Technoeconomic evaluation of bio-based styrene production by engineered Escherichia coli.

Styrene is an important commodity chemical used in polymers and resins, and is typically produced from the petrochemical feedstocks benzene and ethylene. Styrene has recently been produced biosynthetically for the first time using engineered Escherichia coli, and this bio-based route may represent a lower energy and renewable alternative to petroleum-derived styrene. However, the economics of such an approach has not yet been investigated. Using an early-stage technoeconomic evaluation tool, a preliminary economic analysis of bio-based styrene from C(6)-sugar feedstock has been conducted. Owing to styrene's limited water solubility, it was assumed that the resulting fermentation broth would spontaneously form two immiscible liquid phases that could subsequently be decanted. Assuming current C(6) sugar prices and industrially achievable biokinetic parameter values (e.g., product yield, specific growth rate), commercial-scale bio-based styrene has a minimum estimated selling price (MESP) of 1.90 USD kg(-1) which is in the range of current styrene prices. A Monte Carlo analysis revealed a potentially large (0.45 USD kg(-1)) standard deviation in the MESP, while a sensitivity analysis showed feedstock price and overall yield as primary drivers of MESP.

Nutrient recovery in cultured meat systems: Impacts on cost and sustainability metrics.

A growing global meat demand requires a decrease in the environmental impacts of meat production. Cultured meat (CM) can potentially address multiple challenges facing animal agriculture, including those related to animal welfare and environmental impacts, but existing cost analyses suggest it is hard for CM to match the relatively low costs of conventionally produced meat. This study analyzes literature reports to contextualize CM's protein and calorie use efficiencies, comparing CM to animal meat products' feed conversion ratios, areal productivities, and nitrogen management. Our analyses show that CM has greater protein and energy areal productivities than conventional meat products, and that waste nitrogen from spent media is critical to CM surpassing the nitrogen use efficiency of meat produced in swine and broiler land-applied manure systems. The CM nutrient management costs, arising from wastewater treatment and land application, are estimated to be more expensive than in conventional meat production. Overall, this study demonstrates that nitrogen management will be a key aspect of sustainability in CM production, as it is in conventional meat systems.

Perennial groundcovers: an emerging technology for soil conservation and the sustainable intensification of agriculture.

Integrating perennial groundcovers (PGC) - sometimes referred to as living mulches or perennial cover crops - into annual cash-crop systems could address root causes of bare-soil practices that lead to negative impacts on soil and water quality. Perennial groundcovers bring otherwise absent functional traits - namely perenniality - into cash-crop systems to preserve soil and regenerate water, carbon, and nutrient cycles. However, if not optimized, they can also cause competitive interactions and yield loss. When designing PGC systems, the goal is to maximize complementarity - spatial and temporal separation of growth and resource acquisition - between PGC and cash crops through both breeding and management. Traits of interest include complementary root and shoot systems, reduced shade avoidance response in the cash-crop, and PGC summer dormancy. Successful deployment of PGC systems could increase both productivity and profitability by improving water- and nutrient-use-efficiency, improving weed and pest control, and creating additional value-added opportunities like stover harvest. Many scientific questions about the inherent interactions at the cell, plant, and ecosystem levels in PGC systems are waiting to be explored. Their answers could enable innovation and refinement of PGC system design for multiple geographies, crops, and food systems, creating a practical and scalable pathway towards resiliency, crop diversification, and sustainable intensification in agriculture.

Aqueous ammonia soaking of switchgrass followed by simultaneous saccharification and fermentation.

Simultaneous saccharification and fermentation (SSF) of switchgrass was performed following aqueous ammonia pretreatment. Switchgrass was soaked in aqueous ammonium hydroxide (30%) with different liquid-solid ratios (5 and 10 ml/g) for either 5 or 10 days. The pretreatment was carried out at atmospheric conditions without agitation. A 40-50% delignification (Klason lignin basis) was achieved, whereas cellulose content remained unchanged and hemicellulose content decreased by approximately 50%. The Sacccharomyces cerevisiae (D5A)-mediated SSF of ammonia-treated switchgrass was investigated at two glucan loadings (3 and 6%) and three enzyme loadings (26, 38.5, and 77 FPU/g cellulose), using Spezyme CP. The percentage of maximum theoretical ethanol yield achieved was 72. Liquid-solid ratio and steeping time affected lignin removal slightly, but did not cause a significant change in overall ethanol conversion yields at sufficiently high enzyme loadings. These results suggest that ammonia steeping may be an effective method of pretreatment for lignocellulosic feedstocks.

