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Spiller, Ryan

Publications and source records attributed to Spiller, Ryan.

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Muconic acid production from algae hydrolysate as a high-value co-product of an algae biorefinery

Muconic acid is an attractive bio-derived product because it can be easily converted to adipic acid, a high-value and high-volume monomer used in the production of nylon and other valuable consumer plastics. As such, production of muconic acid from algae hydrolysate was explored to expand the suite of products available from algal biomass. Here we have established initial performance parameters and have shown that the range of substrates present in algae hydrolysate that are consumed by Pseudomonas putida includes at least glucose, mannose, glycerol, acetic acid, and lactic acid. We achieved complete utilization of these major carbon sources found in Scenedesmus acutus hydrolysate with a maximum muconic acid productivity of 0.25 g/L h. Final titer was 13.0 g/L (27% molar process yield) at approximately 50 h. In addition, algae hydrolysate does not require any additional nutrients to achieve these performance metrics. Techno-economic analysis showed the potential to support up to 150 algal biorefineries at this yield with significant greenhouse gas reductions.

09 BIOMASS FUELS↗
DOE OSTI2022

Evaluating the Feasibility of Higher Titers and Yields for 2,3-Butanediol Production to Achieve the Biofuel Industry Economic Goal of Under $3.50 GGE

To achieve the economic goal of producing biofuels that can compete with petroleum-based products, we increased titers of 2,3-butanediol (BDO) production. BDO has many advantages over ethanol; including lower toxicity, higher heat of capacity, and is a precursor to various valuable applications. To produce BDO for fuel upgrading, we have genetically modified Zymomonas mobilis (YC-1). Several materials and feed strategies were evaluated to determine the best titer and economic feasibility. Titers from DMR corn stover in a batch process were in the range of 70-80 g/L. The fully hydrolyzed material was easy to work with but suffered from dilution issues. We pushed the concentration of solids to above 25% w/w and were met with numerous challenges. This included an initial sugar concentration above 150 g/L, the high solid concentration altered the oxygen mass transfer rate and affected which products were produced, and the fermentation conditions were not optimal for the enzyme. Despite these challenges, our current results yielded 100 g/L of upgradeable products (70 g/L BDO and 30 g/L acetoin) and 83% fermentation process yield. However, the poor enzymatic hydrolysis yield of 64%, unconverted xylose, and the high acetoin levels warrant further exploration for optimization. Using unhydrolyzed solids as the feed material, we achieved titers in the range of 75-95 g/L BDO. The raw solids feed, though operationally more challenging to work with, proved to be promising as the rate of hydrolysis promoted co-utilization of the sugars. We reached 150 g/L BDO using concentrated DDR liquors under boules and continuous feeding strategies. The clarified liquors showed high titers, high productivity, high yield, and high sugar utilization with little drawback operationally. The target goal of under $3.50 GGE was achieved in several feeding strategies. Scale-up feasibility has also been demonstrated at the 100L scale using both whole slurry and liquor hydrolysates.

BIOMASS FUELS↗
DOE OSTI2022

Muconic Acid Production from P. putida Using High Protein Algae Hydrolysate

The composition of algal biomass is highly dynamic, with protein, lipid, and carbohydrate contents varying in response to nutrient and environmental conditions during cultivation. Because shifts in biomass composition are often associated with reduced biomass productivity, production costs can often increase if targeting higher biomass compositional quality (enriched in carbohydrates or lipids at reduced protein content) as input for the algal biorefinery. The optimal algal biorefinery configuration is thus a function of many factors. One of the key strengths of the Combined Algal Processing (CAP) process is the versatility of feedstocks and products produced. The concept has been demonstrated with ethanol and a variety of carboxylic acids (succinic, butyric, muconic) as coproducts along with lipid upgrading to biofuel. Modification of the approaches, processes and downstream upgrading to fuels has allowed the CAP process to reduce costs and improve efficiency. Muconic acid is a high-value, potential fermentation coproduct of interest because it can be easily converted to adipic acid, a high-volume monomer for the production of nylon and other valuable consumer plastics. As such, the production of muconic acid through CAP was explored to expand the suite of products from algal biomass and to begin exploring the valorization of high protein content biomass from rapidly grown algae biomass. We have established initial performance parameters and shown that the range of substrates consumed by the muconic acid-producing microbe, Pseudomonas putida, includes at least glucose, mannose, glycerol, and lactic acid. We achieved complete utilization of these four major hydrolysate substrates achieving productivities of 0.037 (g/L/h) from Scenedesmus obliquus and 0.029 (g/L/h) from Monoraphidium minutum hydrolysates. Final titer and process yield (mol of muconic acid per mol of substrate (molP/molS)) were 0.99 g/L and 0.42 molP/molS from S. obliquus hydrolysate and 0.75 g/L and 0.23 molP/molS from M. minutum hydrolysate, respectively.

