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1.
Microalgae were screened from seawater for greenhouse gas CO2 fixation and d-lactic acid production by self-fermentation and tested for their growth rate, starch content, and conversion rate from starch
into d-lactic acid. More than 300 strains were isolated, and some of them were found to have suitable properties for this purpose.
One of the best strains, Nannochlorum, sp. 26A4, which was isolated from Sakito Island, had a starch content of 40% (dry weight), and a conversion rate from consumed
starch into d-lactic acid of 70% in the dark under anaerobic conditions. The produced d-lactic acid showed a high optical purity compared with the conventional one. The proposed new d-lactic acid production system using Nannochlorum sp. 26A4 should also be an effective technology for greenhouse gas CO2 fixation and/or conversion into industrial raw materials. 相似文献
2.
This study documents the similar pH-dependent shift in pyruvate metabolism exhibited byZymomonas mobilis ATCC 29191 and ATCC 39676 in response to controlled changes in their steady-state growth environment. The usual high degree
of ethanol selectivity associated with glucose fermentation by Z.mobilis is associated with conditions that promote rapid and robust growth, with about 95% of the substrate (5% w/v glucose) being
converted to ethanol and CO2, and the remaining 5% being used for the synthesis of cell mass. Conditions that promote energetic uncoupling cause the conversion
efficiency to increase to 98% as a result of the reduction in growth yield (cell mass production). Under conditions of glucose-limited
growth in a chemostat, with the pH controlled at 6.0, the conversion efficiency was observed to decrease from 95% at a specific
growth rate of 0.2/h to only 80% at 0.042/h. The decrease in ethanol yield was solely attributable to the pH-dependent shift
in pyruvate metabolism, resulting in the production of lactic acid as a fermentation byproduct. At a dilution rate (D) of
0.042/h, decreasing from pH 6.0 to 5.5 resulted in a decrease in lactic acid from 10.8 to 7.5 g/L. Lactic acid synthesis depended
on the presence of yeast extract (YE) or tryptone in the 5% (w/v) glucose-mineral salts medium. At D = 0.15/h, reduction in
the level of YE from 3 to 1 g/L caused a threefold decrease in the steady-state concentration of lactic acid at pH 6. No lactic
acid was produced with the same mineral salts medium, with ammonium chloride as the sole source of assimilable nitrogen. With
the defined salts medium, the conversion efficiency was 98% of theoretical maximum. When chemostat cultures were used as seed
for pH-stat batch fermentations, the amount of lactic acid produced correlated well with the activity of the chemostat culture;
however, the mechanism of this prolonged induction 相似文献
3.
Hasegawa H Fukushima T Lee JA Tsukamoto K Moriya K Ono Y Imai K 《Analytical and bioanalytical chemistry》2003,377(5):886-891
d-Lactic and l-lactic acids were simultaneously determined by means of a column-switching high-performance liquid chromatography (HPLC) with fluorescence detection. As a fluorescence reagent, 4-nitro-7-piperazino-2,1,3-benzoxadiazole (NBD-PZ) was employed for the fluorescence derivatization of lactic acid. The proposed HPLC system adopted both octylsilica (Cadenza CD-C8) and amylose-based chiral columns (CHIRALPAK AD-RH), which proved to give a sufficient enantiomeric separation of the lactic acid derivatives with a separation factor () of 1.32 and a resolution (Rs) of 1.98. Moreover, the features of the first elution of d-lactic acid peak in the proposed HPLC were convenient for the determination of trace amount of serum d-lactic acid, which is known to increase under diabetes. Intra-day and inter-day accuracies were in the range of 90.5–101.2 and 89.0–100.7%, and the intra-day and inter-day precisions were 0.3–1.2 and 0.4–4.8%, respectively. The proposed method was applied to determine d-lactic and l-lactic acids in human serum of normal subjects and diabetic patients, showing that both d-lactic and l-lactic acid concentrations were significantly increased in the serum of diabetic patients (n=31) as compared with normal subjects (n=21). This fact was found for the first time owing to the development of the proposed HPLC method which is able to determine d-lactic and l-lactic acid simultaneously. Finally, serum d-lactic acid concentrations determined by the proposed HPLC method were compared with those from a reported enzymatic assay, and the smaller p value between normal subjects and diabetic patients was shown by the proposed HPLC method. 相似文献
4.
