Enhancing levan biosynthesis by destroying the strongly acidic environment caused by membrane-bound glucose dehydrogenase (mGDH) in Gluconobacter sp. MP2116.

Levan produced by Gluconobacter spp. has great potential in biotechnological applications. However, Gluconobacter spp. can synthesize organic acids during fermentation, resulting in environmental acidification. Few studies have focused on the effects of environmental acidification on levan synthesis. This study revealed that the organic acids, mainly gluconic acid (GA) and 2-keto-gluconic acid (2KGA) secreted by Gluconobacter sp. MP2116 created a highly acidic environment (pH < 3) that inhibited levan biosynthesis. The levansucrase derived from strain MP2116 had high enzyme activity at pH 4.0 âˆ¼ pH 6.5. When the ambient pH was less than 3, the enzyme activity decreased by 67 %. Knocking out the mgdh gene of membrane-bound glucose dehydrogenase (mGDH) in the GA and 2KGA synthesis pathway in strain MP2116 eliminated the inhibitory effect of high acid levels on levansucrase function. As a result, the levan yield increased from 7.4 g/l (wild-type) to 18.8 g/l (Δmgdh) during fermentation without pH control. This study provides a new strategy for improving levan production by preventing the inhibition of polysaccharide synthesis by environmental acidification.

Could future ocean acidification be affecting the energy budgets of marine fish?

With the unprecedented environmental changes caused by climate change including ocean acidification, it has become crucial to understand the responses and adaptive capacity of fish to better predict directional changes in the ecological landscape of the future. We conducted a systematic literature review to examine if simulated ocean acidification (sOA) could influence growth and reproduction in fish within the dynamic energy budget theory framework. As such, we chose to examine metabolic rate, locomotion, food assimilation and growth in early life stages (i.e. larvae and juvenile) and adults. Our goal was to evaluate if acclimatization to sOA has any directional changes in these traits and to explore potential implications for energetic trade-offs in these for growth and reproduction. We found that sOA had negligible effects on energetic expenditure for maintenance and aerobic metabolism due to the robust physiological capacity regulating acid-base and ion perturbations but substantive effects on locomotion, food assimilation and growth. We demonstrated evidence that sOA significantly reduced growth performance of fish in early life stages, which may have resulted from reduced food intake and digestion efficiency. Also, our results showed that sOA may enhance reproduction with increased numbers of offspring although this may come at the cost of altered reproductive behaviours or offspring fitness. While these results indicate evidence for changes in energy budgets because of physiological acclimatization to sOA, the heterogeneity of results in the literature suggests that physiological and neural mechanisms need to be clearly elucidated in future studies. Lastly, most studies on sOA have been conducted on early life stages, which necessitates that more studies should be conducted on adults to understand reproductive success and thus better predict cohort and population dynamics under ongoing climate change.

The heat is on: sensitivity of goldsinny wrasse to global climate change.

Unsustainable harvesting practices have drastically reduced fish populations globally and developments in aquaculture have increased. Unexpectedly, Atlantic salmon farming caused the opening of a new fishery in northern European countries, where previously unharvested mesopredatory species, like the goldsinny wrasse (Ctenolabrus rupestris), are captured for use as cleaner fish in pens along the coast and fjords. The goldsinny wrasse is widespread in coastal areas where it plays an ecologically important role as a predator of small invertebrates. Since climate change effects are particularly pronounced in coastal waters, it becomes urgent to understand how fish like the goldsinny will respond to global climate change, including the increasing frequency and intensity of marine heatwaves (MHWs), ocean freshening (OF) and ocean acidification (OA). To address this, we conducted a multi-stressor experiment exposing adult goldsinny to each stressor individually, as well as to all three combined. The results indicated that the goldsinny is highly affected by MHWs and extremely sensitive to a multi-stressor environment, with 34% and 53% mortality, respectively. Additionally, exposure to a MHW event, OF and multi-stressor conditions affected fish metabolism, with the highest standard metabolic- and maximum metabolic-oxygen consumption rates observed for the MHW treatment. Increases in oxidized glutathione (GSSG) and percent oxidized glutathione (% GSSG) in the livers, indicative of oxidative stress, were also seen in the MHW, OF and multi-stressor treatments. As a single stressor, OA showed no significant impacts on the measured parameters. This information is important for conservation of coastal marine environments, given the species' important role in shallow-water habitats and for management of goldsinny or other mesopredatory fish harvested in coastal ecosystems. The sensitivity of the goldsinny wrasse to future stressors is of concern, and any potential reductions in abundance as a result of climate change may lead to cascade effects with ecosystem-wide consequences.

