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1.
Different substrate mixtures of acetic acid and valeric acid were used to synthesize copolymers of poly([R]‐3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHB/HV) with Paracoccus denitrificans under N‐limited conditions. A correlation between the substrate ratio and HV content was found in batch experiments, which seemed to be suitable to produce a number of defined copolymers. In fed‐batch fermentation, such correlation could only be found with carbon substrate mixtures of very restricted composition. Due to the individual substrate consumption rates with this technique, a polymer with 16.5 mol.‐% HV content [w/w] could be reproducibly synthesized. However, under N‐limited chemostatic cultivation conditions it was possible to produce a spectrum of definitely composed copolymers (3.0 %–46.3 mol.‐% HV) from different mixtures of acetic acid and valeric acid. 相似文献
2.
H. E. Valentin A. Schönebaum A. Steinbüchel 《Applied microbiology and biotechnology》1996,46(3):261-267
A recombinant strain of Pseudomonas putida GPp104 (pHP1014::E146), which expressed the polyhydroxyalkanoic acid (PHA) synthase of Thiocapsa pfennigii exhibiting an unusual substrate specificity at a high level was incubated in two-stage batch or fed-batch accumulation experiments
with 5-hydroxyhexanoic acid (5HHx) as carbon source in the second cultivation phase, copolyesters of 3-hydroxybutyric acid
(3HB) plus 5HHx, or of 3HB, 3-hydroxyhexanoic acid (3HHx) plus 5HHx were accumulated as revealed by gas-chromatographic and
13C-NMR spectroscopic analysis. When the recombinant P. putida GPp104 was incubated with 4-hydroxyheptanoic acid (4HHp) as carbon source in the second cultivation phase, a copolyester
consisting of 3HB, 3-hydroxyvaleric acid and 3- and 4-hydroxyheptanoic acid accumulated. Providing 4-hydroxyoctanoic acid
as carbon source in the second cultivation phase led to the accumulation of a polyester that contained 1–2 mol% 4-hydroxyoctanoic
acid besides 3-hydroxyoctanoic acid, 3HHx, 3-hydroxyvaleric acid and 3HB. In addition to PHA containing these new constituents,
PHA with 4-hydroxyvaleric acid was accumulated from laevulinic acid. Eleven strains from five genera have been also analysed
for their ability to utilize different carbon sources for colony growth, which might serve as potential precursors for the
biosynthesis of PHA with unusual constituents. Although most of the carbon sources were utilized by some strains for colony
growth, accumulation experiments gave no evidence for the accumulation of new PHA by these wild-type strains.
Received: 22 April/Received revision: 23 May 1996/Accepted: 2 June 1996 相似文献
3.
《Bioscience, biotechnology, and biochemistry》2013,77(8):1716-1718
Recombinant strains of Ralstonia eutropha and Pseudomonas putida harboring a chimeric polyhydroxyalkanoate (PHA) synthase, which consisted of PHA synthases of Aeromonas caviae and R. eutropha, produced 3-hydroxybutyrate (3HB)-based PHA copolymers comprised of 3-hydroxyhexanoate and 3-hydroxyoctanoate units from dodecanoate (87–97 mol % 3HB), indicating that the chimeric PHA synthase possesses desirable substrate specificity leading to the production of 3HB-rich copolymers. 相似文献
4.
A. Rahayu Z. Zaleha Ahmad R. M. Yahya M. I. A. Majid A. A. Amirul 《World journal of microbiology & biotechnology》2008,24(11):2403-2409
A one-step cultivation process for the production of biodegradable polymer poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] by Cupriavidus sp. USMAA2-4 was carried out using various carbon sources. It was found that Cupriavidus sp. USMAA2-4 could produce approximately 44 wt.% copolymer of P(3HB-co-4HB) with 27 mol% 4HB composition when the combination of oleic acid and 1,4-butanediol are used as carbon sources in 60 h
cultivation. The manipulation of carbon-to-nitrogen ratio (C/N) resulted in the increase of dry cell weight, PHA content as
well as 4HB composition. A new strategy of introducing oleic acid and 1,4-butanediol together and separately at different
concentration demonstrated different yield in PHA content ranging from 47 to 58 wt.%. The molecular weight obtained was 234 kDa
(by adding 1,4-butanediol and oleic acid together) and 212 kDa (by adding 1,4-butanediol separately). The copolymer of P(3HB-co-4HB) produced by Cupriavidus sp. USMAA2-4 was detected statistically as a random copolymer when analysed by nuclear magnetic resonance (NMR) spectroscopy. 相似文献
5.