Healthy Food as a New Technology-The Implications of Technological Diffusion and Food Price for Changes in Eating Habits.

Diet influences health and poor diets drive up healthcare costs for individuals and society as a whole. Multiple governmental programs in the US have aimed to educate citizens about diet choices, resulting in documented successes, as well as, unintended consequences such as increased food waste. Here we examine some of the relationships between healthy diets, food prices, and wealth by drawing parallels between the diffusion of technological innovation and healthy food diets. We introduce a simple modeling framework to estimate the adoption rates of healthy diets based on income and food prices, and describe the implications of the modeling results for the food industry and for government.

Using a chemical equilibrium model to predict amendments required to precipitate phosphorus as struvite in liquid swine manure.

Precipitation of phosphate minerals from liquid swine manure is an established means of reducing the orthophosphate (OP) concentration. This project investigated the usefulness of a chemical equilibrium model, Visual Minteq, for prescribing the amendments needed to maximize struvite precipitation from liquid swine manure and thus reduce the OP phosphorus concentration. The actual concentrations of Mg(2+), Ca(2+), K(+), OP, NH(4)(+), alkalinity and pH from a liquid swine manure system were used as inputs to the model. The model was modified to remove species with extremely low formation rates, because they would not significantly precipitate in the reaction occurring in a short retention-time process such as those envisioned for swine manure struvite-formation reactors. Using the model's output, a series of 19-L reactors were used to verify the results. Verification results demonstrated that Visual Minteq can be used to pre-determine the concentration of amendments required to maximize struvite recovery.

Imagining tomorrow's university in an era of open science.

As part of a recent workshop entitled "Imagining Tomorrow's University", we were asked to visualize the future of universities as research becomes increasingly data- and computation-driven, and identify a set of principles characterizing pertinent opportunities and obstacles presented by this shift. In order to establish a holistic view, we take a multilevel approach and examine the impact of open science on individual scholars as well as on the university as a whole. At the university level, open science presents a double-edged sword: when well executed, open science can accelerate the rate of scientific inquiry across the institution and beyond; however, haphazard or half-hearted efforts are likely to squander valuable resources, diminish university productivity and prestige, and potentially do more harm than good. We present our perspective on the role of open science at the university.

Development and validation of a technoeconomic analysis tool for early-stage evaluation of bio-based chemical production processes.

By using cost correlations and standard scale-factors, a spreadsheet-based early-stage cost estimation tool was developed. Named BioPET (Biorenewables Process Evaluation Tool), this tool allows users to specify up to seven primary unit operations--fermentation, separation, three catalytic stages, and purification--along with key parameters for each. BioPET then computes an estimated minimum selling price for the pathway. Model validation was conducted by selecting three molecules (ethanol, succinic acid, and adipic acid), and comparing BioPET's results to literature values and to results from a commercial process design tool. BioPET produced virtually identical prices to the process design tool, although the costs were not identically distributed amongst the categories. BioPET produced estimates that were within 40% of other literature values at low feedstock costs, and within 5% at high feedstock costs.

Ultrasonic pretreatment of corn slurry for saccharification: a comparison of batch and continuous systems.

The effects of ultrasound on corn slurry saccharification yield and particle size distribution was studied in both batch and continuous-flow ultrasonic systems operating at a frequency of 20 kHz. Ground corn slurry (28%w/v) was prepared and sonicated in batches at various amplitudes (192-320 microm(peak-to-peak (p-p))) for 20 or 40s using a catenoidal horn. Continuous flow experiments were conducted by pumping corn slurry at various flow rates (10-28 l/min) through an ultrasonic reactor at constant amplitude of 12 microm(p-p). The reactor was equipped with a donut shaped horn. After ultrasonic treatment, commercial alpha- and gluco-amylases (STARGEN 001) were added to the samples, and liquefaction and saccharification proceeded for 3h. The sonicated samples were found to yield 2-3 times more reducing sugars than unsonicated controls. Although the continuous flow treatments released less reducing sugar compared to the batch systems, the continuous flow process was more energy efficient. The reduction of particle size due to sonication was approximately proportional to the dissipated ultrasonic energy regardless of the type of system used. Scanning electron microscopy (SEM) images were also used to observe the disruption of corn particles after sonication. Overall, the study suggests that both batch and continuous ultrasonication enhanced saccharification yields and reduced the particle size of corn slurry. However, due to the large volume involve in full scale processes, an ultrasonic continuous system is recommended.

