On-line near infrared monitoring of glycerol-boosted anaerobic digestion processes: evaluation of process analytical technologies

A study of NIR as a tool for process monitoring of thermophilic anaerobic digestion boosted by glycerol has been carried out, aiming at developing simple and robust Process Analytical Technology modalities for on-line surveillance in full scale biogas plants. Three 5 L laboratory fermenters equipped with on-line NIR sensor and special sampling stations were used as a basis for chemometric multivariate calibration. NIR characterisation using Transflexive Embedded Near Infra-Red Sensor (TENIRS) equipment integrated into an external recurrent loop on the fermentation reactors, allows for representative sampling, of the highly heterogeneous fermentation bio slurries. Glycerol is an important by-product from the increasing European bio-diesel production. Glycerol addition can boost biogas yields, if not exceeding a limiting 5-7 g L(-1) concentration inside the fermenter-further increase can cause strong imbalance in the anaerobic digestion process. A secondary objective was to evaluate the effect of addition of glycerol, in a spiking experiment which introduced increasing organic overloading as monitored by volatile fatty acids (VFA) levels. High correlation between on-line NIR determinations of glycerol and VFA contents has been documented. Chemometric regression models (PLS) between glycerol and NIR spectra needed no outlier removals and only one PLS-component was required. Test set validation resulted in excellent measures of prediction performance, precision: r(2) = 0.96 and accuracy = 1.04, slope of predicted versus reference fitting. Similar prediction statistics for acetic acid, iso-butanoic acid and total VFA proves that process NIR spectroscopy is able to quantify all pertinent levels of both volatile fatty acids and glycerol.     

Using nanovibrations to monitor biofouling

The article proposes the use of the mechatronic surface sensor (MSS) to detect surface contamination. This methodology is based on the analysis of the vibration response of the monitored surface. In the present work a comparison between the responses of the MSS to different structural deposits build-up (Pseudomonas fluorescens biofilm--formed under turbulent and laminar flow and a silica deposit) were made. The results showed that the MSS response depends not only on the amount but also on the viscoelasticity of the attached deposit--different responses were obtained for the deposits according to their viscoelasticity. Another important conclusion is that the MSS response is not highly affected by solids that are not really attached to its surface.     

Effects of water temperature on growth and sex ratio of juvenile Nile tilapia Oreochromis niloticus (Linnaeus) reared in geothermal waters in southern Tunisia

Growth of juvenile Nile tilapia, Oreochromis niloticus (Maryut strain) was studied under laboratory conditions. Four thermal regimes (22, 26, 30, and 34 °C) were tested on 480 20-day-old fry.     

Growth Factors and Steroid Mediated Regulation of Cytoskeletal Protein Expression in Serum-Deprived Primary Astrocyte Cultures

In this research we aimed to investigate the interactions between growth factors (GFs) and dexamethasone (DEX) on cytoskeletal proteins GFAP and vimentin (VIM) expression under different experimental conditions. Condition I: 24 h pretreatment with bFGF, subsequent 72 h switching in serum-free medium (SFM) and final addition of GFs, alone or by two in the last 24 h, after a prolonged (60 h) DEX treatment. Condition II: 36 h pretreatment with DEX (with bFGF in the last 24 h), followed by SFM for 60 h and final addition for 24 h with growth factors alone or two of them togheter. Western blot analysis data showed a marked GFAP expression in cultures submitted to Condition I comparing results to untreated or treated controls. VIM expression was instead significantly reduced after GFs addition in the last 24 h of 60 h DEX treatment, respect to control DEX-pretreated ones. Referring data to untreated controls, VIM expression was significantly enhanced after GFs addition. GFAP showed also a significant increase in astrocytes submitted to Condition II, respect to untreated or treated control cultures. VIM expression was up and down regulated under Condition II. Collectively, our findings evidence an interactive dialogue between GFs and DEX in astroglial cultures, co-pretreated with DEX and bFGF, regulating cytoskeletal network under stressfull conditions. Special issue article in honor of Dr. Anna Maria Giuffrida-Stella.     