Henry E. Valentin Andreas Schönebaum Alexander Steinbüchel 《Applied microbiology and biotechnology》1992,36(4):507-514
Summary Twenty-four different strains of aerobic Gram-negative bacteria, mainly belonging to the genera Alcaligenes, Paracoccus, Pseudomonas and Methylobacterium, were examined with respect to their ability to utilize 4-hydroxyvaleric acid (4HV), 4-valerolactone (4VL) and 3-hydroxypropionic acid (3HP) as carbon sources for growth and for accumulation of polyhydroxyalkanoic acid (PHA). A gas chromatographic (GC) method for the detection of 3-hydroxyalkanoic acid methyl esters has been extended for the detection of derivatives obtained from the methanolysis of 4-hydroxybutyric acid (4HB) and 4HV. Most of the Alcaligenes species and P. oxalaticus Ox1 accumulated a terpolyester consisting of 3-hydroxybutyric acid (3HB), 3-hydroxyvaleric acid (3HV) and 4HV as constituents from 4HV or 4VL as sole carbon sources in batch, fed-batch or two-stage fed-batch cultures. Poly(3HB-co-3HV-co-4HV) accumulated from 4HV by A. eutrophus strain NCIB 11599 amounted to approximately 50% of the cell dry matter and was composed of 42.0 mol % 3HB, 52.2 mol % 3HV and 5.6 mol % 4HV, respectively. Pseudomonads, which belong to the rRNA homology group I, were not able to incorporate 4HV. With 3HP as carbon source, the GC analysis provided evidence for the presence of 3HP in the PHA of many bacteria. Nuclear magnetic resonance spectroscopic analysis confirmed that, for example, A. eutrophus strain TF93 accumulated poly(3HB-co-3HP) with 98 mol % 3HB and 2 mol % 3HP if the cells were cultivated in the presence of 0.5% (w/v) 3HP.
Offprint requests to: A. Steinbüchel 相似文献
6.
Aims: This study aimed at isolating thermophilic bacteria that utilize cheap carbon substrates for the economically feasible production of poly(3‐hydroxybutyrate), poly(3HB), at elevated temperatures. Methods and Results: Thermophilic bacteria were enriched from an aerobic organic waste treatment plant in Germany, and from hot springs in Egypt. Using the viable colony staining method for hydrophobic cellular inclusions with Nile red in mineral salts medium (MSM) containing different carbon sources, six Gram‐negative bacteria were isolated. Under the cultivation conditions used in this study, strains MW9, MW11, MW12, MW13 and MW14 formed stable star‐shaped cell‐aggregates (SSCAs) during growth; only strain MW10 consisted of free‐living rod‐shaped cells. The phylogenetic relationships of the strains as derived from 16S rRNA gene sequence comparisons revealed them as members of the Alphaproteobacteria. The 16S rRNA gene sequences of the isolates were very similar (>99% similarity) and exhibited similarities ranging from 93 to 99% with the most closely related species that were Chelatococcus daeguensis, Chelatococcus sambhunathii , Chelatococcus asaccharovorans, Bosea minatitlanensis, Bosea thiooxidans and Methylobacterium lusitanum. Strains MW9, MW10, MW13 and MW14 grew optimally in MSM with glucose, whereas strains MW11 and MW12 preferred glycerol as sole carbon source for growth and poly(3HB) accumulation. The highest cell density and highest poly(3HB) content attained were 4·8 g l?l (cell dry weight) and 73% (w/w), respectively. Cells of all strains grew at temperatures between 37 and 55°C with the optimum growth at 50°C. Conclusions: New PHA‐accumulating thermophilic bacterial strains were isolated and characterized to produce poly(3HB) from glucose or glycerol in MSM at 50°C. SSCAs formation was reported during growth. Significance and Impact of the Study: To the best of our knowledge, this is the first report on the formation of SSCAs by PHA‐accumulating bacteria and also by thermophilic bacteria. PHA‐producing thermophiles can significantly reduce the costs of fermentative PHA production. 相似文献
7.
