THE STUDY OF POLYHYDROXYALKANOATES PRODUCTION BY Haloferax mediterranei IN CELL-RECYCLING AND CONTINUOUS CULTIVATION

• Main Authors: Kai-Ming Liu, 劉凱銘
• Other Authors: C. Will Chen
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/05149957341060552977

碩士 === 大同大學 === 生物工程學系(所) === 96 === In order to decrease the demand of petroleum, and also to reduce the pollution problem caused by misusing of petroleum-based plastic, it is urgent to develop a substitutive plastic that has the similar physical-chemical and mechanical properties as the petroleum-based plastic. It is known that the extremely halophilic Archaea, Haloferax mediterranei, can accumulate biodegradable polyhydroxyalknoates (PHA) of similar properties as petroleum-based plastic. But, the production cost of PHA is expensive. In order to increase the productivity of PHA, it need to increase cell concentration during a long-term continuous fermentation, meanwhile, we also need to reduce the accumulation of inhibitive metabolites that will damage the cell growth and also the yield of PHA. In this study, by using a continuous cultivation of dilution rate at 0.025 h-1, and also by feeding glucose and yeast extract at fixed ratio we obtained the cell concentration and PHA content at 24 g/l and 27 % respectively, and the volumetric productivity of PHA was 0.162 gL-1h-1. By using a cell recycling continuous cultivation with ceramic filter membrane at the dilution rate of 0.028 h-1, the cell concentration and the PHA content could be maintained at 35 g/l and 22 % respectively, and the volumetric productivity of PHA was 0.215 gL-1h-1, but there was a problem of filter blocking by the viscous cell mass. If we preceded cell recycling and continuous fermentation by feeding carbon and nitrogen sources independently, the cell concentration of 40 g/l and PHA content of 54 % could be obtained, and the PHA volumetric productivity could reach 0.216 gL-1h-1; in such operation, we can keep low ammonia concentration (below 3 g/l), that will facilitate cells growth, better PHA content and also without filter blocking by viscous cell. By utilizing extruded rice bran (ERB) and extruded cornstarch (ECS) as carbon sources to produce PHA, we could obtain the cell concentration of 47 g/l, PHA content of 45 % and the PHA volumetric productivity of 0.212 gL-1h-1 in the cell recycling and continuous cultivation by feeding carbon and nitrogen sources independently.