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All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Paenibacillus aquistagni sp. nov., isolated from an artificial lake accumulating industrial wastewater

Strain 11 T was isolated from water of an artificial lake accumulating industrial wastewater on the outskirts of Celje, Slovenia. In this paper, phenotypic characterisation showed strain 11 T to be a Gram-stain positive, spore forming bacterium. The 16S rRNA gene sequence identified strain 11 T as a member of the genus Paenibacillus, closely related to Paenibacillus alvei (96.2%). Genomic similarity with P. alvei 29 T was 73.1% (gANI), 70.2% (ANIb), 86.7% (ANIm) and 21.7 ± 2.3% (GGDC). The DNA G+C content of strain 11 T was determined to be 47.5%. The predominant menaquinone of strain 11 T was identified as MK-7 and the major fatty acid as anteiso-C 15:0 . The peptidoglycan was found to contain meso-diaminopimelic acid. In contrast to its close relatives P. alvei DSM 29 T , Paenibacillus apiarius DSM 5581 T and Paenibacillus profundus NRIC 0885 T , strain 11 T was found to be able to ferment d-fructose, d-mannose and d-xylose. A draft genome of strain 11 T contains a cluster of genes associated with type IV pilin synthesis usually found in clostridia, and only sporadically in other Gram-positive bacteria. Finally, genotypic, chemotaxonomic, physiological and biochemical characteristics of strain 11 T presented in this study support the creation of a novel species within the genus Paenibacillus, for which the name Paenibacillus aquistagni sp. nov. is proposed, with strain 11 T (=ZIM B1027 T =LMG 29561 T =CCM 8679 T ) as the type strain.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

The role of methane in future climate strategies: mitigation potentials and climate impacts

This study examines model-specific assumptions and projections of methane (CH 4 ) emissions in deep mitigation scenarios generated by integrated assessment models (IAMs). For this, scenarios of nine models are compared in terms of sectoral and regional CH 4 emission reduction strategies, as well as resulting climate impacts. The models’ projected reduction potentials are compared to sector and technology-specific reduction potentials found in literature. Significant cost-effective and non-climate policy related reductions are projected in the reference case (10–36% compared to a “frozen emission factor” scenario in 2100). Still, compared to 2010, CH 4 emissions are expected to rise steadily by 9–72% (up to 412 to 654 Mt CH 4 /year). Ambitious CO 2 reduction measures could by themselves lead to a reduction of CH 4 emissions due to a reduction of fossil fuels (22–48% compared to the reference case in 2100). However, direct CH 4 mitigation is crucial and more effective in bringing down CH 4 (50–74% compared to the reference case). Given the limited reduction potential, agriculture CH 4 emissions are projected to constitute an increasingly larger share of total anthropogenic CH 4 emissions in mitigation scenarios. Enteric fermentation in ruminants is in that respect by far the largest mitigation bottleneck later in the century with a projected 40–78% of total remaining CH 4 emissions in 2100 in a strong (2 °C) climate policy case.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Effects of Copolymer Structure on Enzyme-Catalyzed Polyester Recycling

Polyesters are an omnipresent material used for a variety of applications (e.g., bottles, packaging, textile, windshield), roughly comprising 8% of plastics produced worldwide. Enzymatic recycling is an emerging solution to deal with the increasingly diverse polyesters that are not suitable for mechanical recycling. However, enzyme activity and efficiency are still the limiting factors impeding enzymatic recycling for different plastic waste forms. The effects of thermal and structural properties (e.g., glass transition temperature, crystallinity, specific surface area), which are determined by chemical composition and preprocessing, directly influence enzyme recycling efficiency. This work investigates two extrusion methods (single screw and twin-screw extrusion) to pretreat a range of copolyesters (RPET, PETG, Ecozen, Tritan and PBT) and modify their properties (i.e., glass transition temperature (T g ), crystallinity (%), and molecular weight (M n )). A PET-specific enzyme, leaf-branch compost cutinase (LCC ICCG ), produced from a fed-batch fermentation of Escherichia coli BL21(DE3), was used for the enzymatic depolymerization of different polyesters. Several copolyesters showed improved depolymerization after pretreatment, as measured by rate and amount of monomers produced. Furthermore, those that did not depolymerize were found to have exceptionally high glass transition temperature or percent crystallinity, highlighting the importance of these physical parameters on conversion efficiency.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Effects of the Organic Loading Rate on Polyhydroxyalkanoate Production from Sugarcane Stillage by Mixed Microbial Cultures

