Biotrapping Ureolytic Bacteria on Sand to Improve the Efficiency of Biocementation

Microbially induced calcium carbonate precipitation (MICP) has emerged as a novel technology with the potential to produce building materials through lower-temperature processes. The formation of calcium carbonate bridges in MICP allows the biocementation of aggregate particles to produce biobricks. Current approaches require several pulses of microbes and mineralization media to increase the quantity of calcium carbonate minerals and improve the strength of the material, thus leading to a reduction in sustainability. One potential technique to improve the efficiency of strength development involves trapping the bacteria on the aggregate surfaces using silane coupling agents such as positively charged 3-aminopropyl-methyl-diethoxysilane (APMDES). This treatment traps bacteria on sand through electrostatic interactions that attract negatively charged walls of bacteria to positively charged amine groups. The APMDES treatment promoted an abundant and immediate association of bacteria with sand, increasing the spatial density of ureolytic microbes on sand and promoting efficient initial calcium carbonate precipitation. Though microbial viability was compromised by treatment, urea hydrolysis was minimally affected. Strength was gained much more rapidly for the APMDES-treated sand than for the untreated sand. Three injections of bacteria and biomineralization media using APMDES-treated sand led to the same strength gain as seven injections using untreated sand. The higher strength with APMDES treatment was not explained by increased calcium carbonate accrual in the structure and may be influenced by additional factors such as differences in the microstructure of calcium carbonate bridges between sand particles. Overall, incorporating pretreatment methods, such as amine silane coupling agents, opens a new avenue in biomineralization research by producing materials with an improved efficiency and sustainability.

Understanding phycosomal dynamics to improve industrial microalgae cultivation

Algal-bacterial interactions are ubiquitous in both natural and industrial systems, and the characterization of these interactions has been reinvigorated by potential applications in biosystem productivity. Different growth conditions can be used for operational functions, such as the use of low-quality water or high pH/alkalinity, and the altered operating conditions likely constrain microbial community structure and function in unique ways. However, research is necessary to better understand whether consortia can be designed to improve the productivity, processing, and sustainability of industrial-scale cultivations through different controls that can constrain microbial interactions for maximal light-driven outputs. The review highlights current knowledge and gaps for relevant operating conditions, as well as suggestions for near-term and longer-term improvements for large-scale cultivation and polyculture engineering.

Biofilm reactors for the treatment of used water in space:potential, challenges, and future perspectives

Water is not only essential to sustain life on Earth, but also is a crucial resource for long-duration deep space exploration and habitation. Current systems in space rely on the resupply of water from Earth, however, as missions get longer and move farther away from Earth, resupply will no longer be a sustainable option. Thus, the development of regenerative reclamation water systems through which useable water can be recovered from "waste streams" (i.e., used waters) is sorely needed to further close the loop in space life support systems. This review presents the origin and characteristics of different used waters generated in space and discusses the intrinsic challenges of developing suitable technologies to treat such streams given the unique constrains of space exploration and habitation (e.g., different gravity conditions, size and weight limitations, compatibility with other systems, etc.). In this review, we discuss the potential use of biological systems, particularly biofilms, as possible alternatives or additions to current technologies for water reclamation and waste treatment in space. The fundamentals of biofilm reactors, their advantages and disadvantages, as well as different reactor configurations and their potential for use and challenges to be incorporated in self-sustaining and regenerative life support systems in long-duration space missions are also discussed. Furthermore, we discuss the possibility to recover value-added products (e.g., biomass, nutrients, water) from used waters and the opportunity to recycle and reuse such products as resources in other life support subsystems (e.g., habitation, waste, air, etc.).

[Skull base surgery in the German DRG system-New categorization of important procedures]

Surgery of the skull base includes interventions between the nose or paranasal sinuses (anterior skull base) or ear/temporal bone (lateral skull base) and the intracranial space. As interventions at the anterior skull base almost exclusively involve complex pathologies in a demanding anatomical region, in many cases two experienced surgeons from different disciplines are required who should be experienced in operating together. The technical and time requirements are also considerable in many cases; however, for many procedures there are no specific skull base operational and procedural keys (OPS) codes that take the considerable personnel and structural effort into account. A change in the diagnosis-related groups (DRG) system, implemented since the beginning of 2023, now adjusts the remuneration of the abovementioned effort for malignant pathologies of the anterior and lateral skull base. The reallocation of procedures 5‑015.0/1/3/4 and 5‑016.0/2/4/6 results in a significant upgrade of anterior and lateral skull base surgery. Since the beginning of 2023 skull base surgery will no longer be charged under DRG D25C with a (former) relative weight of 1.893, but with DRG D25B with a current relative weight of 3.753 when a code of the aforementioned groups is used. Nevertheless, further adjustments are necessary, for example, in the available reconstructive steps in order to provide the Institute for the Remuneration System in Hospitals (InEK) with the most differentiated data possible on the procedural effort of the intervention and to achieve a more balanced distribution of the reimbursements of skull base surgery in the long term.

Algal amendment enhances biogenic methane production from coals of different thermal maturity

The addition of small amounts of algal biomass to stimulate methane production in coal seams is a promising low carbon renewable coalbed methane enhancement technique. However, little is known about how the addition of algal biomass amendment affects methane production from coals of different thermal maturity. Here, we show that biogenic methane can be produced from five coals ranging in rank from lignite to low-volatile bituminous using a coal-derived microbial consortium in batch microcosms with and without algal amendment. The addition of 0.1 g/l algal biomass resulted in maximum methane production rates up to 37 days earlier and decreased the time required to reach maximum methane production by 17–19 days when compared to unamended, analogous microcosms. Cumulative methane production and methane production rate were generally highest in low rank, subbituminous coals, but no clear association between increasing vitrinite reflectance and decreasing methane production could be determined. Microbial community analysis revealed that archaeal populations were correlated with methane production rate (p = 0.01), vitrinite reflectance (p = 0.03), percent volatile matter (p = 0.03), and fixed carbon (p = 0.02), all of which are related to coal rank and composition. Sequences indicative of the acetoclastic methanogenic genus Methanosaeta dominated low rank coal microcosms. Amended treatments that had increased methane production relative to unamended analogs had high relative abundances of the hydrogenotrophic methanogenic genus Methanobacterium and the bacterial family Pseudomonadaceae. These results suggest that algal amendment may shift coal-derived microbial communities towards coal-degrading bacteria and CO2-reducing methanogens. These results have broad implications for understanding subsurface carbon cycling in coal beds and the adoption of low carbon renewable microbially enhanced coalbed methane techniques across a diverse range of coal geology.

