Screening, identification and ethanol production of xylose-fermenting yeasts from soil and organic materials

• Main Authors: Lin, Yu-Ching, 林玉靜
• Other Authors: Lee, Ching-Fu
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/52822395237330003231

碩士 === 國立新竹教育大學 === 應用科學系碩士班 === 100 === The objective of this study is isolation, identification and ethanol of xylose-fermenting yeasts isolated from soil, organic materials in Taiwan. The two stages of selection strategy was applied to screen xylose-fermenting yeast strains: xylose-assimilation (XA) yeasts were enriched and selected from samples with medium YNO (yeast nitrogen base- chloramphenicol), then glucose-fermenting (GF) yeast strains were screened among the XA yeasts. Totally, two hundred and twelve yeast strains with ability of xylose - assimilation and glucose-fermention were isolated from 249 samples collected from forest area distributed in 10 counties and 16 villages in Taiwan. DNA fingerprinting profiles with primer (GTG)5 and cell morphology of the selected yeast strains were applied to eliminate the identical yeast strains in a sample, and one hundred and seventy-one isolated were recovered after the two steps. The yeast strains representing 20 genus, such as Barnettozyma, Blastobotrys, Candida, Cyberlindnera, Debaryomyces, Hanseniaspora, Kloeckera, Lindnera, Meyerozyma, Millerozyma, Ogataea, Pichia, Saturnispora, Scheffersomyces, Schwanniomyces, Wickerhamomyces, Yamadazyma, Yushanniozyma, Zygoascus and Cryptococcus and 70 species were identified based on traditional and molecular approaches including cell and spore morphology, physiology and LSU (large subunit) D1 ⁄ D2 and ITS (Internal transcribed spacers) fragments of ribosomal DNA. The ethanol productivity from 5% D-xylose of all these selected strains were detected. Among the strains of sixty-four species of 70 species, their ethanol productivity were less than 0.1 % (w/v), strains of 12 species ramged from 0.1-0.5 % (w/v), while 10 strains representing 5 species, such as Scheffersomyces stipitis, Candida sp. (125), Candida sp. (112), Candida coipomoensis, Candida solani produced greater than 0.5 % (w/v) of ethanol productivity. The ethanol productivity of the top five strains Scheffersomyces stipitis BCRC 21775, NN6S71, Candida sp. (125) NN15S71, Candida sp. (112) NF17S80, Candida coipomoensis NY1W01, Candida solani NF1M81, were detected after culture at 30 ℃ for 48 hours with continuous shaking 100 rpm in 50 ml medium containing 5 % xylose under microaerobic conditions, their ethanol productivity were 2.0, 1.888, 1.561, 0.619, 0.539 and 0.538 % (w/v), resepectively. The optimum fermentation time of Sch. stipitis BCRC 21775 and NN6S71, C. sp. (125) NN15S71, C. sp. (112) NF17S80 is 60 hours, 40 hours, 60 hours, 72 hours resepectively. Furthermore, Sch. stipitis BCRC 21775 and C. sp. (125) NN15S71 have similar ethanol production,but C. sp. (125) NN15S71 can grow at 42 ℃. According to the results described above, C. sp. (125) NN15S71 with high ethanol productivity from xylose revealed favorable characteristics for xylose fermentation, such as high growth temperature, which could be as a good potential for xylose-fermenting in industry.