Stillage is an abundant wastewater from the sugarcane ethanol industry. It is rich in fermentable substrates and presents low-nutrient content, constituting a promising substrate for polyhydroxyalkanoate (PHA) production by mixed microbial cultures (MMC). This work assessed the enrichment of a PHA-accumulating MMC from acidified sugarcane stillage in a sequencing batch reactor under increasing organic loading rates (OLR) and no external nutrient supplementation. The OLR was increased from 1.0 to 7.1 kg COD m{sup −3} day{sup −1} in four steps. A PHA-producing MMC with high storage response was selected in all experimental conditions. The volumetric biomass productivity and the maximal PHA storage capacity increased continuously with the OLR, reaching 0.061 g VSS L{sup −1} h{sup −1} and 0.49 g PHA g VSS{sup −1}, respectively. The highest observed PHA storage yield (0.60 g COD{sub PHA} g COD.t{sup −1}) and specific PHA storage rate (0.169 g COD{sub PHA} g of COD{sub X} h{sup −1}) were obtained for the OLR of 4.5 kg COD m{sup −3} day{sup −1}. The PHA produced was a co-polymer of 3-hydroxybutyrate (86–77%mol) and 3-hydroxyvalerate (14–23%mol). The performance of the biomass enrichment was comparable to those attained with other agro-industrial wastewaters, indicating the potential of acidified sugarcane stillage as a feedstock for MMC PHA production.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Reduction of ethanol yield from switchgrass infected with rust caused by Puccinia emaculata

Switchgrass ( Panicum virgatum ) is an important biofuel crop candidate thought to have low disease susceptibility. As switchgrass production becomes more prevalent, monoculture and production fields in close proximity to one another may increase the spread and severity of diseases such as switchgrass rust caused by the pathogen Puccinia emaculata . The objective of this research was to examine the impact of rust on ethanol yield in switchgrass. In 2010 and 2012, naturally infected leaves from field-grown Alamo and Kanlow in Knoxville, TN (2010, 2012) and Crossville, TN (2012) were visually categorized as exhibiting low, medium, or high disease based on the degree of chlorosis and sporulation. P. emaculata was isolated from each disease range to confirm infection. Samples from 2010 were acid/heat pretreated and subjected to two runs of simultaneous saccharification and fermentation (SSF) with Saccharomyces cerevisiae D 5 A to measure ethanol yield. Near-infrared spectroscopy (NIRS) was used to estimate ethanol yield for 2012 samples. SSF and NIRS data were analyzed separately using ANOVA. Disease level effects were significant within both models (P < 0.05) and both models explained a large amount of variation in ETOH (SSF: R 2 = 0.99, NIRS: R 2 = 0.99). In the SSF dataset, ethanol was reduced by 35 % in samples exhibiting medium disease symptoms and by 55 % in samples exhibiting high disease symptoms. In the NIRS dataset, estimated ethanol was reduced by 10 % in samples exhibiting medium disease symptoms and by 21 % in samples exhibiting high disease symptoms. Lastly, results indicate that switchgrass rust will likely have a negative impact on ethanol yield in switchgrass grown as a biofuel crop.

09 BIOMASS FUELS↗
DOE OSTI2015

Sources of biomass feedstock variability and the potential impact on biofuels production

In this study, terrestrial lignocellulosic biomass has the potential to be a carbon neutral and domestic source of fuels and chemicals. However, the innate variability of biomass resources, such as herbaceous and woody materials, and the inconsistency within a single resource due to disparate growth and harvesting conditions, presents challenges for downstream processes which often require materials that are physically and chemically consistent. Intrinsic biomass characteristics, including moisture content, carbohydrate and ash compositions, bulk density, and particle size/shape distributions are highly variable and can impact the economics of transforming biomass into value-added products. For instance, ash content increases by an order of magnitude between woody and herbaceous feedstocks (from ~0.5 to 5 %, respectively) while lignin content drops by a factor of two (from ~30 to 15 %, respectively). This increase in ash and reduction in lignin leads to biofuel conversion consequences, such as reduced pyrolysis oil yields for herbaceous products as compared to woody material. In this review, the sources of variability for key biomass characteristics are presented for multiple types of biomass. Additionally, this review investigates the major impacts of the variability in biomass composition on four conversion processes: fermentation, hydrothermal liquefaction, pyrolysis, and direct combustion. Finally, future research processes aimed at reducing the detrimental impacts of biomass variability on conversion to fuels and chemicals are proposed.