In Situ Enhancement and Isotopic Labeling of Biogenic Coalbed Methane

Subsurface microbial (biogenic) methane production is an important part of the global carbon cycle that has resulted in natural gas accumulations in many coal beds worldwide. Laboratory studies suggest that complex carbon-containing nutrients (e.g., yeast or algae extract) can stimulate methane production, yet the effectiveness of these nutrients within coal beds is unknown. Here, we use downhole monitoring methods in combination with deuterated water (D₂O) and a 200-liter injection of 0.1% yeast extract (YE) to stimulate and isotopically label newly generated methane. A total dissolved gas pressure sensor enabled real-time gas measurements (641 days preinjection and for 478 days postinjection). Downhole samples, collected with subsurface environmental samplers, indicate that methane increased 132% above preinjection levels based on isotopic labeling from D₂O, 108% based on pressure readings, and 183% based on methane measurements 266 days postinjection. Demonstrating that YE enhances biogenic coalbed methane production in situ using multiple novel measurement methods has immediate implications for other field-scale biogenic methane investigations, including in situ methods to detect and track microbial activities related to the methanogenic turnover of recalcitrant carbon in the subsurface.

Subsurface hydrocarbon degradation strategies in low- and high-sulfate coal seam communities identified with activity-based metagenomics

Environmentally relevant metagenomes and BONCAT-FACS derived translationally active metagenomes from Powder River Basin coal seams were investigated to elucidate potential genes and functional groups involved in hydrocarbon degradation to methane in coal seams with high- and low-sulfate levels. An advanced subsurface environmental sampler allowed the establishment of coal-associated microbial communities under in situ conditions for metagenomic analyses from environmental and translationally active populations. Metagenomic sequencing demonstrated that biosurfactants, aerobic dioxygenases, and anaerobic phenol degradation pathways were present in active populations across the sampled coal seams. In particular, results suggested the importance of anaerobic degradation pathways under high-sulfate conditions with an emphasis on fumarate addition. Under low-sulfate conditions, a mixture of both aerobic and anaerobic pathways was observed but with a predominance of aerobic dioxygenases. The putative low-molecular-weight biosurfactant, lichysein, appeared to play a more important role compared to rhamnolipids. The methods used in this study—subsurface environmental samplers in combination with metagenomic sequencing of both total and translationally active metagenomes—offer a deeper and environmentally relevant perspective on community genetic potential from coal seams poised at different redox conditions broadening the understanding of degradation strategies for subsurface carbon.

OS05.9.A Short-term fasting in glioma patients - Analysis of diet diaries and metabolic parameters of the ERGO2 trial

BACKGROUND

The prospective, randomized ERGO2 trial investigated the effect of fasting / calorie restricted ketogenic diet (KD-IF) on re-irradiation for recurrent brain tumors (Clinicaltrials.gov number: NCT01754350). The study did not meet its primary endpoint of improved progression-free survival in comparison to a standard diet (SD). We here report the results of the quality of life questionnaire, neurocognition testing, detailed analysis of the diet diaries and the alterations of metabolic parameters.

MATERIAL AND METHODS

50 Patients were randomized 1:1 to re-irradiation combined with either SD or KD-IF. The KD-IF schedule included 3 days of ketogenic diet (KD: 21–23 kcal/kg/d, carbohydrate intake limited to 50 g/d), followed by 3 days of fasting and again 3 days of KD. Follow-up included examination of cognition, quality of life and serum samples.

RESULTS

The 20 patients who completed KD-IF met the prespecified goals for calorie and carbohydrate restriction. In these, a decrease in leptin and insulin and an increase in uric acid was observed. The SD group had a lower calorie intake of 21 kcal/kg/d than the expected 30 kcal/kg/d. Neither quality of life nor cognition were affected by the diet. Low glucose emerged as a significant prognostic parameter in a best responder analysis.

CONCLUSION

The strict caloric goals of the ERGO2 trial could be achieved by patients with recurrent brain tumor. The unexpected lower calorie intake of the SD group might have hampered the interpretation of the trial. However, the short diet schedule already led to significant metabolic alterations, suggesting that short-term dietary interventions might be therapeutically useful, possibly combined with other modalities.

Potential use of fungal-bacterial co-cultures for the removal of organic pollutants

Fungi and bacteria coexist in a wide variety of natural and artificial environments which can lead to their association and interaction - ranging from antagonism to cooperation - that can affect the survival, colonization, spatial distribution and stress resistance of the interacting partners. The use of polymicrobial cultivation approaches has facilitated a more thorough understanding of microbial dynamics in mixed microbial communities, such as those composed of fungi and bacteria, and their influence on ecosystem functions. Mixed (multi-domain) microbial communities exhibit unique associations and interactions that could result in more efficient systems for the degradation and removal of organic pollutants. Several previous studies have reported enhanced biodegradation of certain pollutants when using combined fungal-bacterial treatments compared to pure cultures or communities of either fungi or bacteria (single domain systems). This article reviews: (i) the mechanisms of pollutant degradation that can occur in fungal-bacterial systems (e.g.: co-degradation, production of secondary metabolites, enhancement of degradative enzyme production, and transport of bacteria by fungal mycelia); (ii) case studies using fungal-bacterial co-cultures for the removal of various organic pollutants (synthetic dyes, polycyclic aromatic hydrocarbons, pesticides, and other trace or volatile organic compounds) in different environmental matrices (e.g. water, gas/vapors, soil); (iii) the key aspects of engineering artificial fungal-bacterial co-cultures, and (iv) the current challenges and future perspectives of using fungal-bacterial co-cultures for environmental remediation.

