JIANG Xuejun

zoologistpollockBiotechnology

Feb 12, 2013 (4 years and 5 months ago)

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1

Research

Overview


Research group for microbial carbohydrate metabolic engineering


Introduction

Research group for microbial carbohydrate metabolic engineering
is engaged in

the development of
commercial
ly important microorganisms by means of
metabolic
en
gineering.

At
present
, the main research program is
focuse
d

on

the improvement
of yeast
strains, which

can effectively ferment both glucose and xylose from
lignocellulosic biomass to produce ethanol. Also, the group has engineered other
yeast strains to
produce pyruvate and xylitol respectively. Pyruvate and xylitol are
the important bio
-
products and intermediates of microbial
carbohydrate

metabolism.

Professor Ning Jiang, head of the group, graduated from the Graduate School of
Chinese Academy of Scienc
es in 1981. He has worked in the fields of applied
microbiology and microbial biotechnology for more than twenty years in the Institute
of Microbiology, CAS. Since the mid 1990s, his research interest has focused on
metabolic engineering

to improve indus
trial microbial strains. He is the member of
the board of the Chinese Journal of Biotechnology and the Chinese Journal of Applied
and Environmental Biology.

The group has four other staffs and seven
doctorial

students. The staffs are An
Shen (associate p
rofessor), Peng He (research associate), Shuhao Wang (research
associate) and Dajun Lu (
technician
). The students are Changying Guo, Hua Yan,
Changsheng Wu, Hairong Chen, Pingying Wei, Zilong Li and Yuping Lin.


Background and Significance

Yeast, especial
ly
Saccharomyces cerevisiae

is the main material for the research
of the group.
Saccharomyces cerevisiae

has a lot of advantages such as well studied
genetic background,
high

fermentation rates with the ability to grow under both
aerobic and anaerobic con
ditions, ethanol tolerance and osmo
-
tolerance, easy to

2

manipulate and safety for foods.

Fuel ethanol as an
alter
native
energ
y
source

i
s

becoming more and more
important triggered by the world energy crisis. Lignocellulosic biomass composed
of cellulose, h
emicellulose and lignin is the most abundant and cheap bio
-
resource on
the earth. Using
lignocelluloses

as raw material to produce ethanol faces great
opportunities and
challenges
.
Saccharomyces cerevisiae

is an ideal ethanol producer
but can

t ferment x
ylose, the main degradation product of hemicellulose. One of the
key problems for producing ethanol from lignocellulosic biomass is to make the
microorganism xylose fermentable. Many efforts of the group are to introduce
xylose metabolic pathway and set
up the balance of co
-
factors in
Saccharomyces
cerevisiae

cells.


Major Achievements

The
group

is
presently

working on the National High
-
tech R&D Program of
China
titled


research of recombinant strains for fuel ethanol and efficient cellulase
”,

the Nationa
l Basic Research Program of China
titled


basic research of key processes
for applications of lignocellulosic biomass


and the National Knowledge Innovation
Project of CAS
titled


breeding and optimization of microorganism for effective
conversion of bioma
ss

. The major
achievements

of the group in the past four years
were:

1, Construction of novel
Saccharomyces cerevisiae

strain which can co
-
ferment
glucose and xylose to produce ethanol
effectively

Xylose reductase gene (
XYL1
), xylitol dehydrogenase gene
(
XYL2
) and xylulose
kinase gene (
XKS1
) from various yeasts were expressed in
Saccharomyces cerevisiae
.
Also, bacterial transhydrogenase gene (
udhA
) from
E. coli

was cloned and expressed
in the recombinant yeast. The novel engineered strain could ferment x
ylose and
regenerate

NADPH
simultaneously so that it could

effectively

ferment both glucose
and xylose to produce ethanol under oxygen
-
limited condition. The conversion
yields of glucose and xylose to ethanol were 90% and 85% respectively.

2, Improvement
of various producing
behaviors

of
Saccharomyces cerevisiae

for

3

ethanol production

Various producing
behaviors

of
Saccharomyces cerevisiae

for ethanol production
were improved by mutagenesis and DNA recombination. These
behaviors

included
conversion yield,

productivity and rate of ethanol fermentation, osmo
-
tolerance,
ethanol tolerance and thermo
-
tolerance. In
laboratory

experiments, the strains
obtained by the group could ferment glucose or sucrose to produce ethanol with the
yield of 95%, the productivit
y of 18 % (v/v) and the rate of 3 g/l.h. The yeast could
grow and ferment in the medium containing 300 g/l glucose and tolerant 20% ethanol.
Also, 10 % (v/v) of ethanol was produced when fermented at 42

C.

3, Construction of pyruvate hyper
-
producing str
ain

The
pdc

gene
encoding pyruvate decarboxylase
in
Torulopsis

glabrata

was
spec
ifically disrupted
.

The disruptant displayed higher

pyruvate
accumulation and

less
ethanol production.

It

accumulated
80
g
/l

of pyruvate

in 100 L jar pilot fermentation
under
favor
able conditions.

