High Quality Butanol Production Directly Utilizing Waste Pichia Pastoris Based Butyrate Supernatants And Glucose As The Co-substrate

Bio-butanol is a powerful liquid fuel.The products of butanol fermentation（acetone-butanol-ethanol fermentation or ABE fermentation）are the mixture of butanol,acetone and ethanol,weight ratios of the primary product butanol over the major by-product acetone（B/A ratio）and butanol over total solvent products（B/ABE ratio）are about 2.0 and60%,respectively.Butyric acid is an important precursor for butanol synthesis in ABE fermentation.Directly utilizing the mixture of butyric acid fermentation supernatant（BFS II）harvested using waste Pichia pastoris as nitrogen source and glucose,could produce high quality bio-butanol featured with high B/A ratio,save raw materials,simplify pre-treatment process of ABE fermentation,and improve the ABE fermentation economics.This thesis proposed a novel ABE fermentation strategy by directly mixing glucose with the above mentioned BFS II as ABE fermentation medium,followed by consecutively feeding the concentrated glucose solution and the original BFS II solution during fermentations when necessary.The research objective is to increase the quality of ABE fermentation products（with high B/A ratio）without declining butanol concentration,reduce the residual nutrients in BFS II to relieve the working loads of downstream wastewater treatment process,and raise products diversity and operation flexibility of butyric acid and ABE fermentation processes according the marketing situations and prices variations.The main results are as follows:（1）In 100 mL anaerobic bottles,BFS II was mixed with glucose for ABE fermentation.B/A ratio reached 3.70,much higher than that of control,indicating its potential feasibility in improving ABE fermentation products quality.（2）ABE fermentation was carried out in a 7 L anaerobic fermentor using the proposed strategy.Compared with traditional fermentation using 150 g×L^-1 corn as the medium,B/A ratio and B/ABE ratio largely increased from 2.0/60%to 4.4-5.0/80%,while butanol concentration retained at equivalently high level of 12.8 g×L^-1,the quality of ABE fermentation products was significantly improved.Butanol yield over total carbon source also increased from 0.33 to 0.40（mole base）,and the raw materials was effectively used.（3）The reasons of large B/A ratio increment was theoretically analyzed.The results showed that with the proposed strategy,butyric acid,oligosaccharides and amino acids in BFS II were effectively utilized;butyrate/glucose consumption ratio reached high levels of37%-53%;NADH utilization efficiency was improved.Thus,B/A ratio was greatly raised.（4）The proposed strategy could save raw materials and operating costs;largely reduced residual oligosaccharides(7.06 g×L^-1（?）0.52 g×L^-1)and SO₄^2-(8.86 g×L^-1（?）2.81 g×L^-1)concentrations in BFS II,which relieved the working loads of wastewater treatment process;promoted the economics and environmental effects of butyrate/ABE fermentation processes.（5）The possibility of completely using waste Pichia pastoris as nitrogen to produce BFS II,further reducing ABE fermentation costs and increasing the waste Pichia pastoris handling ability per batch were also preliminarily explored in this thesis.