Biohydrogen production by dark fermentation of glycerol using Enterobacter and Citrobacter Sp

Glycerol is an attractive substrate for biohydrogen production because, in theory, it can produce 3 mol of hydrogen per mol of glycerol. Moreover, glycerol is produced in substantial amounts as a byproduct of producing biodiesel, the demand for which has increased in recent years. Therefore, hydrogen production from glycerol was studied by dark fermentation using three strains of bacteria: namely, Enterobacter spH1, Enterobacter spH2, and Citrobacter freundii H3 and a mixture thereof (1:1:1). It was found that, when an initial concentration of 20 g/L of glycerol was used, all three strains and their mixture produced substantial amounts of hydrogen ranging from 2400 to 3500 mL/L, being highest for C. freundii H3 (3547 mL/L) and Enterobacter spH1 (3506 mL/L). The main nongaseous fermentation products were ethanol and acetate, albeit in different ratios. For Enterobacter spH1, Enterobacter spH2, C. freundii H3, and the mixture (1:1:1), the ethanol yields (in mol EtOH/mol glycerol consumed) were 0.96, 0.67, 0.31, and 0.66, respectively. Compared to the individual strains, the mixture (1:1:1) did not show a significantly higher hydrogen level, indicating that there was no synergistic effect. Enterobacter spH1 was selected for further investigation because of its higher yield of hydrogen and ethanol. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2013     

Health seeking behavior and use of medicinal plants among the Hamer ethnic group,South Omo zone,southwestern Ethiopia

Background

Health seeking behavior of people around the globe is affected by different socio-cultural and economic factors. In Ethiopia, people living in rural areas in particular, are noted for their use of medicinal plants as a major component of their health care option. This study was conducted to document ethnopharmacological information of the Hamer semi-pastoralists ethnic group in southwestern Ethiopia.

Methods

A cross-sectional study was carried out whereby information on demographic characteristics, prevalence of perceived illnesses, factors associated with preference of health care seeking options, medicinal plants used and hoarded as well as some healers’ socio-economic characteristics were collected using two sets of semi-structured questionnaires – one for household (HH) heads and the other for traditional healers supplemented by focus group discussions (FGDs). Households were selected using a cluster sampling followed by systematic sampling techniques; whereas healers and FGD participants were purposively selected with the assistance of local leaders and elders from the community.

Results

The study revealed that the use of traditional medicine among the Hamer ethnic group is very high. Females preferred traditional medicine more than males. The main reasons for this preference include effectiveness, low cost and ease of availability. Malaria (gebeze) was the most frequently occurring illness in the area identified by all FGD participants. A total of 60 different medicinal plants were reported [34 by HH respondents, 14 by traditional healers and 12 by both]. Fifty-one medicinal plants were fully identified, 3 at generic level and 6 have not yet been identified.

Conclusion

It can be concluded that traditional medical practices, particularly herbal aspect, is widely used by the Hamer ethnic group, although health seeking behavior of the community is affected by different socio-economic and cultural factors.

     

A randomised controlled feasibility trial of a BabyWASH household playspace: The CAMPI study

BackgroundWater, sanitation and hygiene (WASH) interventions should support infant growth but trial results are inconsistent. Frequently, interventions do not consider behaviours or transmission pathways specific to age. A household playspace (HPS) is one intervention component which may block faecal-oral transmission. This study was a two-armed, parallel-group, randomised, controlled feasibility trial of a HPS in rural Ethiopia. It aimed to recommend proceeding to a definitive trial. Secondary outcomes included effects on infant health, injury prevention and women’s time.MethodsNovember 2019−January 2020 106 households were identified and assessed for eligibility. Recruited households (N = 100) were randomised (blinded prior to the trial start) to intervention or control (both n = 50). Outcomes included recruitment, attrition, adherence, and acceptability. Data were collected at baseline, two and four weeks.FindingsRecruitment met a priori criteria (≥80%). There was no loss to follow-up, and no non-use, meeting adherence criteria (both ≤10%). Further, 48.0% (95% CI 33.7−62.6; n = 24) of households appropriately used and 56.0% (41.3−70.0; n = 28) cleaned the HPS over four weeks, partly meeting adherence criteria (≥50%). For acceptability, 41.0% (31.3−51.3; n = 41) of infants were in the HPS during random visits, failing criteria (≥50%). Further, the proportion of HPS use decreased during some activities, failing criteria (no decrease in use). A modified Barrier Analysis described good acceptability and multiple secondary benefits, including on women’s time burden and infant injury prevention.InterpretationDespite failing some a priori criteria, the trial demonstrated mixed adherence and good acceptability among intervention households. A definitive trial to determine efficacy is warranted if recommended adjustments are made.FundingPeople In Need; Czech Development Agency.Trial registrationRIDIE-ID-5de0b6938afb8.     

System delimitation in life cycle assessment (LCA) of aquaculture: striving for valid and comprehensive environmental assessment using rainbow trout farming as a case study

Purpose

Life cycle assessment (LCA) has been in the last one decade used as a standardized and structured method of evaluating the environmental impacts of aquaculture arising throughout the entire life cycle. However, aquaculture system hardly applied system expansion whenever a multifunctional process has more than one functional flow. The objective of this study is to develop a methodological approach for consequential LCA and model the system expansion of the different affected processes of aquaculture.