Corncob is an economic feedstock and more than 20 million tons of corncobs are produced annually in China. Abundant xylose
can be potentially converted from the large amount of hemicellulosic materials in corncobs, which makes the crop residue an
attractive alternative substrate for a value-added production of a variety of bioproducts. Lactic acid can be used as a precursor
for poly-lactic acid production. Although current industrial lactic acid is produced by lactic acid bacteria using enriched
medium, production by Rhizopus oryzae is preferred due to its exclusive formation of the l-isomer and a simple nutrition requirement by the fungus. Production of l-(+)-lactic acid by R. oryzae using xylose has been reported; however, its yield and conversion rate are poor compared with that of using glucose. In this
study, we report an adapted R. oryzae strain HZS6 that significantly improved efficiency of substrate utilization and enhanced production of l-(+)-lactic acid from corncob hydrolysate. It increased l-(+)-lactic acid final concentration, yield, and volumetric productivity more than twofold compared with its parental strain.
The optimized growth and fermentation conditions for Strain HZS6 were defined. 相似文献
5.
Chemical modification was evaluated to stabilize pig kidney d-amino acid oxidase (pkDAAO), which is required for analytical determination of d-amino acids. Optimization of modification conditions was performed to obtain high recovery yield and stability, and chemical
modification at 30°C for 12 h with a highly concentrated enzyme solution gave dextran-conjugated pkDAAO with a 70% yield of
activity. pkDAAO was stable at less than 55°C at pH 6.0, while the conjugated enzyme was stable even at 70°C. In addition,
the conjugated enzyme showed decreased K
m values for d-amino acids. Because of these outstanding charcteristics, this new material is expected to be available for use as a liquid
assay reagent. 相似文献
6.
Balasubramanian Niru Seok Kim Jun Lee Y. Y. 《Applied biochemistry and biotechnology》2001,91(1-9):367-376
For optimum fermentation, fermenting xylose into acetic acid by Clostridium thermoaceticum (ATCC 49707) requires adaptation of the strain to xylose medium. Exposed to a mixture of glucose and xylose, it preferentially
consumesxylose over glucose. The initial concentration of xylose in the medium affects the final concentration and the yield
of acetic acid. Batch fermentation of 20 g/L of xylose with 5g/L of yeast extract as the nitrogen source results in a maximum
acetate concentration of 15.2 g/L and yield of 0.76 g of acid/g of xylose. Corn steep liquor (CLS) is a good substitute for
yeast extract and results in similar fermentation profiles. The organism consumes fructose, xylose, and glucose from a mixture
of sugars in batch fermentation. Arabinose, mannose, and galactose are consumed only slightly. This organism loses viability
on fed-batch operation, even with supplementation of all the required nutrients. In fed-batch fermentation with CSL supplementation,
d-xylulose (an intermediate in the xylose metabolic pathway) accumulates in large quantities. 相似文献
7.
Nobuhiro Ishida Satoshi Saitoh Toru Ohnishi Kenro Tokuhiro Eiji Nagamori Katsuhiko Kitamoto Haruo Takahashi 《Applied biochemistry and biotechnology》1996,131(1-3):795-807
We developed a metabolically engineered Saccharomyces cerevisiae, which produces optically pure l-lactic acid efficiently using cane juice-based medium. In this recombinant, the coding region of pyruvate decarboxylase (PDC)1 was completely deleted, and six copies of the bovine l-lactate dehydrogenase (l-LDH) genes were introduced on the genome under the control of the PDC1 promoter. To confirm optically pure lactate production in lowcost medium, cane juice-based medium was used in fermentation
with neutralizing conditions. l-lactate production reached 122 g/L, with 61% of sugar being transformed into l-lactate finally. The optical purity of this l-lactate, that affects the physical characteristics of poly-l-lactic acid, was extremely high, 99.9% or over.
These two authors contributed equally to this work. 相似文献
8.
Gao Qiang Zhang Min McMillan James D. Kompala Dhinakar S. 《Applied biochemistry and biotechnology》2002,98(1-9):341-355
Zymomonas mobilis has been metabolically engineered to broaden its substrate utilization range to include d-xylose and l-arabinose. Both genomically integrated and plasmid-bearing Z. mobilis strains that are capable of fermenting the pentose d-xylose have been created by incorporating four genes: two genes encoding xylose utilization metabolic enzymes (xylA/xylB) and two genes encoding pentose phosphate pathway enzymes (talB/tktA). We have characterized the activities of the four newly introduced enzymes for xylose metabolism, along with those of three
native glycolytic enzymes, in two different xylose-fermenting Z. mobilis strains. These strains were grown on glucose-xylose mixtures in computer-controlled fermentors. Samples were collected and
analyzed to determine extracellular metabolite concentrations as well as the activities of several intracellular enzymes in
the xylose and glucose uptake and catabolism pathways. These measurements provide new insights on the possible bottlenecks
in the engineered metabolic pathways and suggest methods for further improving the efficiency of xylose fermentation. 相似文献
9.
