The acid pretreatment process is the most employed technique used to disrupt the lignocellulosic matrix. Thus, this paper provides an overview of the acid pretreatment considering important aspects ...related to the operation conditions, yields, future improvements and the potential use to upgrade lignocellulosic biomass in energy vectors. Moreover, this paper is focused on technical and economic aspects of the use of the acid pretreatment in bioethanol production using olive tree biomass as a case study. This review will provide the framework of the acid pretreatment based on reported applications, experimental and theoretical data. The most well-studied applications of the acid pretreatment are in bioethanol and biogas production. Furthermore, this pretreatment has been improved using solid catalysts and by increasing the solids loading. These options have advantages compared to the traditional way. Even so, improvements in the technical and energy aspects must be performed to make the implementation of this process viable from an economic and environmental perspective. Instead, the kinetic modelling and statistical analysis of the acid pretreatment can be postulated as strong tools to predict the behaviour of different feedstocks under acidic conditions. Moreover, new alternatives to increase the mass and heat transfer in this process related to reactor design conform a new research field. Regarding the case study, the acid pretreatment is one of the most energy-consuming stages of bioethanol production. Low solids loadings are recommended to obtain production costs that are comparable with those reported on the industrial level. In contrast, a high solids loading allows the environmental impact of the process to be reduced in terms of liquid waste generation and carbon dioxide emissions. Finally, the acid pretreatment should be included as an effective method for the biotechnological conversion of lignocellulosic biomass to produce energy vectors once the technical, economic and environmental drawbacks have been overcome.
•Energy vectors production can be improved using optimal acid pretreatment operating conditions.•Operation conditions and kinetic modelling are shown as key information of the acid pretreatment.•Solid catalyst and dry acid pretreatment can serve as alternative methods for biomass upgrading.•The impact of solids loading on the bioethanol production process is demonstrated and discussed.•Low solids loading in acid pretreatment increases the feasibility of bioethanol production.
Many people around the world suffer from some form of paralysis caused by spinal cord injury (SCI), which has an impact on quality and life expectancy. The spinal cord is part of the central nervous ...system (CNS), which in mammals is unable to regenerate, and to date, there is a lack of full functional recovery therapies for SCI. These injuries start with a rapid and mechanical insult, followed by a secondary phase leading progressively to greater damage. This secondary phase can be potentially modifiable through targeted therapies. The growing literature, derived from mammalian and regenerative model studies, supports a leading role for mitochondria in every cellular response after SCI: mitochondrial dysfunction is the common event of different triggers leading to cell death, cellular metabolism regulates the immune response, mitochondrial number and localization correlate with axon regenerative capacity, while mitochondrial abundance and substrate utilization regulate neural stem progenitor cells self-renewal and differentiation. Herein, we present a comprehensive review of the cellular responses during the secondary phase of SCI, the mitochondrial contribution to each of them, as well as evidence of mitochondrial involvement in spinal cord regeneration, suggesting that a more in-depth study of mitochondrial function and regulation is needed to identify potential targets for SCI therapeutic intervention.
Olive‐derived biomass as a source of energy and chemicals Ruiz, Encarnación; Romero‐García, Juan Miguel; Romero, Inmaculada ...
Biofuels, bioproducts and biorefining,
November/December 2017, Letnik:
11, Številka:
6
Journal Article
Aim
No human activity has changed natural habitat availability and ecosystem functioning more than agriculture. As a consequence, species may be forced to use croplands as foraging habitat, resulting ...in potential conflicts with farmers. To assess the causes and consequences of wildlife–agriculture interactions, we investigated the underlying associations among species traits, climate and landscapes factors that determine parrot species to use croplands, and related them to their conservation status.
Location
Global.
Methods
We used parrots as a model due to their global distribution, high behavioural plasticity, high proportion of species using croplands (43%) and threatened species (26%). Within the distribution range of the 398 extant parrot species, we calculated annual averages and seasonality of ecosystem productivity, climate conditions and land‐use patterns from satellite data. We then categorized species conservation status using information provided by IUCN.
Results
We found that habitat degradation, where biodiversity is low and primary productivity is low and intermittent, together with the plasticity of species to use different habitats, is key interrelated conditions that increase the likelihood of species to use croplands worldwide. The persecution of parrots as crop pests varied among regions, being higher for large‐bodied species, those with small distributions, and in highly human‐impacted areas. Moreover, persecution is contributing to the global population decline and extinction risk of parrots, especially in those species with small distribution ranges.
Main conclusions
Parrot–agriculture conflicts may affect both the conservation of parrot species and their key ecological functions. Our results highlight the importance of using multi‐specific and multi‐source information to understand and predict where and why human–wildlife conflicts may arise, as their main drivers interact and are heterogeneous at large spatial scales. Further studies should evaluate the actual extent and economic impact of crop losses caused by wild species to help solve agriculture–wildlife conflicts.
During neuronal development and regeneration axons extend a cytoskeletal-rich structure known as the growth cone, which detects and integrates signals to reach its final destination. The guidance ...cues “signals” bind their receptors, activating signaling cascades that result in the regulation of the growth cone cytoskeleton, defining growth cone advance, pausing, turning, or collapse. Even though much is known about guidance cues and their isolated mechanisms during nervous system development, there is still a gap in the understanding of the crosstalk between them, and about what happens after nervous system injuries. After neuronal injuries in mammals, only axons in the peripheral nervous system are able to regenerate, while the ones from the central nervous system fail to do so. Therefore, untangling the guidance cues mechanisms, as well as their behavior and characterization after axotomy and regeneration, are of special interest for understanding and treating neuronal injuries. In this review, we present findings on growth cone guidance and canonical guidance cues mechanisms, followed by a description and comparison of growth cone pathfinding mechanisms after axotomy, in regenerative and non-regenerative animal models.
