Othmane Merah

Bio: Othmane Merah is an academic researcher from University of Toulouse. The author has contributed to research in topics: Chemistry & Food science. The author has an hindex of 20, co-authored 24 publications receiving 1836 citations. Previous affiliations of Othmane Merah include Arts et Métiers ParisTech & Entertainments National Service Association.

Morphology, composition, production, processing and applications of Chlorella vulgaris: A review

Abstract: Economic and technical problems related to the reduction of petroleum resources require the valorisation of renewable raw material Recently, microalgae emerged as promising alternative feedstock that represents an enormous biodiversity with multiple benefits exceeding the potential of conventional agricultural feedstock Thus, this comprehensive review article spots the light on one of the most interesting microalga Chlorella vulgaris It assembles the history and a thorough description of its ultrastructure and composition according to growth conditions The harvesting techniques are presented in relation to the novel algo-refinery concept, with their technological advancements and potential applications in the market

Aqueous extraction of proteins from microalgae: Effect of different cell disruption methods

Abstract: The microalgal structure has been investigated to evaluate the release of proteins in aqueous media from five microalgae after conducting different cell disruption techniques: manual grinding, ultrasonication, alkaline treatment, and high-pressure treatment. After conducting cell disruption, the protein concentration in water was determined for all the microalgae and the results are discussed within the context of their cell wall structure. It was found that the aqueous media containing most protein concentration followed the order: high-pressure cell disruption>chemical treatment>ultrasonication>manual grinding. Fragile cell-walled microalgae were mostly attacked according to the following order: Haematococcus pluvialis < Nannochloropsis oculata < Chlorella vulgaris < Porphyridium cruentum ≤ Arthrospira platensis.

QTLs for grain carbon isotope discrimination in field-grown barley.

Abstract: In several crops including cereals, carbon isotope discrimination (Δ) has been associated with drought tolerance in terms of water-use efficiency and yield stability in drought-prone environments. By using a complete genetic map generated from 167 recombinant inbred lines from a cross between Tadmor and Er/Apm, QTLs associated with grain Δ have been detected in barley grown in three Mediterranean field environments, two differing only in water availability. Ten QTLs were identified: one was specific to one environment, two presented interaction with the environment, six presented main effects across three or two environments and one presented both effects. Heading date did not contribute to the environment (E) and G × E effects acting on Δ. Seasonal rainfall and the ratio of rainfall to evapo-transpiration made large contributions to the environmental effect, but their influence on G × E was weaker. Eight QTLs for Δ co-located with QTLs for physiological traits related to plant water status and/or osmotic adjustment, and/or for agronomic traits previously measured on the same population. Some perspectives in terms of characterising drought tolerance are evoked.

Potential importance of water status traits for durum wheat improvement under Mediterranean conditions

Abstract: Water status traits have been proposed as criteria for drought tolerance improvement in several species especially in bread wheat, oat and barley. In order to test this possibility in durum wheat, in 1995 and 1997, a collection of 144 genotypes from different geographical origins was cultivated under rainfed Mediterranean conditions in Montpellier (southern France). Relative water content (RWC), osmotic potential (OP), as well as leaf morphological traits, grain yield (GY), total above-ground biomass and harvest index (HI) were measured. Large genotypic variations were observed for all traits. Differences between the 2 years were also noticed for all the traits which could be attributed to differences in water availability between the 2 growing seasons. The correlation analysis has revealed significant positive associations between water status traits and both GY and HI within and across years. These results suggest that genotypes which can maintain higher water status and then higher transpiration rates during grain filling, are more efficient in dry matter partitioning to grain and hence higher yield. Heritabilities of water status characters were higher than those of productivity traits. Our results emphasized the value of RWC and OP as criteria for durum wheat grain yield improvement under rainfed Mediterranean conditions. Relationships between RWC, OP and flag leaf morphological traits are also discussed.

Breeding for high water-use efficiency.

