| Summary: | 碩士 === 國立交通大學 === 生物科技學系 === 106 === Recently, bio-based chemical feedstock from renewable resources has widely been used because it has prospects and environmental benefits.
Lactate is an important chemical which is listed as one of the top value added chemicals from biomass mandated by the U.S Department of Energy. It was used as acidulant and taste enhancer in beverage and food industry. In addition, lactate can be converted into polylactate by polymerization, which is a biodegradable and thermoplastics. Some of lactate are produced through pretroleum, which can increase greenhouse gas releasing like CO2. In order to solve this problem, using metabolic engineering for production of chemical feedstocks from renewable resource is more popular.
Unlike sugar, methanol is non-food feedstock for the production of high value chemical. It can be produced from methane, which is an abundant gas from shale. With the increasing availability of natural gas source, the price of methanol will be low.
The goal of this research is using methanol as a carbon source to produce lactate in Escherichi coli and native methylotrophic bacteria. E. coli is a gram negative and facultatively anaerobic bacteria. It is easy to modify because of well-developed genetic tool. However, wild type E. coli cannot use methanol as carbon source. To construct a strain of E. coli can produce lactate by methanol, we will introduce a synthetic methanol conversion pathway into E. coli. In this work, we first choose different genes for methanol conversion and lactate production. Lactate synthesis from recombinant E. coli with RuMP pathway was possible but unstable. Furthermore, we also try native methylotrophy to produce lactate by expressing lactate dehydrogenase and test production.Interesting, we can see that wildtype PB1 can secret about 15 mg/L lactate and also consume a small amout of lactate. At this stage, using methanol to produce lactate by B. methanolicus is more effective.
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