25,588 research outputs found
Influence of nutritional and operational parameters on the production of butanol or 1,3-propanediol from glycerol by a mutant Clostridium pasteurianum
Butanol and 1,3-propanediol (1,3-PDO) are simultaneously produced by Clostridium pasteurianum from glycerol. In this study, random chemical mutagenesis of C. pasteurianum DSM 525 was conducted to improve its tolerance to butanol. Selected nutritional and operational parameters were evaluated to identify strategies that favour the production of each metabolite. From those experiments, it was possible to isolate cells able to produce 22% more butanol than the parent strain in serum bottles. The supplementation of the culture medium with 2 mg l1 of iron increased the production of butanol by 163%, and the optimum inoculum age was found to be 12 h. Overall, the experiments conducted in bioreactor led to lower butanol titers than in serum bottles, which is attributed to the higher pressure present in the bottles. At pH 6.0, N2 sparging notoriously favoured the production of biomass and 1,3-PDO, while a lower pH (5.0) led to a higher butanol yield, although growth was negatively affected. The results herein gathered allowed the identification of specific conditions that favour the production of either butanol or 1,3-PDO. Furthermore, it was found that N2 sparging is a suitable strategy to maximize the titer, yield and productivity of 1,3-PDO using C. pasteurianum.The authors acknowledge the financial support from the Strategic funding of UID/BIO/04469/2013 unit and project ref. RECI/BBB-EBI/0179/2012 (project number FCOMP-01-0124-FEDER-027462) and R. Gallardo's doctoral grant (ref SFRH/BD/42900/2008) funded by Fundação para a Ciência e a Tecnologia. The authors thank the MIT-Portugal Program for the support given to R. Gallardo
Slow down of a globally neutral relativistic beam shearing the vacuum
The microphysics of relativistic collisionless sheared flows is investigated
in a configuration consisting of a globally neutral, relativistic beam
streaming through a hollow plasma/dielectric channel. We show through
multidimensional PIC simulations that this scenario excites the Mushroom
instability (MI), a transverse shear instability on the electron-scale, when
there is no overlap (no contact) between the beam and the walls of the
hollow plasma channel. The onset of the MI leads to the conversion of the
beam's kinetic energy into magnetic (and electric) field energy, effectively
slowing down a globally neutral body in the absence of contact. The
collisionless shear physics explored in this configuration may operate in
astrophysical environments, particularly in highly relativistic and supersonic
settings where macroscopic shear processes are stable
Anaerobic granular sludge as a biocatalyst for 1,3-propanediol production from glycerol in continuous bioreactors
1,3-propanediol (1,3-PDO) was produced from glycerol in three parallel Expanded Granular Sludge Blanket (EGSB) reactors inoculated with granular sludge (control reactor-R1), heat-treated granular sludge (R2) and disrupted granular sludge (R3) at Hydraulic Retention Times (HRT) between 3 and 24 h. Maximum 1,3-PDO yield (0.52 mol mol-1) and productivity (57 g L-1 d-1) were achieved in R1 at HRTs of 12 h and 3 h, respectively. DGGE profiling of PCR-amplified 16S rRNA gene fragments showed that variations in the HRT had a critical impact in the dominant community of microorganisms. However, no appreciable differences in the bacterial population were observed between R2 and R3 at low HRTs. Production of H2 was observed at the beginning of the operation, but no methane production was observed. This study proves the feasibility of 1,3-PDO production in EGSB reactors and represents a novel strategy to valorise glycerol generated in the biodiesel industry
Avaliação da gestão das UC do Sistema Estadual de Áreas Protegidas de Minas Gerais.
As Unidades de Conservação (UC) são espaços territoriais especialmente protegidos para a conservação dos recursos naturais. O estado de Minas Gerais abriga diversas UC federais, estaduais e municipais. Objetiva-se neste trabalho levantar, caracterizar e analisar como vem sendo implantado o Sistema Estadual de Unidades de Conservação em Minas Gerais. Especificamente, os objetivos foram: levantar as UC estaduais e sua distribuição por bioma e regionais do IEF, sua infra-estrutura básica, regularização fundiária, recursos humanos, existência de planos de manejo, conselhos consultivos, relação com a comunidade do entorno, existência de fluxo turístico, atividade de pesquisa e caracterizar os parceiros e voluntários que atuam na gestão das mesmas. A metodologia utilizada foi a de entrevistas semi-estruturadas e questionários sobre as UC aplicados a todos os gerentes, avaliando a situação espacial, fundiária, humana, estrutural entre outras. Os principais resultados encontrados foram: existem 74 UC estaduais que ocupam áreas significativas e representativas de todos os biomas presentes no estado; inexistem planos de manejo na maioria das UC; há carência de recursos humanos na gestão das UC, principalmente de gerentes; há sobreposição de funções, quantidade insuficiente de funcionários com capacitação para funções específicas; as UC com maior representatividade de área são as “Áreas de Proteção Ambiental” (APA) que enfrentam maiores carências em recursos humanos, materiais e financeiros, além da dificuldade de gerir o território em conjunto com os proprietários; as UC de proteção integral são as que possuem maiores problemas de regularização fundiári
Exact solution for the energy density inside a one-dimensional non-static cavity with an arbitrary initial field state
We study the exact solution for the energy density of a real massless scalar
field in a two-dimensional spacetime, inside a non-static cavity with an
arbitrary initial field state, taking into account the Neumann and Dirichlet
boundary conditions. This work generalizes the exact solution proposed by Cole
and Schieve in the context of the Dirichlet boundary condition and vacuum as
the initial state. We investigate diagonal states, examining the vacuum and
thermal field as particular cases. We also study non-diagonal initial field
states, taking as examples the coherent and Schrodinger cat states.Comment: 10 pages, 8 figure
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