Investigating the feasibility of light (in)dependent continuous cultivation of an Extremophilic Algae, Galdieria sp. RTK37.1

The extremophilic nature and metabolic flexibility of Galdieria spp. have major potential in several biotechnological applications1. However, limiting research into successful large scale continuous cultivation of Galdieria sulphuraria has restricted industrial application of the species1. This research focused on investigating the feasibility of light dependant and independent continuous cultivation of Galdieria sp. RTK37.1 in various trophic and light conditions. Stable growth of Galdieria sp. RTK37.1 was achieved during photoautotrophic, mixotrophic and heterotrophic conditions, highlighting the ability to achieve submaximal specific growth while continuous collecting biomass for product retrieval. These results have potential industrial ramifications as they demonstrate that the growth of Galdieria sp. RTK37.1 can be manipulated to obtain desired biomass and product yields over long cultivation periods. Continuous cultivation of Galdieria sp. RTK37.1 under various light intensities highlighted that operating chemostats under non-optimal light conditions not only affect the growth of Galdieria sp. RTK37.1 but also the ability to control and achieve desired stable growth. Light intensities greater than ~ 101 mol m-2 s-1 increased wall adhesion and decreased overall photosynthesis rates in photoautotrophically grown Galdieria sp. RTK37.1. Although biomass production increased during cultivation under warm white LED lighting at 191.3 mol m-2 s-1, the presence of immobilised cells is not desired during chemostat cultivation as can lead to non-optimal operation and the inability to obtain steady state growth. Mixotrophic growth is defined as the ability for a cell to combine the mechanisms of photoautotrophic and heterotrophic growth, utilising both inorganic carbons through photosynthesis and organic carbon through respiration simultaneously6. Mixotrophic cultivation of Galdieria sp. RTK37.1 was shown to be an ideal growth condition for obtaining greater biomass production compared to photoautotrophically and heterotrophically grown Galdieria sp. RTK37.1. During steady state mixotrophic growth, Galdieria sp. RTK37.1 achieved a biomass concentration of 1.43 ( 0.12) g L-1, significantly greater than biomass concentrations during photoautotrophic and heterotrophic growth, which were only 0.93 ( 0.01) g L-1 and 0.63 ( 0.02) g L-1 respectively (t-test: p-value < 0.0001). The increased biomass production, along with the decreased net specific oxygen evolution rates and crude protein percentage (which indicated a decrease in photosynthesis compared with photoautotrophy) lead to the conclusion that Galdieria sp. RTK37.1 is a true mixotroph. The results demonstrated a synergistic effect between photosynthesis and aerobic respiration during mixotrophy, indicating both metabolism methods being utilised simultaneously in mixotrophic Galdieria sp. RTK37.1. This research demonstrated that Galdieria sp. RTK37.1 is a promising strain for larger scale production, with evidence towards its ability to be used for large scale continuous cultivation in a range of applications such as phycocyanin production. Biomass production and growth of Galdieria sp. RTK37.1 can be controlled during continuous cultivation by limiting nutrients such as carbon or ammonia, or through various light intensity and wavelength conditions. Additionally, this research highlighted the ability for Galdieria sp. RTK37.1 to adapt to a wide range of conditions, achieving stable growth even under multiply limiting factors

Nutrient and drought stress:Implications for phenology and biomass quality in miscanthus

Background and Aims : The cultivation of dedicated biomass crops, including miscanthus, on marginal land provides a promising approach to the reduction of dependency on fossil fuels. However, little is known about the impact of environmental stresses often experienced on lower-grade agricultural land on cell-wall quality traits in miscanthus biomass crops. In this study, three different miscanthus genotypes were exposed to drought stress and nutrient stress, both separately and in combination, with the aim of evaluating their impact on plant growth and cell-wall properties. Methods : Automated imaging facilities at the National Plant Phenomics Centre (NPPC-Aberystwyth) were used for dynamic phenotyping to identify plant responses to separate and combinatorial stresses. Harvested leaf and stem samples of the three miscanthus genotypes (Miscanthus sinensis, Miscanthus sacchariflorus and Miscanthus × giganteus) were separately subjected to saccharification assays, to measure sugar release, and cell-wall composition analyses. Key Results : Phenotyping showed that the M. sacchariflorus genotype Sac-5 and particularly the M. sinensis genotype Sin-11 coped better than the M. × giganteus genotype Gig-311 with drought stress when grown in nutrient-poor compost. Sugar release by enzymatic hydrolysis, used as a biomass quality measure, was significantly affected by the different environmental conditions in a stress-, genotype- and organ-dependent manner. A combination of abundant water and low nutrients resulted in the highest sugar release from leaves, while for stems this was generally associated with the combination of drought and nutrient-rich conditions. Cell-wall composition analyses suggest that changes in fine structure of cell-wall polysaccharides, including heteroxylans and pectins, possibly in association with lignin, contribute to the observed differences in cell-wall biomass sugar release. Conclusions: The results highlight the importance of the assessment of miscanthus biomass quality measures in addition to biomass yield determinations and the requirement for selecting suitable miscanthus genotypes for different environmental conditions

Clinical and clinicopathological features and outcomes of cats with suspected dietary induced pancytopenia

Background: After a strong epidemiological link to diet was established in an outbreak of pancytopenia in cats in spring 2021 in the United Kingdom, 3 dry diets were recalled. Concentrations of the hemato- and myelotoxic mycotoxins T-2, HT-2 and diacetoxyscirpenol (DAS) greater than the European Commission guidance for dry cat foods were detected in the recalled diets. Objectives: To describe clinical and clinicopathological findings in cats diagnosed with suspected diet induced pancytopenia. Animals: Fifty cats presenting with pancytopenia after exposure to a recalled diet. Methods: Multicenter retrospective case series study. Cats with known exposure to 1 of the recalled diets were included if presented with bi- or pancytopenia and underwent bone marrow examination. Results: Case fatality rate was 78%. Bone marrow aspirates and biopsy examination results were available in 23 cats; 19 cats had a bone marrow aspirate, and 8 cats had a biopsy core, available for examination. Bone marrow hypo to aplasia—often affecting all cell lines—was the main feature in all 31 available core specimens. A disproportionately pronounced effect on myeloid and megakaryocytic cells was observed in 19 cats. Myelofibrosis or bone marrow necrosis was not a feature. Conclusion and Clinical Importance: Mycotoxin induced pancytopenia should be considered as differential diagnosis in otherwise healthy cats presenting with bi- or pancytopenia and bone marrow hypo- to aplasia