[Accreditation and certification of skull base centres in Germany by the German Society for Skull Base Surgery (Gesellschaft für Schädelbasischirurgie, GSB). German version]

The German Society for Skull Base Surgery (Gesellschaft für Schädelbasischirurgie, GSB) has developed a protocol for the certification of GSB skull base centres. The development of such a protocol has led to numerous open and sometimes controversial discussions among the GSB members. The various critical discussion points will be reviewed and the ensuing results, which will then be included in the accreditation protocol, presented. The current GSB accreditation protocol will be presented and explained in an international comparison.

Potential biofilm control strategies for extended spaceflight missions

Biofilms, surface-adherent microbial communities, are associated with microbial fouling and corrosion in terrestrial water-distribution systems. Biofilms are also present in human spaceflight, particularly in the Water Recovery System (WRS) on the International Space Station (ISS). The WRS is comprised of the Urine Processor Assembly (UPA) and the Water Processor Assembly (WPA) which together recycles wastewater from human urine and recovered humidity from the ISS atmosphere. These wastewaters and various process streams are continually inoculated with microorganisms primarily arising from the space crew microbiome. Biofilm-related fouling has been encountered and addressed in spacecraft in low Earth orbit, including ISS and the Russian Mir Space Station. However, planned future missions beyond low Earth orbit to the Moon and Mars present additional challenges, as resupplying spare parts or support materials would be impractical and the mission timeline would be in the order of years in the case of a mission to Mars. In addition, future missions are expected to include a period of dormancy in which the WRS would be unused for an extended duration. The concepts developed in this review arose from a workshop including NASA personnel and representatives with biofilm expertise from a wide range of industrial and academic backgrounds. Here, we address current strategies that are employed on Earth for biofilm control, including antifouling coatings and biocides and mechanisms for mitigating biofilm growth and damage. These ideas are presented in the context of their applicability to spaceflight and identify proposed new topics of biofilm control that need to be addressed in order to facilitate future extended, crewed, spaceflight missions.

Mineralogy of microbially induced calcium carbonate precipitates formed using single cell drop-based microfluidics

Microbe-mineral interactions are ubiquitous and can facilitate major biogeochemical reactions that drive dynamic Earth processes such as rock formation. One example is microbially induced calcium carbonate precipitation (MICP) in which microbial activity leads to the formation of calcium carbonate precipitates. A majority of MICP studies have been conducted at the mesoscale but fundamental questions persist regarding the mechanisms of cell encapsulation and mineral polymorphism. Here, we are the first to investigate and characterize precipitates on the microscale formed by MICP starting from single ureolytic E. coli MJK2 cells in 25 µm diameter drops. Mineral precipitation was observed over time and cells surrounded by calcium carbonate precipitates were observed under hydrated conditions. Using Raman microspectroscopy, amorphous calcium carbonate (ACC) was observed first in the drops, followed by vaterite formation. ACC and vaterite remained stable for up to 4 days, possibly due to the presence of organics. The vaterite precipitates exhibited a dense interior structure with a grainy exterior when examined using electron microscopy. Autofluorescence of these precipitates was observed possibly indicating the development of a calcite phase. The developed approach provides an avenue for future investigations surrounding fundamental processes such as precipitate nucleation on bacteria, microbe-mineral interactions, and polymorph transitions.

OS6.5 ERGO2: A prospective randomized trial of a 9-day schedule of calorically restricted ketogenic diet and fasting or standard diet in addition to re-irradiation for malignant glioma

BACKGROUND

Ketogenic diet (KD) and fasting have anticancer effects in tumor models, possibly due to a differential stress response with sensitization of tumor cells and protection of normal tissue. We therefore set up ERGO2 (NCT01754350), the first randomized clinical trial of calorically-restricted KD and intermittent fasting (KD-IF) in addition to re-irradiation for recurrent malignant gliomas.

MATERIAL AND METHODS

Patients were randomized 1:1 to re-irradiation combined with either calorically unrestricted diet (standard diet, SD) or KD-IF. The KD-IF schedule included 3 days of KD (21–23 kcal/kg/d), followed by 3 days of fasting and again 3 days of KD. The primary endpoint was progression-free survival (PFS) rate at 6 months (PFS6). Secondary endpoints were PFS, local control, overall survival (OS), frequency of epileptic seizures, rate of ketosis and quality of life.

RESULTS

50 patients were included. Four patients quit the trial before treatment and three patients stopped KD-IF prematurely. Of the 20 patients who completed KD-IF, 17 patients developed ketosis at day 6, and glucose levels declined significantly. KD-IF was well-tolerated with a modest weight loss of -2.1±1.8 kg. No severe adverse events attributable to the diet occurred. There was no difference in PFS6 between the two groups (KD-IF: 20%, SD: 16%). Similarly, no difference in PFS, local PFS6 and OS were observable. Explorative analysis revealed that among patients of the KD-IF group, those who achieved ketosis of at least 1.5 mmol/l had significantly longer PFS compared to those with lesser or no ketosis.

CONCLUSION

KD-IF is feasible and effective in inducing ketosis in heavily pretreated patients with recurrent glioblastoma. However, the short schedule reported here failed to increase the efficacy of re-irradiation.

