Escalado de la producción de bioproducto de origen microbiano obtenido por fermentación estática

The development of bioproducts with agricultural applications requires that the results obtained at the laboratory level can be scaled up. The objective of this work was to scale the production of a microbial based bioproduct obtained by static fermentation of a mixed culture. A mixed batch culture was carried out with a mixture of molasses and whey in water as sources of nutrients and inoculum. The global growth kinetics were estimated through the biomass as well as the variations of pH and ºBrix. Based on the results, a laboratory scale-up (5 liters) and a pilot plant scale (24, 200 and 2100 liters) were carried out. The microbial biomass increased over time, the pH and ºBrix decreased. The values were adjusted to a second order polynomial model, with regression coefficients R2 0.8. Both pH and ºBrix showed a significant negative correlation with biomass and between them. The pH and ºBrix could be used as indicators to monitor the development of the fermentation and to control the product. The fermentation process can last between 7 and 10 days. With the design conceived and maintaining the proportions of raw materials, it was possible to scale the production process of the microbial based bioproduct from the laboratory to the pilot plant. The characteristics of the bioproduct measured through the pH, ºBrix, color and odor indicators were preserved.El desarrollo de bioproductos con aplicaciones agrícolas se requiere que los resultados obtenidos a nivel de laboratorio puedan escalarse. El objetivo de este trabajo fue escalar la producción de un bioproducto de origen microbiano obtenido por fermentación estática de un cultivo mixto. Se realizó un cultivo discontinuo mixto con una mezcla de melaza y suero de leche en agua como fuentes de nutrientes e inóculo. Se estimó la cinética de crecimiento global a través de la biomasa así como las variaciones del pH y ºBrix. A partir de los resultados se realizó un escalado de laboratorio (5 litros) y otro de planta piloto (24, 200 y 2100 L).  La biomasa microbiana se incrementó en el tiempo, el pH y los ºBrix decrecieron. Los valores se ajustaron a un modelo polinómico de segundo orden, con coeficientes de regresión R20.8. Tanto el pH como los ºBrix mostraron una correlación negativa significativa con la biomasa y entre ellos. El pH y los ºBrix se podrían utilizar como indicadores para monitorear el desarrollo de la fermentación y para el control del producto. El proceso de fermentación puede tener una duración entre 7 y 10 días. Con el diseño concebido y manteniendo las proporciones de materias primas se logró escalar el proceso de producción del bioproducto de origen microbiano desde el laboratorio hasta planta piloto. Se conservaron las características del bioproducto medidas a través de los indicadores pH, ºBrix, color y olor

Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins

Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.Peer reviewe

El zooplancton como integrante de la estructura trófica de los ecosistemas lénticos

Uno de los componentes principales de las comunidades biológicas de los sistemas acuáticos es el zooplancton. Representa el eslabón entre el fitoplancton y los consumidores secundarios (peces y algunas aves). El conocimiento de su estructura permite caracterizar los sistemas acuáticos y conocer algunas de las interacciones dominantes en ellos

A Non-Stressful Temperature Rise and Greater Food Availability Could Increase Tolerance to Calcium Limitation of Daphnia cf. pulex (Sensu Hebert, 1995) Populations in Cold Soft-Water Lakes

Calcium (Ca) is an important driver of community structure in freshwaters. We examined the combined effects of increased temperatures and variations in food quantity on the tolerance to low Ca of Daphnia pulex. The aim was to predict the impact of climate warming on this keystone zooplanktonic species in cold-climate lakes. We conducted a factorial life-history experiment in a clone of North American Daphnia cf. pulex to analyse the interaction effects of a temperature increase (17.5 °C–21 °C) within their physiological preferred range and expected by climate warming over the next few decades and a narrow Ca gradient (0.25–1.74 mg Ca L−1) under stressful vs. abundant food conditions. We found a striking positive synergistic effect of Ca and temperature on D. pulex reproduction at high food conditions. Although the increase in temperature to 21 °C greatly reduced survival, high energy allocation to reproduction at high food levels allowed the population to succeed in poor Ca (<0.25 mg Ca L−1). Results suggest that climate warming and higher food availability will make the populations of many cold and Ca-limited lakes more tolerant to low Ca levels with higher growth population rates, thereby altering zooplanktonic community structures and inducing potential cascading effects on the food web

Strict stoichiometric homeostasis of Cryptomonas pyrenoidifera (Cryptophyceae) in relation to N:P supply ratios