4, Construction of xylitol producing strain

The xylose reductase gene from
Pichia stipitis

was cloned and expressed in
Saccharomyces cerevisiae
. The recombinant yeast could convert xylose to xylitol
with the yield of 90 %.

5, Publica
tions

P He,

D
-
J Lu,

A Shen,

N Jiang*

:
Cloning and expression of bacterial hemoglobin
gene in D
-
arabitol producing yeast, Acta Microbiol. Sinica,
41

3
):
315

319

2001

Q
-
H Wang,

P He,

D
-
J Lu,

A Shen,

N Jiang*

:
Screening of pyruvate
-
producing
yeast and effect
of nutritional conditions on pyruvate production

Lett. Appl.
Microbiol., 35: 338


342, 2002

Q
-
H Wang,

P He,

D
-
J Lu,

A Shen,

N Jiang*

:

Purification, Characterization,
Cloning and Expression of Pyruvate Decarboxylase from
Torulopsis glabrata

IFO005
,
J. Bio
chem.
,

136: 447
-

455, 2004

X
-
L

Liu
, P He,

D
-
J Lu,

A Shen

N, Jiang*
:
Construction of
flocculation

selective
vector and expression of
β
-
glucosidase gene in
Saccharomyces cerevisiae

Chin. J.

4

Biotechnol.,
21(1)

167
-
170,2005

Q
-
H Wang,

P He,

D
-
J Lu,

A Shen,

N Ji
ang*

:
Metabolic Engineering of
Torulopsis glabrata
for Improved Pyruvate Production

Enzyme Microb. Technol.

36:832
-
839,
2005

X
-
L

Liu
, N Jiang*, P He,

D
-
J Lu,

A Shen

:
Fermentation of xylose to produce
ethanol by recombinant
Saccharomyces cerevisiae

strain co
ntaining
XYLA

and
XKS1
,
Chinese Sci. Bull.,50:652
-
657,2005

H
-
R Cheng
,
N Jiang
,*

A Shen, Y
-
J Feng: Molecular cloning and functional
expression of D
-
arabitol dehydrogenase gene from
Gluconobacter oxydans

in
Escherichia coli
, submitted to FEMS Microbiol Lett.

H
-
R Cheng and N Jiang
*

:
Extremely rapid and efficient extraction of DNA from
bacteria and yeasts

using a novel method
, submitted to Biotechnol. Lett.

C
-
Y

Guo, P He, D Lu, A Shen
,

N Jiang*

: Screening and
characterization

of
xylose
-
utilizing microorganism

for xylitol production
, submitted to Lett Appl
Microbiol.

C
-
Y

Guo, P He, D Lu, A Shen
,

N Jiang*

:
Cloning, molecular characterization
and enzymatic analysis of
CsXYL3

(D
-
Xylulokinase) from
Candida sp
. Xu316 and its
expression in
Saccharomyces cerevisiae

su
bmitted to
J
.

Appl
.

Microbiol
.

C
-
Y

Guo, P He, D Lu, A Shen
,

N Jiang*

:

R
edox cofactor regeneration in
recombinant
Saccharomyces cerevisiae

to improve ethanol production from xylose
submitted to Meta. Engin.

6, Patents:

N. Jiang et al: A novel method for pr
oducing xylitol by cell conversion,
ZL96120000.6

(2001)

N. Jiang et al: A novel method for producing D
-
arabitol from glucose by yeast
cells,

ZL99119504.3

(2002)

N. Jiang et al: Xylitol production by multiple reused free yeast cells,

ZL011110778.2

(2004)

N.

Jiang et al: Pyruvate production by fermentation
02122657.8

N. Jiang et al: A recombinant yeast strain for pyruvate production,
03109214.4


5

N. Jiang et al: Pyruvate production method and its specific strain,

200410033847.6

N. Jiang et al: Xylitol productio
n by nixed fermentation,
200410031949.4

N. Jiang et al: Xylitol production method and its specific strain,
200510008756.1


Future Research Plan

The main research interest of the group in the near future will still focus on fuel
ethanol according to the urg
ent request for energy source in China. Also, pyruvate
and xylitol producing strains will be commercialized.

1, Development of economically feasible processes for ethanol production from
lignocellulosic biomass

The hexose
-
pentose co
-
fermentation yeast str
ains will be further improved.
The group will try to solve the problem of how to degrade lignocellulose effectively,
economically

and
environment

friendly
. It is the most important problem for using
lignocellulosic materials to produce ethanol.

2, Improv
ement of industrial ethanol producing yeast

Various ethanol producing yeast strains that possess different favorable
characteristics have been obtained. The further effort is to integrate multiple
favorable characteristics in one strain by genome shufflin
g and high
-
throughput
screening. The novel strain will be more useful for industrial ethanol production.

3, Commercialization of pyruvate and xylitol

Pyruvate and xylitol producing strains will be further improved and applied in
commercial production by c
o
-
operation

with
companies
.