Heterogeneity in pure microbial systems: experimental measurements and modeling

Cellular heterogeneity influences bioprocess performance in ways that until date are not completely elucidated. In order to account for this phenomenon in the design and operation of bioprocesses, reliable analytical and mathematical descriptions are required. We present an overview of the single cell analysis, and the mathematical modeling frameworks that have potential to be used in bioprocess control and optimization, in particular for microbial processes. In order to be suitable for bioprocess monitoring, experimental methods need to be high throughput and to require relatively short processing time. One such method used successfully under dynamic conditions is flow cytometry. Population balance and individual based models are suitable modeling options, the latter one having in particular a good potential to integrate the various data collected through experimentation. This will be highly beneficial for appropriate process design and scale up as a more rigorous approach may prevent a priori unwanted performance losses. It will also help progressing synthetic biology applications to industrial scale

Integrating dark and light biohydrogen production strategies: towards the hydrogen economy

Biological methods of hydrogen production are preferable to chemical methods because of the possibility to use sunlight, CO2 and organic wastes as substrates for environmentally benign conversions, under moderate conditions. By combining different microorganisms with different capabilities, the individual strengths of each may be exploited and their weaknesses overcome. Mechanisms of bio-hydrogen production are described and strategies for their integration are discussed. Dual systems can be\ud divided broadly into wholly light-driven systems (with microalgae/cyanobacteria as the 1st stage) and partially light-driven systems (with a dark, fermentative initial reaction). Review and evaluation of published data suggests that the latter type of system holds greater promise for industrial application. This is because the calculated land area required for a wholly light-driven dual system would be too large for either centralised (macro-) or decentralised(micro-) energy generation. The potential contribution to the hydrogen economy of partially light-driven dual systems is overviewed alongside that of other biofuels such as bio-methane and bio-ethanol

Optimization and characterization of microbial rhamnolipid production from renewable resources

The thesis at hand is based on a compendium of peer-reviewed works that were independently published during the last three years. These publications compose of one general introducing book chapter, two original papers which reflect a part of the laboratory work, and a review article that is concluding the last years of rhamnolipid research and gives an outlook of the possible and necessary works for the future

Bioreactor and bioprocess design issues in enzymatic hydrolysis of lignocellulosic biomass

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ECUT (Energy Conversion and Utilization Technologies Program). Biocatalysis Project

Presented are the FY 1985 accomplishments, activities, and planned research efforts of the Biocatalysis Project of the U.S. Department of Energy, Energy Conversion and Utilization Technologies (ECUT) Program. The Project's technical activities were organized as follows: In the Molecular Modeling and Applied Genetics work element, research focused on (1) modeling and simulation studies to establish the physiological basis of high temperature tolerance in a selected enzyme and the catalytic mechanisms of three species of another enzyme, and (2) determining the degree of plasmid amplification and stability of several DNA bacterial strains. In the Bioprocess Engineering work element, research focused on (1) studies of plasmid propagation and the generation of models, (2) developing methods for preparing immobilized biocatalyst beads, and (3) developing an enzyme encapsulation method. In the Process Design and Analysis work element, research focused on (1) further refinement of a test case simulation of the economics and energy efficiency of alternative biocatalyzed production processes, (2) developing a candidate bioprocess to determine the potential for reduced energy consumption and facility/operating costs, and (3) a techno-economic assessment of potential advancements in microbial ammonia production

Theoretical and Experimental Study of Biobased Succinic Acid Production

Biomass based succinic acid is gaining increasing interest as a potential platform chemical for replacing a large petroleum-based bulk chemical market. Biomass as a renewable resource has proved the economic and sustainable potential to produce succinic acid by fermentation method. Biobased succinic acid has yet faced with the challenge of becoming competitive with petrochemical method because of its higher production cost. To lower the production cost, extensive research efforts have been undertaken in upstream technology that involves strain development via metabolic engineering, and downstream technology that aims to improve efficiency of purification method. Many research studies have focused on either one of two technological areas, with little interest on interaction between them. This present work integrates the processing steps from upstream and downstream technologies using a systematic approach and presents an optimal production pathway from a large number of possible process configurations. The development of such a process pathway involves selection of bioproducts, feedstock, pre-treatment technology, microorganism and product separation method. Performance criteria such as titre, rate, yield and minimum production cost, express the optimality of production pathway. Optimization study indicates that succinic acid seems to be the most promising bioproduct among all other bioproducts. Corn stover is the suitable feedstock to produce succinic acid. Based on the findings from optimization study, experimental work was performed with an aim of achieving better performance criteria than it is reported in literature. This work selected corn stover as feedstock, and a bacterium called, Basfia succiniciproducens for converting corn stover-derived glucose into succinic acid. To date, no deliberate experiment has been done on this bacterium to improve succinic acid production, despite its promising features. Highest succinic acid yield of 18 g/100g total sugar (glucose plus xylose) was observed in this experiment. Genetically modified strain of the bacterium reported a much higher yield of 71 gm succinic acid/ 100gm of glucose

ECUT (Energy Conversion and Utilization Technologies) program: Biocatalysis Project

Fiscal year 1987 research activities and accomplishments for the Biocatalysis Project of the U.S. Department of Energy, Energy Conversion and Utilization Technologies (ECUT) Division are presented. The project's technical activities were organized into three work elements. The Molecular Modeling and Applied Genetics work element includes modeling and simulation studies to verify a dynamic model of the enzyme carboxypeptidase; plasmid stabilization by chromosomal integration; growth and stability characteristics of plasmid-containing cells; and determination of optional production parameters for hyper-production of polyphenol oxidase. The Bioprocess Engineering work element supports efforts in novel bioreactor concepts that are likely to lead to substantially higher levels of reactor productivity, product yields, and lower separation energetics. The Bioprocess Design and Assessment work element attempts to develop procedures (via user-friendly computer software) for assessing the economics and energetics of a given biocatalyst process

Insight into the large-scale upstream fermentation environment using scaled-down models

Scaled‐down models are small‐scale bioreactors, used to mimic the chemical (pH, nutrient and dissolved oxygen) and physical gradients (pressure, viscosity and temperature) known to occur in the large‐scale fermenter. Conventionally, before scaling up any bioprocess, small‐scale bioreactors are used for strain selection, characterisation and optimisation. The typical small‐scale environment is homogenous, hence all the cells held within the small‐scale bioreactor can be assumed to experience the same condition at any point in time. However, for the large‐scale bioreactor, this is not the case, due to its inhomogeneous environment. Three different scaled‐down models are reviewed here, and the results suggest that a bacterium responds to changes in its environment rapidly and the magnitude of response to environmental oscillations is organism‐specific. The reaction and adaption of a bacterium to an inhomogeneous environment in most cases result in productivity and quality losses. This review concludes that consideration of fermentation gradients should be paramount when researchers screen for high yielding mutants in bioprocess development and doing this would help mitigate performance loss on scale‐up

Solvent-based approaches to evaluate the ABE extractive fermentation

The reindustrialization of ABE fermentation is hampered by significant production costs, linked to high product inhibition and limited intrinsic yield. The reduction of these costs depends on the effective application of integrated toxic product removal techniques. The evaluation of ABE extractive fermentation with solvents of different nature in terms of extraction capacity or biocompatibility is the main objective of this thesis. Attention is focused on the assessment of the solvent influence, not only on the physical effects but also on the metabolism and microbial population dynamics evolution. A mathematical model based on the evolution of the heterogeneous culture inside the bioreactor was proposed and validated ABE extractive fermentation is techno and economically evaluated on a solvent-based comparative basis. The integration of this process within a LCB biorefinery using a 2G type substrate is also considered