Laboratory scale evaluation of volatile organic compound emissions as indication of swine carcass degradation inside biosecure composting units.

Biosecure livestock mortality composting systems have been used to dispose of diseased livestock mortalities. In those types of system, visual inspection of carcass degradation is not possible and monitoring VOCs (volatile organic compounds) released by carcasses is a new approach to assess progress of the composting process. In this study, field-scale livestock mortality composting systems were simulated and a laboratory scale composting system with aerobic and anaerobic test units was designed to collect VOC samples from the headspace of decaying plant materials (70 g dry weight) and swine tissues (70 g dry weight) at controlled operating temperatures. Headspace samples were collected with SPME (solid phase microextraction) and analyzed by a GC-MS (gas chromatography-mass spectrometry) system. Among the 43 VOCs identified, dimethyl disulfide, dimethyl trisulfide, and pyrimidine were found to be marker compounds of the mortality composting process. These compounds were only found to be produced by decaying swine tissues but not produced by decaying plant materials. The highest marker VOC emissions were measured during the first three weeks, and VOCs were not detected after the 6th week of the process, which indicates degradation processes were completed and compost materials microbially stabilized (no additional VOC production). Results of respiration tests also showed that compost materials were stabilized. Results of this study can be useful for field-scale composting operations but more studies are needed to show the effects of size and aeration rate of the composting units.

Pilot-scale fermentation of aqueous-ammonia-soaked switchgrass.

Aqueous-ammonia-steeped switchgrass was subject to simultaneous saccharification and fermentation (SSF) in two pilot-scale bioreactors (50- and 350-L working volume). Switchgrass was pretreated by soaking in ammonium hydroxide (30%) with solid to liquid ratio of 5 L ammonium hydroxide per kilogram dry switchgrass for 5 days in 75-L steeping vessels without agitation at ambient temperatures (15 to 33 degrees C). SSF of the pretreated biomass was carried out using Saccharomyces cerevisiae (D(5)A) at approximately 2% glucan and 77 filter paper units per gram cellulose enzyme loading (Spezyme CP). The 50-L fermentation was carried out aseptically, whereas the 350-L fermentation was semiaseptic. The percentage of maximum theoretical ethanol yields achieved was 73% in the 50-L reactor and 52-74% in the 350-L reactor due to the difference in asepsis. The 350-L fermentation was contaminated by acid-producing bacteria (lactic and acetic acid concentrations approaching 10 g/L), and this resulted in lower ethanol production. Despite this problem, the pilot-scale SSF of aqueous-ammonia-pretreated switchgrass has shown promising results similar to laboratory-scale experiments. This work demonstrates challenges in pilot-scale fermentations with material handling, aseptic conditions, and bacterial contamination for cellulosic fermentations to biofuels.

Air sampling and analysis method for volatile organic compounds (VOCs) related to field-scale mortality composting operations.

In biosecure composting, animal mortalities are so completely isolated during the degradation process that visual inspection cannot be used to monitor progress or the process status. One novel approach is to monitor the volatile organic compounds (VOCs) released by decaying mortalities and to use them as biomarkers of the process status. A new method was developed to quantitatively analyze potential biomarkers--dimethyl disulfide, dimethyl trisulfide, pyrimidine, acetic acid, propanoic acid, 3-methylbutanoic acid, pentanoic acid, and hexanoic acid--from field-scale biosecure mortality composting units. This method was based on collection of air samples from the inside of biosecure composting units using portable pumps and solid phase microextraction (SPME). Among four SPME fiber coatings, 85 microm CAR/PDMS was shown to extract the greatest amount of target analytes during a 1 h sampling time. The calibration curves had high correlation coefficients, ranging from 96 to 99%. Differences between the theoretical concentrations and those estimated from the calibration curves ranged from 1.47 to 20.96%. Method detection limits of the biomarkers were between 11 pptv and 572 ppbv. The applicability of the prepared calibration curves was tested for air samples drawn from field-scale swine mortality composting test units. Results show that the prepared calibration curves were applicable to the concentration ranges of potential biomaker compounds in a biosecure animal mortality composting unit.