Purification and reversible immobilization of d-amino acid oxidase from Trigonopsis variabilis could be simultaneously accomplished by hydrophobic interaction on Phenyl Sepharose CL-4B in the presence of 50 mM pyrophosphate buffer (pH 8.5). The presence of a high salt concentration of 2M, which is generally required for the hydrophobic interactions, was not essential for the hydrophobic immobilization. The
enzyme in free as well as immobilized form was optimally active between pH 7.0 and 9.0. The immobilized preparation could
be reused in a batch process for the conversion of d-amino acids to α-keto acids. When the activity of the preparation dropped below practical limits, the gel could be regenerated
by water wash and recharged with fresh crude extract from yeast. 相似文献
10.
Substrate selectivity of Gluconobacter oxydans (ATCC 9937) for 2,5-diketo-d-gluconic acid (2,5-DKG) production was investigated with glucose, gluconic acid, and gluconolactone in different concentrations
using a resting-cell system. The results show that gluconic acid was utilized favorably by G. oxydans as substrate to produce 2,5-DKG. The strain was coupled with glucose dehydrogenase (GDH) and 2,5-DKG reductase for synthesis
of 2-keto-l-gulonic acid (2-KLG), a direct precursor of l-ascorbic acid, from glucose. NADP and NADPH were regenerated between GDH and 2,5-DKG reductase. The mole yield of 2-KLG of
this multienzyme system was 16.8%. There are three advantages for using the resting cells of G. oxydans to connect GDH with 2,5-DKG reductase for production of 2-KLG: gluconate produced by GDH may immediately be transformed into
2,5-DKG so that a series of problems generally caused by the accumulation of gluconate would be avoided; 2,5-DKG is supplied
directly and continuously for 2,5-DKG reductase, so it is unnecessary to take special measures to deal with this unstable
substrate as it was in Sonoyama’s tandem fermentation process; and NADP(H) was regenerated within the system without any other
components or systems. 相似文献
11.
Yan Liu Wei Liao Chuanbin Liu Shulin Chen 《Applied biochemistry and biotechnology》1996,131(1-3):844-853
Lactic acid is used as a food additive for flavor and preservation and a precursor in the development of poly-lactic acid,
a product used to make biodegradable plastics and textiles. Rhizopus oryzae NRRL 395 is known to be a strain that produces optically pure l-(+)-lactic acid. The morphology of Rhizopus cultures is complex, forming filamentous, clumps, and pellet mycelia. Different morphology growth has significant effects
on lactic acid production. In bioreactors, the filamentous or clump mycelia increase the viscosity of the medium, wrap around
impellers, and block the nutrient transportation, leading to a decrease in production efficiency and bioreactor performance.
Growing fungi in pellet form can significantly improve these problems. In this study, factors that affect lactic acid production
in pelletized flask cultures using R. oryzae NRRL 395 were investigated in detail. Completely randomized designs were used to determine the influence of culture temperature,
time, concentration of glucose, and inoculum size. Lactic acid fermentation using clump and pellet morphologies were performed
in a 5 L fermentor at the optimal values obtained from flask culture. Finally, fed-batch culture was used to enhance the lactate
concentration in broth. The final lactate concentration of fed-batch culture reached 92 g/L. The data presented in the article
can provide useful information on optimizing lactic acid production using alternative source materials. 相似文献
12.
Lawford Hugh G. Rousseau Joyce D. McMillan James D. 《Applied biochemistry and biotechnology》1997,(1):269-286
The five-carbon sugard-xylose is a major component of hemicellulose and accounts for roughly one-third of the carbohydrate content of many lignocellulosic
materials. The efficient fermentation of xylose-rich hemicellulose hydrolyzates (prehydrolyzates) represents an opportunity
to improve significantly the economics of large-scale fuel ethanol production from lignocellulosic feedstocks. The National
Renewable Energy Laboratory (NREL) is currently investigating a simultaneous saccharification and cofermentation (SSCF) process
for ethanol production from biomass that uses a dilute-acid pretreatment and a metabolically engineered strain ofZymomonas mobilis that can coferment glucose and xylose. The objective of this study was to establish optimal conditions for cost-effective
seed production that are compatible with the SSCF process design.