The site-specific mutagenesis for PHA synthase PhaC2Ps1317 from Pseudomonas stutzeri 1317 was conducted for optimizing production of short-chain-length and medium-chain-length polyhydroxyalkanoates (scl-mcl
PHA). Recombinant Ralstonia eutropha PHB-4 harboring double mutated phaC2
Ps1317
gene (phaC2
Ps
QKST) produced 42 wt.% PHA content in the cell dry weight (CDW) with 93 mol% 3-hydroxybutyrate (HB) as monomer in the PHA copolymer.
Compared to that of wild-type phaC2
Ps1317
, the higher PHA content indicated the effectiveness of the specific point mutations for improvement on PhaC2Ps1317 activity and PHA production. The physical characterization revealed that the PHA produced by the recombinant strain was scl-mcl
PHA copolymers with molecular weights and polydispersity reasonable for practical applications. Recombinant R. eutropha PHB-4 containing mutated phaC2
Ps1317
termed phaC2
Ps
QKST was demonstrated to be able to produce scl-mcl PHA copolymers consisting of even-numbered, odd-numbered, or a combination
of even- and odd-numbered monomers covering the carbon chain lengths from C4 to C12 when related substrates were provided.
Recombinant R. eutropha PHB-4 containing phaC2PsQKST could be used as a strain for production of copolymers consisting of dominated HB and medium-chain-length 3-hydroxyalkanoates
(HA) with better application properties. 相似文献
8.
En route to economical eco‐friendly solvent system in enhancing sustainable recovery of poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) copolymer
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Nik Murniati Nik Man Irdahayu Kannusamy Shantini Kai‐Hee Huong Sevakumaran Vigneswari Nursolehah Abdul Aziz Mohd. Noor Mohd. Azizan Al‐Ashraf Abdullah Amirul 《Engineering in Life Science》2017,17(9):1050-1059
Separation of poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) [P(3HB‐co‐4HB)] from bacterial cell matter is a critical step in the downstream process with respect to material quality and eco‐balance as P(3HB‐co‐4HB) is widely used for biomedical applications. Therefore, an efficient and eco‐based extraction of P(3HB‐co‐4HB) using a combination of NaOH and Lysol in digesting the non‐polymeric cell material (NPCM) digestion is developed. The NaOH and Lysol show synergistic influence on the copolymer extraction at a high purity and recovery of 97 and 98 wt% respectively. The optimized cell digestion method was found applicable to a vast batch of cells containing copolymers from various 4HB monomer compositions. At the largest extraction volume of 100 L, P(3HB‐co‐4HB) with a purity of 89 wt% was extracted with a maximum recovery of 90 wt%. The method developed has also eliminated the cell pretreatment step. The extraction method developed in this research has not only produced an economic and efficient copolymer recovery but has also retained the copolymer quality, in term of its molecular weight and thermal properties. It demonstrates a practical and promising downstream processing method in recovering the copolymer effectively from the bacterial biomass. 相似文献
9.
Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) production from biodiesel by‐product and propionic acid by mutant strains of Pandoraea sp.
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Fabrício C. de Paula Carolina B. C. de Paula José Gregório C. Gomez Alexander Steinbüchel Jonas Contiero 《Biotechnology progress》2017,33(4):1077-1084
Pandoraea sp. MA03 wild type strain was subjected to UV mutation to obtain mutants unable to grow on propionic acid (PA) but still able to produce poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [P(3HB‐co‐3HV)] from glycerol and PA at high 3HV yields. In shake flask experiments, mutant prp25 was selected from 52 mutants affected in the propionate metabolism exhibiting a conversion rate of PA into 3HV units of 0.78 g g?1. The use of crude glycerol (CG) plus PA or valeric acid resulted in a copolymer with 3HV contents varying from 21.9 to 30 mol% and 22.2 to 36.7 mol%, respectively. Fed‐batch fermentations were performed using CG and PA and reached a 3HV yield of 1.16 g g?1, which is 86% of the maximum theoretical yield. Nitrogen limitation was a key parameter for polymer accumulation reaching up to 63.7% content and 18.1 mol% of 3HV. Henceforth, mutant prp25 is revealed as an additional alternative to minimize costs and support the P(3HB‐co‐3HV) production from biodiesel by‐products. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:1077–1084, 2017 相似文献
10.