Morphological, physiological, and transcriptomic analyses indicate that cell wall properties and antioxidant processes are potential targets for improving the aluminium tolerance of broad beans.

Aluminium (Al) stress is the second-leading abiotic stress on crops. An improved understanding of the response mechanisms of plants to Al stress will provide scientific guidance for enhancing the crops' tolerance to Al stress. In this study, Al stress (50-200 µM AlCl3) caused visible damage to broad bean (Vicia faba L.) roots rather than shoots, which was attributed to Al accumulation and distribution in different tissues. Root transcriptomic analysis revealed that Al stress altered cell wall properties by downregulating lignin synthesis and several xyloglucan endotransglucosylase/hydrolase-, expansin- and peroxidase (POD)-encoding genes, which likely weakened cell extensibility to inhibit root growth. Additionally, Al stress impeded reactive oxygen species scavenging pathways involving POD activity and flavonoid biosynthesis, leading to oxidative damage characterised by malondialdehyde accumulation. These results indicate that optimising cell wall properties and/or enhancing antioxidant processes are crucial for alleviating Al toxicity to broad beans. Interestingly, exogenous application (500 and 1000 µM) of the flavonoid apigenin effectively alleviated Al toxicity in broad bean roots by partially improving the total antioxidant capacity of the roots. This study contributes to understanding the interaction between plants and Al and provides new strategies to alleviate Al toxicity in crops.

Effect of acidification pretreatment on two-phase anaerobic digestion of acidified food waste.

Acidified food waste significantly disrupts anaerobic digestion, highlighting the need for effective solutions to mitigate its impact. This study presents a method that utilizes acidified sludge to pretreat acidified food waste, thereby significantly improving the efficiency of hydrolysis and acidogenesis. After acidification pretreatment, hydrolysis efficiency improved from 64.54 % to 96.51 %, while acidogenesis efficiency increased from 34.82 % to 49.95 %. Additionally, the concentration of short-chain fatty acids and hydrogen production in the acidification pretreatment group increased by 45.89 % and 48.67 %, respectively. The pretreatment group exhibited a biochemical methane potential of 512.84 ± 13.73 mL/(g volatile suspended solids), which was 35.77 % higher than that of the control group. Mechanism analysis revealed that the higher abundance of genes associated with lactate dehydrogenase in the acidified sludge facilitated the rapid degradation of lactic acid. Moreover, the abundant Clostridium butyricum in the acidified sludge promoted the targeted conversion of lactic acid and other organic matter into butyric acid within the food waste system. This efficient butyric acid fermentation improved the fermentation environment and provided abundant substrates for methane production. This study introduces a promising bio-based strategy to improve the anaerobic digestion efficiency of acidified food waste.

Mn-CDF family genes enhance the manganese tolerance of the tea plants (Camellia sinensis) under acidic condition.

The tea plants cultivated in acidic soils are vulnerable to excessive manganese (Mn), which increases the risk of Mn2+ toxicity to physiology and development. Mn-cation diffusion facilitator (CDF) family genes have been implicated in regulating Mn homeostasis and tolerance. However, the mechanism of Mn tolerance of tea plants in acidic environments is still unknown. In this study, we initially examined the phenotypic characteristics and Mn contents variability in different tissues of tea plants under various Mn concentration at pH 5 and 4. We observed that tea plants exhibited remarkably high Mn tolerance at pH 4, with Mn accumulation notably elevated in the aboveground tissues under pH 4 condition after 28-day treatment. We found the expression levels of Mn-CDF genes, had different subcellular localization, were tissue-specific and significantly induced by high Mn concentrations at pH 4 condition. Furthermore, the yeast complementation assays indicated that the heterologous expression of Mn-CDF genes restored the growth of a Mn2+ sensitive yeast strain, Δpmr1. Taken together, these results suggest that Mn-CDF family genes function as Mn transporters to participate in Mn tolerance in acidic environments. This study provides reference for further study on the mechanism of maintaining Mn homeostasis in tea plants under soil acidification.

