Novel strategies to improve co-fermentation of pentoses with D-glucose by recombinant yeast strains in lignocellulosic hydrolysates

Economically feasible production of second-generation biofuels requires efficient co-fermentation of pentose and hexose sugars in lignocellulosic hydrolysates under very harsh conditions. Baker’s yeast is an excellent, traditionally used ethanol producer but is naturally not able to utilize pentoses. This is due to the lack of pentose-specific transporter proteins and enzymatic reactions. Thus, natural yeast strains must be modified by genetic engineering. Although the construction of various recombinant yeast strains able to ferment pentose sugars has been described during the last two decades, their rates of pentose utilization is still significantly lower than D-glucose fermentation. Moreover, pentoses are only fermented after D-glucose is exhausted, resulting in an uneconomical increase in the fermentation time. In this addendum, we discuss novel approaches to improve utilization of pentoses by development of specific transporters and substrate channeling in enzyme cascades. Addendum to: T Subtil, E Boles. Competition between pentoses and glucose during uptake and catabolism in recombinant Saccharomyces cerevisiae. Biotechnol Biofuels 2012; 5: 14 PMID: 22424089 DOI: 10.1186/1754-6834-5-1

Brown shrimp (Crangon crangon) processing remains as ingredient for Litopenaeus vannamei feeds: Biochemical characterisation and digestibility

Processing remains of brown shrimp, Crangon crangon, account for up to 60 % of the catch while only the small muscle fraction is used for human consumption. Incorporation into aquafeeds for high-valued species would reduce waste, create by-product value and promote sustainable aquaculture development. A detailed chemical characterisation of the remains from mechanically peeled brown shrimp was made and apparent nutrient digestibility coefficients in Litopenaeus vannamei were investigated. Brown shrimp processing remains (BSPR) contain substantial amounts of key nutrients (521 g⋅kg-1 crude protein, 74 g⋅kg-1 total lipid, 15 MJ⋅kg-1 gross energy) and valuable functional ingredients were detected (cholesterol, astaxanthin). Apparent energy (82 %) and protein (86 %) digestibility coefficients reveal good bioavailability of these nutrients. Dry matter digestibility was lower (64 %) presumably due to the high ash content (244 g⋅kg-1). The amino acid profile meets dietary requirements of penaeid shrimp with high apparent lysine and methionine digestibility coefficients. Analysis of macro- and micro minerals showed reasonable levels of required dietary minerals (phosphorus, magnesium, copper, manganese, selenium, zinc) and apparent copper digestibility was high (93 %). Contamination levels present in BSPR were below European standards acceptable for human consumption. Processing remains of brown shrimp have a high potential as alternative feed ingredient in sustainable diets for L. vannamei in recirculating aquaculture systems

Porcine and Chicken Intestinal Epithelial Cell Models for Screening Phytogenic Feed Additives—Chances and Limitations in Use as Alternatives to Feeding Trials

Numerous bioactive plant additives have shown various positive effects in pigs and chickens. The demand for feed additives of natural origin has increased rapidly in recent years to support the health of farm animals and thus minimize the need for antibiotics and other drugs. Although only in vivo experiments can fully represent their effect on the organism, the establishment of reliable in vitro methods is becoming increasingly important in the goal of reducing the use of animals in experiments. The use of cell models requires strict control of the experimental conditions so that reliability and reproducibility can be achieved. In particular, the intestinal porcine epithelial cell line IPEC-J2 represents a promising model for the development of new additives. It offers the possibility to investigate antioxidative, antimicrobial, anti- or pro-proliferative and antiviral effects. However, the use of IPEC-J2 is limited due to its purely epithelial origin and some differences in its morphology and functionality compared to the in vivo situation. With regard to chickens, the development of a reliable intestinal epithelial cell model has attracted the attention of researchers in recent years. Although a promising model was presented lately, further studies are needed to enable the standardized use of a chicken cell line for testing phytogenic feed additives. Finally, co-cultivation of the currently available cell lines with other cell lines and the development of organoids will open up further application possibilities. Special emphasis was given to the IPEC-J2 cell model. Therefore, all publications that investigated plant derived compounds in this cell line were considered. The section on chicken cell lines is based on publications describing the development of chicken intestinal epithelial cell models

The redox-sensitive transcription factor Rap2.4a controls nuclear expression of 2-Cys peroxiredoxin A and other chloroplast antioxidant enzymes

Shaikhali J, Heiber I, Seidel T, et al. The redox-sensitive transcription factor Rap2.4a controls nuclear expression of 2-Cys peroxiredoxin A and other chloroplast antioxidant enzymes. BMC Plant Biology. 2008;8(1):48