Yun‐Zhen Xu Ni‐Ni Guo Zong‐Ming Zheng Xian‐Jin Ou Hong‐Juan Liu De‐Hua Liu 《Biotechnology and bioengineering》2009,104(5):965-972
Klebsiella pneumoniae HR526, a new isolated 1,3‐propanediol (1,3‐PD) producer, exhibited great productivity. However, the accumulation of lactate in the late‐exponential phase remained an obstacle of 1,3‐PD industrial scale production. Hereby, mutants lacking D ‐lactate pathway were constructed by knocking out the ldhA gene encoding fermentative D ‐lactate dehydrogenase (LDH) of HR526. The mutant K. pneumoniae LDH526 with the lowest LDH activity was studied in aerobic fed‐batch fermentation. In experiments using pure glycerol as feedstock, the 1,3‐PD concentrations, conversion, and productivity increased from 95.39 g L?1, 0.48 and 1.98 g L?1 h?1 to 102. 06 g L?1, 0.52 mol mol?1 and 2.13 g L?1 h?1, respectively. The diol (1,3‐PD and 2,3‐butanediol) conversion increased from 0.55 mol mol?1 to a maximum of 0.65 mol mol?1. Lactate would not accumulate until 1,3‐PD exceeded 84 g L?1, and the final lactate concentration decreased dramatically from more than 40 g L?1 to <3 g L?1. Enzymic measurements showed LDH activity decreased by 89–98% during fed‐batch fermentation, and other related enzyme activities were not affected. NADH/NAD+ enhanced more than 50% in the late‐exponential phase as the D ‐lactate pathway was cut off, which might be the main reason for the change of final metabolites concentrations. The ability to utilize crude glycerol from biodiesel process and great genetic stability demonstrated that K. pnemoniae LDH526 was valuable for 1,3‐PD industrial production. Biotechnol. Bioeng. 2009; 104: 965–972. © 2009 Wiley Periodicals, Inc. 相似文献
11.
T. M. Fahima Azira A. A. Nursolehah Y. Norhayati M. I. A. Majid A. A. Amirul 《World journal of microbiology & biotechnology》2011,27(10):2287-2295
A locally isolated Gram-negative bacterium, Cupriavidus sp. USMAA2-4 was found capable of producing terpolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxybutyrate) [P(3HB-co-3HV-co-4HB)] using γ-butyrolactone or 1,4-butanediol with either valeric acid or 1-pentanol as the carbon source. The present of
3HB, 3HV and 4HB monomers were confirmed by gas chromatography (GC) and nuclear magnetic resonance (NMR) analysis. PHA concentration
of 1.9 g/l was the highest value obtained using the combination of 1,4-butanediol and 1-pentanol through one-step cultivation
process. PHA concentration obtained through two-step cultivation process was higher for all the combinations and the highest
value achieved was 2.5 g/l using γ-butyrolactone and 1-pentanol as carbon source. Various molar fractions of 4HB and 3HV ranging
from 6 to 14 mol% and 39 to 87 mol%, respectively were produced through two-step cultivation process by manipulating the concentration
of γ-butyrolactone. As the culture aeration was reduced, the molar fraction of 3HV and 4HB increased from 40 to 67 mol% and
10 to 24 mol%, respectively while the dry cell weight and PHA content decreased. The terpolymer produced was characterized
using gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The number-average molecular weight
(M
n) and the melting temperature (T
m)) of the terpolymer were in the range of 177–484 kDa and 160–164°C, respectively. 相似文献
12.
