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Co-expression of α-amylase and Glucoamylase in Zymomonas mobilis and Direct Ethanol Production from Sweet Potato(PDF)

Chinese Journal of Applied & Environmental Biology[ISSN:1006-687X/CN:51-1482/Q]

Issue:
2012 05
Page:
785-790
Research Field:
Articles
Publishing date:

Info

Title:
Co-expression of α-amylase and Glucoamylase in Zymomonas mobilis and Direct Ethanol Production from Sweet Potato
Author(s):
WANG Guangjun HE Mingxiong ZHANG Yizheng
(Sichuan Key Laboratory of Molecular Biology and Biotechnology, College of Life Sciences, Sichuan University, Chengdu 610064, China)
Keywords:
Zymomonas mobilis ethanol production sweet potato α-amylase glucoamylase co-expression
CLC:
TK63 : TQ920.1
PACS:
DOI:
10.3724/SP.J.1145.2012.00785
DocumentCode:

Abstract:
The gram-negative bacterium Zymomonas mobilis is one of the best ethanol producers found in nature, however, this ethanologenic bacterium cannot hydrolyze starch abundantly existed in nature because of its narrow spectrum of fermentable carbohydrates. In this research, three genetic recombined strains were constructed to express amylolytic enzymes: (1) α-amylase expressing strain Z. mobilis (pAmyE), (2) glucoamylase expressing strain Z. mobilis (pGA) and (3) α-amylase and glucoamylase co-expressing strain Z. mobilis (pAmyGA). Most of the enzyme activity was detected in the medium, and the enzyme activity of amylolytic enzyme in co-expression strain was higher than the sum of each enzyme expressed individually, suggesting there was combined effect between α-amylase and glucoamylase in the hydrolysis of starch. For recombinant strain Z. mobilis (pAmyGA), 59.5% of the enzyme activity was detected in the extracellular fraction. Using the raw material of sweet potato xushu 18 with high starch content and good storage character and adding 5 g/L of glucose as medium, the direct ethanol production was determined via fermentation of the three recombined Z. mobilis strains. The results revealed that the recombinant Z. mobilis (pAmyGA) exhibited the highest level of ethanol production, 54.7 g/L ethanol in 3.5 days, which was 83.2% of the theoretical yield. Fig 5, Tab 1, Ref 20

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