Salix as a biorefinery feedstock : an inquiry into factors affecting conversion performance

Lignocellulosic biomass is one of the world’s greatest natural resources, with po-tential for replacing a considerable portion of current fossil resource use. Although lignocellulosic biomass can be readily utilized for generating heat and power via combustion, its conversion into storable fuels such as ethanol and biogas presents a greater challenge. Biomass can be converted into such fuels in biorefineries, although the inherent resistance of lignocellulosic biomass to deconstruction, biomass recalci-trance, incurs financial penalties. The genus Salix contains several woody species known for their high biomass production, low requirements for agricultural inputs, and short harvest rotations. These species could serve as optimal feedstocks for the production of transportation biofuels, if their recalcitrance can be overcome. In this thesis, several aspects related to Salix as a biomass feedstock for use in biorefineries are considered, including breeding, conversion methodology, and cultivation. Biomass recalcitrance and several other traits relevant to the breeding of improved Salix varieties were quantified in a population of natural accessions of S. viminalis, and narrow-sense heritabilities and genetic and phenotypic correlations were calculated. Narrow-sense heritabilities (h2) for biomass recalcitrance were 0.23 to 0.29, indicating a certain level of genetic control. Shoot weights and ratios of syringyl to guaiacyl monomers in lignin were negatively correlated with biomass recalcitrance, serving as possible proxy traits for selection of improved variants in breeding programs. The conversion performance of a subset of clones from the aforementioned pop-ulation were further evaluated using two different conversion systems, enzymatic hydrolysis (EH) and anaerobic digestion (AD). Despite fundamental differences be-tween these systems, measures of conversion performance correlated well, indicating that recalcitrance improvements are not specific to one conversion system. In AD, biomass recalcitrance more strongly affected conversion rates than final yields, and the AD system was overall less sensitive to variations in recalcitrance. Several other aspects related to the use of Salix as an AD feedstock were evaluated. By using a sequential reactor setup, methane yields of non-pretreated Salix were shown to be similar to those reported for steam pretreated material, allowing its use in smaller-scale facilities where pretreatment may not be feasible. Moreover, the choice of clone and rotation length were shown to affect conversion yields under AD, whereas there was no apparent effect of nitrogen fertilization. Making biofuels cost-competitive with their fossil counterparts will likely require a considerable amount of further work in several scientific and engineering disciplines. The contents of this thesis will hopefully contribute toward that goal

Cheap Sentiment

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Growth Effects of Government Expenditure and Taxation in Rich Countries: A Comment

In a recent article Stefan Fölster and Magnus Henrekson [2001] argue that “…the more the econometric problems that are addressed, the more robust the relationship between government size and economic growth appears”. But in failing to control for simultaneity in a valid manner the regressions reported by Fölster/Henrekson are flawed. Moreover, using theoretically valid instruments we find that the estimated partial correlation between size of the public sector and economic growth is statistically insignificant and highly unstable across specifications. A policy-maker who wants to promote growth is well-advised to look for other evidence than cross-country growth regressions.Economic growth; public sector; cross-country regressions; panel regressions

Catabolism and interactions of syntrophic propionate- and acetate oxidizing microorganisms under mesophilic, high-ammonia conditions