Controlling the Distribution of Microbially Precipitated Calcium Carbonate in Radial Flow Environments

Bacterially driven reactions such as ureolysis can induce calcium carbonate precipitation, a well-studied process called microbially induced calcium carbonate precipitation (MICP). MICP is of interest in subsurface applications such as sealing leaks around wells. For effective field deployment, it is important to study MICP under radial flow conditions, which are relevant to near-well environments. In this study, a laboratory-scale radial flow reactor of 23 cm diameter, with a 1 mm glass bead monolayer serving as a porous medium, was used to investigate the effects of fluid flow rates and calcium concentrations on the mass and distribution of MICP by the ureolytic bacterium Sporosarcina pasteurii. Experiments were performed at hydraulic residence times of 14, 7, and 3.5 min and calcium to urea molar ratios of 0.5:1, 1:1, and 2:1. The total amount of CaCO₃ precipitated in the reactor increased with increasing residence time and with decreasing Ca²⁺ to urea molar ratios. Increased bacterial attachment and increased CaCO₃ precipitation were observed with distance from the center inlet of the reactor in all experiments. More uniform calcium distribution was achieved at lower flow rates. The relationship between reaction and transport rate (i.e., the Damköhler number) is identified as a useful parameter for the prediction of MICP in radial flow environments.

Biological treatment of selenium-laden wastewater containing nitrate and sulfate in an upflow anaerobic sludge bed reactor at pH 5.0

This study investigated the removal of selenate (SeO₄^2-), sulfate (SO₄^2-) and nitrate (NO₃^-) at different influent pH values ranging from 7.0 to 5.0 and 20 °C in an upflow anaerobic sludge blanket (UASB) reactor using lactate as an electron donor. At pH 5.0, the UASB reactor showed a 20-30% decrease in reactor performance compared to operation at pH 5.5 to 7.0, reaching removal efficiencies of 79%, 15%, 43% and 61% for NO₃^-, SO₄^2-, Se_total and Se_diss, respectively. However, the reactor stability was an issue upon lowering the pH to 5.0 and further experiments are recommended. The sludge formed during low pH operation had a fluffy, floc-like appearance with filamentous structure, possibly due to the low polysaccharide (PS) to protein (PN) ratio (0.01 PS/PN) in the soluble extracellular polymeric substances (EPS) matrix of the biomass. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) analysis of the sludge confirmed Se oxyanion reduction and deposition of Se⁰ particles inside the biomass. Microbial community analysis using Illumina MiSeq sequencing revealed that the families of Campylobacteraceae and Desulfomicrobiaceae were the dominant phylotypes throughout the reactor operation at approximately 23% and 10% relative abundance, respectively. Furthermore, approximately 10% relative abundance of both Geobacteraceae and Spirochaetaceae was observed in the granular sludge during the pH 5.0 operation. Overall, this study demonstrated the feasibility of UASB operation at pH values ranging from 7.0 to 5.0 for removing Se and other oxyanions from wastewaters.

Carbon-dependent chromate toxicity mechanism in an environmental Arthrobacter isolate

Arthrobacter spp. are widespread in soil systems and well-known for their Cr(VI) reduction capabilities making them attractive candidates for in situ bioremediation efforts. Cellulose drives carbon flow in soil systems; yet, most laboratory studies evaluate Arthrobacter-Cr(VI) interactions solely with nutrient-rich media or glucose. This study aims to determine how various cellulose degradation products and biostimulation substrates influence Cr(VI) toxicity, reduction, and microbial growth of an environmental Arthrobacter sp. isolate. Laboratory culture-based studies suggest there is a carbon-dependent Cr(VI) toxicity mechanism that affects subsequent Cr(VI) reduction by strain LLW01. Strain LLW01 could only grow in the presence of, and reduce, 50 μM Cr(VI) when glucose or lactate were provided. Compared to lactate, Cr(VI) was at least 30-fold and 10-fold more toxic when ethanol or butyrate was the sole carbon source, respectively. The addition of sulfate mitigated toxicity somewhat, but had no effect on the extent of Cr(VI) reduction. Cell viability studies indicated that a small fraction of cells were viable after 8 days suggesting cell growth and subsequent Cr(VI) reduction may resume. These results suggest when designing bioremediation strategies with Arthrobacter spp. such as strain LLW01, carbon sources such as glucose and lactate should be considered over ethanol and butyrate.

Stellenwert der Thrombelastometrie für das Monitoring von Faktor XIII

Recently published studies give evidence, that an increased maximum lysis in the APTEM® – test (ML60 > 12%) of the ROTEM® (Tem International GmbH, Munich, Germany) might indicate a factor XIII deficiency (FXIII < 70%). It was the aim of this study to investigate the feasibility of thrombelastometric measurements with the ROTEM device to reflect the isolated influence of FXIII on clot stability and therefore to indicate potential factor XIII deficiencies. Patients, method: After approval by the local Scientific and Ethic Review Board, 26 consecutive patients, scheduled for elective craniotomy for tumour resection, were prospectively enrolled into this study. Blood samples were taken for conventional laboratory coagulation analyses, FXIII analyses and thrombelastometric measurements (EXTEM, FIBTEM and APTEM tests) after induction of general anaesthesia (T1), before skin incision (T2) as well as at (T3) and 24 hours after (T4) postoperative admission to ICU, respectively. Statistical analyses included Spearman rank order correlations and multiple linear regressions. Results: FXIII concentrations did not correlate with the ML60 in the APTEM test at any measuring point. Neither platelet count nor fibrinogen nor FXIII concentrations were of predictive value for ML60 of the APTEM test. Conclusion: The results lead to the assumption that thrombelastometric measurements may not be appropriate for the perioperative monitoring of FXIII concentration.