Aeromonas hydrophila CGMCC 0911 isolated from lake water was found to be able to synthesize a polyhydroxyalkanoate (PHA) copolymer (PHBHHx) consisting of 3-hydroxybutyrate (HB) and 4–6 mol% 3-hydroxyhexanoate (HHx). The wild-type bacterium accumulated 49% PHBHHx containing 6 mol% HHx in terms of cell dry weight (CDW) when grown on lauric acid for 48 h. When A. hydrophila CGMCC 0911 expressed the Acyl-CoA dehydrogenase gene (yafH) of Escherichia coli, the recombinant strain could accumulate 47% PHBHHx, while the HHx content reached 17.4 mol%. The presence of changing glucose concentration in the culture changed the HHx content both in wild type and recombinant A. hydrophila CGMCC 0911. When 5 g l–1 glucose was added to a culture containing 5 g l–1 lauric acid as co-substrate, 45% PHBHHx/CDW consisting of 8.8 mol% HHx was produced by wild-type A. hydrophila CGMCC 0911 compared with only 5% in the absence of glucose. When the recombinant A. hydrophila CGMCC 0911 was grown on a mixed substrate containing lauric acid and 8–10 g l–1 glucose, the HHx content could be further increased to 35.6 mol%. When the glucose concentration exceeded 10 g l–1, cell growth, PHA content and mole percentages of HHx in PHBHHx were significantly reduced. 相似文献
13.
Zhiyong Sun Juliana A. Ramsay Martin Guay Bruce A. Ramsay 《Applied microbiology and biotechnology》2009,82(4):657-662
Unsaturated medium-chain-length polyhydroxyalkanoates (MCL-PHA) were produced at a productivity of 0.63–1.09 g PHA l−1 h−1 with final PHA content ranging from 42.6 to 55.8% in single-stage, carbon-limited, fed-batch fermentations of Pseudomonas putida KT2440. A mixture of nonanoic acid (NA) and 10-undecenoic acid (UDA=) was fed exponentially to control growth rate. Varying the specific growth rate (0.14 h−1 vs. 0.23 h−1) at similar substrate feed ratios (NA:UDA= = 5:1) had little effect on the final PHA content and relative composition. However, decreasing the NA:UDA= ratio decreased the final amount of PHA produced from 56% with NA:UDA= = 5.07:1 to only 42% at NA:UDA= = 2.47:1. The molar fraction of all 3-hydroxyalkanoate monomers in the PHA product was relatively constant throughout each
fermentation, indicating that the final product was homogeneous rather than a mixture of different copolymers. A linear relationship
between unsaturation of the PHA produced and unsaturation of the carbon feed was found, which demonstrates the feasibility
of producing unsaturated MCL-PHAs with controlled polymeric composition in a fed-batch process. 相似文献
14.
Complete Dehydrogenation of N2H4BH3 over Noble‐Metal‐Free Ni0.5Fe0.5–CeOx/MIL‐101 with High Activity and 100% H2 Selectivity
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Si‐Jia Li Hong‐Li Wang Ba‐Ri Wulan Xin‐bo Zhang Jun‐Min Yan Qing Jiang 《Liver Transplantation》2018,8(21)
Efficient and selective dehydrogenation of hydrazine borane (HB), a novel hydrogen storage material with very high hydrogen content (HB, 15.4 wt%), is a key challenge for a fuel‐cell‐based hydrogen economy. However, even using the noble metal catalysts for HB decomposition, the activities are still far from satisfying, to say nothing of non‐noble‐metal‐containing catalysts. In response, as a proof‐of‐concept experiment, herein, noble‐metal‐free NiFe–CeOx nanoparticles are successfully immobilized on an MIL‐101 support without surfactant by a simple liquid impregnation method. Unexpectedly, the resultant Ni0.5Fe0.5–CeOx/MIL‐101 catalyst shows good performance, including 100% H2 selectivity, 100% conversion, and record catalytic activity (351.3 h?1) for hydrogen generation at mild temperature, which is even better than most of the noble metal heterogeneous catalysts and might be attributed to the good dispersion and uniform particle size of the Ni0.5Fe0.5–CeOx nanoparticles due to steric restrictions effect of the MIL‐101 support. Additionally, extending MIL‐101 to some other important kinds of metal–organic framework (MOF) structures, the resultant NiFe–CeOx/MOF catalysts all show good catalytic activity toward HB decomposition, showing the universality of the MOF supported NiFe–CeOx catalysts. 相似文献
15.