Microbial inhibition by high ammonia concentrations is a recurring problem that significantly restricts methane formation from intermediate acids, i.e., propionate and acetate, during anaerobic digestion of protein-rich waste material. Studying the syntrophic communities that perform acid conversion is challenging, due to their relatively low abundance within the microbial communities typically found in biogas processes and disruption of their cooperative behavior in pure cultures. To overcome these limitations, this study examined growth parameters and microbial community dynamics of highly enriched mesophilic and ammonia-tolerant syntrophic propionate and acetate-oxidizing communities and analyzed their metabolic activity and cooperative behavior using metagenomic and metatranscriptomic approaches. Cultivation in batch set-up demonstrated biphasic utilization of propionate, wherein acetate accumulated and underwent oxidation before complete degradation of propionate. Three key species for syntrophic acid degradation were inferred from genomic sequence information and gene expression: a syntrophic propionate-oxidizing bacterium (SPOB) "Candidatus Syntrophopropionicum ammoniitolerans", a syntrophic acetate-oxidizing bacterium (SAOB) Syntrophaceticus schinkii and a novel hydrogenotrophic methanogen, for which we propose the provisional name "Candidatus Methanoculleus ammoniitolerans". The results revealed consistent transcriptional profiles of the SAOB and the methanogen both during propionate and acetate oxidation, regardless of the presence of an active propionate oxidizer. Gene expression indicated versatile capabilities of the two syntrophic bacteria, utilizing both molecular hydrogen and formate as an outlet for reducing equivalents formed during acid oxidation, while conserving energy through build-up of sodium/proton motive force. The methanogen used hydrogen and formate as electron sources. Furthermore, results of the present study provided a framework for future research into ammonia tolerance, mobility, aggregate formation and interspecies cooperation

Dairy fat biomarkers and cardiometabolic health

Commonly held dietary guidelines discourage full-fat dairy consumption due its to high levels of saturated fatty acids, which are believed to aversely influence cardiovascular disease risk. Cardiovascular diseases cause more than one third of deaths in the developed world. With dairy often providing a large part of energy and nutrients in Western diets, research into its effects on human health is warranted. Several recent studies have suggested a protective role of dairy in the development of cardiometabolic disease. However, many of these have used imprecise methods of dietary assessment, based on questionnaires or interviews. Biomarkers are emerging as a means of evaluating diet in a more objective way. Currently used dairy fat biomarkers are minor fatty acid constituents of dairy that preferably are unique to dairy and not influenced by endogenous metabolism. These compounds can be measured in blood or adipose tissue samples, and can be good indicators of short (weeks) and long (years) term intakes, depending on the sampling medium. The most reliable indicator of dairy fat intake seems to be pentadecanoic acid (C15:0), however research in this area is somewhat lacking. Studies where these biomarkers have been evaluated in relation to cardiometabolic disease endpoints (incident cardiovascular disease or type-2 diabetes) have generally found dairy to elicit a protective effect. Crosssectional studies evaluating indices of the metabolic syndrome suggest that dairy fat may slow down disease progression. Further standardization of methodologies and validation of biomarker concentrations in relation to intake could improve reliability of biomarkerbased dietary assessments. Furthermore, combining chemical and traditional methods could provide even better precision than using either method alone.Många av dagens kostråd avråder från konsumtion av fullfeta mejeriprodukter p.g.a. höga halter mättade fettsyror, vilka anses påverka kardiovaskulär hälsa negativt. Hjärt–kärlsjukdomar orsakar mer än en tredjedel av alla dödsfall i den industrialiserade världen. Då mejeriprodukter ofta bidrar med en betydande del av energi och näringsämnen i den västerländska kosten är det motiverat att studera dess effekter på human hälsa. Ett antal studier har de senaste åren funnit resultat som antytt att konsumtion av mejeriprodukter kan ha en skyddande inverkan på risken för insjuknande i hjärt–kärlsjukdom, men många av dessa har använt osäkra metoder för att mäta deltagarnas kostvanor. Mer precisa mätningar kan göras med biomarkörer, något som ökat i användning under senare tid. De biomarkörer för mjölkfettintag som används i dag är fettsyror som förekommer i låga halter i mjölken, och som bör vara både unika för mejeriprodukter och inte påverkade av endogen metabolism. Dessa ämnen kan mätas i blod eller i fettvävnad, och kan vara goda indikatorer för konsumtion över korta (veckor) eller långa (år) perioder. En av de mest tillförlitliga markörerna anses vara pentadekansyra (C15:0), men ytterligare forskning behövs för att säkerställa detta. Studier som utvärderat dessa biomarkörer i förhållande till kliniska ändpunkter (incidens av hjärt–kärlsjukdom eller diabetes typ 2) har generellt visat på en skyddande effekt. Tvärsnittsstudier som undersökt olika aspekter av metabola syndromet antyder att mjölkfettskonsumtion kan fördröja dess utveckling. Ytterligare standardisering av metoder och validering av samband mellan biomarkörer och intag skulle kunna förbättra precisionen hos kemiska kostskattningsmetoder. Precisionen skulle ytterligare kunna förbättras om kemiska och traditionella metoder kombinerades

De svenska tidningsstiftelserna: Partipressens sista bastion?

art

Fodder yeast and biogas production: A fruitful symbiosis?