Effect of long-term application of pig slurry and NPK fertilizers on trace metal content in the soil.

One of the goals of sustainable agricultural production is to avoid soil contamination by elements defined as trace metals (TMs). The aim of this study was to assess the long-term impact of the use of pig slurry (PS) and NPK mineral fertilizers on the soil content of cadmium (Cd), copper (Cu), lead (Pb) and zinc (Zn). In a 9-year crop rotation, PS was used three times only before root crops. The same four levels of NPK doses (N0P0K0, N1P1K1, N3P2K2, N4P2K2) were applied to both plots with and without PS. Soil samples were collected in early spring from topsoil (0-0.3 m) and subsoil (0.3-0.6 m). Three forms of TMs were determined in the soil: pseudo-total (Aqua regia); bioavailable (Mehlich 3 method) and readily bioavailable (mobile) forms (1 M NH4NO3). The tested factors did not have a significant impact on the Cd, Cu and Pb content, regardless of the form analyzed and the soil depth. PS application significantly increased the content of bioavailable forms of Zn regardless of the year, and the content of pseudo-total Zn only in the sugar beet year, i.e. after manure application. Increasing NPK doses increased the content of mobile Zn in the topsoil, especially in PS plots. A tendency to accumulate mobile forms of Cd and Pb was also observed on NPK-fertilized plots. Thus, long-term application of high NPK doses may increase the risk of contamination of the food chain with these metals. The content of mobile Cd and Zn was positively related to the content of total nitrogen in the soil and negatively related to pH.

Natural light driven plastic leaching effects on carbon chemistry in the tropical coastal waters of eastern Arabian sea: An experimental study.

This study examined the effects of solar light driven plastic degradation on carbon chemistry in the coastal waters of eastern Arabian Sea along the west coast of India. The research was conducted through experimental incubations exposed to natural sunlight at multiple locations between December 2023-February 2024. Photodegradation induced a significant pH decrease (up to 0.38 ± 0.02) between controls and plastic incubations ranging from 8.17 ± 0.01 to 7.54 ± 0.02 with the highest variation in the Mumbai coast ranging from 8.13 ± 0.01 to 7.75 ± 0.03. pH variations are primarily caused by the leaching of organic acids and CO2 release during solar irradiated incubation. Plastic leaching due to natural light irradiation and subsequent changes in the water chemistry is of prime significance with dissolved organic carbon (DOC) leaching of 0.002-0.03% of plastic weight into the coastal waters. Our estimations suggest 15-75 metric tonnes (MT) of DOC release per year by plastic pollution in the eastern Arabian Sea coastal waters. Further, the fluorescent dissolved organic matter (FDOM) fragmentation, a part of DOC, may act as an organic source of synthetic contaminants and would promote heterotrophic microbial action in the coastal waters. Photodegradation of plastic and the interaction of natural DOC and plastic-derived DOC resulted in longer wavelengths FDOM, which may affect the penetration of photosynthetically active radiation in the water column, thereby impacting primary production. Finally, future research work focussing on the role of plastic pollution in coastal ocean acidification and vice-versa is essential and will be increasingly intense in the upcoming decades.

Physiological resilience of intertidal chitons in a persistent upwelling coastal region.

