Optimization of the IPP-bypass mevalonate pathway and fed-batch fermentation for the production of isoprenol in Escherichia coli.

Isoprenol (3-methyl-3-buten-1-ol) is a drop-in biofuel and a precursor for commodity chemicals. Biological production of isoprenol via the mevalonate pathway has been developed and optimized extensively in Escherichia coli, but high ATP requirements and isopentenyl diphosphate (IPP) toxicity have made it difficult to achieve high titer, yield, and large-scale production. To overcome these limitations, an IPP-bypass pathway was previously developed using the promiscuous activity of diphosphomevalonate decarboxylase, and enabled the production of isoprenol at a comparable yield and titer to the original pathway. In this study, we optimized this pathway, substantially improving isoprenol production. A titer of 3.7 g/L (0.14 g isoprenol per g glucose) was achieved in batch conditions using minimal medium by pathway optimization, and a further optimization of the fed-batch fermentation process enabled an isoprenol titer of 10.8 g/L (yield of 0.105 g/g and maximum productivity of 0.157 g L-1 h-1), which is the highest reported titer for this compound. The substantial increase in isoprenol titer via the IPP-bypass pathway in this study will facilitate progress toward commercialization

Patterns of Passage into protected areas: drivers and outcomes of Fulani immigration, settlement and integration into the Kachia Grazing Reserve, Northwest Nigeria

Abstract Increasing land use and associated competition for natural resources in the wake of high human and livestock population pressures have been major challenges confronting pastoralists of West Africa. This is especially true in Nigeria where Fulani make up 4% of the national population and prevailing national insecurity issues are impacting on pastoral livelihoods, including violent conflicts over land and ethnic, religious and political disparities. This study examined the dynamics of immigration within the Kachia Grazing Reserve (KGR), an exclusively Fulani pastoralist community in Kaduna State, northwest Nigeria, prompted by concerns from both the farming communities and the authorities about mounting pressure on existing limited resources, particularly in regard to availability of cattle grazing resources. Drawing from a household census conducted in 2011 and employing a range of qualitative methods (focus group discussions and key informant interviews), this study explored the drivers and consequences of immigration and subsequent integration within the KGR community. The study revealed two types of immigration: a steady trickle of pastoralists migrating to the reserve to settle and acquire land, secure from the stresses of competition from cultivators, and the sudden influx of internally displaced persons fleeing violent clashes in their areas of origin. Population pressure within the reserve has risen steadily over the past three decades, such that it is severely overgrazed (as evidenced by reports from the KGR community that the animals run short of pasture even during the wet season due to desertification and the spread of non-edible weeds). The newer immigrants, fleeing conflict, tended to arrive in the reserve with significantly larger herds than those kept by established residents. Pastoralists in the reserve have been forced back into the practice of seasonal transhumance in both wet and dry seasons to support their herds, with all the attendant risks of theft, clashes with cultivators and increased disease transmission

Inherited determinants of Crohn's disease and ulcerative colitis phenotypes: a genetic association study

Crohn's disease and ulcerative colitis are the two major forms of inflammatory bowel disease; treatment strategies have historically been determined by this binary categorisation. Genetic studies have identified 163 susceptibility loci for inflammatory bowel disease, mostly shared between Crohn's disease and ulcerative colitis. We undertook the largest genotype association study, to date, in widely used clinical subphenotypes of inflammatory bowel disease with the goal of further understanding the biological relations between diseases

Optimization of the IPP-bypass mevalonate pathway and fed-batch fermentation for the production of isoprenol in Escherichia coli.

Isoprenol (3-methyl-3-buten-1-ol) is a drop-in biofuel and a precursor for commodity chemicals. Biological production of isoprenol via the mevalonate pathway has been developed and optimized extensively in Escherichia coli, but high ATP requirements and isopentenyl diphosphate (IPP) toxicity have made it difficult to achieve high titer, yield, and large-scale production. To overcome these limitations, an IPP-bypass pathway was previously developed using the promiscuous activity of diphosphomevalonate decarboxylase, and enabled the production of isoprenol at a comparable yield and titer to the original pathway. In this study, we optimized this pathway, substantially improving isoprenol production. A titer of 3.7 g/L (0.14 g isoprenol per g glucose) was achieved in batch conditions using minimal medium by pathway optimization, and a further optimization of the fed-batch fermentation process enabled an isoprenol titer of 10.8 g/L (yield of 0.105 g/g and maximum productivity of 0.157 g L-1 h-1), which is the highest reported titer for this compound. The substantial increase in isoprenol titer via the IPP-bypass pathway in this study will facilitate progress toward commercialization

Engineering of Bacterial Methyl Ketone Synthesis for Biofuels

We have engineered Escherichia coli to overproduce saturated and monounsaturated aliphatic methyl ketones in the C11 to C15 (diesel) range; this group of methyl ketones includes 2-undecanone and 2-tridecanone, which are of importance to the flavor and fragrance industry and also have favorable cetane numbers (as we report here). We describe specific improvements that resulted in a 700-fold enhancement in methyl ketone titer relative to that of a fatty acid-overproducing E. coli strain, including the following: (i) overproduction of β-ketoacyl coenzyme A (CoA) thioesters achieved by modification of the β-oxidation pathway (specifically, overexpression of a heterologous acyl-CoA oxidase and native FadB and chromosomal deletion of fadA) and (ii) overexpression of a native thioesterase (FadM). FadM was previously associated with oleic acid degradation, not methyl ketone synthesis, but outperformed a recently identified methyl ketone synthase (Solanum habrochaites MKS2 [ShMKS2], a thioesterase from wild tomato) in β-ketoacyl-CoA-overproducing strains tested. Whole-genome transcriptional (microarray) studies led to the discovery that FadM is a valuable catalyst for enhancing methyl ketone production. The use of a two-phase system with decane enhanced methyl ketone production by 4- to 7-fold in addition to increases from genetic modifications