| Summary: | 碩士 === 國立臺灣海洋大學 === 食品科學系 === 101 === Algae have been considered to be a potential biomass for the production of ethanol due to their high carbohydrate compositions, no presence of lignin and relatively short generation times. Saccharification of algae for ethanol production can be conveniently achieved by using dilute sulfuric acids. However, acid hydrolysis is accompanied by side products that inhibit microbial growth. Based on their origin the inhibitors are usually divided into four major groups: weak acids, furan derivatives, phenolic compounds and salts. In this study, acid hydrolysate of Pterocladiella capillacea (P. capillacea) is fermented by Kluyveromyces marxianus (K. marxianus) for ethanol production, and biomass loadings, electrodialysis, and immobilized cells techniques are investigated to improve the processs for bioethanol production. The acid hydrolysate of 12.75% (w/v) P. capillacea [5% (v/v) H2SO4, 30 min and 121oC] gave a higher fermentable sugars and relatively fewer yeast growth inhibitor 5-hydromethylfurfural (5-HMF). Whereas 10% (w/v) P. capillacea,gave a relatively fewer inhibitor formic acid and levulinic acid. The electrodialysis results showed that the acid and salt were reduced by 75 and 90%, respectively, of all tested acid hydrolysates after 2 hr electrodialysis. But fermentable sugars were also reduced by 25%. K. marxianus fermenting the 10% and 12.75% P. capillacea hydrolysates gave a maximal ethanol concentrations of 6.05 (36 hr) and 8.23 g/L ethanol (24 hr), respectively, at 40oC and 150 rpm. Encapsulated K. marxianus were tested for anti-inhibitory effects of selected inhibitors and ethanol production. Our data indicated encapsulated K. marxianus elevated cell growth by 1.09 ,1.08 , 1.34 and 1.38 time in the YPD medium containing furfural (0.01 M), 5-HMF (0.008 M), vanillin (0.01 M) and syringaldehyde (0.01 M), respectively, when compared with the unencapsulated cells. For the biothanol production encapsulated K. marxianus fermenting 10% P. capillacea hydrolysate increased the ethanol concentration, yield and productivity from 6.05 to 8.34 g/L, 0.27 to 0.37 g/g sugar, and 0.17 to 0.35 g/L h, respectively, when compared with the unencapsulated cells.
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