Selective Growth Of Type Ii Methanotrophic Bacteria In A Biological Fluidized Bed Reactor

Author : Andrew Ross Pfluger
Publisher : Stanford University
ISBN 13 :
Total Pages : 152 pages
Book Rating : 4.43/5 ( download)

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Download or read book Selective Growth of Type II Methanotrophic Bacteria in a Biological Fluidized Bed Reactor written by Andrew Ross Pfluger and published by Stanford University. This book was released on 2010 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: Type II methanotrophic bacteria are superior to Type I methanotrophs in accumulating polyhydroxybutyrate (PHB), a biodegradable alternative to polypropylene and other petro-chemical plastics, under nutrient limiting conditions. We evaluated the growth of Type I and Type II methanotrophs in a 15.2-liter bench-scale fluidized bed reactor (FBR) over a 270-day period. The aim was to identify operational characteristics and selection pressures that would favor Type II over Type I methanotrophs. The results indicate that Type II methanotrophs can be grown in an FBR under the appropriate conditions and that such a method may be a viable means of producing large quantities of biomass for PHB production.

Author : Andrew Ross Pfluger
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.18/5 ( download)

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Download or read book Selective Growth of Type II Methanotrophic Bacteria in a Biological Fluidized Bed Reactor written by Andrew Ross Pfluger and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Type II methanotrophic bacteria are superior to Type I methanotrophs in accumulating polyhydroxybutyrate (PHB), a biodegradable alternative to polypropylene and other petro-chemical plastics, under nutrient limiting conditions. We evaluated the growth of Type I and Type II methanotrophs in a 15.2-liter bench-scale fluidized bed reactor (FBR) over a 270-day period. The aim was to identify operational characteristics and selection pressures that would favor Type II over Type I methanotrophs. The results indicate that Type II methanotrophs can be grown in an FBR under the appropriate conditions and that such a method may be a viable means of producing large quantities of biomass for PHB production.

Author : Eric Robert Sundstrom
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.67/5 ( download)

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Download or read book Selection and Optimization Strategies for Production of Polyhydroxybutyrate (PHB) in Methanotrophic Bacteria written by Eric Robert Sundstrom and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Disposal of petrochemical plastics is of major environmental concern worldwide, with plastics continuing to accumulate in landfills and oceans. Polyhydroxybutyrate (PHB) is a biologically produced and biodegradable polymer that can functionally replace many recalcitrant, petroleum-based polymers. Production cost of PHB currently prevents wider adoption, with much of this cost attributable to use of agricultural sugars as a production substrate. Methane gas is attractive as an alternative substrate because it is inexpensive, widely available, and naturally converted to PHB by methanotrophic bacteria. Production of PHB by methanotrophic bacteria is well documented, but continued gains in production efficiency must be realized to allow implementation on an industrial scale. In this dissertation, a combination of high throughput screening and application of selective pressure was used to optimize production of PHB by methanotrophic bacteria. Culturing and isolation of methanotrophs is labor-intensive due to slow growth rates and the requirement of gas-phase substrate delivery. Measurement of PHB content is similarly labor-intensive, with culture and analysis time combining to limit experimental throughput. To address this issue, a novel microplate-based system was designed, enabling high-throughput culture and integrated analysis of PHB content. This system was used to optimize growth medium for PHB production in the Type II methanotroph Methylocystis parvus OBBP. Modification of copper and calcium concentrations in the growth medium lead to a five-fold increase in final PHB content in this organism, validating the efficacy of the high-throughput system and underscoring the importance of media composition for optimal PHB production. As compared to aseptic production in pure culture systems, use of diverse mixed culture for PHB production reduces sterilization costs and allows selection for improved fitness over time. In methanotrophs, PHB production has been identified only in Type II strains, a subset of total diversity. Selection for Type II methanotrophs and exclusion of other types is therefore critical to the development of effective mixed culture PHB production. Combinations of growth on ammonium, nitrate, and urea nitrogen sources were therefore investigated as potential selectors for PHB-producing methanotrophs. In enrichment cultures inoculated with activated sludge, PHB production was observed only in replicates enriched with ammonium and PHB was detected only at low concentrations. These low concentrations are attributed to competitive inhibition of methane monooxygenase by ammonium, and to accumulation of toxic hydroxylamine produced by ammonium co-oxidation. Alternating between selective growth with ammonium and rapid growth with nitrate mitigated these negative effects, allowing rapid growth and PHB production. Hydroxylamine tolerance was also tested in pure cultures as a potential selector for Type II methanotrophs, with tolerance found to vary strain-by-strain. Added reducing equivalents increased hydroxylamine tolerance in two of four strains tested, indicating that in some strains hydroxylamine reduction plays an important role in hydroxylamine detoxification. Stored PHB serves as a source of reducing equivalents in methanotrophs, and may therefore increase fitness of methanotrophs exposed to cometabolically produced hydroxylamine. Combining selection for Type II methanotrophs with selection for increasing PHB production over time would increase yields of PHB without requiring metabolic engineering. Methane limitation during PHB consumption is known to select for increasing PHB over time, with stored PHB used to supply necessary reducing equivalents in the absence of sufficient methane. In the final study, two cycling reactors were operated with alternating application of ammonium and nitrate nitrogen sources for selection of Type II methanotrophs. Methane was limited during PHB consumption in one reactor and supplied consistently in a second, control reactor. PHB production remained stable in both reactors for 35 days, and no trend towards increasing PHB production was observed during this period. PHB produced by both reactors was of high molecular weight, and molecular weight remained consistent over time despite a shift in community composition. A period of instability was observed after 35 days, during which time biomass and PHB concentrations declined for six consecutive reactor cycles. This instability is attributed to long-term exposure to products of ammonium oxidation, and may be mitigated by reducing the duration and intensity of ammonium exposure. Full exploration of the long-term effects of methane limitation on PHB production is contingent upon operational stability. Despite this instability, cycling of nitrogen sources as described is promising due to the observed robust selection, rapid growth, short cycle times, and consistent production high molecular weight PHB.

