Suchergebnisse

Lipid-based biofuels, such as biodiesel and hydroprocessed esters, are a central part of the global initiative to reduce the environmental impact of the transport sector. The vast majority of production is currently from first-generation feedstocks, such as rapeseed oil, and waste cooking oils. However, the increased exploitation of soybean oil and palm oil has led to vast deforestation, smog emissions and heavily impacted on biodiversity in tropical regions. One promising alternative, potentially capable of meeting future demand sustainably, are oleaginous yeasts. Despite being known about for 143 years, there has been an increasing effort in the last decade to develop a viable industrial system, with currently around 100 research papers published annually. In the academic literature, approximately 160 native yeasts have been reported to produce over 20% of their dry weight in a glyceride-rich oil. The most intensively studied oleaginous yeast have been Cutaneotrichosporon oleaginosus (20% of publications), Rhodotorula toruloides (19%) and Yarrowia lipolytica (19%). Oleaginous yeasts have been primarily grown on single saccharides (60%), hydrolysates (26%) or glycerol (19%), and mainly on the mL scale (66%). Process development and genetic modification (7%) have been applied to alter yeast performance and the lipids, towards the production of biofuels (77%), food/supplements (24%), oleochemicals (19%) or animal feed (3%). Despite over a century of research and the recent application of advanced genetic engineering techniques, the industrial production of an economically viable commodity oil substitute remains elusive. This is mainly due to the estimated high production cost, however, over the course of the twenty-first century where climate change will drastically change global food supply networks and direct governmental action will likely be levied at more destructive crops, yeast lipids offer a flexible platform for localised, sustainable lipid production. Based on data from the large majority of oleaginous ...

BACKGROUND: Lipids produced from oleaginous yeasts are a promising alternative to terrestrial oils. Despite promising cellular yields of lipid however, an industrial process remains elusive. One key processing bottleneck is the need to provide nutrient-rich conditions for cellular growth and then extended nutrient-depleted conditions for lipid accumulation. Surprisingly, investigations detailing process development, particularly with a focus on kinetics, are rare in this field. RESULTS: In this investigation we report on the unique oleaginous yeast Metschnikowia pulcherrima , where lipid accumulation ≥ 29.8% (w/w) was achieved without apparent nutrient limitation. The process was developed in stirred tank reactors through determining the influence of temperature, pH and nutrition on lipid production. A temperature of up to 25 °C and initial pH 5 could be applied to enhance initial reaction kinetics. Through the increased supply of yeast extract of up to 5% (w/w) of glucose, a maximum lipid production rate of 0.60 g L −1 h −1 (4 h-average), productivity of 0.29 g L −1 h −1 , and yield of 0.17 g g −1 glucose were achieved – the highest yet recorded with this yeast. Suitable to combat the excessive secretion of polyols of up to 0.11 g g −1 glucose was an excess nutrient supply as well as a low cultivation temperature of 15 °C and moderate pH 5. CONCLUSIONS: This study demonstrates that the lack of a starvation stage, coupled with effective process development is required for oleaginous yeasts to achieve the yields and productivities required for commercial lipid production. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 665992

Microbial lipids have the potential to displace terrestrial oils for fuel, value chemical, and food production, curbing the growth in tropical oil plantations and helping to reduce deforestation. However, commercialization remains elusive partly due to the lack of suitably robust organisms and their low lipid productivity. Extremely high cell densities in oleaginous cultures are needed to increase reaction rates, reduce reactor volume, and facilitate downstream processing. In this investigation, the oleaginous yeast Metschnikowia pulcherrima , a known antimicrobial producer, was cultured using four different processing strategies to achieve high cell densities and gain suitable lipid productivity. In batch mode, the yeast demonstrated lipid contents more than 40% (w/w) under high osmotic pressure. In fed‐batch mode, however, high‐lipid titers were prevented through inhibition above 70.0 g L −1 yeast biomass. Highly promising were a semi‐continuous and continuous mode with cell recycle where cell densities of up to 122.6 g L −1 and maximum lipid production rates of 0.37 g L −1 h −1 (daily average), a nearly two‐fold increase from the batch, were achieved. The findings demonstrate the importance of considering multiple fermentation modes to achieve high‐density oleaginous yeast cultures generally and indicate the limitations of processing these organisms under the extreme conditions necessary for economic lipid production. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 665992

