Extractive Fermentation With Surfactant To Enchance Butanol Production

Abstract

newline Abstract newlineExtractive butanol fermentation with non-ionic surfactant, a recently explored area, has shown newlinepromising results with several advantages but is relatively less investigated. Non-ionic newlinesurfactants (L62 and L62D) were selected for the extractive fermentation to enhance butanol newlineproduction using butanol producing strain Clostridium beijerinckii MCMB 581 and newlineClostridium sporogenes. Biocompatibility studies with both the surfactants showed bacterial newlinegrowth. Higher concentrations of surfactant (gt5%) affected the cell count. Effect of mixing newlinewas studied and it was found that mixing does not improve butanol production. Further, the newlinestudy was undertaken in order to investigate effect of diverse parameters such as fermentation newlinemedia, pH, initial concentration of biomass and various substrate on increasing butanol and newlinetotal solvent production. Cheng s fermentation media was successfully tested and perceived newlineto increase final solvents concentration. Controlled pH at 12th and 24th hours had negative newlineeffect on butanol enhancement; however, it resulted in more butyric acid production which newlineremained accumulated. Ten percent (v/v) biomass was evaluated to increase final solvents newlineconcentration and hence butanol yield compared to 20% and 30% (v/v) of initial biomass newlineconcentrations. Glucose was found to be the best substrate among the studied substrates. Effect newlineof surfactant concentration (3 20%) was studied on butanol production and it was found that newline6% (v/v) L62 resulted in 49% higher final butanol concentration compared to control. Effect newlineof different concentrations of glucose was also studied, 60 g/L was found to be best for butanol newlinefermentation. Earlier studies had shown improved butanol production with non-ionic newlinesurfactant and immobilized cells independently. Thus, combined effect of extractive newlinefermentation and immobilized cells on butanol production was studied. Different matrices newline(brick, bamboo, cotton fiber, flannel cloth, and polyurethane foam) were tested for newlinesimultaneous immobilization and extractive fermentation. Immobilized biomass was used in newlinean extractive fermentation study with non-ionic surfactantL62. Biomass immobilized on newlinepolyurethane foam (PF) doubled the butanol production in presence of 6% (v/v) L62 with newlinerespect to control (free cells without surfactant). Immobilized cells on PF were successfully newlinereused for 4 cycles. newlineFurther work investigates microemulsion based butanol extraction from simulated and newlinemicrobial fermentation broth. Alkanes C5-C7 (pentane, hexane and heptane) were used for newlineextraction of butanol from fermentation broth using microemulsion technique. Conditions for newlineii newlineWinsor microemulsion with C5, C6 and C7 alkanes were established. Hexane and heptane newlineformed Winsor-III microemulsion at 45-50°C. Hexane based microemulsion resulted into newlineorganic phase (Om) containing more butanol (62% w/w) than pentane (12.4% w/w) and newlineheptane (57.3% w/w). Bi-continuous phase (i.e. the surfactant phase or BC) had negligible newlineamount of butanol. Surfactant was retained in bi-continuous and water phase (Wm). Thus, newlinehexane was found to be a better microemulsion extractant than other two alkanes. Studies with newlinetwo step approach i.e. coacervation followed by back-extraction resulted in less extraction newlineefficiency of butanol. However, the single stage approach with hexane not only reduced a step newlinebut also yielded into 4 times more extraction than two stage approach. newlineKeywords: Butanol, ABE, Non-ionic surfactant, Extractive fermentation, Immobilization,