Author : Allison Jill Pieja
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.38/5 ( download)

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Download or read book From Waste to Plastic written by Allison Jill Pieja and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Poly-3-hydroxybutyrate (PHB) is a biologically produced, biodegradable polyester that can be used to replace conventional, petrochemical-based plastics. The relatively high production cost of PHB has thus far prevented it from becoming more widely available. The production cost can be reduced by using less expensive feedstocks and non-sterile production conditions. Methane is an attractive substrate for PHB production because it is inexpensive and its use generates positive environmental externalities. This dissertation studies how natural selection can be used to obtain high PHB production in methanotrophic bacteria through the application of environmental stresses. The first study ascertains that PHB production is only found in Type II, serine pathway methanotrophs through a screen of Type I and II methanotrophs for PHB production and the presence of the phaC gene. Environmental conditions that select for Type II, serine pathway methanotrophs from a diverse inoculum of activated sludge were then evaluated. Providing nitrogen gas as the sole nitrogen source and using a dilute mineral salts media, both in the absence of copper, were found to enrich predominantly Type II methanotrophs capable of PHB production. Lower pH levels (pH = 4-5) were also found to preferentially enrich Type II methanotrophs that produced PHB. Environmental conditions can thus be used to enrich Type II methanotrophs capable of high levels of PHB production. The second study focuses on understanding the role of PHB in the Type II methanotroph Methylocystis parvus OBBP in order to understand what conditions favor PHB accumulation and utilization. Previous work has demonstrated that PHB may function as a growth substrate during periods of carbon absence. In this study, M. parvus OBBP did not replicate using stored PHB in the absence of an exogenous carbon source, even when all other nutrients were provided in sufficiency. When methane and nitrogen were present, PHB and methane were simultaneously consumed. Cells with PHB had significantly higher specific growth rates compared to cells without PHB. Addition of formate (a source of reducing power) to PHB-rich cells delayed PHB consumption but addition of glyoxylate (a source of C-2 units) did not. It is hypothesized that PHB contributes to the reducing power available for methane oxidation and carbon and nitrogen assimilation, thus facilitating survival in environments with intermittent availability of nutrients. The third study applies this knowledge of PHB metabolism to inform the design of three cyclically stressed bioreactors. Three reactors were operated as sequencing batch reactors on 24-hour cycles and were subject to cyclic nitrogen limitation. In addition to nitrogen limitation, two reactors were subject to periodic methane or oxygen limitation while nitrogen was present. Reactors were all inoculated with the same defined, Type II methanotrophic community and operated for eleven days. PHB content and the ultimate capacity of samples to produce PHB in offline incubations were monitored. The PHB content of the nitrogen-limited reactor decreased over operation, whereas PHB production increased in the nitrogen and methane-limited reactor. Communities in all three reactors were highly enriched for Methylocystis parvus OBBP, but there were differences in the minority representatives in each reactor. PHB apparently provided cells with a stronger competitive advantage under cyclic nitrogen and carbon limitation than under nitrogen limitation alone or nitrogen and oxygen limitation. The findings in this work suggest that it will be possible to maintain a culture of methanotrophic bacteria capable of producing high levels of PHB under non-sterile conditions using a combination of environmental pressures and cyclically applied stresses.