Impact of Mineral Precipitation on Flow and Mixing in Porous Media Determined by Microcomputed Tomography and MRI

Precipitation reactions influence transport properties in porous media and can be coupled to advective and dispersive transport. For example, in subsurface environments, mixing of groundwater and injected solutions can induce mineral supersaturation of constituents and drive precipitation reactions. Magnetic resonance imaging (MRI) and microcomputed tomography (μ-CT) were employed as complementary techniques to evaluate advection, dispersion, and formation of precipitate in a 3D porous media flow cell. Two parallel fluids were flowed concentrically through packed glass beads under two relative flow rates with Na₂CO₃ and CaCl₂ in the inner and outer fluids, respectively. CaCO₃ became supersaturated and formed a precipitate at the mixing interface between the two solutions. Spatial maps of changing local velocity fields and dispersion in the flow cell were generated from MRI, while high resolution μ-CT imaging visualized the precipitate formed in the porous media. Formation of a precipitate minimized dispersive and advective transport between the two fluids and the shape of the precipitation front was influenced by the relative flow rates. This work demonstrates that the combined use of MRI and μ-CT can be highly complementary in the study of reactive transport processes in porous media.

Using life cycle assessment and techno-economic analysis in a real options framework to inform the design of algal biofuel production facilities

This study investigates the use of "real options analysis" (ROA) to quantify the value of greater product flexibility at algal biofuel production facilities. A deterministic optimization framework is integrated with a combined life cycle assessment/techno-economic analysis model and subjected to an ensemble of 30-year commodity price trajectories. Profits are maximized for two competing plant configurations: 1) one that sells lipid-extracted algae as animal feed only; and 2) one that can sell lipid-extracted algae as feed or use it to recover nutrients and energy, due to an up-front investment in anaerobic digestion/combined heat and power. Results show that added investment in plant flexibility does not result in an improvement in net present value, because current feed meal prices discourage use of lipid-extracted algae for nutrient and energy recovery. However, this study demonstrates that ROA provides many useful insights regarding plant design that cannot be captured via traditional techno-economic modeling.

Evaluating the relative impacts of operational and financial factors on the competitiveness of an algal biofuel production facility

Algal biofuels are becoming more economically competitive due to technological advances and government subsidies offering tax benefits and lower cost financing. These factors are linked, however, as the value of technical advances is affected by modeling assumptions regarding the growth conditions, process design, and financing of the production facility into which novel techniques are incorporated. Two such techniques, related to algal growth and dewatering, are evaluated in representative operating and financing scenarios using an integrated techno-economic model. Results suggest that these techniques can be valuable under specified conditions, but also that investment subsidies influence cost competitive facility design by incentivizing development of more capital intensive facilities (e.g., favoring hydrothermal liquefaction over transesterification-based facilities). Evaluating novel techniques under a variety of operational and financial scenarios highlights the set of site-specific conditions in which technical advances are most valuable, while also demonstrating the influence of subsidies linked to capital intensity.

Effect of selenite on the morphology and respiratory activity of Phanerochaete chrysosporium biofilms

The temporal and spatial effects of selenite (SeO3(2-)) on the physical properties and respiratory activity of Phanerochaete chrysosporium biofilms, grown in flow-cell reactors, were investigated using oxygen microsensors and confocal laser scanning microscopy (CLSM) imaging. Exposure of the biofilm to a SeO3(2-) load of 1.67mgSeL(-1)h(-1) (10mgSeL(-1) influent concentration), for 24h, resulted in a 20% reduction of the O2 flux, followed by a ∼10% decrease in the glucose consumption rate. Long-term exposure (4days) to SeO3(2-) influenced the architecture of the biofilm by creating a more compact and dense hyphal arrangement resulting in a decrease of biofilm thickness compared to fungal biofilms grown without SeO3(2-). To the best of our knowledge, this is the first time that the effect of SeO3(2-) on the aerobic respiratory activity on fungal biofilms is described.

Fracture Sealing with Microbially-Induced Calcium Carbonate Precipitation: A Field Study

A primary environmental risk from unconventional oil and gas development or carbon sequestration is subsurface fluid leakage in the near wellbore environment. A potential solution to remediate leakage pathways is to promote microbially induced calcium carbonate precipitation (MICP) to plug fractures and reduce permeability in porous materials. The advantage of microbially induced calcium carbonate precipitation (MICP) over cement-based sealants is that the solutions used to promote MICP are aqueous. MICP solutions have low viscosities compared to cement, facilitating fluid transport into the formation. In this study, MICP was promoted in a fractured sandstone layer within the Fayette Sandstone Formation 340.8 m below ground surface using conventional oil field subsurface fluid delivery technologies (packer and bailer). After 24 urea/calcium solution and 6 microbial (Sporosarcina pasteurii) suspension injections, the injectivity was decreased (flow rate decreased from 1.9 to 0.47 L/min) and a reduction in the in-well pressure falloff (>30% before and 7% after treatment) was observed. In addition, during refracturing an increase in the fracture extension pressure was measured as compared to before MICP treatment. This study suggests MICP is a promising tool for sealing subsurface fractures in the near wellbore environment.

Investigating the Influence of the Initial Biomass Distribution and Injection Strategies on Biofilm-Mediated Calcite Precipitation in Porous Media

Attachment of bacteria in porous media is a complex mixture of processes resulting in the transfer and immobilization of suspended cells onto a solid surface within the porous medium. Quantifying the rate of attachment is difficult due to the many simultaneous processes possibly involved in attachment, including straining, sorption, and sedimentation, and the difficulties in measuring metabolically active cells attached to porous media. Preliminary experiments confirmed the difficulty associated with measuring active Sporosarcina pasteurii cells attached to porous media. However, attachment is a key process in applications of biofilm-mediated reactions in the subsurface such as microbially induced calcite precipitation. Independent of the exact processes involved, attachment determines both the distribution and the initial amount of attached biomass and as such the initial reaction rate. As direct experimental investigations are difficult, this study is limited to a numerical investigation of the effect of various initial biomass distributions and initial amounts of attached biomass. This is performed for various injection strategies, changing the injection rate as well as alternating between continuous and pulsed injections. The results of this study indicate that, for the selected scenarios, both the initial amount and the distribution of attached biomass have minor influence on the Ca $$^{2+}$$ 2 + precipitation efficiency as well as the distribution of the precipitates compared to the influence of the injection strategy. The influence of the initial biomass distribution on the resulting final distribution of the precipitated calcite is limited, except for the continuous injection at intermediate injection rate. But even for this injection strategy, the Ca $$^{2+}$$ 2 + precipitation efficiency shows no significant dependence on the initial biomass distribution.