09 BIOMASS FUELS↗
DOE OSTI2025

Understanding the Effects of Ash Content on Various Pretreatment Technologies for the Bioconversion of Corn Stover

Here, the study aimed to examine the effects of adding biomass ash on the biochemical processes involved in fermentable sugar production. Corn stover was pretreated using several methods—hot water, dilute acid, alkaline, γ-valerolactone, and ionic liquid methods, each examined with ash loadings of 7.18% and 21.07%. The findings demonstrated that increased ash content adversely affected both pretreatment and enzymatic hydrolysis. Specifically, the total sugar yield was 3 to 16% lower at the higher ash content across all pretreatment methods, and up to 4.01% lower during enzymatic hydrolysis. For acidic pretreatment, the sugar yield decreased as ash content increased. In contrast, ash content had a lesser impact on alkaline pretreatment compared to acidic pretreatment. For example, using corn stover with an ash content as high as 22.65% resulted in only a 2.90% decrease in total sugar yield compared to corn stover without added ash. Further, the primary reasons for the reduced sugar yield in higher ash biomass during acidic pretreatments were likely the neutralizing effect of the ash and decreased acid access to the substrates. During enzymatic hydrolysis, ash reduced the sugar yield by limiting enzyme access to cellulose.

09 BIOMASS FUELS↗
DOE OSTI2022

The effects of sequential hydrothermal-mechanical refining pretreatment on cellulose structure changes and sugar recoveries

The recalcitrance of lignocellulosic biomass necessitates an efficient pretreatment protocol for operating a successful cellulosic biorefinery. It is critical to improve cellulose accessibility for hydrolysis and fermentation by altering the plant cell wall’s physical structure and chemical composition. Sequential hydrothermal-mechanical refining pretreatment (HMR) allows efficient recovery of cellulosic sugars without utilizing any hazardous chemicals. HMR has been successfully applied to Liberty switchgrass, a bioenergy cultivar released by the USDA, and now it is being applied to oilcane, a recently developed transgenic sugarcane variety engineered to accumulate lipids in its vegetative tissues. Sugar yields of oilcane bagasse (OCB) and switchgrass (SG) treated with HMR are 96.4% and 75.4%, respectively. This study sought to correlate cellulosic sugar yields with structural changes within the cell wall caused by HMR on two distinct bioenergy crops. Simon’s staining technique for the specific surface area analysis showed that HMR increased the specific surface area of pretreated biomass residues by 80–112%. In addition, ATR-FTIR was performed to determine the effects of HMR on physical structures based on the total crystallinity index (TCI) and hydrogen bonding intensity (HBI). Irrespective of biomass type, HMR decreased the initial crystalline cellulose contents of untreated biomass residues by 3.5% and reduced TCI and HBI by 7–13%. Here, the study found that sugar yields were negatively correlated to reducing values of hydrogen bonding intensity, crystalline cellulose content, and total crystallinity index.

09 BIOMASS FUELS↗
DOE OSTI2020

Chapter 21: Sustainable Technologies for Seaweed Conversion to Biofuels and Bioproducts

Seaweeds are attractive candidates to supply the future sustainable, photosynthetic, bioenergy feedstocks thanks to their cultivation promise in offshore marine farms, with year-round production, and no external nutrient requirements. Despite this potential, there are significant challenges associated with realizing both the cultivation and harvesting logistics, as well as in developing an efficient conversion platform to fuels and products. Effective and scalable and economically viable conversion processes tailored to a seaweed are discussed in detail and gaps on identified needs for yield and efficiency improvements. Among the conversion processes discussed here, anaerobic fermentation of seaweeds to bioenergy products, including organic acids and biomass, is promising to disrupt the current bioenergy landscape.

