuclear aromatic hydrocarbons, and chlorinated organic pollutants; (iii) trends on the use of surfactants to improve availability of contaminants and supplementation with degradable carbon sources to enhance cometabolism of pollutants; (iv) recent findings on the utilization of electron acceptors other than oxygen; (v) bioaugmentation and advances made on characterization of microbial communities of SB; (vi) developments on ecotoxicity assays aimed at evaluating bioremediation efficiency of the process

Isolation and characterisation of polychlorinated biphenyl (PCB) degrading fungi from a historically contaminated soil

<p>Abstract</p> <p>Background</p> <p>Polychlorinated biphenyls (PCBs) are widespread toxic pollutants. Bioremediation might be an effective, cost competitive and environment-friendly solution for remediating environmental matrices contaminated by PCBs but it is still unsatisfactory, mostly for the limited biodegradation potential of bacteria involved in the processes. Very little is known about mitosporic fungi potential in PCB bioremediation and their occurrence in actual site historically contaminated soils. In the present study, we characterised the native mycoflora of an aged dump site soil contaminated by about 0.9 g kg^-1of Aroclor 1260 PCBs and its changing after aerobic biotreatment with a commercial complex source of bacteria and fungi. Fungi isolated from the soil resulting from 120 days of treatment were screened for their ability to adsorb or metabolise 3 target PCBs.</p> <p>Results</p> <p>The original contaminated soil contained low loads of few fungal species mostly belonging to the Scedosporium, Penicillium and Aspergillus genera. The fungal load and biodiversity generally decreased throughout the aerobic treatment. None of the 21 strains isolated from the treated soil were able to grow on biphenyl (200 mg L^-1) or a mixture of 2-chlorobiphenyl, 4,4'-dichlorobiphenyl and 2,2',5,5'-tetrachlorobiphenyl (20 mg L^-1each) as sole carbon sources. However, 16 of them grew in a mineral medium containing the same PCBs mixture and glucose (10 g L^-1). Five of the 6 isolates, which displayed the faster and more extensive growth under the latter conditions, were found to degrade the 3 PCBs apparently without the involvement of ligninolytic enzymes; they were identified as Penicillium chrysogenum, Scedosporium apiospermum, Penicillium digitatum and Fusarium solani. They are the first PCB degrading strains of such species reported so far in the literature.</p> <p>Conclusion</p> <p>The native mycoflora of the actual site aged heavily contaminated soil was mainly constituted by genera often reported as able to biodegrade organopollutants. It was generally remarkably reduced after the biotreatment, which however resulted in the selection of few mitosporic fungal species able to biodegrade PCBs. This is the first study in which an extensive characterisation of the cultivable indigenous mycoflora of an actual site aged PCB contaminated soil, as well as its changes upon soil bioremediation treatment, was conducted. Moreover, this is the first paper in which 5 strains ascribable to 4 mitosporic species able to biodegrade PCB are reported in the literature.</p

D1 and D2 inhibitions of the soleus H-reflex are differentially modulated during plantarflexion force and position tasks

