{"id":{"repo_id":"mit","oai_identifier":"oai:dspace.mit.edu:1721.1/38974"},"canonical_url":"https://search.dev.ndltd.org/etd/mit/oai:dspace.mit.edu:1721.1/38974","repository":{"repo_id":"mit","name":"MIT","base_url":"https://dspace.mit.edu/oai/request"},"display":{"title":"Molecular weight modulation in polyhydroxybutyrate fermentations","abstract":"Polyhydroxybutyrate (PHB) is a material with significant potential for commercial applications. It has material properties similar to isotactic polypropylene; it can be produced from renewable resources; it is biodegradable. Unfortunately, it is very brittle when compared to polypropylene. The physical property that most significantly affects elastic behavior is molecular weight. In an effort to understand how molecular weight is formed in PHB production, kinetic studies of PHB fermentations have been performed using fermentation conditions which allow biomass growth and PHB production phases to be separated. These data indicate that molecular weight increases very quickly and then remains fairly constant in PHB fermentations. Additional studies have indicated that only slight changes in molecular weight can be caused by changing fermentation process conditions or using mutants of the polymerization enzyme. Additionally, one mutant polymerization enzyme has been shown to excrete moderate levels of PHB monomer, 3-hydroxybutyrate, into the fermentation media. This may have application in achieving synthetic production of PHB.","abstract_html":"Polyhydroxybutyrate (PHB) is a material with significant potential for commercial applications. It has material properties similar to isotactic polypropylene; it can be produced from renewable resources; it is biodegradable. Unfortunately, it is very brittle when compared to polypropylene. The physical property that most significantly affects elastic behavior is molecular weight. In an effort to understand how molecular weight is formed in PHB production, kinetic studies of PHB fermentations have been performed using fermentation conditions which allow biomass growth and PHB production phases to be separated. These data indicate that molecular weight increases very quickly and then remains fairly constant in PHB fermentations. Additional studies have indicated that only slight changes in molecular weight can be caused by changing fermentation process conditions or using mutants of the polymerization enzyme. Additionally, one mutant polymerization enzyme has been shown to excrete moderate levels of PHB monomer, 3-hydroxybutyrate, into the fermentation media. This may have application in achieving synthetic production of PHB.","abstract_has_math":false,"creators":["Waters, Benjamin Ragan"],"institution":"Massachusetts Institute of Technology","degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Massachusetts Institute of Technology. Dept. of Chemical Engineering.","school":null,"contributors":[],"advisors":["Charles L. Cooney."],"committee_chairs":[],"committee_members":[],"year":2007,"date_issued":"2007","date_published":"2007","updated_at":"2026-07-22T22:21:45Z","subjects":["Chemical Engineering."],"languages":["eng"],"rights":["M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission."],"rights_urls":["http://dspace.mit.edu/handle/1721.1/38974","http://dspace.mit.edu/handle/1721.1/7582"],"identifier_entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://dspace.mit.edu/handle/1721.1/38974"],"render_values":[{"text":"http://dspace.mit.edu/handle/1721.1/38974","href":"http://dspace.mit.edu/handle/1721.1/38974","code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/1721.1/38974","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Charles L. Cooney."]},{"key":"dc:contributor.department","label":"Department","values":["Massachusetts Institute of Technology. Dept. of Chemical Engineering."]},{"key":"dc:contributor.other","label":"Dc Contributor Other","values":["Massachusetts Institute of Technology. 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They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission."]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://dspace.mit.edu/handle/1721.1/38974","http://dspace.mit.edu/handle/1721.1/7582"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://dspace.mit.edu/handle/1721.1/38974","http://hdl.handle.net/1721.1/38974"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, June 2007.","Includes bibliographical references."]},{"key":"dc:description.abstract","label":"Abstract","values":["Polyhydroxybutyrate (PHB) is a material with significant potential for commercial applications. It has material properties similar to isotactic polypropylene; it can be produced from renewable resources; it is biodegradable. Unfortunately, it is very brittle when compared to polypropylene. The physical property that most significantly affects elastic behavior is molecular weight. In an effort to understand how molecular weight is formed in PHB production, kinetic studies of PHB fermentations have been performed using fermentation conditions which allow biomass growth and PHB production phases to be separated. These data indicate that molecular weight increases very quickly and then remains fairly constant in PHB fermentations. Additional studies have indicated that only slight changes in molecular weight can be caused by changing fermentation process conditions or using mutants of the polymerization enzyme. Additionally, one mutant polymerization enzyme has been shown to excrete moderate levels of PHB monomer, 3-hydroxybutyrate, into the fermentation media. This may have application in achieving synthetic production of PHB."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph.D."]},{"key":"dc:title","label":"Title","values":["Molecular weight modulation in polyhydroxybutyrate fermentations"]}]}],"canonical_facts":{"dc:contributor.advisor":["Charles L. Cooney."],"dc:contributor.department":["Massachusetts Institute of Technology. Dept. of Chemical Engineering."],"dc:contributor.other":["Massachusetts Institute of Technology. Dept. of Chemical Engineering."],"dc:creator":["Waters, Benjamin Ragan"],"dc:date.accessioned":["2008-11-10T19:52:56Z"],"dc:date.available":["2008-11-10T19:52:56Z"],"dc:date.issued":["2007"],"dc:description":["Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, June 2007.","Includes bibliographical references."],"dc:description.abstract":["Polyhydroxybutyrate (PHB) is a material with significant potential for commercial applications. It has material properties similar to isotactic polypropylene; it can be produced from renewable resources; it is biodegradable. Unfortunately, it is very brittle when compared to polypropylene. The physical property that most significantly affects elastic behavior is molecular weight. In an effort to understand how molecular weight is formed in PHB production, kinetic studies of PHB fermentations have been performed using fermentation conditions which allow biomass growth and PHB production phases to be separated. These data indicate that molecular weight increases very quickly and then remains fairly constant in PHB fermentations. Additional studies have indicated that only slight changes in molecular weight can be caused by changing fermentation process conditions or using mutants of the polymerization enzyme. Additionally, one mutant polymerization enzyme has been shown to excrete moderate levels of PHB monomer, 3-hydroxybutyrate, into the fermentation media. This may have application in achieving synthetic production of PHB."],"dc:description.degree":["Ph.D."],"dc:identifier.uri":["http://dspace.mit.edu/handle/1721.1/38974","http://hdl.handle.net/1721.1/38974"],"dc:language.iso":["eng"],"dc:publisher":["Massachusetts Institute of Technology"],"dc:rights":["M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission."],"dc:rights.uri":["http://dspace.mit.edu/handle/1721.1/38974","http://dspace.mit.edu/handle/1721.1/7582"],"dc:subject":["Chemical Engineering."],"dc:title":["Molecular weight modulation in polyhydroxybutyrate fermentations"],"dc:type":["Thesis"]},"updated_at":"2026-07-22T22:21:45Z"}