Study On Ethanol Fuel Production From Different Components Of Laminaria Japonica With Pichia Angophorae

Nowadays fossil energy occupies80%of the world’s energy market. However, the increase of the fossil energy utilization for years raises serious concerns about environmental problems such as global warming, atmospheric pollution and so on. In comparison with fossil energy, bioethanol has many advantages as an alternative energy, including high completeness of combustion as well as reduction of pollutant emissions and carbon dioxide. As feedstocks for ethanol production, Laminaria japonica has a high content of carbonhydrates and several advantages over other types of terrestrial feedstocks. These include high area productivity,3to4times higher photosynthetic effciency than terrestrial plants, no competition with agriculture for land and water resources, great adaptation of different waters, significant absorption of carbon dioxide. The cultivated area of L. Japonica in our country has risen from18thousand hectares in1978to currently41thousand hectares and China has already leaded the world in the production and cultivated scale of kelps. If the kelps can be used efficiently as feedstocks for ethanol fuel, the stress caused by global energy crisis and environmental problem will be greatly released.Pichia angophorae was used as an ethanol-fermentative microoganism in this work. Firstly, the optimization of ethanol production from mannitol was investigated. Secondly, on the basis of the conditons aquired by mannitol fermentation, ethanol produciton tests from kelp polysaccharids and corresponding monosaccharides were evaluated with P. angophorae. Finally, after hydrolysis of kelp powder derived from L. japonica with high temperature and diluted sulfuric acid added, the kelp extract was inoculated with P. angophorae for primary research of ethanol fermentation. All the work done above was devoted to a convenient reference for further conditional optimization of ethanol production from kelp extract with P. angophorae.Results indicated that the optimum composition of fermentation medium, which was used for ethanol production from mannitol in250ml Erlenmeyer flasks inoculated with P. angophorae, was20g/L mannitol,0.3g/L yeast extract,0.3g/L malt extract,5g/L (NH4)SO42g/L KH2PO4and0.4g/L MgSO4·7H2O. On that basis, a L9(34) orthogonal test was designed and performed. The results showed that the best fermentation condition was32℃,150rpm, pH value4.5and150ml fermentation liquor. At72h, ethanol concerntration reached the highest of8.42g/L and the ethanol conversion rate of mannitol was44.7%, which corresponds to87.48%of the theoretical yield.On the basis of conditonal optimization of ethanol production from mannitol, the experiments on the conditons of ethanol fermentation from polysaccharides and corresponding monosaccharides derived from L.japonica was carried out. Results concluded that apart from sodium alginate and galactose, P. angophorae could utilize all the other sugars for ethanol convertion. The glucose fermentation yielded the highest ethanol concentration of8.81g/L at24h, followed by mannitol and mannose with yields of8.42g/L(72h) and8.23g/L(36h), respectively. In conclusion, P. angophorae has a broad substrate range and especially, the ethanol conversion rate of mannitol, mannose and glucose was as high as0.42-0.45g ethanol/g substrate, which revealed the great potential of P. angophorae as an efficient strain for ethanol production with L.japonica.Preliminary, experiments was run for the investigaton of ethanol production from kelp extract with P. angophorae. To begin with, four groups of single factor experiment was carried out in order to determine the best conditons for hydrolysis of kelp powder derived from L. japonica. And results showed that in our lab, the optimum conditons was120℃,60min,2%(v/v) sulfuric acid,5%(w/v) substrate, and the molar ratio of sulfuric acid vs. substrate was0.4:1. Then, the kelp powder was hydrolyzd under above conditions and2%(w/v) activated carbon was added for decoloration and detoxification. At last, the kelp extract was fermented by P. angophorae for84h. Results showed that the highest yield of ethanol is1.58g/L(24h), corresponding ethanol conversion rate was0.415g ethanol/g reducing sugar.