Utilization Of Waste Biomass For ?-Farnesene Production By Fermentation Based On Metabolic Pathway Modification In Engineered Escherichia Coli

In this thesis,three types of waste biomass including biodiesel by-product,whey powder and lignocellulosic(corncob)were applied for?-farnesene production through material pretreatment,development of fermentation process and investigation of fermentation conditions using Escherichia coli cell factory.The main contents are as follows:(1)Investigation of fermentation conditions of biodiesel by-products for high-production of?-farnesene:Through analyzing by-products'components and fermentation performance,the results showed that CG-2 didn't contain harmful impurities such as methanol and black solid impurities,and the?-farnesene production was up to 2.7 g/L from CG-2,which was higher than that(2.21 g/L)from CG-1.Therefore,CG-2 was more suitable for?-farnesene production than CG-1.Afterward,a variety of important fermentation conditions were explored using CG-2 as a substrate in shaken flasks.Under the optimal conditions(including induced cell density 1.0,initial cell density 0.25,temperature after induction 33?,initial medium p H 6.5),the yield of?-farnesene from CG-2 reached 7.68 g/L in shake flasks,which was 184%higher than before,and reached 10.31 g/L in a 5-L bioreactor,which was the highest yield of?-farnesene produced from biodiesel by-products by fermentation.(2)Bifunctional utilization of whey powder as substrate and inducer for production of?-farnesene:This study developed a new strategy with the bifunctional utilization of whey powder for?-farnesene production in an engineered E.coli BL21(DE3)strain.Our researches demonstrated that lactose in whey powder could be metabolized as a carbon source for cell growth and could also be used as an inducer for expression of lac promoter in E.coli BL21(DE3).Then,whey powder was used as a substrate and inducer for the production of?-farnesene in an engineered E.coli BL21(DE3)strain.Under the optimal concentration of whey powder of 80 g/L,the yield of?-farnesene reached 2.41 g/L in shake flasks and reached 4.87 g/L in a 5-L bioreactor.Furthermore,this is the first report on bifunctional utilization of whey powder for?-farnesene production by an engineered Escherichia coli.(3)The production of?-farnesene from corncobs using SHF after recycling-combined pretreatment:This study developed a recycling strategy for corncob pretreatment and the separate hydrolysis and fermentation(SHF)of corncobs for?-farnesene production.During the corncob pretreatment,the dilute H₂SO₄ solution could be recycled up to seven times and the dilute Na OH solution could be recycled two times.Compared with the batch mode,the recycling method for pretreating 1.52 kg of corncobs only consumed 4.0 L of a 2%H₂SO₄solution and 5.39 L of a 2%Na OH solution,which was only 26.3%and 59.4%of which in batch mode.Then,we investigated the utilization of corncobs for?-farnesene production by the engineered strain F15 using SHF.Under the optimal concentration of corncob hydrolysate with 20g/L glucose,the yield of?-farnesene reached 4.58 g/L in shake flasks and reached 4.80g/L in a 5-L bioreactor.Furthermore,this is the first report on the utilization of corncobs for?-farnesene production by an engineered Escherichia coli.