Item – Theses Canada

​
OCLC number
681019823
Link(s) to full text
LAC copy
LAC copy
Author
Adegbola, Olufemi.
Title
High cell density methanol cultivation of Methylosinus trichosporium OB3b.
Degree
M. Sc. -- Queen's University, 2008
Publisher
Ottawa : Library and Archives Canada = Bibliothèque et Archives Canada, [2009]
Description
1 microfiche
Notes
Includes bibliographical references.
Abstract
<?Pub Inc> 'Methylosinus trichosporium OB3b' is a wild type, obligate methanotroph that grows only on one-carbon compounds and, in the absence of copper, produces high levels of soluble methane monooxygenase (sMMO) to metabolize methane to methanol. SMMO has gained a great deal of attention in the bioremediation and chemical industries because of its low substrate specificity and its ability to oxidize chlorinated hydrocarbons. Much literature exists on cultivating this organism on methane, however no one has achieved dry cell weight densities exceeding 18 g/L. Biomass growth is limited due to mass transfer of methane to cells. This study investigated the growth of 'M. trichosporium' on the water soluble carbon source, methanol while retaining sMMO activity. Methanol was found to completely inhibit growth at 40 g/L. For online methanol measurements during fed-batch cultivation, an in situ probe was constructed from autoclavable materials and equipped with a Figaro TGS822 vapor sensor. The probe was designed to prevent the sensor coming in contact with water aerosols which affect its performance. The probe was an essential component of a feedback methanol control system. The cumulative CO2 production (CCP) strategy was used to feed methanol in fed-batch experiments. In an initial bioreactor study, growth nutrients were fed in excess. The yields of biomass to nutrients were determined and the growth medium modified accordingly. A biomass density of 19 g/L (growth rate of 0.013-0.065 h -1) was achieved with sMMO activity of 300 to 500 [[mu]mol naphthol][g of biomass]-1[h]-1. The subsequent bioreactor study involved feeding of nutrients based on their yields in relation to methanol, a biomass density of 62 g/L (growth rate of 0.034-0.08 h -1) was achieved. The inoculum cultures utilized in the bioreactor studies were maintained on Noble agar plates containing nitrogen minimal salts medium and methane. After 6 months of subsequent plate transfers, 'M. trichosporium' lost the ability to produce high levels of sMMO. The enzyme activity in methanol grown cells was recovered by subculturing in liquid NMS medium with methane as the sole carbon source, the activity increased from 8 to 600 [[mu]mol naphthol][g of biomass]-1[h]-1. It is recommended that further studies be carried out on stimulating sMMO activity during cultivation on methanol.
ISBN
9780494428627
0494428627