Author : Joana Cassidy
Publisher : CRC Press
ISBN 13 : 0429606168
Total Pages : 114 pages
Book Rating : 4.68/5 ( download)

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Download or read book Optimization of Biological Sulphate Reduction to Treat Inorganic Wastewaters written by Joana Cassidy and published by CRC Press. This book was released on 2020-04-27 with total page 114 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work investigated two different approaches to optimize biological sulphate reduction in order to develop a process control strategy to optimize the input of an electron donor and to study how to increase the feasibility of using a cheap carbon source. Feast/famine regimes, applied to design the control strategy, were shown to induce the accumulation of storage compounds in the sulphate reducing biomass. This study showed that delays in the response time and a high control gain can be considered as the most critical factors affecting a sulphide control strategy in bioreactors. The delays are caused by the induction of different metabolic pathways in the anaerobic sludge, including the accumulation of storage products. On this basis, a mathematical model was developed and validated. This can be used to develop optimal control strategies. In order to understand the microbial pathways in the anaerobic oxidation of methane coupled to sulphate reduction (AOM-SR), diverse potential electron donors and acceptors were added to in vitro incubations of an AOM-SR enrichment at high pressure. Acetate was formed in the control group, probably resulting from the reduction of CO2. These results support the hypothesis that acetate may serve as an intermediate in the AOM-SR process.

Author :
Publisher :
ISBN 13 :
Total Pages : 2520 pages
Book Rating : 4.2I/5 ( download)

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Download or read book Index Medicus written by and published by . This book was released on 2004 with total page 2520 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vols. for 1963- include as pt. 2 of the Jan. issue: Medical subject headings.

Author :
Publisher :
ISBN 13 :
Total Pages : 1808 pages
Book Rating : 4.19/5 ( download)

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Download or read book Cumulated Index Medicus written by and published by . This book was released on 1999 with total page 1808 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Author : C. P. Leslie Grady Jr.
Publisher : CRC Press
ISBN 13 : 142000963X
Total Pages : 994 pages
Book Rating : 4.37/5 ( download)

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Download or read book Biological Wastewater Treatment written by C. P. Leslie Grady Jr. and published by CRC Press. This book was released on 2011-05-09 with total page 994 pages. Available in PDF, EPUB and Kindle. Book excerpt: Following in the footsteps of previous highly successful and useful editions, Biological Wastewater Treatment, Third Edition presents the theoretical principles and design procedures for biochemical operations used in wastewater treatment processes. It reflects important changes and advancements in the field, such as a revised treatment of the micr

Author : National Academies of Sciences, Engineering, and Medicine
Publisher : National Academies Press
ISBN 13 : 0309444799
Total Pages : 137 pages
Book Rating : 4.98/5 ( download)

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Download or read book The Changing Landscape of Hydrocarbon Feedstocks for Chemical Production written by National Academies of Sciences, Engineering, and Medicine and published by National Academies Press. This book was released on 2016-12-10 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: A decade ago, the U.S. chemical industry was in decline. Of the more than 40 chemical manufacturing plants being built worldwide in the mid-2000s with more than $1 billion in capitalization, none were under construction in the United States. Today, as a result of abundant domestic supplies of affordable natural gas and natural gas liquids resulting from the dramatic rise in shale gas production, the U.S. chemical industry has gone from the world's highest-cost producer in 2005 to among the lowest-cost producers today. The low cost and increased supply of natural gas and natural gas liquids provides an opportunity to discover and develop new catalysts and processes to enable the direct conversion of natural gas and natural gas liquids into value-added chemicals with a lower carbon footprint. The economic implications of developing advanced technologies to utilize and process natural gas and natural gas liquids for chemical production could be significant, as commodity, intermediate, and fine chemicals represent a higher-economic-value use of shale gas compared with its use as a fuel. To better understand the opportunities for catalysis research in an era of shifting feedstocks for chemical production and to identify the gaps in the current research portfolio, the National Academies of Sciences, Engineering, and Medicine conducted an interactive, multidisciplinary workshop in March 2016. The goal of this workshop was to identify advances in catalysis that can enable the United States to fully realize the potential of the shale gas revolution for the U.S. chemical industry and, as a result, to help target the efforts of U.S. researchers and funding agencies on those areas of science and technology development that are most critical to achieving these advances. This publication summarizes the presentations and discussions from the workshop.

Author : Water Environment Federation
Publisher : McGraw Hill Professional
ISBN 13 : 0071737081
Total Pages : 608 pages
Book Rating : 4.81/5 ( download)

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Download or read book Biofilm Reactors WEF MOP 35 written by Water Environment Federation and published by McGraw Hill Professional. This book was released on 2010-09-29 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: The latest Methods for Wastewater Treatment Using Fixed-Film Processes This Water Environment Federation resource provides complete coverage of pure fixed-film and hybrid treatment systems, along with details on their design, performance, and operational issues. Biofilm Reactors discusses factors that affect the design of the various processes, appropriate design criteria and procedures, modeling techniques, equipment requirements, and construction methods. Operational issues associated with each type of process are presented, including potential problems and corrective actions. Real-world case studies illustrate the application of the technologies presented in this authoritative volume. Biofilm Reactors covers: Biology of fixed-film processes Trickling filter and combined trickling filter suspended-growth process design and operation Rotating biological contactors Moving-bed biofilm reactors Hybrid processes Biological filters New and emerging fixed-film technologies Clarification Effluent filtration Development and application of models for integrated fixed-film activated sludge, moving-bed reactors, biological aerated filters, and trickling filters