This study is the first to evaluate the effects of five seaweeds (Ulva sp., Laminaria ochroleuca, Saccharina latissima, Gigartina sp., and Gracilaria vermiculophylla) on gas and methane production and ruminal fermentation parameters when incubated in vitro with two substrates (meadow hay and corn silage) for 24 h. Seaweeds led to lower gas production, with Gigartina sp. presenting the lowest value. When incubated with meadow hay, Ulva sp., Gigartina sp. and G. vermiculophylla decreased methane production, but with corn silage, methane production was only decreased by G. vermiculophylla. With meadow hay, L. ochroleuca and S. latissima promoted similar methane production as the control, but with corn silage, L. ochroleuca increased it. With the exception of S. latissima, all seaweeds promoted similar levels of total volatile fatty acid production. The highest proportion of acetic acid was produced with Ulva sp., G. vermiculophylla, and S. latissima; the highest proportion of butyric acid with the control and L. ochroleuca; and the highest proportion of iso-valeric acid with Gigartina sp. These results reveal the potential of seaweeds to mitigate ruminal methane production and the importance of the basal diet. To efficiently use seaweeds as feed ingredients with nutritional and environmental benefits, more research is required to determine the mechanisms underlying seaweed and substrate interactions.

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Here we introduce a novel strategy for turbidimetric monitoring of bacterial growth in liquid culture. The instrumentation comprises a light source, a customized 3D printed culture tube holder and a miniaturized spectrophotometer, connected through optical cables. Due to its small footprint and the possibility to operate with external light, bacterial growth was directly monitored from culture tubes in a simple and versatile fashion. This new portable measurement technique was used to monitor the growth of facultative (Escherichia coli ATCC/25922, and Staphylococcus aureus ATCC/29213) and strictly (Butyrivibrio fibrisolvens JW11, Butyrivibrio proteoclasticus P18, and Propionibacterium acnes DSMZ 1897) anaerobic bacteria. For E. coli and S. aureus, the growth rates calculated from normalized optical density values were compared with those ones obtained using a benchtop spectrophotometer without significant differences (P = 0.256). For the strictly anaerobic species, a high precision (relative standard deviation < 3.5%) was observed between replicates up to 48 h. Regarding its potential for customization, this manifold could accommodate further developments for customized turbidimetric monitoring, such as the use of light-emitting diodes as a light source or flow cells.

This paper introduces the preliminary design and optimization of a micro-Sequential Injection lab-on-valve system (μSI-LOV) with fluorescence detection for the direct determination of trace Zn(2+) in an unacidified seawater matrix. The method capitalizes on the sensitivity and selectivity of FluoZin-3, which was originally designed to measure zinc in living cells. The optimum reaction conditions, sources of blank signal and physical parameters of the μSIA-LOV are evaluated with the requirements of trace metal analysis in mind, namely high sensitivity and low background signals. A detailed investigation of the effect of sample and reagent sequencing on sensitivity is presented for the first time using μSIA-LOV. We find that the order of sequencing greatly influences peak shape and analytical sensitivity with the highest and smoothest peaks obtained when a large volume of sample (75 μL) is aspirated last in the sequence prior to flow reversal and detection. The optimized reaction conditions and reagent/sample sequencing protocol yield a detection limit of 0.3 nM Zn(2+), high precision (RSD < 2.5%), a linear quantification range up to 40 nM and an analytical cycle of ∼1 min per sample. This work demonstrates that μSI-LOV is capable of attaining detection limits that are close to those needed for open ocean determinations of Zn(2+) without preconcentration or separation of the analyte from the seawater matrix. The low reagent consumption (50 μL per sample), full automation and minimal maintenance requirements of μSI-LOV make it well suited for shipboard analysis and, eventually, for development to meet the pressing need for trace element measurements in unattended locations.

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