A common freshwater cryptophyte, Cryptomonas pyrenoidifera, was cultivated in batch-cultures to analyze intraspecific variation in elemental stoichiometry along a broad gradient of pulsed phosphorus (P) enrichment during the early acclimation period and to determine the immediate homeostatic capacity of the nitrogen-to-phosphorus (N:P) ratio of this alga when nutrients are at saturating levels. Experimental results revealed that nitrogen (N) and P cell quotas significantly increased with increasing P concentration. However, despite the wide range of N:P ratios in the medium, Cryptomonas N:P ratios were highly stable at higher P-level treatments, indicating a highly conservative behavior and suggesting strict elemental homeostasis when nutrients are at saturating levels. The strictly homeostatic N:P ratio appears to be attributable to their high potential for a fast luxury consumption of both N and P after a brief and intense episode of increased resource availability and to physiological limits on their nutrient storage capacity. Most importantly, the N:P biomass ratio at nutrient saturating levels converged around 11:1, which was the observed ratio of maximum internal cell quotas for N and P (i.e. Qmax,N:Qmax,P) under the prevailing experimental conditions. This value is particularly informative for C. pyrenoidifera because it represents cell storage quotients and may be a taxon-specific evolutionary optimum, providing a reference point to infer the grade of nutrient-limitation. The experimental data give ranges of variation in C. pyrenoidifera elemental composition permitting, among others, proper parameterization of cryptophyte stoichiometry models.</p

Ecotoxicological assessment of the effects of fluoxetine on Daphnia magna based on acute toxicity, multigenerational reproduction effects, and attraction-repellence responses

Fluoxetine, a common pharmaceutical used as an antidepressant, is already considered potentially hazardous to biota due to its increasing use and detection in European, North American, and Asian rivers. We studied the effects of fluoxetine on Daphnia magna, as we hypothesized that fluoxetine might have harmful effects, short and long-term, at different levels: survival, behaviour, and reproduction (offspring production). We applied two different approaches: (i) a scenario at environmentally relevant concentrations (0.1-1.0 μg/L) and (ii) a scenario simulating a future worsening of contamination (1-800 μg/L) until the reach of lethal concentrations. In the former, we examined whether there are multigenerational effects on reproduction and on the avoidance/colonisation behaviour in previously exposed populations. In the latter, three responses were assessed: survival, avoidance behaviour and reproduction. We did not detect differences in the reproduction output of D. magna among the treatments over the three generations examined. Irrespective of the multigenerational treatment, D. magna colonised the environments with fluoxetine in a similar way. In the second scenario, we determined the lethal concentration for 50% of the population (96 h-LC50 = 365 μg/L), which, in spite of the toxic effect, was attractive to organisms during the avoidance tests (24 h); in fact, D. magna were attracted (no repellence) even to the highest concentrations of fluoxetine tested (800 μg/L). Lastly, in a 21-day chronic toxicity test the reproduction output of D. magna increased with higher concentrations of fluoxetine. This effect might be related to the fact that the organisms in the contaminated treatment began their first reproduction earlier, when compared to that in the control treatments. In conclusion, this study discusses an identified hazard for aquatic biota due to the fluoxetine attraction effect and a predictive assessment of the consequences expected if its indiscriminate use increases.H. Stremmel thanks the PROMOS scholarship of the DAAD and the RUB. C.V.M. Araújo is grateful for the grant (Ramón y Cajal contract: RYC-2017-22324) funded by MCIN/AEI/10.13039/501100011033 and “ESF Investing in your future”. This research was funded by MCIN/AEI/10.13039/501100011033 (BrEStress project: PID 2019-105868RA-I00).Peer reviewe

Diatom abundance from sediment cores (2008-2011) from six lakes of Sierra Nevada Mountains (Spain)

This dataset presents relative abundance data of subfossil diatoms obtained from sediment cores retrieved from six lakes at Sierra Nevada Mountains (Granada, Spain) during 2008 and 2011. The files show data over the past 180 years approximately. Sediment cores were taken from the deepest part of the lake by a slide-hammer gravity corer (Aquatic Research Instruments, USA), with a 6.9 cm inner diameter during the summer of 2011, except for Río Seco Lake core which was sampled in 2008. The cores were sectioned on-site into 0.25 cm thick layers for the upper sections of the cores and into 0.5 cm intervals for the remainder of the cores, except for Río Seco Lake core which was sectioned at 0.5 cm contiguous intervals for the entire core length. Sediment cores were dated using gamma spectrometry (DSPec, Ortec®) techniques by measuring activities of radioisotopes (210Pb, 214Bi and 137Cs) and sediment ages were estimated from unsupported 210Pb activities using the constant rate of supply (CRS) model. Diatom samples were processed by digesting sediment samples with a 50:50 mixture solution of H2SO4 and HNO3 and mounted onto slides with Naphrax®. For each sample, a minimum of 300 diatom valves were counted using a Leica microscope fitted with a 100× fluotar objective (N.A. = 1.4) and using differential interference contrast optics under oil-immersion at 1000× magnification. Diatoms were identified to the species level or lower using a selection of taxonomic sources and diatom counts were expressed as a percent abundance relative to the total number of diatom valves counted in each sedimentary interval