Two-level and three-level full factorial experimental designs were employed to characterize efficiently the growth performance
of recombinantZ. mobilis CP4:pZB5 as a function of nutrient level, pH, and acetic acid concentration using a synthetic hardwood hemicellulose hydrolyzate
containing 4% (w/v) xylose and 0.8% (w/v) glucose. Fermentations were run batchwise and were pH-controlled at low levels of
clarified corn steep liquor (cCSL, 1-2% v/v), which were used as the sole source of nutrients. For the purpose of assessing
comparative fermentation performance, seed production was also carried out using a “benchmark” yeast extract-based laboratory
medium. Analysis of variance (ANOVA) of experimental results was performed to determine the main effects and possible interactive
effects of nutrient (cCSL) level, pH, and acetic acid concentration on the rate of xylose utilization and the extent of cell
mass production. Results indicate that the concentration of acetic acid is the most significant limiting factor for the xylose
utilization rate and the extent of cell mass production; nutrient level and pH exerted weaker, but statistically significant
effects. At pH 6.0, in the absence of acetic acid, the final cell mass concentration was 1.4 g dry cell mass/L (g DCM/L),
but decreased to 0.92 and 0.64 g DCM/L in the presence of 0.5 and 1.0% (w/v) acetic acid, respectively. At concentrations
of acetic acid of 0.75 (w/v) or lower, fermentation was complete within 1.5 d. In contrast, in the presence of 1.0% (w/v)
acetic acid, 25% of the xylose remained after 2 d. At a volumetric supplementation level of 1.5–2.0% (v/v), cCSL proved to
be a cost-effective single-source nutritional adjunct that can support growth and fermentation performance at levels comparable
to those achieved using the expensive yeast extract-based laboratory reference medium. 相似文献
13.
Ying Zhou José M. Domínguez Ningjun Cao Jianxin Du George T. Tsao 《Applied biochemistry and biotechnology》1999,78(1-3):401-407
The effect of nutrients on L(+)-lactic acid production from glucose was investigated using Rhizopus oryzae ATCC 523 11. From the shake-flask experiments, the optimal medium composition was defined for improved lactic-acid production.
In order to enhance lactic-acid production rate and product yield, controlled aeration in a bubble column was conducted under
optimal conditions. Results showed a maximum lactic-acid production rate of 2.58 g/L/h was obtained with an initial glucose
concentration of 94 g/L. Finallactic-acid concentration of 83 g/L was achieved after 32 h of fermentation with a weight of
0.88 glactic acid/g glucose consumed. 相似文献
14.
Du Jianxin Cao Ningjun Gong Cheng S. Tsao George T. 《Applied biochemistry and biotechnology》1998,(1):323-329
Two distinctive forms of growth (mycelial filamentous and mycelial pellets) ofRhizopus oryzae were obtained by manipulating the initial pH of the medium with the controlled addition of CaCO3 in a bubble fermenter. In the presence of CaCO3, diffused filamentous growth was obtained when the initial pH of the substrate was 5.5. In the absence of CaCO3, mycelial
pellet growth was obtained when the initial pH was 2.0. The fermentation study indicated that the mycelial growth has a shorter
lag period before the onset of acid formation. Both physical forms of growth ofRhizopus exhibited a high yield of L-lactic acid in the bubble fermenter when the initial glucose concentration exceeded 70 g/L. A
final lactic acid concentration of 62 g/L was produced by the filamentous form ofRhizopus from 78 g/L glucose after 27 h. This showed a weight yield of 80% of glucose consumed, with an average specific productivity
of 1.46 g/h/g. Similarly, the pellet form ofRhizopus produced a final lactic acid concentration of 66 g/L from 76 g/L glucose after 43 h, with a weight yield of 86% and an average
specific productivity of 1.53 g/h/g. 相似文献
15.