Environmental drivers in mangrove establishment and early development: A review

Mangroves have a global distribution within coastal tropical and subtropical climates, and have even expanded to some temperate locales. Where they do occur, mangroves provide a plethora of goods and services, ranging from coastal protection from storms and erosion to direct income for human societies. The mangrove literature has become rather voluminous, prompting many subdisciplines within a field that earlier in the 20th century received little focus. Much of this research has become diffuse by sheer numbers, requiring detailed syntheses to make research results widely available to resource managers. In this review, we take an inclusive approach in focusing on eco-physiological and growth constraints to the establishment and early development of mangrove seedlings in the intertidal zone. This is a critical life stage for mangroves, i.e., the period between dispersal and recruitment to the sapling stage. We begin with some of the research that has set the precedent for seedling-level eco-physiological research in mangroves, and then we focus on recent advances (circa. 1995 to present) in our understanding of temperature, carbon dioxide, salinity, light, nutrient, flooding, and specific biotic influences on seedling survival and growth. As such, we take a new approach in describing seedling response to global factors (e.g., temperature) along with site-specific factors (e.g., salinity). All variables will strongly influence the future of seedling dynamics in ways perhaps not yet documented in mature forests. Furthermore, understanding how different mangrove species can respond to global factors and regional influences is useful for diagnosing observed mortality within mangrove wetlands, managed or natural. This review provides an updated eco-physiological knowledge base for future research and reforestation activity, and for understanding important links among climate change, local physico-chemical condition, and establishment and early growth of mangrove seedlings.     

Biocatalytic properties of native and immobilized subtilisin 72 in aqueous-organic and low water media

Subtilisin 72 was immobilized on cryogel of poly(vinyl alcohol), the macroporous carrier prepared by the freeze-thaw-treatment of concentrated aqueous solution of the polymer. The obtained biocatalyst was active and stable in aqueous, aqueous-organic, as well as in low water media. The stability of immobilized biocatalyst was substantially higher than that of native enzyme in all mixtures especially in aqueous buffer containing 5–8 M Urea and in acetonitrile/60–90%DMF mixtures. The ability of native and immobilized subtilisin to catalyze peptide bond formation between Z-Ala-Ala-Leu-OMe and Phe-pNA was studied in non-aqueous media. Considerable enzyme stabilization in acetonitrile/90%DMF mixture, induced by the immobilization, resulted in higher product yield (57%) than in case of native subtilisin suspension (32%). Detailed study of synthesis reaction revealed that notable increase in product yield could be reached using increase in both substrate concentrations up to 200 mM.     

Population dynamics, biomass and productivity of Limapontia depressa (Gastropoda, Opisthobranchia) at Bull Island, Dublin, Ireland

Limapontia depressa was present in the saltmarsh pools at Bull Island, Dublin from October to June each year. Numbers peaked in December, with a secondary peak in April, and the maximum density recorded was just under 23000 indiv m^–2. The strong population seasonal cycle was not linked to salinity or chlorophyll-a cycles but did coincide with the drying of the pools. Average production (P) was 233 kJ m^–2 y^–1, with a P:B ratio of just 2:1, which is rather low for such a small animal and may be a function of the low growth rate. These conclusions must be treated with caution due to uncertainty over recruitment mechanisms. Gamete output (G) was calculated at a maximum of 28.6 kJ m^–2 y^–1. This is a higher secondary production than previously reported for saltmarsh herbivores, and may be an important link into the wider estuarine trophic system and a vital food resource for small waders. The low G:P ratio suggests that not all semelparous species necessarily adopt an r-strategy of 'reproductive recklessness'.     