Due to a growing world population and strained wild fish stocks, aquaculture is expected to provide a large part of the increased global demand for animal protein, as the majority of wild fish stocks are already being fished at or above their sustainable capacity. However, fish feed often contains a significant amount of fish meal, produced from wild-caught fish. Thus, increasing farmed fish production may not be sustainable as long as fish meal remains a major ingredient. Microbial biomass, commonly known as single-cell protein (SCP), can replace fish meal in feed formulations. The financial viability of SCP production is dependent on the availability of cheap growth media. Biogas substrates, often mixtures of waste derived from food industry, agriculture, and households, could be ideal media due to their low cost and ubiquitous availability. The aims of this thesis were: first, to investigate whether yeast SCP can be produced on a biogas substrate consisting of household and agricultural waste; second, to screen several yeast strains and growth conditions for optimal biomass production; and third, to evaluate the effects on biogas production if part of input substrate stream is diverted into SCP production prior to further digestion in the biogas reactor. Several yeast strains were screened for biomass yield at several pH levels and temperatures. After screening, best-performing strains were cultivated on biogas substrate in continuously-stirred bioreactors, analyzing the resultant biomass. Strains were Wickerhamomyces anomalus J121, Pichia kudriavzevii J550, and Blastobotrys adeninivorans J564. Harvested biomass ranged from 7.0–14.8 g dry matter per l substrate, and protein contents were 22.6–32.7 %. Levels of the amino acid lysine were high in all biomass samples, which is important for replacing fish meal in feed formulations. Supernatants from the bioreactor fermentations were combined with whole biogas substrate, and the effects on biogas production were evaluated, as methane produced per g of volatile solids, using a batch methane potential assay. At the highest inclusion levels (1:1 control/supernatant (w/w)) P. kudriavzevii provided an increased output compared to W. anomalus (25 %, p = 0.04). P. kudriavzevii provided a 24% increase compared to control, but results were not significant ( p = 0.06). Filtered, untreated supernatant provided the largest increase in biogas production compared both to control substrate (30 %, p = 0.02) and to W. anomalus (31 %, p = 0.01).I takt med en ständigt växande världsbefolkning förväntas efterfrågan på animaliskt protein öka. Akvakultur, eller fiskodling, kommer sannolikt att bidra till en stor del av den förväntat ökande produktionen. Produktionen från majoriteten av vilda fiskbestånd beräknas inte kunna öka ytterligare, och en stor andel klassas redan som överfiskade. Då fiskmjöl, som framställs från vildfångad fisk, utgör en viktig ingrediens i fiskfoder är det inte säkert att en utökad produktion av odlad fisk är hållbar, och alternativa proteinkällor är därför efterfrågade. En sådan proteinkälla utgörs av mikrobiell biomassa, eller singelcell- protein (SCP). För storskalig produktion av SCP krävs tillgång till billigt tillväxtmedium. Biogassubstrat, ofta en blandning av avfall från livsmedels- och jordbrukssektorn samt hushåll, skulle kunna utgöra ett idealt sådant medium p.g.a. dess låga kostnad samt höga tillgänglighet. Syftet med detta arbete var tredelat: att undersöka om SCP från jäst kan produceras på biogassubstrat bestående av hushålls- och jordbruksavfall; vidare att utvärdera flera jäststammar samt odlingsbetingelser för optimal tillväxt; och slutligen att utvärdera effekten på biogasproduktion om jäst odlas på en del av biogassubstratet före dess introduktion i biogasreaktorn. Ett antal jäststammar utvärderades för biomasseproduktion vid flera temperaturer samt pH-nivåer. De mest högproducerande stammarna odlades sedan på biogassubstrat i fermentorer, och den producerade biomassan analy- serades. Dessa var Wickerhamomyces anomalus J121, Pichia kudriavzevii J550 och Blastobotrys adeninivorans J564. Fermentationerna resulterade i slutlig biomassa på 7.0–14.8 g per l substrat, och innehöll 22.6–32.7 % protein. Supernatanterna från odlingarna blandades med orört biogassubstrat och utvärderades för metanproduktion, som mängd metan per g glödförlust, i ett batchförsök. Vid den högsta graden inblandning (obehandlat substrat och supernatant i ett 1:1-förhållande baserat på vikt) producerade prover base- rade på P. kudriavzevii 25 % mer biogas jämfört med motsvarande från W. anomalus ( p = 0.04). En 24 %-ig ökning kunde ses då supernatant från P. kud- riavzevii J550 jämfördes med kontrollsubstrat, men detta resultat uppnådde inte statistisk signifikans (p = 0.06). Den största ökningen av biogaspro- duktion sågs vid tillsats av obehandlat, filtrerat substrat, som presterade bättre än både obehandlad kontroll (30 %), p = 0.02) och W. anomalus (31 %, p = 0.01)