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Presynaptic inhibition (PSI) has been shown to modulate several neuronal pathways of functional relevance by selectively gating the connections between sensory inputs and spinal motoneurons, thereby regulating the contribution of the stretch reflex circuitry to the ongoing motor activity. In this study, we investigated whether a differential regulation of Ia afferent inflow by PSI may be associated with the performance of two types of plantarflexion sensoriomotor tasks. The subjects (in a seated position) controlled either: 1) the force level exerted by the foot against a rigid restraint (force task, FT); or 2) the angular position of the ankle when sustaining inertial loads (position task, PT) that required the same level of muscle activation observed in FT. Subjects were instructed to maintain their force/position at target levels set at similar to 10% of maximum isometric voluntary contraction for FT and 90 degrees for PT, while visual feedback of the corresponding force/position signals were provided. Unconditioned H-reflexes (i.e. control reflexes) and H-reflexes conditioned by electrical pulses applied to the common peroneal nerve with conditioning-to-test intervals of 21 ms and 100 ms (corresponding to D1 and D2 inhibitions, respectively) were evoked in a random fashion. A significant main effect for the type of the motor task (FT vs PT) (p = 0.005, eta(2)(p) = 0.603) indicated that PTs were undertaken with lower levels of Ia PSI converging onto the soleus motoneuron pool. Additionally, a significant interaction between the type of inhibition (D1 vs D2) and the type of motor task (FT vs PT) (p = 0.038, eta(2)(p) = 0.395) indicated that D1 inhibition was associated with a significant reduction in PSI levels from TF to TP (p = 0.001, eta(2)(p) = 0.731), whereas no significant difference between the tasks was observed for D2 inhibition (p = 0.078, eta(2)(p) = 0.305). These results suggest that D1 and D2 inhibitions of the soleus H-reflex are differentially modulated during the performance of plantarflexion FT and PT. The reduced level of ongoing PSI during PT suggests that, in comparison to FT, there is a larger reliance on inputs from muscle spindles primary afferents when the neuromuscular system is required to maintain position-controlled plantarflexion contractions.PPresynaptic inhibition (PSI) has been shown to modulate several neuronal pathways of functional relevance by selectively gating the connections between sensory inputs and spinal motoneurons, thereby regulating the contribution of the stretch reflex circu1011FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2011/17193-0, 2011/13222-6, 2013/10433-1, 2012/09321-1, 2013/14667-7]CNPq [303313/2011-0]2011/17193-0; 2011/13222-6; 2013/10433-1; 2012/09321-1; 2013/14667-7303313/2011-

Optimization of washing conditions with biogenic mobilizing agents for marine fuel-contaminated beach sands

Washing is a rapid and effective treatment to remediate contaminated sands impacted by oil spills, although synthetic additives used to increase extraction efficiency may cause additional pollution issues due to their intrinsic toxicity and very often low biodegradability. In this study, different biogenic mobilizing agents (soybean lecithins, cyclodextrins, cholic acids, plant-derived cleaners, rhamnolipids and sophorolipids) were tested in the washing of beach sands artificially contaminated with the Intermediate Fuel Oil IFO-180. Among these, a de-oiled soybean lecithin (SL-1), hydroxypropyl-beta-cyclodextrins (HPB-CD) and sophorolipids (SR) achieved hydrocarbon removals close to those attained with the synthetic surfactant Triton X-100 (TX) in preliminary washing tests carried out at constant mixing rate, water/sand ratio and IFO-180 contamination level using agents concentrations close to their critical micelle concentration (0.1% and 1% w/v for microbial and non-microbial agents, respectively). The effects of agent concentration, water/sand ratio, mixing rate and IFO-180 contamination on hydrocarbons removal were modelled using face-centred central composite design and ANOVA. Optimal washing parameters for sand contamination levels in the range 0.5-20 g/kg were identified with response surface methodology. While HPB-CD and SR performed equally to TX only at low sand contaminations, SL-1 attained hydrocarbon removal higher or equal to that of TX at any IFO-180 contamination and at lower application rates. SL-1 also outperformed TX when minimizing the water/sand ratio, i.e., the volume of water used. Considering its lower toxicity, higher biodegradability and higher hydrocarbon removal efficiencies, SL-1 is an effective and environmentally sustainable alternative to synthetic surfactants in washing treatments for marine fuel-contaminated sands

The Benefits of Sugarcane Chain Development in Africa

As consumers continue to be concerned about the future of sustainable agriculture and the scarcity of natural resources, biofuels can be an important component of the "people" solution through job creation, development and interiorizing economic activities of a country through moving money from cities into rural areas. The Brazilian sugarcane industry is well developed in terms of corporate social responsibility and can serve as an example for other countries such as Africa. The objective of this article is to show how sugar cane can contribute to the development of Africa by producing renewable fuel for use in booming African cities. A supply of sugar can be developed for use in local markets and exports. Other opportunities exist to produce bioelectricity from the process of burning the bagasse and other new products such as plastic and diesel. In the case of Ethanol, this fuel has proven to be the most efficient in competing with gasoline in the last 40 years, and Africa may gain with a strategic plan on ethanol