Abstract: There is a pressing need to improve the water-use efficiency of rain-fed and irrigated crop production. Breeding crop varieties with higher water-use efficiency is seen as providing part of the solution. Three key processes can be exploited in breeding for high water-use efficiency: (i) moving more of the available water through the crop rather than it being wasted as evaporation from the soil surface or drainage beyond the root zone or being left behind in the root zone at harvest; (ii) acquiring more carbon (biomass) in exchange for the water transpired by the crop, i.e. improving crop transpiration efficiency; (iii) partitioning more of the achieved biomass into the harvested product. The relative importance of any one of these processes will vary depending on how water availability varies during the crop cycle. However, these three processes are not independent. Targeting specific traits to improve one process may have detrimental effects on the other two, but there may also be positive interactions. Progress in breeding for improved water-use efficiency of rain-fed wheat is reviewed to illustrate the nature of some of these interactions and to highlight opportunities that may be exploited in other crops as well as potential pitfalls. For C3 species, measuring carbon isotope discrimination provides a powerful means of improving water-use efficiency of leaf gas exchange, but experience has shown that improvements in leaf-level water-use efficiency may not always translate into higher crop water-use efficiency or yield. In fact, the reverse has frequently been observed. Reasons for this are explored in some detail. Crop simulation modelling can be used to assess the likely impact on water-use efficiency and yield of changing the expression of traits of interest. Results of such simulations indicate that greater progress may be achieved by pyramiding traits so that potential negative effects of individual traits are neutralized. DNA-based selection techniques may assist in such a strategy.

Algae as nutritional and functional food sources: revisiting our understanding

Abstract: Global demand for macroalgal and microalgal foods is growing, and algae are increasingly being consumed for functional benefits beyond the traditional considerations of nutrition and health. There is substantial evidence for the health benefits of algal-derived food products, but there remain considerable challenges in quantifying these benefits, as well as possible adverse effects. First, there is a limited understanding of nutritional composition across algal species, geographical regions, and seasons, all of which can substantially affect their dietary value. The second issue is quantifying which fractions of algal foods are bioavailable to humans, and which factors influence how food constituents are released, ranging from food preparation through genetic differentiation in the gut microbiome. Third is understanding how algal nutritional and functional constituents interact in human metabolism. Superimposed considerations are the effects of harvesting, storage, and food processing techniques that can dramatically influence the potential nutritive value of algal-derived foods. We highlight this rapidly advancing area of algal science with a particular focus on the key research required to assess better the health benefits of an alga or algal product. There are rich opportunities for phycologists in this emerging field, requiring exciting new experimental and collaborative approaches.

Improving Intrinsic Water-Use Efficiency and Crop Yield.

Abstract: Greater yield per unit rainfall is one of the most important challenges in dryland agriculture. Improving intrinsic water-use efficiency (W(T)), the ratio of CO(2) assimilation rate to transpiration rate at the stomata, may be one means of achieving this goal. Carbon isotope discrimination (Delta(13)C) is recognized as a reliable surrogate for W(T) and there have now been numerous studies which have examined the relationship between crop yield and W(T) (measured as Delta(13)C). These studies have shown the relationship between yield and W(T) to be highly variable. The impact on crop yield of genotypic variation in W(T) will depend on three factors: (i) the impact of variation in W(T) on crop growth rate, (ii) the impact of variation in W(T) on the rate of crop water use, and (iii) how growth and water use interact over the crop's duration to produce grain yield. The relative importance of these three factors will differ depending on the crop species being grown and the nature of the cropping environment. Here we consider these interactions using (i) the results of field trials with bread wheat (Triticum aestivum L.), durum wheat (T. turgidum L.), and barley (Hordeum vulgare L.) that have examined the association between yield and Delta(13)C and (ii) computer simulations with the SIMTAG wheat crop growth model. We present details of progress in breeding to improve W(T) and yield of wheat for Australian environments where crop growth is strongly dependent on subsoil moisture stored from out-of-season rains and assess other opportunities to improve crop yield using W(T).

Quantitative Trait Loci and Crop Performance under Abiotic Stress: Where Do We Stand?

Abstract: The improvement of crop yield has been possible through the indirect manipulation of quantitative trait loci (QTLs) that control heritable variability of the traits and physiological mechanisms that determine biomass production and its partitioning. This article surveys how QTL-based approaches