Sebastian L. Riedel Christopher J. Brigham Charles F. Budde Johannes Bader ChoKyun Rha Ulf Stahl Anthony J. Sinskey 《Biotechnology and bioengineering》2013,110(2):461-470
Reduced downstream costs, together with high purity recovery of polyhydroxyalkanoate (PHA), will accelerate the commercialization of high quality PHA‐based products. In this work, a process was designed for effective recovery of the copolymer poly(hydroxybutyrate‐co‐hydroxyhexanoate) (P(HB‐co‐HHx)) containing high levels of HHx (>15 mol%) from Ralstonia eutropha biomass using non‐halogenated solvents. Several non‐halogenated solvents (methyl isobutyl ketone, methyl ethyl ketone, and butyl acetate and ethyl acetate) were found to effectively dissolve the polymer. Isoamyl alcohol was found to be not suitable for extraction of polymer. All PHA extractions were performed from both dry and wet cells at volumes ranging from 2 mL to 3 L using a PHA to solvent ratio of 2% (w/v). Ethyl acetate showed both high recovery levels and high product purities (up to 99%) when using dry cells as starting material. Recovery from wet cells, however, eliminates a biomass drying step during the downstream process, potentially saving time and cost. When wet cells were used, methyl isobutyl ketone (MIBK) was shown to be the most favorable solvent for PHA recovery. Purities of up to 99% and total recovery yields of up to 84% from wet cells were reached. During polymer recovery with either MIBK or butyl acetate, fractionation of the extracted PHA occurred, based on the HHx content of the polymer. PHA with higher HHx content (17–30 mol%) remained completely in solution, while polymer with a lower HHx content (11–16 mol%) formed a gel‐like phase. All PHA in solution could be precipitated by addition of threefold volumes of n‐hexane or n‐heptane to unfiltered PHA solutions. Effective recycling of the solvents in this system is predicted due to the large differences in the boiling points between solvent and precipitant. Our findings show that two non‐halogenated solvents are good candidates to replace halogenated solvents like chloroform for recovery of high quality PHA. Biotechnol. Bioeng. 2013; 110: 461–470. © 2012 Wiley Periodicals, Inc. 相似文献
16.
Enzymatic lipase transesterification of palm oil to biodiesel in a packed‐bed reactor (PBR) using a novel strain of the fungus Aspergillus niger, immobilized within polyurethane biomass support particles (BSPs), was investigated. A three‐step addition of methanol was used to reduce lipase inhibition by immiscible methanol. The influence of water content and PBR flow rate was investigated. FAME yield was enhanced with an increase of PBR flow rate in the range of 0.15–30 L h?1, where inefficient mixing of the reaction mixture at lower flow rates resulted in low conversion rates i.e. 69% after 72‐h reaction. Adding the third mole equivalent of methanol resulted in lipase inhibition due to methanol migration into the accumulated glycerol layer. Glutaraldehyde (GA) solution (0.5 vol.%) was used to stabilize lipase activity, which led to a high FAME yield (>90%) in the PBR after 72‐h of reaction time at a flow rate of 15 L h?1, and a water content of 15%. Moreover, a high conversion rate (>85%) was maintained after four palm oil batch conversion cycles in the PBR. In contrast, lipase activity of non‐GA‐treated cells decreased with each PBR batch cycle, where only 70% FAME was produced after the forth PBR cycle. Transesterification of palm oil in a PBR system using BSPs‐immobilized A. niger as a whole‐cell biocatalyst is a viable process for enzymatic biodiesel production. 相似文献
17.
de Vrije T Mars AE Budde MA Lai MH Dijkema C de Waard P Claassen PA 《Applied microbiology and biotechnology》2007,74(6):1358-1367
NMR analysis of 13C-labelling patterns showed that the Embden–Meyerhof (EM) pathway is the main route for glycolysis in the extreme thermophile
Caldicellulosiruptor saccharolyticus. Glucose fermentation via the EM pathway to acetate results in a theoretical yield of 4 mol of hydrogen and 2 mol of acetate
per mole of glucose. Previously, approximately 70% of the theoretical maximum hydrogen yield has been reached in batch fermentations.