Current climate projections for mid-latitude regions globally indicate an intensification of wind-driven coastal upwelling due to warming conditions. The dynamics of mid-latitude coastal upwelling are marked by environmental variability across temporal scales, which affect key physiological processes in marine calcifying organisms and can impact their large-scale distribution patterns. In this context, marine invertebrates often exhibit phenotypic plasticity, enabling them to adapt to environmental change. In this study, we examined the physiological performance (i.e., metabolism, Thermal Performance Curves, and biomass and calcification rates) of individuals of the intertidal mollusk Chiton granosus, a chiton found from northern Peru to Cape Horn (5° to 55°S). Our spatial study design indicated a pattern of contrasting conditions among locations. The Talcaruca site, characterized by persistent upwelling and serving as a biogeographic break, exhibited lower pH and carbonate saturation states, along with higher pCO2, compared to the sites located to the north and south of this location (Huasco and Los Molles, respectively). In agreement with the spatial pattern in carbonate system parameters, long-term temperature records showed lower temperatures that changed faster over synoptic scales (1-15 days) at Talcaruca, in contrast to the more stable conditions at the sites outside the break. Physiological performance traits from individuals from the Talcaruca population exhibited higher values and more significant variability, along with significantly broader and greater warming tolerance than chitons from the Huasco and Los Molles populations. Moreover, marked changes in local abundance patterns over three years suggested population-level responses to the challenging environmental conditions at the biogeographic break. Thus, C. granosus from the Talcaruca upwelling zone represents a local population with wide tolerance ranges that may be capable of withstanding future upwelling intensification on the Southern Eastern Pacific coast and likely serving as a source of propagules for less adapted populations.

Post-acidification of fermented milk and its molecular regulatory mechanism.

The fermented milk products with lactic acid bacteria (LAB) are widely accepted by consumers. During the chilled-chain transportation and storage, LAB in the product keep producing lactic acid, and this will lead to post-acidification, which can affect the flavor, consumer acceptance and even shelf-life of the product. LAB is the determining factor affecting post-acidification. The acid production pathway in LAB and methods inhibiting post-acidification received widespread attention. This review will focus on the post-acidification from the perspective of fermentation starters, including acid production pathway in LAB, main factors and key enzymes affecting post-acidification. Lactobacillus delbrueckii subsp. bulgaricus is a key bacterial species responsible for post acidification in the fermented milk products. The different species and strains presented various differences in process like acid production, acid resistance and post-acidification. Furthermore, multiple factors, such as milk composition, fermentation temperature, and homogenization, also can influence post-acidification. Lactose transport and utilization pathways, as well as its subsequent products metabolic pathway directly influence the post-acidification. F0F1-ATPase, ß-galactosidase, and lactate dehydrogenase are recognized as important enzymes related to post-acidification. The degree of post-acidification is mainly related to the acid production and acid resistance abilities of the fermentation starters, so the key enzymes related to post-acidification are mostly taking part in these two capacities. Recently, some new post-acidification related biomarker genes were found, providing a reference adjusting post-acidification without affecting fermentation rate and bacteria viability. To clarify the post-acidification mechanism at the molecular level will help control post- acidification.

Reprint: Acclimatization and Adaptive Capacity of Marine Species in a Changing Ocean.

To persist in an ocean changing in temperature, pH and other stressors related to climate change, many marine species will likely need to acclimatize or adapt to avoid extinction. If marine populations possess adequate genetic variation in tolerance to climate change stressors, species might be able to adapt to environmental change. Marine climate change research is moving away from single life stage studies where individuals are directly placed into projected scenarios ('future shock' approach), to focus on the adaptive potential of populations in an ocean that will gradually change over coming decades. This review summarizes studies that consider the adaptive potential of marine invertebrates to climate change stressors and the methods that have been applied to this research, including quantitative genetics, laboratory selection studies and trans- and multigenerational experiments. Phenotypic plasticity is likely to contribute to population persistence providing time for genetic adaptation to occur. Transgenerational and epigenetic effects indicate that the environmental and physiological history of the parents can affect offspring performance. There is a need for long-term, multigenerational experiments to determine the influence of phenotypic plasticity, genetic variation and transgenerational effects on species' capacity to persist in a changing ocean. However, multigenerational studies are only practicable for short generation species. Consideration of multiple morphological and physiological traits, including changes in molecular processes (eg, DNA methylation) and long-term studies that facilitate acclimatization will be essential in making informed predictions of how the seascape and marine communities will be altered by climate change.