Estimation of a biofilm-specific reaction rate: kinetics of bacterial urea hydrolysis in a biofilm

Background/Objectives:

Biofilms and specifically urea-hydrolysing biofilms are of interest to the medical community (for example, urinary tract infections), scientists and engineers (for example, microbially induced carbonate precipitation). To appropriately model these systems, biofilm-specific reaction rates are required. A simple method for determining biofilm-specific reaction rates is described and applied to a urea-hydrolysing biofilm.

Methods:

Biofilms were grown in small silicon tubes and influent and effluent urea concentrations were determined. Immediately after sampling, the tubes were thin sectioned to estimate the biofilm thickness profile along the length of the tube. Urea concentration and biofilm thickness data were used to construct an inverse model for the estimation of the urea hydrolysis rate.

Results/Conclusions:

It was found that urea hydrolysis in Escherichia coli MJK2 biofilms is well approximated by first-order kinetics between urea concentrations of 0.003 and 0.221 mol/l (0.186 and 13.3 g/l). The first-order rate coefficient (k₁) was estimated to be 23.2±6.2 h⁻¹. It was also determined that advection dominated the experimental system rather than diffusion, and that urea hydrolysis within the biofilms was not limited by diffusive transport. Beyond the specific urea-hydrolysing biofilm discussed in this work, the method has the potential for wide application in cases where biofilm-specific rates must be determined.

Whole cell kinetics of ureolysis by Sporosarcina pasteurii

AIMS

Ureolysis drives microbially induced calcium carbonate precipitation (MICP). MICP models typically employ simplified urea hydrolysis kinetics that do not account for cell density, pH effect or product inhibition. Here, ureolysis rate studies with whole cells of Sporosarcina pasteurii aimed to determine the relationship between ureolysis rate and concentrations of (i) urea, (ii) cells, (iii) NH4+ and (iv) pH (H(+) activity).

METHODS AND RESULTS

Batch ureolysis rate experiments were performed with suspended cells of S. pasteurii and one parameter was varied in each set of experiments. A Michaelis-Menten model for urea dependence was fitted to the rate data (R(2)  = 0·95) using a nonlinear mixed effects statistical model. The resulting half-saturation coefficient, Km , was 305 mmol l(-1) and maximum rate constant, Vmax , was 200 mmol l(-1)  h(-1) . However, a first-order model with k1  = 0·35 h(-1) fit the data better (R(2)  = 0·99) for urea concentrations up to 330 mmol l(-1) . Cell concentrations in the range tested (1 × 10(7) -2 × 10(8)  CFU ml(-1) ) were linearly correlated with ureolysis rate (cell dependent Vmax' = 6·4 × 10(-9)  mmol CFU(-1)  h(-1) ).

CONCLUSIONS

Neither pH (6-9) nor ammonium concentrations up to 0·19 mol l(-1)  had significant effects on the ureolysis rate and are not necessary in kinetic modelling of ureolysis. Thus, we conclude that first-order kinetics with respect to urea and cell concentrations are likely sufficient to describe urea hydrolysis rates at most relevant concentrations.

SIGNIFICANCE AND IMPACT OF THE STUDY

These results can be used in simulations of ureolysis driven processes such as microbially induced mineral precipitation and they verify that under the stated conditions, a simplified first-order rate for ureolysis can be employed. The study shows that the kinetic models developed for enzyme kinetics of urease do not apply to whole cells of S. pasteurii.

Dissolved inorganic carbon enhanced growth, nutrient uptake, and lipid accumulation in wastewater grown microalgal biofilms

Microalgal biofilms grown to evaluate potential nutrient removal options for wastewaters and feedstock for biofuels production were studied to determine the influence of bicarbonate amendment on their growth, nutrient uptake capacity, and lipid accumulation after nitrogen starvation. No significant differences in growth rates, nutrient removal, or lipid accumulation were observed in the algal biofilms with or without bicarbonate amendment. The biofilms possibly did not experience carbon-limited conditions because of the large reservoir of dissolved inorganic carbon in the medium. However, an increase in photosynthetic rates was observed in algal biofilms amended with bicarbonate. The influence of bicarbonate on photosynthetic and respiration rates was especially noticeable in biofilms that experienced nitrogen stress. Medium nitrogen depletion was not a suitable stimulant for lipid production in the algal biofilms and as such, focus should be directed toward optimizing growth and biomass productivities to compensate for the low lipid yields and increase nutrient uptake.

Fe(III) mineral reduction followed by partial dissolution and reactive oxygen species generation during 2,4,6-trinitrotoluene transformation by the aerobic yeast Yarrowia lipolytica

Understanding the factors that influence pollutant transformation in the presence of ferric (oxyhydr)oxides is crucial to the efficient application of different remediation strategies. In this study we determined the effect of goethite, hematite, magnetite and ferrihydrite on the transformation of 2,4,6-trinitrotoluene (TNT) by Yarrowia lipolytica AN-L15. The presence of ferric (oxyhydr)oxides led to a small decrease in the rate of TNT removal. In all cases, a significant release of NO₂⁻ from TNT and further NO₂⁻ oxidation to NO₃⁻ was observed. A fraction of the released NO₂⁻ was abiotically decomposed to NO and NO₂, and then NO was likely oxidized abiotically to NO₂ by O₂. ESR analysis revealed the generation of superoxide in the culture medium; its further protonation at low pH resulted in the formation of hydroperoxyl radical. Presumably, a fraction of NO released during TNT degradation reacted with superoxide and formed peroxynitrite, which was further rearranged to NO₃⁻ at the acidic pH values observed in this study. A transformation and reduction of ferric (oxyhydr)oxides followed by partial dissolution (in the range of 7–86% of the initial Fe(III)) were observed in the presence of cells and TNT. Mössbauer spectroscopy showed some minor changes for goethite, magnetite and ferrihydrite samples during their incubation with Y. lipolytica and TNT. This study shows that i) reactive oxygen and nitrogen species generated during TNT transformation by Y. lipolytica participate in the abiotic conversion of TNT and ii) the presence of iron(III) minerals leads to a minor decrease in TNT transformation.