In this study, hydrogen and acetate yields have been determined at different dilution rates during continuous cultivation.
The yields were dependent on the growth rate. The highest hydrogen yields of 82 to 90% of theoretical maximum (3.3 to 3.6 mol
H2 per mol glucose) were obtained at low growth rates when a relatively larger part of the consumed glucose is used for maintenance.
The hydrogen productivity showed the opposite effect. Both the specific and the volumetric hydrogen production rates were
highest at the higher growth rates, reaching values of respectively 30 mmol g−1 h−1 and 20 mmol l−1 h−1. An industrial process for biohydrogen production will require a bioreactor design, which enables an optimal mix of high
productivity and high yield. 相似文献
18.
Pseudomonas putida KT2440 grew on glucose at a specific rate of 0.48 h−1 but accumulated almost no poly-3-hydroxyalkanoates (PHA). Subsequent nitrogen limitation on nonanoic acid resulted in the
accumulation of only 27% medium-chain-length PHA (MCL-PHA). In contrast, exponential nonanoic acid-limited growth (μ = 0.15 h−1) produced 70 g l−1 biomass containing 75% PHA. At a higher exponential feed rate (μ = 0.25 h−1), the overall productivity was increased but less biomass (56 g l−1) was produced due to higher oxygen demand, and the biomass contained less PHA (67%). It was concluded that carbon-limited
exponential feeding of nonanoic acid or related substrates to cultures of P. putida KT2440 is a simple and highly effective method of producing MCL-PHA. Nitrogen limitation is unnecessary. 相似文献
19.
Yeehn Yech 《Biotechnology letters》1996,18(4):411-416
Summary Continuous cultivation of Rhodotorula sp. Y-38 was carried out on ethanol, acetic acid or acetaldehyde. At a feed concentration of 1.0 % (w/v) ethanol, the cell yield of 64 g/100 g ethanol and crude protein of 52 g/100 g biomass were obtained at D=0.5 h-1. The respective value of the content of amino acids and nucleic acids was 42.6 and 9.4 g/100 g biomass. At 2.0 % (w/v) acetic acid, cell yield was found to be 50 g/100 g acetic acid at D=0.4 h-1. The optimum dilution rate ranged between 0.3 and 0.4 h-1. At 0.05 % (w/v) acetaldehyde, the maximum cell yield was obtained at D=0.14 h-1. 相似文献
20.
Chanprateep S Katakura Y Visetkoop S Shimizu H Kulpreecha S Shioya S 《Journal of industrial microbiology & biotechnology》2008,35(11):1205-1215
A new isolated bacterial strain A-04 capable of producing high content of polyhydroxyalkanoates (PHAs) was morphologically
and taxonomically identified based on biochemical tests and 16S rRNA gene analysis. The isolate is a member of the genus Ralstonia and close to Ralstonia eutropha. Hence, this study has led to the finding of a new and unexplored R. eutropha strain A-04 capable of producing PHAs with reasonable yield. The kinetic study of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] production by the R. eutropha strain A-04 was examined using butyric acid and γ–hydroxybutyric acid as carbon sources. Effects of substrate ratio and mole
ratio of carbon to nitrogen (C/N) on kinetic parameters were investigated in shake flask fed-batch cultivation. When C/N was
200, that is, nitrogen deficient condition, the specific production rate of 3-hydroxybutyrate (3HB) showed the highest value,
whereas when C/N was in the range between 4 and 20, the maximum specific production rate of 4-hydroxybutyrate (4HB) was obtained.
Thus, the synthesis of 3HB was growth-limited production under nitrogen-deficient condition, whereas the synthesis of 4HB
was growth-associated production under nitrogen-sufficient condition. The mole fraction of 4HB units increased proportionally
as the ratio of γ–hydroxybutyric acid in the feed medium increased at any value of C/N ratio. Based on these kinetic studies,
a simple strategy to improve P(3HB-co-4HB) production in shake flask fed-batch cultivation was investigated using C/N and substrate feeding ratio as manipulating
variable, and was successfully proved by the experiments.
The nucleotide sequence 1,378 bp reported in this study will appear in the GenBank nucleotide sequence database under accession
number EF988626. 相似文献