BACKGROUND: Microbial oils, often termed single cell oils (SCOs), offer an alternative to terrestrial oil crops across the energy, food, and chemical industries. In addition to oils, a range of secondary metabolites can be produced from the heterotrophic organisms as part of a bio-refinery system. Techno-economic analysis (TEA) is an important tool for evaluating economic viability, and while TEA is subject to high uncertainties where production is still at the laboratory scale, the tool can play a significant role in directing further research to evaluate suitability of scale-up. RESULTS: SCO production from the oleaginous yeast Metschnikowia pulcherrima using sucrose, wheat straw and distillery waste feedstocks was evaluated at two production scales. At a scale of 100 tonnes a-1 oil production a minimum estimated selling price (MESP) of €14k per tonne was determined for sucrose. This reduced to €4-8k per tonne on scaling to 10,000 tonne a-1, with sucrose and wheat straw yielding the lowest MESP. CONCLUSIONS: Feedstock price and lipid yield had the greatest impact on overall economic return, though the valorisation of co-products also had a large effect, and further play between feedstock and system productivity strategies could bring the price down to be competitive with terrestrial oils in the future. The novel approach demonstrated here for the first time integrates uncertainty into economic analysis whilst facilitating decision-support at an early technology development stage. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 665992

Marine macroalgae (seaweed) has many advantages over terrestrial crops as a source of renewable biomass but is severely underutilised at present, especially within Europe. In particular, macroalgae has elevated poly- and monosaccharide content, making it an ideal feedstock as a heterotrophic fermentation sugar source for the production of higher value chemicals. Recent reports have detailed the suitability of seaweeds as a feedstock for the production of single-cell oils (SCOs) which have application in food, oleochemicals and fuels. It is proposed that a biorefinery system based on the production of SCOs alongside other secondary metabolites, has the potential to provide a sustainable replacement to terrestrial oils such as palm oil. This work therefore evaluates, for the first time, the environmental and economic sustainability of a production process for SCOs from seaweed Saccharina latissima using the oleaginous yeast Metschnikowia pulcherrima. Two alternative fermentation systems were considered, and uncertainties associated with the seasonal variation in seaweed carbohydrate yield and fermentation performance were integrated into the analysis. From an environmental perspective, the work indicates that seaweed derived SCO lipids and fats can be comparable to a terrestrial oil mix, with a potential climate change impact ranging between 2.5 and 9.9 kg CO 2 eq. kg −1 refined SCO. Interestingly and of particular significance, environmental impacts are mainly dominated by energy demand within fermentation and upstream processing steps. From an economic perspective, a break-even selling price for the oil was determined as between €5,300-€31,000 tonne −1 refined SCO, which was highly dependent on cost of the seaweed feedstock. Overall, we demonstrate that key uncertainties relating to seaweed cultivation costs and hydrolysate fermentation at scale result in a large range in values for environmental impact and economic return on investment. Yet even within the constraints and limitations of current knowhow, seaweed already offers a viable proposition for the competitive production of exotic oils similar to cocoa or shea butter in price and nature. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 665992