Summary
Covid‐19 has triggered an unprecedented global health crisis. The highly contagious nature and airborne transmission route of SARS‐CoV‐2 virus requires extraordinary measures for its ...containment. It is necessary to know the behaviour of aerosols carrying the virus to avoid this contagion. This paper describes the behaviour of aerosols and their role in the transmission of SARS‐CoV‐2 according to published models using a scoping review based on the PubMed, Scopus, and WOS databases. From an initial 530 references, 9 papers were selected after applying defined inclusion criteria. The results reinforce the airborne transmission route as a means of contagion of the virus and recommend the use of face masks, extending social distance to more than 2 metres, and natural ventilation of enclosed spaces as preventive measures. These results contribute to a better understanding of SARS‐CoV‐2 and help design effective strategies to prevent its spread.
Colombia's agriculture, forestry and other land use sector accounts for nearly half of its total greenhouse gas (GHG) emissions. The importance of smallholder deforestation is comparatively high in ...relation to its regional counterparts, and livestock agriculture represents the largest driver of primary forest depletion. Silvopastoral systems (SPSs) are presented as agroecological solutions that synergistically enhance livestock productivity, improve local farmers' livelihoods and hold the potential to reduce pressure on forest conversion. The department of Caquetá represents Colombia's most important deforestation hotspot. Targeting smallholder livestock farms through survey data, in this work we investigate the GHG mitigation potential of implementing SPSs for smallholder farms in this region. Specifically, we assess whether the carbon sequestration taking place in the soil and biomass of SPSs is sufficient to offset the per-hectare increase in livestock GHG emissions resulting from higher stocking rates. To address these questions we use data on livestock population characteristics and historic land cover changes reported from a survey covering 158 farms and model the carbon sequestration occurring in three different scenarios of progressively-increased SPS complexity using the CO2 fix model. We find that, even with moderate tree planting densities, the implementation of SPSs can reduce GHG emissions by 2.6 Mg CO2e ha−1 yr−1 in relation to current practices, while increasing agriculture productivity and contributing to the restoration of severely degraded landscapes.
Summary
The marked trend and consumers growing interest in natural and healthy products have forced researches and industry to develop novel products with functional ingredients. Microalgae have been ...recognized as source of functional ingredients with positive health effects since these microorganisms produce polyunsaturated fatty acids, polysaccharides, natural pigments, essential minerals, vitamins, enzymes and bioactive peptides. For this reason, the manuscript reviews two of the main high‐value metabolites which can be obtained from microalgae: pigments and essential lipids. Therefore, the extraction and purification methods for polyunsaturated fatty acids, astaxanthin, phycoerythrin and phycocyanin are described. Also, the effect that environmental growth conditions have in the production of these metabolites is described. This review summarizes the existing methods to extract and purify such metabolites in order to develop a feasible and sustainable algae industry.
This article based on literature framework describes lipids and pigments as two representative classes of high value compounds synthesized by algae.In the case of lipids, metabolic production, extraction and quantification methods are discussed. For pigments, the extraction and purification methods for astaxanthin, phycocyanin and phycoerytrin are described.
•A case fatality rate decline may not imply that vaccines are effective in reducing deaths.•A constant case fatality rate can still mean that vaccines are effective in reducing deaths.•Detecting ...infections among both the vaccinated and unvaccinated population is key.•Unless vaccinated people are tested for COVID-19 infection, the case fatality rate loses meaning in tracking the pandemic.
This study aimed to test the behavior of the case fatality rate (CFR) in a mixed population of vaccinated and unvaccinated individuals by illustrating the role of both the effectiveness of vaccines in preventing deaths and the detection of infections among both the vaccinated (breakthrough infections) and unvaccinated individuals.
We simulated three hypothetical CFR scenarios that resulted from a different combination of vaccine effectiveness in preventing deaths and the efforts in detecting infections among both the vaccinated and unvaccinated individuals.
In the presence of vaccines, the CFR depends not only on the effectiveness of vaccines in preventing deaths but also on the detection of breakthrough infections. As a result, a decline in the CFR may not imply that vaccines are effective in reducing deaths. Likewise, a constant CFR can still mean that vaccines are effective in reducing deaths.
Unless vaccinated people are also tested for COVID-19 infection, the CFR loses its meaning in tracking the pandemic. This shows that unless efforts are directed at detecting breakthrough infections, it is hard to disentangle the effect of vaccines in reducing deaths from the probability of detecting infections on the CFR.
Reversible protein phosphorylation is the most widespread regulatory mechanism in signal transduction. Autophosphorylation in a dimeric sensor histidine kinase is the first step in two-component ...signalling, the predominant signal-transduction device in bacteria. Despite being the most abundant sensor kinases in nature, the molecular bases of the histidine kinase autophosphorylation mechanism are still unknown. Furthermore, it has been demonstrated that autophosphorylation can occur in two directions, cis (intrasubunit) or trans (intersubunit) within the dimeric histidine kinase. Here, we present the crystal structure of the complete catalytic machinery of a chimeric histidine kinase. The structure shows an asymmetric histidine kinase dimer where one subunit is caught performing the autophosphorylation reaction. A structure-guided functional analysis on HK853 and EnvZ, two prototypical cis- and trans-phosphorylating histidine kinases, has allowed us to decipher the catalytic mechanism of histidine kinase autophosphorylation, which seems to be common independently of the reaction directionality.
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