Natural acidified marine systems: Lessons and predictions.

Natural acidified marine systems (ASs) are environments with relatively low pH levels due to natural causes such as volcanic activity, geochemical reactions, and biological processes. These systems act as natural laboratories for the study of the effects of ocean acidification, allowing for the observation of long-term ecological and evolutionary responses. Understanding these systems is crucial for predicting the effects of anthropogenic ocean acidification (OA) on marine ecosystems. There are 23 ASs in which scientific research has shown significant parallelisms in their results worldwide, such as the disappearance of calcareous organisms and the loss of species with key ecological functions under OA conditions. Future research should emphasize continuous collaboration among teams, as well as public access to oceanographic and biological data along with the monitoring of environmental variables at each AS. To preserve these areas, it is imperative to employ non-destructive methods and protect them as human heritage sites.

Genomic synergistic efficient carbon fixation and nitrogen removal induced by excessive inorganic carbon in the anammox-centered coupling system.

Given the significance of HCO3- for autotrophic anammox bacteria (AnAOB), excessive HCO3- was always provided in anammox-related systems and engineering applications. However, its impact mechanism on anammox process at genome-level remains unknown. This study firstly established an anammox-centered coupling system that entails heterotrophic partial denitrification (PD) and hydrolytic acidification (A-PDHA) fed mainly with inorganic carbon (high HCO3- concentration and low C/N ratio). Metagenomic binning and metatranscriptomics analyses indicated that high HCO3- concentration enhanced expression of natural most efficient phosphoenolpyruvate (PEP) carboxylase within AnAOB, by up to 30.59 folds. This further induced AnAOB to achieve high-speed carbon-fixing reaction through cross-feeding of phosphate and PEP precursors with heterotrophs. Additionally, the enhanced activity of transporters and catalytic enzymes (up to 4949-fold) induced by low C/N ratio enabled heterotrophs to eliminate extracellular accumulated energy precursors mainly derived from carbon fixation products of AnAOB. This maintained high-speed carbon-fixing reaction within AnAOB and supplemented heterotrophs with organics. Moreover, assimilated energy precursors stimulated nitrogen metabolism enzymes, especially NO2- reductase (968.14 times), in heterotrophs. This established an energy-saving PD-A process mediated by interspecies NO shuttle. These variation resulted in efficient nitrogen removal (>95 %) and reduced external organic carbon demand (67 %) in A-PDHA system. This study unveils the great potential of an anammox-centered autotrophic-heterotrophic coupling system for achieving cost-effective nitrogen removal and enhancing carbon fixation under excessive HCO3- doses.

Widespread scope for coral adaptation under combined ocean warming and acidification.

Reef-building coral populations are at serious risk of collapse due to the combined effects of ocean warming and acidification. Nonetheless, many corals show potential to adapt to the changing ocean conditions. Here we examine the broad sense heritability (H2) of coral calcification rates across an ecologically and phylogenetically diverse sampling of eight of the primary reef-building corals across the Indo-Pacific. We show that all eight species exhibit relatively high heritability of calcification rates under combined warming and acidification (0.23-0.56). Furthermore, tolerance to each factor is positively correlated and the two factors do not interact in most of the species, contrary to the idea of trade-offs between temperature and pH sensitivity, and all eight species can co-evolve tolerance to elevated temperature and reduced pH. Using these values together with historical data, we estimate potential increases in thermal tolerance of 1.0-1.7°C over the next 50 years, depending on species. None of these species are probably capable of keeping up with a high global change scenario and climate change mitigation is essential if reefs are to persist. Such estimates are critical for our understanding of how corals may respond to global change, accurately parametrizing modelled responses, and predicting rapid evolution.

Ocean acidification will not affect the shell strength of juveniles of the commercial clam species Chamelea gallina: Implications of the local alkalinization of seawater.