Delayed luminescence of Prorocentrum minimum under controlled conditions

Delayed luminescence (DL), also termed delayed fluorescence or delayed light emission, is the phenomenon of long-lived light emission by plants and cyanobacteria after being illuminated with light and put into darkness. Culture growth of three Prorocentrum minimum strains was studied with DL measurements. DL decay kinetics was measured from 1–60 s after a pulse of white light. The strains used were from the Adriatic Sea (PmK), from Chesapeake Bay, USA (D5), and from the Baltic Sea (BAL), cultured at salinity of 32, 16, and 8 (practical salinity scale), respectively. The strains differed in cell size and chlorophyll a content (PmK > D5 > BAL), as well as in DL parameters. The DL results were compared to standard measurements of culture density and carbon content (calculated from biovolumes). DL decay curves had a specific peak, which changed with culture growth and showed more similarities between the strains PmK and D5. The DL intensity increased with cell density and carbon content in a two-stage process, corresponding to the lag and exponential phases of growth. DL intensity was best correlated with carbon content irrespective of strain and is proposed as an estimate of biomass and for differentiating between lag and exponential phases of growth.     

Growth dynamics of non-toxic Pseudo-nitzschia delicatissima and toxic P. seriata (Bacillariophyceae) under simulated spring and summer photoperiods

Marine planktonic diatoms of the genus Pseudo-nitzschia Peragallo have been responsible for amnesic shellfish poisoning (ASP) events worldwide through the production of the neurotoxin domoic acid (DA). The appearance and toxicity of Pseudo-nitzschia species is variable throughout the year and potentially linked to changes in environmental parameters; many ASP events occur in relatively high latitudes where day length is particularly variable with season. In UK waters, shellfish monitoring has prevented any impact on human health but has led to long-term closures of fisheries, with severe economic consequences. Laboratory experiments on two Pseudo-nitzschia species typically found in Scottish West Coast waters during spring (short photoperiod (SP)) and summer (long photoperiod (LP)) conditions were conducted to determine the influence of photoperiod on their growth and toxicity. Results indicated that non-toxic P. delicatissima (Cleve) Heiden achieved a greater cell density under SP (9-h light:15-h dark (L:D) cycle). For toxin-producing P. seriata (Cleve) H. Peragallo, a LP (18-h L:6-h D cycle) resulted in an enhanced growth rate, cell yield and total toxin production, but it decreased the toxin production per cell. A better understanding of the response of Pseudo-nitzschia species to photoperiod and other foreseeable environmental variables may help predict the appearance of toxic strains.     

Growth characteristics of flagellated cells of Phaeocystis pouchetii revealed by diel changes in cellular DNA content

The present study reports on effects of different light:dark periods, light intensities, N:P ratios and temperature on the specific growth rate of flagellated cells of Phaeocystis pouchetii in culture. The specific growth rate was estimated by diel changes in cellular DNA content. The cellular DNA content and cell cycle of flagellated cells of P. pouchetii are shown, and the importance of light:dark period in cell division is demonstrated. Diel patterns of the cellular DNA content showed that cell division was confined to the dark period. The cells dealt with more than one division per day by rapid divisions shortly after each other.The specific growth rates (μ_DNA) based on the DNA cell cycle model were in close agreement with specific growth rates (μ_Cell) determined from cell counts. The temperature affected the specific growth rates (multiple regression, p < 0.01) and were higher at 5 °C (μ ≤ 2.2 d⁻¹) than at 10 °C (μ ≤1.6 d⁻¹). Increasing the light:dark period from 12:12 h to 20:4 h affected the specific growth rate of P. pouchetii at the lower temperature tested (5 °C) (multiple regression, p < 0.01), resulting in higher specific growth rates than at 10 °C. At 10 °C, the effect of light:dark period was severely reduced. Neither light nor nutrients could compensate the reduction in specific growth rates caused by elevated temperature. The specific growth rates was not affected by the N:P ratios tested (multiple regression, p = 0.21). The experiments strongly suggest that the flagellated cells have a great growth potential and could play a dominating role in northern areas at increased day length.