Optimized inorganic carbon regime for enhanced growth and lipid accumulation in Chlorella vulgaris

BACKGROUND

Large-scale algal biofuel production has been limited, among other factors, by the availability of inorganic carbon in the culture medium at concentrations higher than achievable with atmospheric CO2. Life cycle analyses have concluded that costs associated with supplying CO2 to algal cultures are significant contributors to the overall energy consumption.

RESULTS

A two-phase optimal growth and lipid accumulation scenario is presented, which (1) enhances the growth rate and (2) the triacylglyceride (TAG) accumulation rate in the oleaginous Chlorophyte Chlorella vulgaris strain UTEX 395, by growing the organism in the presence of low concentrations of NaHCO3 (5 mM) and controlling the pH of the system with a periodic gas sparge of 5 % CO2 (v/v). Once cultures reached the desired cell densities, which can be "fine-tuned" based on initial nutrient concentrations, cultures were switched to a lipid accumulation metabolism through the addition of 50 mM NaHCO3. This two-phase approach increased the specific growth rate of C. vulgaris by 69 % compared to cultures sparged continuously with 5 % CO2 (v/v); further, biomass productivity (g L(-1) day(-1)) was increased by 27 %. Total biodiesel potential [assessed as total fatty acid methyl ester (FAME) produced] was increased from 53.3 to 61 % (FAME biomass(-1)) under the optimized conditions; biodiesel productivity (g FAME L(-1) day(-1)) was increased by 7.7 %. A bicarbonate salt screen revealed that American Chemical Society (ACS) and industrial grade NaHCO3 induced the highest TAG accumulation (% w/w), whereas Na2CO3 did not induce significant TAG accumulation. NH4HCO3 had a negative effect on cell health presumably due to ammonia toxicity. The raw, unrefined form of trona, NaHCO3∙Na2CO3 (sodium sesquicarbonate) induced TAG accumulation, albeit to a slightly lower extent than the more refined forms of sodium bicarbonate.

CONCLUSIONS

The strategic addition of sodium bicarbonate was found to enhance growth and lipid accumulation rates in cultures of C. vulgaris, when compared to traditional culturing strategies, which rely on continuously sparging algal cultures with elevated concentrations of CO2(g). This work presents a two-phased, improved photoautotrophic growth and lipid accumulation approach, which may result in an overall increase in algal biofuel productivity.

Sources and resources: importance of nutrients, resource allocation, and ecology in microalgal cultivation for lipid accumulation

Regardless of current market conditions and availability of conventional petroleum sources, alternatives are needed to circumvent future economic and environmental impacts from continued exploration and harvesting of conventional hydrocarbons. Diatoms and green algae (microalgae) are eukaryotic photoautotrophs that can utilize inorganic carbon (e.g., CO2) as a carbon source and sunlight as an energy source, and many microalgae can store carbon and energy in the form of neutral lipids. In addition to accumulating useful precursors for biofuels and chemical feed stocks, the use of autotrophic microorganisms can further contribute to reduced CO2 emissions through utilization of atmospheric CO2. Because of the inherent connection between carbon, nitrogen, and phosphorus in biological systems, macronutrient deprivation has been proven to significantly enhance lipid accumulation in different diatom and algae species. However, much work is needed to understand the link between carbon, nitrogen, and phosphorus in controlling resource allocation at different levels of biological resolution (cellular versus ecological). An improved understanding of the relationship between the effects of N, P, and micronutrient availability on carbon resource allocation (cell growth versus lipid storage) in microalgae is needed in conjunction with life cycle analysis. This mini-review will briefly discuss the current literature on the use of nutrient deprivation and other conditions to control and optimize microalgal growth in the context of cell and lipid accumulation for scale-up processes.

Direct measurement and characterization of active photosynthesis zones inside wastewater remediating and biofuel producing microalgal biofilms

Microalgal biofilm based technologies are of keen interest due to their high biomass concentrations and ability to utilize light and CO2. While photoautotrophic biofilms have long been used for wastewater remediation, biofuel production represents a relatively new and under-represented focus area. However, the direct measurement and characterization of fundamental parameters required for industrial control are challenging due to biofilm heterogeneity. This study evaluated oxygenic photosynthesis and respiration on two distinct microalgal biofilms cultured using a novel rotating algal biofilm reactor operated at field- and laboratory-scales. Clear differences in oxygenic photosynthesis and respiration were observed based on different culturing conditions, microalgal composition, light intensity and nitrogen availability. The cultures were also evaluated as potential biofuel synthesis strategies. Nitrogen depletion was not found to have the same effect on lipid accumulation compared to traditional planktonic microalgal studies. Physiological characterizations of these microalgal biofilms identify fundamental parameters needed to understand and control process optimization.