anaerobic digestion↗
DOE OSTI2021

Photosynthesis | The Heliobacteria

The heliobacteria are the only phototrophs in the Gram-positive group of bacteria. They are strict anaerobes that grow in a primarily fermentative mode in the dark. In the light, they use a homodimeric Type I photochemical reaction center to drive cyclic electron transport. They are unique in using the pigment bacteriochlorophyll g. All heliobacteria are unable to fix CO 2 but able to fix N2. Their core metabolism includes a complete TCA cycle with several reversible enzymes in common with the reverse (reductive) TCA cycle, but they lack an (ATP) citrate lyase that would allow CO 2 fixation. There are now several sequenced genomes available for different heliobacterial species, allowing hypotheses to be made concerning their metabolic potential. Here, techniques to introduce replicating plasmids into Heliobacterium modesticaldum, as well as leveraging its endogenous CRISPR/Cas system to edit its chromosome, have recently been pioneered, contributing to making this species a model system for this family.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

Production of Biofuels from Biomass by Fungi

The use of abundantly available lignocellulosic biomass as a feedstock for biofuels has emerged as a sustainable alternative to fossil fuels. Industries across the world have shifted their focus to enhancing bioconversion through fungi, efficient and tractable organisms capable of producing valuable cost-effective enzymes. The many capabilities of fungal species offer opportunities for the tailored production of valuable compounds from a variety of substrates. This review details a high level examination of how fungal enzymes degrade plant polysaccharides to simple sugars through the sensitive coordination of transcription factors. Scientists have used a variety of tools like genetically engineering fungi, combining various species, and altering industrial/process conditions to enhance biomass deconstruction and fermentation while solving obstacles like inhibitory compounds. While ethanol and biodiesel are highlighted, additional biofuels are mentioned. These advances have uncovered themes like synergism and biocatalysis, led to the discovery of new fungal species, and revealed unique enzymatic mechanisms. Notably, this research highlights the complexity of metabolic systems within and between fungi. Fungi have been indispensable to the biofuel industry and future research will be crucial for energy sustainability.

Ottum, Eva MN↗
DOE OSTI2016

One-pot bioconversion of algae biomass into terpenes for advanced biofuels and bioproducts

In this study, rising demand for transportation fuels, diminishing reserved of fossil oil, and the concerns with fossil fuel derived environmental pollution as well as the green-house gas emission derived climate change have resulted in the compelling need for alternative, sustainable new energy sources(1). Algae-based biofuels have been considered one of the promising alternatives to fossil fuels as they can overcome some of these issues (2-4). The current state-of-art of algal biofuel technologies have primarily focused on biodiesel production through prompting high algal lipid yields under the nutrient stress conditions. There are less interests of using algae-based carbohydrate and proteins as carbon sources for the fermentative production of liquid fuel compounds or other high-value bioproducts(5-7).

09 BIOMASS FUELS↗
DOE OSTI2017

Evaluation of a high-moisture stabilization strategy for harvested microalgae blended with herbaceous biomass: Part I—Storage performance

Here, algal biomass is becoming increasingly attractive as a feedstock for biofuel production. However, the swing in algal biomass production between summer and winter months poses a challenge for delivering predictable, constant feedstock supply to a conversion facility. Drying is one approach for stabilizing algal biomass produced in excess during high productivity summer months for utilization during low productivity months, yet drying is energy intensive and thus costly. Wet, anaerobic storage, or ensiling, is a low-cost approach that is commonly used to preserve high moisture herbaceous feedstock. The potential for microalgae stabilization without the need for drying was investigated in this study by simulating ensiling, in which oxygen limitation drives anaerobic fermentation of soluble sugars to organic acids, dropping the pH and thereby stabilizing the material. Algal biomass, Scenedesmus obliquus , was blended with corn stover and stored in acidic, anaerobic conditions at 60% moisture (wet basis) to simulate wet storage by means of ensiling. Results demonstrate that algae and corn stover blends were successfully preserved in anaerobic, acidic conditions for 30 days with < 2% dry matter loss occurring during storage compared to 21% loss in aerobic, non-acidified conditions. Likewise, Scenedesmus obliquus stored alone at 80% moisture (wet basis) in acidified, anaerobic conditions for 30 days, resulted in dry matter losses of 6–14%, compared to 44% loss in neutral pH, anaerobic storage and 37% loss in a neutral pH, aerobically stored condition. Additional experiments were performed at a larger scale in which an algae and corn stover blend was subject to mechanical oxygen exclusion and a Lactobacillus acidophilus inoculum, resulting in 8% loss over 35 days and further indicating that acidic, anaerobic conditions can stabilize microalgae biomass. In summary, the stabilization of harvested algae can be achieved through anaerobic storage, securing a feedstock that is labile yet of high value.