Physical and cognitive doping in university students using the unrelated question model (UQM): Assessing the influence of the probability of receiving the sensitive question on prevalence estimation

Study objectives: In order to increase the value of randomized response techniques (RRTs) as tools for studying sensitive issues, the present study investigated whether the prevalence estimate for a sensitive item π̂$_{s}$ assessed with the unrelated questionnaire method (UQM) is influenced by changing the probability of receiving the sensitive question p. Material and methods: A short paper-and-pencil questionnaire was distributed to 1.243 university students assessing the 12-month prevalence of physical and cognitive doping using two versions of the UQM with different probabilities for receiving the sensitive question (p ≈ 1/3 and p ≈ 2/3). Likelihood ratio tests were used to assess whether the prevalence estimates for physical and cognitive doping differed significantly between p ≈ 1/3 and p ≈ 2/3. The order of questions (physical doping and cognitive doping) as well as the probability of receiving the sensitive question (p ≈ 1/3 or p ≈ 2/3) were counterbalanced across participants. Statistical power analyses were performed to determine sample size. Results: The prevalence estimate for physical doping with p ≈ 1/3 was 22.5% (95% CI: 10.8-34.1), and 12.8% (95% CI: 7.6-18.0) with p ≈ 2/3. For cognitive doping with p ≈ 1/3, the estimated prevalence was 22.5% (95% CI: 11.0-34.1), whereas it was 18.0% (95% CI: 12.5-23.5) with p ≈ 2/3. Likelihood-ratio tests revealed that prevalence estimates for both physical and cognitive doping, respectively, did not differ significantly under p ≈ 1/3 and p ≈ 2/3 (physical doping: χ2 = 2.25, df = 1, p = 0.13; cognitive doping: χ2 = 0.49, df = 1, p = 0.48). Bayes factors computed with the Savage-Dickey method favored the null (‟the prevalence estimates are identical under p ≈ 1/3 and p ≈ 2/3“) over the alternative (‟the prevalence estimates differ under p ≈ 1/3 and p ≈ 2/3“) hypothesis for both physical doping (BF = 2.3) and cognitive doping (BF = 5.3). Conclusion: The present results suggest that prevalence estimates for physical and cognitive doping assessed by the UQM are largely unaffected by the probability for receiving the sensitive question p

Development of a D-xylose fermenting and inhibitor tolerant industrial Saccharomyces cerevisiae strain with high performance in lignocellulose hydrolysates using metabolic and evolutionary engineering

Background: The production of bioethanol from lignocellulose hydrolysates requires a robust, D-xylose-fermenting and inhibitor-tolerant microorganism as catalyst. The purpose of the present work was to develop such a strain from a prime industrial yeast strain, Ethanol Red, used for bioethanol production. Results: An expression cassette containing 13 genes including Clostridium phytofermentans XylA, encoding D-xylose isomerase (XI), and enzymes of the pentose phosphate pathway was inserted in two copies in the genome of Ethanol Red. Subsequent EMS mutagenesis, genome shuffling and selection in D-xylose-enriched lignocellulose hydrolysate, followed by multiple rounds of evolutionary engineering in complex medium with D-xylose, gradually established efficient D-xylose fermentation. The best-performing strain, GS1.11-26, showed a maximum specific D-xylose consumption rate of 1.1 g/g DW/h in synthetic medium, with complete attenuation of 35 g/L D-xylose in about 17 h. In separate hydrolysis and fermentation of lignocellulose hydrolysates of Arundo donax (giant reed), spruce and a wheat straw/hay mixture, the maximum specific D-xylose consumption rate was 0.36, 0.23 and 1.1 g/g DW inoculum/h, and the final ethanol titer was 4.2, 3.9 and 5.8% (v/v), respectively. In simultaneous saccharification and fermentation of Arundo hydrolysate, GS1.11-26 produced 32% more ethanol than the parent strain Ethanol Red, due to efficient D-xylose utilization. The high D-xylose fermentation capacity was stable after extended growth in glucose. Cell extracts of strain GS1.11-26 displayed 17-fold higher XI activity compared to the parent strain, but overexpression of XI alone was not enough to establish D-xylose fermentation. The high D-xylose consumption rate was due to synergistic interaction between the high XI activity and one or more mutations in the genome. The GS1.11-26 had a partial respiratory defect causing a reduced aerobic growth rate. Conclusions: An industrial yeast strain for bioethanol production with lignocellulose hydrolysates has been developed in the genetic background of a strain widely used for commercial bioethanol production. The strain uses glucose and D-xylose with high consumption rates and partial cofermentation in various lignocellulose hydrolysates with very high ethanol yield. The GS1.11-26 strain shows highly promising potential for further development of an all-round robust yeast strain for efficient fermentation of various lignocellulose hydrolysates