Silage Inoculants Improves Quality and Aerobic Stability in Grass, Clover-Grass and Lucerne Silage

The type of silage additive will influence the characteristics of fermentation, dry matter (DM) losses, hygienic quality and aerobic stability of silage. The appropriate use of an additive also depends on the crop to which it is applied. Homofermentative lactic acid bacteria (LAB) strains are selected for rapid growth under under variable temperatures, herbages and dry matter concentrations. The homofermentative LAB are highly competitive and produce largely lactic acid and reduce pH and ammonia-N content compared to untreated silage (Muck 2012). Heterofermentative LAB such as Lactobacillus buchneri reduce the growth of yeast and mould and increase aerobic stability. These effects are retained when heterofermentative LAB are added in combination with homofermentative LAB (Kleinschmit et al. 2005). An alternative to the combination of homo- and heterofermentative inoculants is to use homofermentative LAB in combination with a chemical component such as sodium benzoate (NaBe). In an experiment by Jaakkola et al. (2010) a combination of Lactobacillus plantarum and sodium benzoate were more efficient than Lactobacillus plantarum and Lactobacillus buchneri to prevent heating of silage. The objective of the study was to investigate efficacy of different inoculant types on fermentation characteristics and aerobic stability of Lucerne (L), ryegrass (R), red clover-ryegrass (RCR) and ryegrass-timothy (RT) silages

MedieSverige 2019

Strukturen på den svenska medieutvecklingen växer fram i ett nära samspel med det omgivande samhället. De sociala, ekonomiska, politiska och teknologiska landskapen formar – och formas av – medielandskapet i en ständigt pågående process. I MedieSverige 2019 ges en aktuell och bred översikt över dagens svenska medielandskap. Genom att först belysa utvecklingen på de medieteknologiska och mediepolitiska områdena i Sverige, går rapporten vidare till att redovisa utvecklingen på publik- och reklammarknaderna, för att avslutningsvis beskriva den svenska mediestrukturen.Strukturen på den svenska medieutvecklingen växer fram i ett nära samspel med det omgivande samhället. De sociala, ekonomiska, politiska och teknologiska landskapen formar – och formas av – medielandskapet i en ständigt pågående process. I MedieSverige 2019 ges en aktuell och bred översikt över dagens svenska medielandskap. Genom att först belysa utvecklingen på de medieteknologiska och mediepolitiska områdena i Sverige, går rapporten vidare till att redovisa utvecklingen på publik- och reklammarknaderna, för att avslutningsvis beskriva den svenska mediestrukturen