Bioethanol Production Of Sargassum Horneri And Comprehensive Utilization Of Fermentation Residue

Research of preparation of bioethanol from macroalgae has become the hotspot in this field. Compared to the traditional terrestrial plants, no matter in raw material supply point, or in value point, macroalgae have incomparable advantages. In this study, scientific research of pretreatment, hydrolysis saccharification and fermentation, ethanol removal and comprehensive utilization of fermentation residue had been accomplished based on a typical macroalgae: Sargassum horneri, which was a preferred species to repair warm temperature marine ecological environments.S.horneri was pretreated by dilute acid for enhancing the enzymatic susceptibility of substrate. The results showed that the optimal values of the parameters were hydrolysis temperature of 120 oC, liquid-solid ratio of 20:1, hydrolysis time of 2.00 h and acid concentration of 4.50%. On this understanding, the recovery of reducing sugar was 25.57%. L-arabinose and L-galactse were sufficient among reducing sugar. Factors was arranged in descending order based on the importance of them to the recovery of reducing sugar: sulfuric acid concentration, hydrolysis temperature, hydrolysis time and liquid to solid ratio. Besides, the interactions of different factors could not be ignored; the nonlinear effect between hydrolysis time and the concentration of sulfuric acid was significant.Nonisothermal simultaneous saccharification and fermentation(NSSF) of acid-pretreated S. horneri slurry using immobilized Pichia stipitis for production of bioethanol was investigated in this study. Optimization of NSSF process resulted in maximal bioethanol concentration(2.89 g/L) and yield(0.11 g/g raw material) at optimum cellulase loading(10 IU/g raw material), pre-hydrolysis temperature(50 ?C), pre-hydrolysis time(53 min), SSF temperature(32 ?C) and SSF time(14 h). SSF temperature and SSF time appeared to have a more dominant influence on bioethanol concentration and pre-hydrolysis time appeared to be relatively less critical. The nonlinear effect between pre-hydrolysis time and SSF temperature, SSF temperature and SSF time were significant. The immobilized P. stipitis was identified as suitable for reutilization. Besides, it was also observed from the kinetic test that both modified Gompertz model and modified Logistic model were able to forecast the behaviour of this particular NSSF system under the defined conditions.Simultaneous ethanol fermentation and separation was carried out in a membrane distillation reactor. The results showed that fermentation with membrane distillation could separate ethanol from the broth which eliminated the inhibition of high ethanol concentration on fermentation.And the production efficency,production rate and final ethanol concentration were greatly improved in the fermentation with membrane distillation.Furthermore, we explored the greenhouse gas(GHG) emission of S. horneri bioethanol production via life cycle assessment(LCA). The GHG emission of S.horneri bioethanol production and bioethanol and adsorbent co-generation is 2.9799 kgCO2/kgEtOH and 2.9799 kgCO2/kgEtOH, respectively. The results showed that S.horneri bioethanol production can reach the targets of relieve energy shortage and reduce GHG emission; transforming the fermentation residue into adsorbent can both reduce GHG emission and lower production cost.