Diatoms for carbon sequestration and bio-based manufacturing

Carbon dioxide (CO2) is a major greenhouse gas responsible for climate change. Diatoms, a natural sink of atmospheric CO2, can be cultivated industrially in autotrophic and mixotrophic modes for the purpose of CO2 sequestration. In addition, the metabolic diversity exhibited by this group of photosynthetic organisms provides avenues to redirect the captured carbon into products of value. These include lipids, omega-3 fatty acids, pigments, antioxidants, exopolysaccharides, sulphated polysaccharides, and other valuable metabolites that can be produced in environmentally sustainable bio-manufacturing processes. To realize the potential of diatoms, expansion of our knowledge of carbon supply, CO2 uptake and fixation by these organisms, in conjunction with ways to enhance metabolic routing of the fixed carbon to products of value is required. In this review, current knowledge is explored, with an evaluation of the potential of diatoms for carbon capture and bio-based manufacturing

Metabolic insights into infochemicals induced colony formation and flocculation in scenedesmus subspicatus unraveled by quantitative proteomics

Microalgae can respond to natural cues from crustacean grazers, such as Daphnia, by forming colonies and aggregations called flocs. Combining microalgal biology, physiological ecology, and quantitative proteomics, we identified how infochemicals from Daphnia trigger physiological and cellular level changes in the microalga Scenedesmus subspicatus, underpinning colony formation and flocculation. We discovered that flocculation occurs at an energy-demanding ‘alarm’ phase, with an important role proposed in cysteine synthesis. Flocculation appeared to be initially stimulated by the production of an extracellular matrix where polysaccharides and fatty acids were present, and later sustained at an ‘acclimation’ stage through mitogen-activated protein kinase (MAPK) signaling cascades. Colony formation required investment into fatty acid metabolism, likely linked to separation of membranes during cell division. Higher energy demands were required at the alarm phase, which subsequently decreased at the acclimation stage, thus suggesting a trade-off between colony formation and flocculation. From an ecological and evolutionary perspective, our findings represent an improved understanding of the effect of infochemicals on microalgae-grazers interactions, and how they can therefore potentially impact on the structure of aquatic communities. Moreover, the mechanisms revealed are of interest in algal biotechnology, for exploitation in low-cost, sustainable microalgal biomass harvesting

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Towards a Phaeodactylum tricornutum biorefinery in an outdoor UK environment

A series of commercial powdered media (Cell-Hi F2P, JWP and WP) and a hydroponics medium (FloraMicroBloom) were investigated for the cultivation of P. tricornutum, and compared with f/2 (a commonly employed laboratory cultivation medium; costlier to scale). Cell-Hi JWP showed good performance characteristics including cost-effectiveness. Outdoor cultivation of P. tricornutum in an airlift photobioreactor, using Cell-Hi JWP in the United Kingdom (UK) during September and October (average daily temperature ranging between 8 and 18 °C and natural sunlight) was comparable to cultivation indoors under controlled temperature and lighting. A strong positive correlation between fucoxanthin and chlorophyll a content, and a weak inverse correlation between eicosapentaenoic (EPA) content and temperature were observed. Commensal bacterial counts revealed a sinusoidal growth profile with a change in community dominance from Halomonas sp. to Marinobacter sp. This investigation reveals for the first time that a multi-product approach can be adopted with P. tricornutum in a UK outdoor environment using commercially viable powdered media

Microbial consortia : concept and application in fruit crop management

Microbial consortia thrive in nature, in a range of environments including biofilms, food products, soils, and wastewater. Borrowing the concept from nature, it is possible to characterize, engineer, and manage consortia, which as a strategy are being explored for applications in varied fields, including agriculture. This is still a broadly conceptual ideology that requires further development. Nevertheless, there are several areas of fruit crop management that can benefit from the managed use of microbial consortia, in particular as environmentally sustainable alternatives to chemical usage. Microbial consortia play a vital role in soil management and nutrient mobilization, in disease prevention and plant defense, in management of stress tolerance, in postharvest fruit management, and in overall ecosystem management. In this chapter, we present the concept of managed consortia and discuss the technology and challenges of microbiome engineering in fruit crop management

The transition away from chemical flocculants: Commercially viable harvesting of Phaeodactylum tricornutum

Harvesting can contribute up to 15% of the total production cost for microalgal biomanufacturing. Using flocculants is potentially a cost-effective approach but there has been considerable debate on the efficacy, cost, toxicity to the cell and environment, and the effect on the biomass further downstream. In this study, a range of biobased flocculants (chitosan from crab shells, Moringa oleifera seed extract, pectin from bananas, tannic acid-based derivatives from Acacia tree bark and egg shell powder) were compared with traditional chemical flocculants (aluminium sulphate, iron chloride and sodium hydroxide) for harvesting the diatom Phaeodactylum tricornutum. It was concluded that Tanac’s tannin based Tanfloc 8025 (SL range) was the most promising, requiring a low concentration (10.4 kg ton−1 biomass), at low cost ($27.04 ton−1 microalgal biomass). The flocculant was effective over a wide pH (7.5–10.0) and temperature (15–28 °C) range and harvesting (>85% efficiency) occurred in 10 mins, which resulted in a biomass concentration factor of ≥ 5.69

Using Production to Assess Learning: An ILE That Fosters Self-Regulated Learning

International audienceCurrent systems aiming at engaging students in Self-Regulated Learning processes are often prompt-based and domain-dependent. Such metacognitive prompts are either difficult to interpret for novices or ignored by experts. Although domain-dependence per se cannot be considered as a drawback, it is often due to a rigid structure which prevents from moving to another domain. We detail here a system that addresses these limitations. This two-loop system provides texts to be learned through summarization. The first loop is called Reading, in which the student formulates a query and is provided with texts related to this query. Then the student judges whether each text presented could be summarized. The second loop is called Writing, in which the student writes out a summary of the texts, then gets an assessment from the system. In order to automatically perform various comprehension-centered tasks (i.e., texts that match queries, assessment of summaries), our system uses LSA (Latent Semantic Analysis), a tool devised for the semantic comparison of texts