Environmental drivers of circum-Antarctic glacier and ice shelf front retreat over the last two decades

The safety band of Antarctica, consisting of floating glacier tongues and ice shelves, buttresses ice discharge of the Antarctic Ice Sheet. Recent disintegration events of ice shelves along with glacier retreat indicate a weakening of this important safety band. Predicting calving front retreat is a real challenge due to complex ice dynamics in a data-scarce environment that are unique for each ice shelf and glacier. We explore the extent to which easy-to-access remote sensing and modeling data can help to define environmental conditions leading to calving front retreat. For the first time, we present a circum-Antarctic record of glacier and ice shelf front change over the last two decades in combination with environmental variables such as air temperature, sea ice days, snowmelt, sea surface temperature, and wind direction. We find that the Antarctic Ice Sheet area decreased by −29 618 ± 1193 km2 in extent between 1997–2008 and gained an area of 7108 ± 1029 km2 between 2009 and 2018. Retreat concentrated along the Antarctic Peninsula and West Antarctica including the biggest ice shelves (Ross and Ronne). In several cases, glacier and ice shelf retreat occurred in conjunction with one or several changes in environmental variables. Decreasing sea ice days, intense snowmelt, weakening easterlies, and relative changes in sea surface temperature were identified as enabling factors for retreat. In contrast, relative increases in mean air temperature did not correlate with calving front retreat. For future studies a more appropriate measure for atmospheric forcing should be considered, including above-zero-degree days and temperature extreme events. To better understand drivers of glacier and ice shelf retreat, it is critical to analyze the magnitude of basal melt through the intrusion of warm Circumpolar Deep Water that is driven by strengthening westerlies and to further assess surface hydrology processes such as meltwater ponding, runoff, and lake drainage

Intensity and Inhalation of Smoking in the Aetiology of Laryngeal Cancer

The carcinogenic effect of smoking on laryngeal cancer is well established; however, the risk pattern for detailed smoking characteristics is less clear. Thus, the aim of this analysis was to quantify the impact of different inhalation behaviours on the risk of laryngeal cancer. We conducted a population-based case control study in Germany, frequency-matched for sex and age, using a standardized questionnaire covering lifelong smoking details, including age at start, time since quitting, types of smoking products, duration, intensity and inhalation behaviour. We found higher risks for increasing duration and intensity of smoking. A clear dose-response relationship was found in all inhalation subgroups, i.e., not only for deep inhalers, but also for those puffing on a cigarette. Clearly reduced risks could be observed for quitting smoking. Changing inhalation habits might be considered as a first step to reducing the risk of developing laryngeal cancer. However, the best way to effectively reduce laryngeal cancer risk is to quit smoking

All-cause and Cardiovascular mortality among ethnic German immigrants from the Former Soviet Union: a cohort study

BACKGROUND: Migration is a phenomenon of particular Public Health importance. Since 1990, almost 2 million ethnic Germans (Aussiedler) have migrated from the former Soviet Union (FSU) to Germany. This study compares their overall and cardiovascular disease (CVD) mortality to that of Germany's general population. Because of high overall and CVD mortality in the FSU and low socio-economic status of Aussiedler in Germany, we hypothesize that their mortality is higher. METHODS: We conducted a retrospective cohort study for 1990–2002 with data of 34,393 Aussiedler. We assessed vital status at population registries and causes of death at the state statistical office. We calculated standardized mortality ratios (SMRs) for the whole cohort and substrata of covariables such as age, sex and family size. To assess multivariate effects, we used Poisson regression. RESULTS: 1657 cohort members died before December 31, 2002, and 680 deaths (41.03%) were due to CVD. The SMR for the whole cohort was 0.85 (95%-CI 0.81–0.89) for all causes of death and 0.79 (95%-CI 0.73–0.85) for CVD. SMRs were higher than one for younger Aussiedler and lower for older ones. There was no clear effect of duration of stay on SMRs. For 1990–93, SMRs were significantly lower than in subsequent years. In families comprising at least five members upon arrival in Germany, SMRs were significantly lower than in smaller families. CONCLUSION: In contrast to our hypothesis on migrants' health, overall and CVD mortality among Aussiedler is lower than in Germany's general population. Possible explanations are a substantially better health status of Aussiedler in the FSU as compared to the local average, a higher perceived socio-economic status of Aussiedler in Germany, or selection effects. SMR differences between substrata need further exploration, and risk factor data are needed