Ocean acidification (OA) is expected to decrease the strength of bivalves' shells, especially during the early stages of development, with negative consequences to the resilience of natural populations and the economy. The objectives of the present study were to assess the long-term effect of increasing pCO2 after 217 days of exposure under controlled conditions of pH of ∼8.2, 8.0, and 7.7 on the strength and integrity of shells of juveniles of the commercial striped venus clam Chamelea gallina. Shell strength was estimated through compression tests and integrity through scanning electron microscopy (SEM) and dispersive X-ray analyses (EDX). The results showed that under increasing pCO2 the shell strength of juveniles is unaffected, which could be related to the locally elevated total alkalinity of seawater with respect to other parts of the coastal lagoon. However, despite this, it was also observed that the juvenile clams exposed to elevated pCO2 decreased their shell thickness and increased the porosity of their prismatic layer. Under future OA conditions, these changes could eventually compromise the integrity of the shells, becoming more vulnerable to the attack of predators and breakable during fishing operations. Future studies should address the plasticity of the organisms and the effect of the alkalinization of seawater on the resilience of shellfish juveniles under global change conditions.

Benthic diatom response to short-term acidification and warming influenced by grazing and nutrients.

This study investigated differences in total biomass (ash-free dry weight) of the periphyton and autotrophic biomass (chlorophyll-a content) of benthic diatoms in the absence or presence (No Grazer vs With Grazer) of two invertebrate grazers (Stichopus cf. horrens and Trochus maculatus) under simulated ambient (PRESENT), independent ocean acidification (OA) and warming (OW), and their combination (FUTURE) over an eight-day period. In the absence of a grazer, there were no significant differences in the average of the total and autotrophic biomass among treatments for both experiments. Stichopus significantly reduced the total and autotrophic biomass after 1 day, except under OW. Trochus significantly reduced the total biomass in the OA and OW treatments after 5 days, and the autotrophic biomass in the OA treatment after 1 and 5 days of grazing. In treatments where total and autotrophic biomass were not reduced, nutrients from the fecal matter and metabolic wastes of grazers seemingly stimulated the regeneration of microalgal biomass. The amount of fecal matter produced also affected the rate of microalgal renewal. In addition, due to the unexpected difference in seawater nutrient concentration during the two experiments, comparison of primary production under PRESENT was done to tease out nutrient effects. In PRESENT, autotrophic biomass was higher in Experiment 1 than Experiment 2, which was likely influenced by differences in nutrient concentrations. Results of this study elucidate underlying mechanisms in microalgal interactions with biotic and abiotic factors in tropical systems under changing ocean conditions.

Ratiometric Fluorescent pH Sensing with Carbon Dots: Fluorescence Mapping across pH Levels for Potential Underwater Applications.

Ocean acidification has become a major climate change concern requiring continuous observation. Additionally, in the industry, pH surveillance is of great importance. Consequently, there is a pressing demand to develop robust and inexpensive pH sensors. Ratiometric fluorescence pH sensing stands out as a promising concept. The application of carbon dots in fluorescent sensing presents a compelling avenue for the advancement of pH-sensing solutions. This potential is underpinned by the affordability of carbon dots, their straightforward manufacturing process, low toxicity, and minimal susceptibility to photobleaching. Thus, investigating novel carbon dots is essential to identify optimal pH-sensitive candidates. In this study, five carbon dots were synthesized through a simple solvothermal treatment, and their fluorescence was examined as a function of pH within the range of 5-9, across an excitation range of 200-550 nm and an emission range of 250-750 nm. The resulting optical features showed that all five carbon dots exhibited pH sensitivity in both the UV and visible regions. One type of carbon dot, synthesized from m-phenylenediamine, displayed ratiometric properties at four excitation wavelengths, with the best results observed when excited in the visible spectrum at 475 nm. Indeed, these carbon dots exhibited good linearity over pH values of 6-9 in aqueous Carmody buffer solution by calculating the ratio of the green emission band at 525 nm to the orange one at 630 nm (I525nm/I630nm), demonstrating highly suitable properties for ratiometric sensing.

Evolution of chitin-synthase in molluscs and their response to ocean acidification.