Background: Heterotrophic microbial oils are potentially a more sustainable alternative to vegetable or fossil oils for food and fuel applications. However, as almost all work in the area is conducted on the laboratory scale, such studies carry limited industrial relevance and do not give a clear indication of what is required to produce an actual industrial process. Metschnikowia pulcherrima is a non-pathogenic industrially promising oleaginous yeast which exhibits numerous advantages for cost-effective lipid production, including a wide substrate uptake, antimicrobial activity and fermentation inhibitor tolerance. In this study, M. pulcherrima was fermented in stirred tank reactors of up to 350 L with 250-L working volume in both batch and semi-continuous operation to highlight the potential industrial relevance. Due to being food-grade, suitable for handling at scale and to demonstrate the oligosaccharide uptake capacity of M. pulcherrima , enzyme-hydrolysed starch in the form of glucose syrup was selected as fermentation feedstock. Results: In batch fermentations on the 2-L scale, a lipid concentration of 14.6 g L −1 and productivity of 0.11 g L −1 h −1 were achieved, which was confirmed at 50 L (15.8 g L −1 ; 0.10 g L −1 h −1 ). The maximum lipid production rate was 0.33 g L −1 h −1 (daily average), but the substrate uptake rate decreased with oligosaccharide chain length. To produce 1 kg of dry yeast biomass containing up to 43% (w/w) lipids, 5.2 kg of the glucose syrup was required, with a lipid yield of up to 0.21 g g −1 consumed saccharides. In semi-continuous operation, for the first time, an oleaginous yeast was cultured for over 2 months with a relatively stable lipid production rate (around 0.08 g L −1 h −1 ) and fatty acid profile (degree of fatty acid saturation around 27.6% w/w), and without contamination. On the 250-L scale, comparable results were observed, culminating in the generation of nearly 10 kg lipids with a lipid productivity of 0.10 g L −1 h −1 . Conclusions: The results establish the importance of M. pulcherrima for industrial biotechnology and its suitability to commercially produce a food-grade oil. Further improvements in the productivity are required to make M. pulcherrima lipid production industrial reality, particularly when longer-chain saccharides are involved. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 665992

Macroalgae (seaweeds) represent an emerging resource for food and the production of commodity and specialty chemicals. In this study, a single-step microwave process was used to depolymerise a range of macroalgae native to the United Kingdom, producing a growth medium suitable for microbial fermentation. The medium contained a range of mono- and polysaccharides as well as macro- and micronutrients that could be metabolised by the oleaginous yeast Metschnikowia pulcherrima . Among twelve macroalgae species, the brown seaweeds exhibited the highest fermentation potential, especially the kelp Saccharina latissima . Applying a portfolio of ten native M. pulcherrima strains, yeast growth kinetics, as well as production of lipids and 2-phenylethanol were examined, with productivity and growth rate being strain dependent. On the 2 L scale, 6.9 g L −1 yeast biomass – a yield of 0.14 g g −1 with respect to the supplied macroalgae – containing 37.2% (w/w) lipid was achieved through utilisation of the proteins, mono- and polysaccharides from S. latissima , with no additional enzymes. In addition, the yeast degraded a range of fermentation inhibitors released upon microwave processing at high temperatures and long holding times. As macroalgae can be cultured to food grade, this system offers a novel, potentially low-cost route to edible microbial oils as well as a renewable feedstock for oleochemicals. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 665992

Current biorefineries are predominantly based around single feedstock sources, extensively hydrolysed using multiple unit operations. The hydrolysate is generally converted to a single product by one of a few well-characterised organisms. Here, we report on a new approach to the biorefinery, combining a rapid, microwave heated, one-step depolymerisation process, with a yeast, Metschnikowia pulcherrima which is able to metabolise an array of oligo- and monosaccharides. During the investigation it was found that the microwave hydrolysis process was able to solubilize upto 50% wheat straw biomass by weight, mainly as oligosaccharides though also containing mixtures of pentose, hexose and anhydro-sugars with concentrations of up to 2 g L -1 . However, a fine balance between elevated monosaccharide yields and the production of inhibitive compounds had to be struck with optimal microwave hydrolytic conditions found to be 190 °C. Further testing utilizing several different types of lignocellulosic biomass demonstrated it was possible to attain ~65% carbon efficiency in the conversion of Laminaria saccharina to hydrolysis products. The system was scaled to 600 mL using DDGS successfully solubilizing 66% of the feedstock, producing 33 g L -1 hydrolysate. M. pulcherrima grew well on this hydrolysate in a controlled stirred tank bioreactor (2L), yielding 8.38 g L -1 yeast biomass, a yeast biomass coefficient of 0.25. This presents an exciting, feedstock agnostic, pathway to the energy efficient production of a wide variety of commercially valuable chemical products without the need for extensive pre and post processing technologies. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 665992