Transforming sugars into fat – lipid biosynthesis using different sugars in Yarrowia lipolytica

In an era of ever‐increasing energy demands, a promising technology is being developed: the use of oleaginous microorganisms such as Yarrowia lipolytica to convert waste materials into biofuels. Here, we constructed two Y. lipolytica strains that displayed both increased lipid accumulation and more efficient use of biomass‐derived sugars, including glucose, fructose, galactose and inulin. The first strain, Y. lipolytica YLZ150, was derived from the French wild‐type strain W29. It had inhibited triacylglycerol mobilization (?tgl4 ) and β‐oxidation (?pox1–6 ), and it overexpressed GPD1 , DGA2 , HXK1 , the native Leloir pathway, SUC2 from Saccharomyces cerevisiae and INU1 from Kluyveromyces marxianus . The second strain, Y. lipolytica Y4779, was derived from the Polish A‐101 strain. It had inhibited β‐oxidation (?mfe2 ) and overexpressed GPD1 , DGA1 , HXK1 , YHT3, SUC2 and INU1 . In the first experiment, strain YLZ150 was batch‐cultured in media containing different hexoses; the highest values for lipid concentration and yield of lipids from the substrate were obtained using fructose (20.3 g dm^?3 and 0.14 g g^?1, respectively). In the second experiment, we grew the two strains in fed‐batch cultures to examine lipid biosynthesis from inulin (a fructose polymer). For Y4779, the lipid concentration was 10.3 g dm^?3 and the yield of lipids from substrate was 0.07 g g^?1; in contrast, for YLZ150, these values were 24 g dm^?3 and 0.16 g g^?1, respectively. The YLZ150 strain is thus able to efficiently exploit glucose, fructose, galactose, sucrose and inulin for lipid biosynthesis. Copyright © 2017 John Wiley & Sons, Ltd.     

Modulation of Starch Digestibility in Breakfast Cereals Consumed by Subjects with Metabolic Risk: Impact on Markers of Oxidative Stress and Inflammation during Fasting and the Postprandial Period

Scope : Decreasing postprandial glycaemic excursions may have a beneficial effect on inflammatory and oxidative stress profiles. In this study, we investigated the impact of carbohydrate digestibility modulation per se, as a means of reducing the glycaemic response, on metabolic and inflammatory responses in subjects with metabolic risk factors. Methods and results : Twenty healthy subjects with metabolic risk consumed a cereal product either high in Slowly Digestible Starch (HSDS) or low in SDS (LSDS) at breakfast daily for 3 weeks, in a cross‐over design. Following each 3‐week session, postprandial glycaemia, insulinaemia, the lipid profile, inflammation and oxidative stress markers were assessed and compared to those induced by ingestion of a glucose solution (as a reference). The 2‐h glycaemic and insulinaemic responses were significantly lower following the HSDS breakfast compared with the LSDS breakfast or glucose. No significant differences between the products were observed in terms of the lipid profile, C‐reactive protein, IL‐6 and tumour necrosis factor alpha. We observed a slight increase in fasting lipid peroxidation markers, including an increase in plasma malondialdehyde (MDA) and a decrease in whole blood glutathione (GSH), without significant alteration of urinary F2‐isoprostanes or plasma glutathione peroxidase (GPx) activity. Conclusion : Consumption of HSDS products for 3 weeks significantly altered both postprandial glycaemia and insulinaemia, but was not sufficient to modify the inflammatory profile. Consumption of both cereal products was associated with a slightly higher fasting oxidative stress profile.     

Cost-effectiveness of greenhouse gas mitigation in transport: A review of methodological approaches and their impact

A review is given of methodological practices for ex ante cost-effectiveness analysis (CEA) of transport greenhouse gas (GHG) mitigation measures, e.g. fuel economy and CO₂ standards for road vehicles in the US and EU. Besides the fundamental differences between different types of policies and abatement options which inherently result in different CEA outcomes, differences in methodological choices and assumptions are another important source of variation in CEA outcomes. Fourteen methodological issues clustered into six groups are identified on which thirty-three selected studies are systematically reviewed. The potential variation between lower and upper cost-effectiveness estimates for GHG mitigation measures in transport, resulting from different methodological choices and assumptions, lies in the order of $400 per tonne CO₂-eq. The practise of using CEA for policy-making could improve considerably by clearly indicating the specific purpose of the CEA and its strengths and limitations for policy decisions. Another improvement is related to the dominant approach in transport GHG mitigation studies: the bottom-up financial technical approach which assesses isolated effects, implying considerable limitations for policy-making. A shift to welfare-economic approaches using a hybrid model has the potential to establish an improved assessment of transport GHG mitigation measures based on realistic market responses and behavioural change.     

Green Alternatives to Nitrates and Nitrites in Meat-based Products–A Review

Several food additives are added in food for their preservation to maintain the freshness of food (antioxidants) or to slow down or stop the growth of microorganisms (preservative agents). Nitrites and nitrates are used as preservative agents in meat. Nitrites give a smoked taste, a pinkish color in the meat and protect the consumers against the risk of bacterial deterioration. Their addition is however very limited as, in high dose, it can have risks on human health and the environment. Nitrites may also combine with secondary or tertiary amines to form N-nitroso derivatives. Certain N-nitroso compounds have been shown to produce cancers in a wide range of laboratory animals. Thus, alternatives of nitrates and nitrites are the object of numerous research studies. Alternatives, such as the addition of vitamins, fruits, chemicals products, natural products containing nitrite or spices, which have similar properties of nitrites, are in evaluation. In fact, spices are considered to have several organoleptic and anti-microbial properties which would be interesting to study. Several spices and combinations of spices are being progressively evaluated. This review discusses the sources of nitrites and nitrates, their use as additives in food products, their physicochemical properties, their negatives effects and the use of alternatives of nitrites and nitrates in preserving meat products.     

Spark Plasma Sintering of Cryomilled Nanocrystalline Al Alloy - Part II: Influence of Processing Conditions on Densification and Properties

In this study, nanostructured Al 5083 powders, which were prepared via cryomilling, were consolidated using spark plasma sintering (SPS). The influence of processing conditions, e.g., the loading mode, starting microstructure (i.e., atomized vs cryomilled powders), sintering pressure, sintering temperature, and powder particle size on the consolidation response and associated mechanical properties were studied. Additionally, the mechanisms that govern densification during SPS were discussed also. The results reported herein suggest that the morphology and microstructure of the cryomilled powder resulted in an enhanced densification rate compared with that of atomized powder. The pressure-loading mode had a significant effect on the mechanical properties of the samples consolidated by SPS. The consolidated compact revealed differences in mechanical response when tested along the SPS loading axis and radial directions. Higher sintering pressures improved both the strength and ductility of the samples. The influence of grain size on diffusion was considered on the basis of available diffusion equations, and the results show that densification was attributed primarily to a plastic flow mechanism during the loading pressure period. Once the final pressure was applied, power law creep became the dominant densification mechanism. Higher sintering temperature improved the ductility of the consolidated compact at the expense of strength, whereas samples sintered at lower temperature exhibited brittle behavior. Finally, densification rate was found to be inversely proportional to the particle size.