09 BIOMASS FUELS↗
DOE OSTI2018

Economic viability of multiple algal biorefining pathways and the impact of public policies

This study presents an extensive systems-level multi-pathway sustainability assessment of algae biofuel production that demonstrates the necessity of high-value co-products, examines the impact of public policy scenarios, and identifies improvements and pathway directions required for economic viability. Engineering process models for several fuel and co-product pathways were leveraged to perform high fidelity techno-economic analysis. These pathways included: baseline hydrothermal liquefaction; protein extraction followed by hydro-thermal liquefaction; fractionation into high-value chemicals with fermentation followed by hydrothermal liquefaction for fuels; and a small-scale first-of-a-kind plant coupled with a wastewater treatment facility. From these models, it was shown that hydrothermal liquefaction as a fuel-only pathway is not economically viable. Likewise, the benefits of coupling with wastewater water treatment are insignificant compared to the impact ofreduced facility size resulting in increased capital costs. These models were also used to examine public policy scenarios, uniquely presenting their impact on the breakeven cost of fuel production and sensitivity to scenario assumptions. Specifically, depreciation type was shown to be irrelevant for write offs faster than 10 years. Due to discounting, short-term subsidies were found to capture 50% of the subsidy value in 6 years with an additional24 years required for full subsidy valuation. Integration of a carbon economy was shown to decrease biofuel production costs, particularly for the protein pathway due to the co-product accounting. Finally, a metric of normalized costs was used to compare algal biorefineries to corn and cellulosic ethanol production, showing that algal systems are uniquely different due to significantly higher capital costs, though operational costs are comparable. Overall, this work demonstrates that, to reach economic viability, algal biofuel production must either utilize higher value non-fuel co-products or achieve drastic reductions in capital costs.

09 BIOMASS FUELS↗
DOE OSTI2019

Process design and economics for production of advanced biofuels from genetically modified lipid-producing sorghum

This study evaluates the potential for making advanced biofuels from genetically modified (GM) lipid–producing sorghum. A biodiesel coproduction process is developed to extract, purify, and upgrade lipids to diesel fuel while carbohydrates are utilized for making ethanol through acid thermal pretreatment, enzymatic hydrolysis, and fermentation. To assess the advantages of coproducing biodiesel from GM–sorghum, process economics are compared to a cellulosic ethanol biorefinery receiving non-GM sorghum. Minimum ethanol selling prices (MESP) that reach a breakeven point after 30 years of service life are calculated as an economic index to compare the two processes. Results indicate that biodiesel coproduction improves the economics by lowering the MESP from 3.08/gal for the ethanol-only process to 2.46/gal. Sensitivity analyses reveal that increasing sorghum’s lipid content, increasing the lipid extraction efficiency, and reducing the solvent-to-solids ratio in lipid extraction columns are the most important process parameters to further enhance technoeconomics. Analyses indicate that a lipid content above 13 wt% (dry basis) or a biomass price less than 65/Mg (dry basis) will result in a 2014 ethanol wholesale price of 2.25/gal for the coproduction process.

09 BIOMASS FUELS↗
DOE OSTI2013

Distinct physiological roles for the two L-asparaginase isozymes of Escherichia coli

Highlights: •Escherichia coli contains two L-asparaginase isozymes with distinct localization, kinetics and regulation. •Mutant strains were used to examine the roles of these enzymes in L-asparagine utilization. •We report that L-asparaginase II permits growth on asparagine and glycerol under anaerobic conditions. •We propose that this enzyme is the first step in a co-regulated pathway leading to fumarate. •The pathway is regulated by anaerobiosis and cAMP and provides a terminal elector acceptor. -- Abstract: Escherichia coli expresses two L-asparaginase (EC 3.5.1.1) isozymes: L-asparaginse I, which is a low affinity, cytoplasmic enzyme that is expressed constitutively, and L-asparaginase II, a high affinity periplasmic enzyme that is under complex co-transcriptional regulation by both Fnr and Crp. The distinct localisation and regulation of these enzymes suggest different roles. To define these roles, a set of isogenic mutants was constructed that lacked either or both enzymes. Evidence is provided that L-asparaginase II, in contrast to L-asparaginase I, can be used in the provision of an anaerobic electron acceptor when using a non-fermentable carbon source in the presence of excess nitrogen.

60 APPLIED LIFE SCIENCES↗