Chitin-synthase (CHS) is found in most eukaryotes and has a complex evolutionary history. Research into CHS has mainly been in the context of biomineralization of mollusc shells an area of high interest due to the consequences of ocean acidification. Exploration of CHS at the genomic level in molluscs, the evolution of isoforms, their tissue distribution, and response to environmental challenges are largely unknown. Exploiting the extensive molecular resources for mollusc species it is revealed that bivalves possess the largest number of CHS genes (12-22) reported to date in eukaryotes. The evolutionary tree constructed at the class level of molluscs indicates four CHS Type II isoforms (A-D) probably existed in the most recent common ancestor, and Type II-A (Type II-A-1/Type II-A-2) and Type II-C (Type II-C-1/Type II-C-2) underwent further differentiation. Non-specific loss of CHS isoforms occurred at the class level, and in some Type II (B-D groups) isoforms the myosin head domain, which is associated with shell formation, was not preserved and highly species-specific tissue expression of CHS isoforms occurred. These observations strongly support the idea of CHS functional diversification with shell biomineralization being one of several important functions. Analysis of transcriptome data uncovered the species-specific potential of CHS isoforms in shell formation and a species-specific response to ocean acidification (OA). The impact of OA was not CHS isoform-dependent although in Mytilus, Type I-B and Type II-D gene expression was down-regulated in both M. galloprovincialis and M. coruscus. In summary, during CHS evolution the gene family expanded in bivalves generating a large diversity of isoforms with different structures and with a ubiquitous tissue distribution suggesting that chitin is involved in many biological functions. These findings provide insight into CHS evolution in molluscs and lay the foundation for research into their function and response to environmental changes.

Effect of ultrasound-attenuation on technological and functional properties of two strains of Lactiplantibacillus plantarum isolated from table olives.

While probiotics have a wide range of beneficial properties, they can also negatively affect the taste or aroma of foods products by resulting in the phenomenon of post-acidification. Ultrasound (US) is a tool to modulate the metabolism of probiotic bacteria, counteracting post-acidification and improving the performance and functional properties of microorganisms without affecting their viability. The purpose of this paper was to evaluate the effect of 10 different combinations of power (20 and 40 %) and duration (2, 4, 6, 8 and 10 min) of US treatment on two functional strains of Lactiplantibacillus plantarum (c16 and c19) isolated from table olives, with the aim of understanding how, some of the main functional and technological traits (viability, acidification, growth profile under different conditions, antibiotic resistance, viability at pH 2.0 and 0.3 % bile salts), were affected. It was found that the effects were strain dependent, and the best results were obtained for strain c19 in the combinations at 20 % for 8 and 10 min and 40 % for 2 min, where an improvement in functional characteristics was found, with some effects on biofilm stability, inhibition of acidification, without adverse results on some technological properties.

Characterization of two carbonic anhydrase isoforms in the pulmonate snail (Lymnaea Stagnalis) and their involvement in Molluskan calcification.

Calcifying organisms are suffering from negative impacts induced by climate change, such as CO2-induced acidification, which may impair external calcified structures. Freshwater mollusks have the potential to suffer more from CO2-induced acidification than marine calcifiers due to the lower buffering capacity of many freshwater systems. One of the most important enzymes contributing to the biomineralization reaction is carbonic anhydrase (CA), which catalyzes the reversible conversion of CO2 to bicarbonate, the major carbon source of the calcareous structure in calcifiers. In this study we characterized two α-CA isoforms (LsCA1 and LsCA4) from the freshwater snail Lymnaea stagnalis using a combination of gene sequencing, gene expression, phylogenetic analysis and biochemical assays. Both CA isoforms demonstrated high expression levels in the mantle tissue, the major site for biomineralization. Furthermore, expression of LsCA4 during development parallels shell formation. The primary protein structure analysis, active site configuration and the catalytic activity of LsCA4 together suggest that the LsCA4 is embedded in the apical and basolateral membranes of mantle cells; while LsCA1 is proposed to be cytosolic and might play an important role in acid-base regulation. These findings of LsCA isoforms form a strong basis for a more detailed physiological understanding of the effects of elevated CO2 on calcification in freshwater mollusks.