Development of a fluorescence-based method for monitoring glucose catabolism and its potential use in a biomass hydrolysis assay.

BACKGROUND: The availability and low cost of lignocellulosic biomass has caused tremendous interest in the bioconversion of this feedstock into liquid fuels. One measure of the economic viability of the bioconversion process is the ease with which a particular feedstock is hydrolyzed and fermented. Because monitoring the analytes in hydrolysis and fermentation experiments is time consuming, the objective of this study was to develop a rapid fluorescence-based method to monitor sugar production during biomass hydrolysis, and to demonstrate its application in monitoring corn stover hydrolysis. RESULTS: Hydrolytic enzymes were used in conjunction with Escherichia coli strain CA8404 (a hexose and pentose-consuming strain), modified to produce green fluorescent protein (GFP). The combination of hydrolytic enzymes and a sugar-consuming organism minimizes feedback inhibition of the hydrolytic enzymes. We observed that culture growth rate as measured by change in culture turbidity is proportional to GFP fluorescence and total growth and growth rate depends upon how much sugar is present at inoculation. Furthermore, it was possible to monitor the course of enzymatic hydrolysis in near real-time, though there are instrumentation challenges in doing this. CONCLUSION: We found that instantaneous fluorescence is proportional to the bacterial growth rate. As growth rate is limited by the availability of sugar, the integral of fluorescence is proportional to the amount of sugar consumed by the microbe. We demonstrate that corn stover varieties can be differentiated based on sugar yields in enzymatic hydrolysis reactions using post-hydrolysis fluorescence measurements. Also, it may be possible to monitor fluorescence in real-time during hydrolysis to compare different hydrolysis protocols.

Effect of agricultural antibiotics on the persistence and transformation of 17beta-estradiol in a Sequatchie loam.

A laboratory incubation study was conducted to investigate the effect of agricultural antibiotics (sulfamethazine, tylosin, and chlortetracycline) on the persistence and transformation of 17beta-estradiol in Sequatchie loam. We measured concentrations of 17beta-estradiol and its primary metabolite (estrone) in soils spiked with antibiotics and 17beta-estradiol. Dehydrogenase activity (DHA) was also measured as an indicator of the total microbial activity of the soils. The presence of antibiotics significantly decreased transformation of 17beta-estradiol to estrone. There was a positive correlation between the DHA and the concentrations of estrone in soil spiked with 17beta-estradiol only, implying that the reaction is mainly catalyzed by dehydrogenases. However, the positive correlation was weakened in soil spiked with 17beta-estradiol and antibiotics together. We recommend that any study evaluating the fate and transport of estrogenic hormones in soil should include the effect of agricultural antibiotics because antibiotics and estrogenic hormones are commonly excreted together in environmental samples.

Estrogen content of dairy and swine wastes.

Naturally occurring estrogens in animal wastes may cause negative environmental impacts, yet their abundance in animal waste treatment and storage structures is poorly documented. To better quantify estrogen concentrations in animal wastes, multiple waste samples were collected from treatment and storage structures at dairy and swine facilities and analyzed for concentrations of 17beta-estradiol (E2), estrone (E1), and 17alpha-estradiol by gas chromatography-mass spectroscopy and by enzyme linked immunosorbent assay (E2 only). Mass ratios of each estrogen to the macronutrients nitrogen, phosphorus, and potassium were also determined. Because manure application rates are typically macronutrient-based, estrogen to macronutrient ratios are proportional to areal mass application rates of estrogen to fields. Swine farrowing waste (from farrowing sows and piglets) had the highest ratios of E2 to macronutrients. Mean ratios in swine farrowing waste were roughly twice those in swine finishing waste (from growing male and nonpregnant female animals) and more than four times higher than those in dairy waste (from lactating cows in various stages of their reproductive cycles); these differences were statistically significant (alpha = 0.05). Estrone followed a similar trend. In contrast, ratios of 17alpha-estradiol to macronutrients were highest in dairy operations. These results can be used to better predict estrogen loading rates on fields receiving swine and dairy wastes.