Methods

In this study, we have considered the system expansion in two different stages in the life cycle of the fish production: aquacultural stage, with case study of trout aquaculture, and feed manufacturing stage. Rainbow trout (Oncorhynchus mykiss) production was used as a case study to illustrate the method using different scenarios of system expansion.

Results and discussion

The results of the six different scenarios of system expansion showed considerable variation among the different scenarios towards the environmental impact of trout aquaculture. Regarding global warming potential, the contributions vary by 5-fold; for acidification, variations were up to 32 %, and for land use, the contributions varied from 0.6 to 1.3 m²a/kg of trout demanded in Germany. It appeared that eutrophication is similar in all the scenarios considered.

Conclusions

This article showed that system expansion can be used to handle the allocation issues of the co-products in the rainbow trout supply chain, thus, can be effectively used when analyzing the environmental consequences of changes in future rainbow trout production. Furthermore, consequential LCA may be important when comparing the impacts of alternative meal choices of aquafeeds. This may increase the incentive for speedy replacement of alternative meals, thus, reducing the dependence on the utilization of the limiting fisheries resources.     

Understanding Triplet Formation Pathways in Bulk Heterojunction Polymer:Fullerene Photovoltaic Devices

Triplet exciton (TE) formation pathways are systematically investigated in prototype bulk heterojunction (BHJ) “super yellow” poly(p‐phenylene vinylene) (SY‐PPV) solar cell devices with varying fullerene compositions using complementary optoelectrical and electrically detected magnetic resonance (EDMR) spectroscopies. It is shown that EDMR spectroscopy allows the unambiguous demonstration of fullerene triplet production in BHJ polymer:fullerene solar cells. EDMR triplet detection under selective photoexcitation of each blend component and of the interfacial charge transfer (CT) state reveals that low lying fullerene TEs are produced by direct intersystem crossing from singlet excitons (SEs). The direct CT‐TE recombination pathway, although energetically feasible, is kinetically suppressed in these devices. However, high energy CT states in the CT manifold can contribute to the population of the fullerene triplet state via a direct CT‐SE conversion. This undesirable energetic alignment could be one of the causes for the severe reduction in photocurrent observed when the open‐circuit voltage of polymer:fullerene solar cells is pushed to 1.0 V or beyond.     

<Emphasis Type="Italic">Vibrio cholerae</Emphasis> in waters of the Sunderban mangrove: relationship with biogeochemical parameters and chitin in seston size fractions

Wetland dynamics are probably linked to cholera endemicity in South Asia. We focus on links between Vibrio cholerae abundance, chitin content and suspended particle load in size fractions of suspended particulate matter (SPM) along the salinity gradient of Sunderban mangrove waters. SPM decreased downstream, while salinity increased from 0.2 to 4. Particulate organic carbon (90 ± 25 μM) and nitrogen (9.1 ± 3.3 μM) highly correlated with SPM and turbidity, suggesting a significant contribution of fine particles to organic matter. Total chitin ranged 1–2 mg/l and decreased downstream. The distribution among size fractions of SPM, chitin and V. cholerae O1 (the bacterial serogroup mainly associated with cholera epidemics) was similar, with ~98% of the total in the fraction <20 μm. In comparison, the number of V. cholerae O1 attached to zooplankton and microplankton size classes >20 μm was almost negligible, in contrast to usual assumptions. Thus, microdetritus, nanoplankton and fungal cells in size classes <20 μm represent a chitinaceous substrate on which V. cholerae can grow and survive. Total bacteria, cultivable vibrios and V. cholera O1 increased 5–10 times downstream, together with salinity and nitrite concentration. Overall, nitrate and silicate concentrations were relatively constant (>22 μM N and 100 μM Si). However, nitrite increased ~9 times in the outer sector, reaching ~1.2 μM N, probably as a result of increased abundance of nitrate-reducing vibrios. A characterization of Vibrio habitats that takes account of the presence of nitrate-reducing bacteria could improve the understanding of both mangrove nitrogen cycling and cholera seasonality.     

Binding of the Bacillus subtilis LexA protein to the SOS operator

The Bacillus subtilis LexA protein represses the SOS response to DNA damage by binding as a dimer to the consensus operator sequence 5′-CGAACN₄GTTCG-3′. To characterize the requirements for LexA binding to SOS operators, we determined the operator bases needed for site-specific binding as well as the LexA amino acids required for operator recognition. Using mobility shift assays to determine equilibrium constants for B.subtilis LexA binding to recA operator mutants, we found that several single base substitutions within the 14 bp recA operator sequence destabilized binding enough to abolish site-specific binding. Our results show that the AT base pairs at the third and fourth positions from the 5′ end of a 7 bp half-site are essential and that the preferred binding site for a LexA dimer is 5′-CGAACATATGTTCG-3′. Binding studies with LexA mutants, in which the solvent accessible amino acid residues in the putative DNA binding domain were mutated, indicate that Arg-49 and His-46 are essential for binding and that Lys-53 and Ala-48 are also involved in operator recognition. Guided by our mutational analyses as well as hydroxyl radical footprinting studies of the dinC and recA operators we docked a computer model of B.subtilis LexA on the preferred operator sequence in silico. Our model suggests that binding by a LexA dimer involves bending of the DNA helix within the internal 4 bp of the operator.