Bioethanol Production From Water Hyacinth And Microalgae Biomass By Fermentation With Domesticated Yeasts

Fuel ethanol is one of the main biomass energy. Ethanol production from biomass through fermentation with yeast has good prospect. Mixed yeasts of Pichia stipitis and Pachysolen tannophilus after domestication by the dilute acid hydrolysate of water hyacinth were used as fermentation strains to increase the ethanol yield significantly to76.3%of the theoretical ethanol yield. Semi-continuous ethanol production from water hyacinth was carried out in a500L pilot-scale bioreactor.In this paper, three ethanol production yeasts:Pichia stipites, Pachysolen tannophilus and Candida shehatae were cultured and selected. Pachysolen tannophilus was good at using hexose, and ethanol yield of glucose was0.43g/g glucose, which was84.64%of theoretical ethanol yield. Pichia stipitis was good at using pentose, and ethanol yield of xylose was0.053g/g. When using75%of glucose and25%of xylose domesticate Pichia stipites, the ethanol yield with xylose increased to0.103g/g, which increased94.3%. Ammonium ion had no inhibitory effect on ethanol production by water hyacinth basically.The ethanol production rate and yield markedly increased when water hyacinth pretreated with microwave-assisted dilute acid was fermented with domesticated yeasts of Pichia stipitis and Pachysolen tannophilus at a volume ratio of1:1through a simultaneous saccharification and fermentation process. The highest ethanol yield obtained was0.2215g/g water hyacinth, which was76.3%of the theoretical ethanol yield when water hyacinth was pretreated with dilute sulfuric acid at a ratio of lg/30ml and the yeast inoculation amount was15%. The maximum ethanol production rate of0.1863g/(L·h) was obtained at24h.Ethanol production from spirulina, Nannochloropsis Salina and Taihunosin biomass with yeasts by fermentation was investigated. It was found that Pichia stipites was dominant yeasts being good at fermenting microalgae biomass to ethanol. Sonication pretreatment of wet spirulina can increase ethanol production, while reducing byproducts such as acetic acid and butyric acid. The highest ethanol yield of0.076g/g dry spirulina was obtained, which increased16.9%than untreated algae. The pretreatment method of high-pressure microwave-assisted dilute acid and domesticated yeasts with cyanobacteria hydrolysate can improve the saccharification efficiency and ethanol production efficiency. Ethanol yield reached to0.0351g/g, which increased55%.50L and500L pilot experiment of water hyacinth fermentated to ethanol were carried out. For500L semi-continuous pilot experiment, stable ethanol production rate was0.319ml/(L·d) and ethanol yield was0.051g/g water hyacinth. Pilot tests provide technical surpport to scale applications and industrial production of ethanol production from water hyacinth.