Archaeal and bacterial communities in three alkaline hot springs in Heart Lake Geyser Basin, Yellowstone National Park

The Heart Lake Geyser Basin (HLGB) is remotely located at the base of Mount Sheridan in southern Yellowstone National Park (YNP), Wyoming, USA and is situated along Witch Creek and the northwestern shore of Heart Lake. Likely because of its location, little is known about the microbial community structure of springs in the HLGB. Bacterial and archaeal populations were monitored via small subunit (SSU) rRNA gene pyrosequencing over 3 years in 3 alkaline (pH 8.5) hot springs with varying temperatures (44°C, 63°C, 75°C). The bacterial populations were generally stable over time, but varied by temperature. The dominant bacterial community changed from moderately thermophilic and photosynthetic members (Cyanobacteria and Chloroflexi) at 44°C to a mixed photosynthetic and thermophilic community (Deinococcus-Thermus) at 63°C and a non-photosynthetic thermophilic community at 75°C. The archaeal community was more variable across time and was predominantly a methanogenic community in the 44 and 63°C springs and a thermophilic community in the 75°C spring. The 75°C spring demonstrated large shifts in the archaeal populations and was predominantly Candidatus Nitrosocaldus, an ammonia-oxidizing crenarchaeote, in the 2007 sample, and almost exclusively Thermofilum or Candidatus Caldiarchaeum in the 2009 sample, depending on SSU rRNA gene region examined. The majority of sequences were dissimilar (≥10% different) to any known organisms suggesting that HLGB possesses numerous new phylogenetic groups that warrant cultivation efforts.

An efficient and scalable extraction and quantification method for algal derived biofuel

Microalgae are capable of synthesizing a multitude of compounds including biofuel precursors and other high value products such as omega-3-fatty acids. However, accurate analysis of the specific compounds produced by microalgae is important since slight variations in saturation and carbon chain length can affect the quality, and thus the value, of the end product. We present a method that allows for fast and reliable extraction of lipids and similar compounds from a range of algae, followed by their characterization using gas chromatographic analysis with a focus on biodiesel-relevant compounds. This method determines which range of biologically synthesized compounds is likely responsible for each fatty acid methyl ester (FAME) produced; information that is fundamental for identifying preferred microalgae candidates as a biodiesel source. Traditional methods of analyzing these precursor molecules are time intensive and prone to high degrees of variation between species and experimental conditions. Here we detail a new method which uses microwave energy as a reliable, single-step cell disruption technique to extract lipids from live cultures of microalgae. After extractable lipid characterization (including lipid type (free fatty acids, mono-, di- or tri-acylglycerides) and carbon chain length determination) by GC-FID, the same lipid extracts are transesterified into FAMEs and directly compared to total biodiesel potential by GC-MS. This approach provides insight into the fraction of total FAMEs derived from extractable lipids compared to FAMEs derived from the residual fraction (i.e. membrane bound phospholipids, sterols, etc.). This approach can also indicate which extractable lipid compound, based on chain length and relative abundance, is responsible for each FAME. This method was tested on three species of microalgae; the marine diatom Phaeodactylum tricornutum, the model Chlorophyte Chlamydomonas reinhardtii, and the freshwater green alga Chlorella vulgaris. The method is shown to be robust, highly reproducible, and fast, allowing for multiple samples to be analyzed throughout the time course of culturing, thus providing time-resolved information regarding lipid quantity and quality. Total time from harvesting to obtaining analytical results is less than 2h.

Bacterially induced calcium carbonate precipitation and strontium coprecipitation in a porous media flow system

Strontium-90 is a principal radionuclide contaminant in the subsurface at several Department of Energy sites in the Western U.S., causing a threat to groundwater quality in areas such as Hanford, WA. In this work, we used laboratory-scale porous media flow cells to examine a potential remediation strategy employing coprecipitation of strontium in carbonate minerals. CaCO(3) precipitation and strontium coprecipitation were induced via ureolysis by Sporosarcina pasteurii in two-dimensional porous media reactors. An injection strategy using pulsed injection of calcium mineralization medium was tested against a continuous injection strategy. The pulsed injection strategy involved periods of lowered calcite saturation index combined with short high fluid velocity flow periods of calcium mineralization medium followed by stagnation (no-flow) periods to promote homogeneous CaCO(3) precipitation. By alternating the addition of mineralization and growth media the pulsed strategy promoted CaCO(3) precipitation while sustaining the ureolytic culture over time. Both injection strategies achieved ureolysis with subsequent CaCO(3) precipitation and strontium coprecipitation. The pulsed injection strategy precipitated 71-85% of calcium and 59% of strontium, while the continuous injection was less efficient and precipitated 61% of calcium and 56% of strontium. Over the 60 day operation of the pulsed reactors, ureolysis was continually observed, suggesting that the balance between growth and precipitation phases allowed for continued cell viability. Our results support the pulsed injection strategy as a viable option for ureolysis-induced strontium coprecipitation because it may reduce the likelihood of injection well accumulation caused by localized mineral plugging while Sr coprecipitation efficiency is maintained in field-scale applications.

Potential CO2 leakage reduction through biofilm-induced calcium carbonate precipitation

Mitigation strategies for sealing high permeability regions in cap rocks, such as fractures or improperly abandoned wells, are important considerations in the long term security of geologically stored carbon dioxide (CO(2)). Sealing technologies using low-viscosity fluids are advantageous in this context since they potentially reduce the necessary injection pressures and increase the radius of influence around injection wells. Using aqueous solutions and suspensions that can effectively promote microbially induced mineral precipitation is one such technology. Here we describe a strategy to homogenously distribute biofilm-induced calcium carbonate (CaCO(3)) precipitates in a 61 cm long sand-filled column and to seal a hydraulically fractured, 74 cm diameter Boyles Sandstone core. Sporosarcina pasteurii biofilms were established and an injection strategy developed to optimize CaCO(3) precipitation induced via microbial urea hydrolysis. Over the duration of the experiments, permeability decreased between 2 and 4 orders of magnitude in sand column and fractured core experiments, respectively. Additionally, after fracture sealing, the sandstone core withstood three times higher well bore pressure than during the initial fracturing event, which occurred prior to biofilm-induced CaCO(3) mineralization. These studies suggest biofilm-induced CaCO(3) precipitation technologies may potentially seal and strengthen fractures to mitigate CO(2) leakage potential.