Production of ethanol from xylose using xylose

bioethanol;xylose;KmXR;KmXDH;KmXK;ScALD6;660

농업생명과학대학 협동과정농업생물공학전공 ;

University:서울대학교 대학원

关键词: bioethanol;    xylose;    KmXR;    KmXDH;    KmXK;    ScALD6;    660;   

Others  :  http://s-space.snu.ac.kr/bitstream/10371/125450/1/000000013985.pdf

美国|英语

来源: Seoul National University Open Repository

【 摘 要 】

EC2.7.1.17) phosphorylates xylulose into xylulose5-phosphate, which is metabolized further via the pentose phosphate pathway.This study was carried out to clone the xylose metabolic genes from Kluyveromyces marxianus and to compare the xylose metabolic activity to ethanol betweenK. marxianus andScheffersomyces stipitis.K. marxianus is thermotolerant and could produce ethanol from xylose naturally. The full genome sequences of K. marxianus were completed recently.The three key genes involved in the xylose metabolism were cloned from K. marxianus such as XYL1 for XR, XYL2 for XDH and XYL3 for XK. These genes were introduced to S. cerevisiae D452-2 used as host.The engineeredS. cerevisiae strain (DX123/KM1) containing the K.marxianus XR gene along with theSch. stipitis XDH and XK genes was able to produce 10.5 g/L ethanol from xylose along with specific activity of XR of 0.48 U/mg. Similarly, the genes for XDH and XK fromK. marxianus were functionally expressed inS. cerevisiae and the engineeredS. cerevisiae strains can convert xylose to ethanol successfully.All three xylose metabolic genes from K. marxianus were introduced toS. cerevisiae and the xylose metabolic activity was evaluated in terms of ethanol yield and ethanol productivity. Specific activitiesof XR, XDH and XK fromSch. stipitis were all higher than the corresponding enzymes from K. marxianus. The recombinantS. cerevisiae strain containing the K. marxianus xylose metabolic genes (KM123) produced 10.1 g/L ethanol, 0.33 g ethanol/ g xylose ethanol yield and 0.14 g/L.h ethanol productivity. While theS. cerevisiae strain transformed with theSch. stipitis(SS123) produced 10.2 g/L ethanol, 0.35 g ethanol/ g xylose ethanol yield and 0.14 g/L.h ethanol productivity.In order to improve an ethanol fermentation performance by reducing acetate formation, theALD6 gene which can convert acetaldehyde to acetate was disrupted to construct theS. cereivisae strain (KM123::∆ALD6). The strain produced 0.2 g/L acetate compared with 2.8 g/L in the control strain. Interestingly, the consumption of xylose and production of ethanol were not affected by disruption of ALD6 This thesis showed production of ethanol from xylose by the recombinantS. cerevisiae containing the three genes (XR, XDH and XK) from K. marxianus. The ethanol performance of theS.cerevisiaeKM123 was comparable to the S. cerevisiae strain transformed with the Sch. stipitis XR and XDH and S. cerevisiae XK.