BIOMASS FUELS↗
DOE OSTI2021

Thermodynamic and Kinetic Modeling of Co-utilization of Glucose and Xylose for 2,3-BDO Production by Zymomonas mobilis

Prior engineering of the ethanologen Zymomonas mobilis has enabled it to metabolize xylose and to produce 2,3-butanediol (2,3-BDO) as a dominant fermentation product. When co-fermenting with xylose, glucose is preferentially utilized, even though xylose metabolism generates ATP more efficiently during 2,3-BDO production on a BDO-mol basis. To gain a deeper understanding of Z. mobilis metabolism, we first estimated the kinetic parameters of the glucose facilitator protein of Z. mobilis by fitting a kinetic uptake model, which shows that the maximum transport capacity of glucose is seven times higher than that of xylose, and glucose is six times more affinitive to the transporter than xylose. With these estimated kinetic parameters, we further compared the thermodynamic driving force and enzyme protein cost of glucose and xylose metabolism. It is found that, although 20% more ATP can be yielded stoichiometrically during xylose utilization, glucose metabolism is thermodynamically more favorable with 6% greater cumulative Gibbs free energy change, more economical with 37% less enzyme cost required at the initial stage and sustains the advantage of the thermodynamic driving force and protein cost through the fermentation process until glucose is exhausted. Glucose-6-phosphate dehydrogenase (g6pdh), glyceraldehyde-3-phosphate dehydrogenase (gapdh) and phosphoglycerate mutase (pgm) are identified as thermodynamic bottlenecks in glucose utilization pathway, as well as two more enzymes of xylose isomerase and ribulose-5-phosphate epimerase in xylose metabolism. Acetolactate synthase is found as potential engineering target for optimized protein cost supporting unit metabolic flux. Pathway analysis was then extended to the core stoichiometric matrix of Z. mobilis metabolism. Growth was simulated by dynamic flux balance analysis and the model was validated showing good agreement with experimental data. Dynamic FBA simulations suggest that a high agitation is preferable to increase 2,3-BDO productivity while a moderate agitation will benefit the 2,3-BDO titer. Taken together, this work provides thermodynamic and kinetic insights of Z. mobilis metabolism on dual substrates, and guidance of bioengineering efforts to increase hydrocarbon fuel production.

23-butanediol↗
DOE OSTI2020

Anaerobic Storage and Conversion of Microalgal Biomass to Manage Seasonal Variation in Cultivation

Seasonal variation in microalgal biomass production is a well-known challenge when optimizing economics for algal fuel conversion, especially given the fluctuation in biomass production between winter and summer. Wet storage offers significant potential for cost and energy savings compared to dewatering and dry storage. This study demonstrates the feasibility of preserving harvested Scenedesmus acutus biomass through wet anaerobic storage for use in biochemical conversion. Anaerobic storage effectively preserved biomass with minimal degradation of carbohydrates and preservation of lipids and proteins. Screening experiments identified optimal pretreatment conditions for stored biomass. Scale-up of pretreatment enabled fermentation of the hydrolysate to butyric acid and indicated no observable difference in conversion between unstored and stored biomass. Lipid extraction improved by a relative 12% for stored biomass. These results suggest that wet anaerobic storage can effectively manage seasonal variation in biomass production and is compatible with biochemical approaches for biofuel production.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