Apartfrom EPSs, researchers have investigated the possibility to
produce other industrially valuable products along with biopolymers.
Marsudi, Unno, and Hori (2008) studied the utilization of
palm oil for simultaneous production of PHAs and rhamnolipids by
Pseudomonas aeruginosa. It was shown that palm oil hydrolysed by
lipase into fatty acids and glycerol were favourable carbon sources
for production of PHAs and rhamnolipids respectively. P. aeruginosa
utilizes fatty acids through -oxidation and glycerol via de novo
fatty acid synthesis pathway. In this study, PHA and rhamnolipid
production started after the nitrogen source was exhausted in the
medium. Oleic acid and glycerol were used as carbon sources for
simultaneous production of PHA and rhamnolipids. Overall, palm
oil was the best carbon source for the simultaneous production of
PHAs and rhamnolipids in a single-stage batch culture and 0.79 g/L
(36% PHA/CDW) PHA and 0.43 g/L rhamnolipid was reported to be
produced from 7 g/L of palm oil.
Jo et al. (2008) manipulated the production of two different
products by controlling the concentration of medium ingredients.
In their study, PHA and glutamate were produced by a twostage
fermentation of using variable biotin concentration in the
Corynebacterium glutamicum medium. It was reported that when
a low concentration of biotin (0.3 g/L) was used, glutamate was
produced. The production shifted towards P(3HB), by the addition
of biotin at a concentration of 9 g/L. As a final concentration, 7 g/L
(36% PHA/CDW) P(3HB) and 18 g/L glutamate were produced using
glucose as the carbon source.
Another interesting approach reported for dual production was
the application of a two-stage chemostat system,for the production
of two different PHAs from Pseudomonas putida (Hartmann, Hany,
Witholt, & Zinn, 2010). The chemostat system was composed oftwo
bioreactors connected in series, operated in a continuous mode. The
main variation from existing two-stage chemostat reactors was the
use of different substrates in the two reactors in order to obtain two
different biopolymers from a single process. The system had three
feed inlets to supply fresh medium and two types of precursors
were added into the culture for the production of biopolymers.
Poly(3-hydroxyoctanoate-co-3-hydroxyhexanoate) (PHO)
and poly(3-hydroxy-10-undecenoate-co-3-hydroxy-8-nonenoateco-3-hydroxy-6-heptenoate)(PHUE)
were successfullyproducedat
levels of 0.155 and 0.645 g/L, respectively,from the strain. The overall
polymer content was reported as 53.8% per cell dry weight, and a
blend of two types of PHA polymers with a structural (monomeric)
purity of 85–95 mol % was obtained. It was found thatthe two-stage
chemostat system was a valuable fermentation system for the production
oflarge amounts of PHAper cell and two different polymers
could be produced in the same cell under conditions, which enable
easy separation. This study is the only continuous culture study that
has been reported in dual bio-polymer production.
As a final example, during the investigation of the enhancement
of PHA production by Pseudomonas putida using in silico-driven
metabolic engineering, it was found that a significant amount of
gluconate was produced along with PHA (Poblete-Castro et al.,
2013). The double production was not intentionally planned and it
was fortuitous. This work is one of the latest publications reporting
double production. Here, 0.9 g/L PHA and 4.4 g/L gluconate were
produced from single-stage batch fermentation.
2
Apartfrom EPSs นักวิจัยได้ตรวจสอบความเป็นไปได้ผลิตผลิตภัณฑ์อื่น ๆ ที่มีคุณค่าทัดกับ biopolymersMarsudi, Unno และ Hori (2008) ศึกษาการใช้ประโยชน์จากน้ำมันปาล์มสำหรับการผลิต PHAs และ rhamnolipids โดยพร้อมกันPseudomonas aeruginosa มันแสดงให้เห็นว่าน้ำมันปาล์มซึ่งจะโดยเอนไซม์ไลเปสเป็นกรดไขมันและกลีเซอรอลเป็นแหล่งคาร์บอนที่ดีสำหรับผลิต PHAs และ rhamnolipids ตามลำดับ P. aeruginosaใช้กรดไขมันผ่าน - ออกซิเดชันและกลีเซอรอลผ่าน de novoเส้นทางการสังเคราะห์กรดไขมัน ในการศึกษา ผา และ rhamnolipidหลังจากที่แหล่งไนโตรเจนได้หมดในการผลิตเริ่มกลาง ใช้เป็นแหล่งคาร์บอนสำหรับกรดครบถ้วนและกลีเซอรอลพร้อมการผลิตผาและ rhamnolipids โดยรวม ปาล์มน้ำมันเป็นแหล่งคาร์บอนที่ดีที่สุดสำหรับการผลิตพร้อมกันPHAs และ rhamnolipids ในขั้นตอนเดียวในชุดวัฒนธรรมและ 0.79 บัญชี(CDW 36% ผา) Rhamnolipid ผาและ 0.43 แยกรายงานเป็นผลิตจาก 7 แยกน้ำมันปาล์มโจ et al. (2008) จัดการการผลิตแตกต่างกันสองผลิตภัณฑ์ โดยการควบคุมความเข้มข้นของส่วนผสมขนาดกลางในการศึกษา ผาและกลูตาเมตผลิต โดย twostage มีหมักใช้โบโอตินแปรความเข้มข้นในการCorynebacterium glutamicum กลาง เป็นรายงานใช้ความเข้มข้นต่ำของโบโอติน (0.3 g/L) กลูตาเมตเป็นผลิต การผลิตที่เปลี่ยนไป P(3HB) โดยการเพิ่มof biotin at a concentration of 9 g/L. As a final concentration, 7 g/L(36% PHA/CDW) P(3HB) and 18 g/L glutamate were produced usingglucose as the carbon source.Another interesting approach reported for dual production wasthe application of a two-stage chemostat system,for the productionof two different PHAs from Pseudomonas putida (Hartmann, Hany,Witholt, & Zinn, 2010). The chemostat system was composed oftwobioreactors connected in series, operated in a continuous mode. Themain variation from existing two-stage chemostat reactors was theuse of different substrates in the two reactors in order to obtain twodifferent biopolymers from a single process. The system had threefeed inlets to supply fresh medium and two types of precursorswere added into the culture for the production of biopolymers.Poly(3-hydroxyoctanoate-co-3-hydroxyhexanoate) (PHO)and poly(3-hydroxy-10-undecenoate-co-3-hydroxy-8-nonenoateco-3-hydroxy-6-heptenoate)(PHUE)were successfullyproducedatlevels of 0.155 and 0.645 g/L, respectively,from the strain. The overallpolymer content was reported as 53.8% per cell dry weight, and ablend of two types of PHA polymers with a structural (monomeric)purity of 85–95 mol % was obtained. It was found thatthe two-stagechemostat system was a valuable fermentation system for the productionoflarge amounts of PHAper cell and two different polymerscould be produced in the same cell under conditions, which enableeasy separation. This study is the only continuous culture study that
has been reported in dual bio-polymer production.
As a final example, during the investigation of the enhancement
of PHA production by Pseudomonas putida using in silico-driven
metabolic engineering, it was found that a significant amount of
gluconate was produced along with PHA (Poblete-Castro et al.,
2013). The double production was not intentionally planned and it
was fortuitous. This work is one of the latest publications reporting
double production. Here, 0.9 g/L PHA and 4.4 g/L gluconate were
produced from single-stage batch fermentation.
2
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