Nghiem Nhuan P. Davison Brian H. Suttle Bruce E. Richardson Gerald R. 《Applied biochemistry and biotechnology》1997,(1):565-576
The effect of an external supply of carbon dioxide and pH on the production of succinic acid byAnaerobiospirillum succiniciproducens was studied. In a rich medium containing yeast extract and peptone, when the external carbon dioxide supply was provided
by a 1.5M Na2CO3 solution that also was used to maintain the pH at 6.0, no additional carbon dioxide supply was needed. In fact, sparging
CO2 gas into the fermenter at 0.025 L/L-min or higher rates resulted in significant decreases in both production rate and yield
of succinate. Under the same conditions, the production of the main by-product acetate was not affected by sparging CO2 gas into the fermenter. The optimum pH (pH 6.0) for the production of succinic acid was found to be in agreement with results
previously reported in the literature. Succinic acid production also was studied in an industrial-type inexpensive medium
in which light steep water was the only source of organic nutrients. At pH 6.0 and with a CO2 gas sparge rate of 0.08 L/L-min, succinate concentration reached a maximum of 32 g/L in 27 h with a yield of 0.99 g succinate/g
glucose consumed. 相似文献
16.
Thereza Christina Vessoni Penna Irene A. Machoshvili Marina Ishii 《Applied biochemistry and biotechnology》2003,106(1-3):287-294
The interference of eight components in the yield of sporulation and thermal resistance to moist heat (121°C) of Bacillus stearothermophilus spores suspended in 0.02 M calcium acetate solution and inoculated on paper strips previously treated with calcium acetate/calcium hydroxide was studied.
The spore yield of 1.0×108/mL was developed at 62°C in 17 media containing different concentrations of d-glucose, sodium chloride, l-glutamic acid, yeast extract, peptone, manganese sulfate, potassium phosphate, and ammonium phosphate. The combined effects
of yeast extract, peptone, and glucose contributed positively to the spore yield and to the stability of the thermal resistance
of both spores in suspension and on strips. 相似文献
17.
In pH-controlled batch fermentations with pure sugar synthetic hardwood hemicellulose (1% [w/v] glucose and 4% xylose) and
corn stover hydrolysate (8% glucose and 3.5% xylose) lacking acetic acid, the xyloseutilizing, tetracycline (Tc)-sensitive,
genomically integrated variant of Zymomonas mobilis ATCC 39676 (designated strain C25) exhibited growth and fermentation performance that was inferior to National Renewable
Energy Laboratory's first-generation, Tc-resistant, plasmid-bearing Zymomonas recombinants. With C25, xylose fermentation following glucose exhaustion wasmarkellyslower, and the ethanol yield (based
on sugars consumed) was lower, owing primarily to an increase in lactic acid formation. There was an apparent increased sensitivity
to acetic acid inhibition with C25 compared with recombinants 39676:pZB4L, CP4:pZB5, and ZM4:pZB5. However, strain C25 performed
well in continous ferm entation with nutrient-rich synthetic corn stover medium over the dilution range 0.03–0.06/h, with
a maximum provess ethanol yield at D=0.03/h of 0.46 g/g and a maximum ethanol productivity of 3 g/(L·h). With 0.35% (w/v) acetic acid in the medium, the process
yield at D=0.04/h dropped to 0.32 g/g, and the maximum productivity decreased by 50% to 1.5 g/(L·h). Under the same operating conditions,
rec Zm Zm 4:pZB5 performed better; however, the medium contained 20 mg/L of Tc to constantly maintain selective pressure.
The absence of any need for antibiotics and antiboitic resistance genes makes the chromosomal integrant C25 more com patible
with current regulatory specifications for biocatalysts in large-scale commercial operations. 相似文献
18.
Using the simultaneoussaccharification and fermentation (SSF) technique, pulp mill solid waste cellulose was converted into
glucose using cellulase enzyme and glucose into lacticacid using NRRL B445. SSF experiments were conducted at various pH levels,
temperatures, and nutrient concentrations, and the lactic acid yield ranged from 86 to 97%. The depletion of xylose in SSF
was further investigated by inoculating NRRL B445 into a xylose-only medium. On prolonged incubation, depletion of xylose
with lactic acid production was observed. An experimental procedure with a nonglucose medium was developed to eliminate the
lag phase. From xylose fermentation, Lactobacillus delbrueckii yielded 88–92% lactic acid and 2–12% acetic acid. 相似文献
19.
Danner H. Neureiter M. Madzingaidzo L. Gartner M. Braun R. 《Applied biochemistry and biotechnology》1998,(1):895-903
A process for the continuous production of high purityL-lactic acid in a membrane bioreactor at 65°C has been developed. Two differentBacillus stearothermophilus strains have been tested in batch experiments. Lactic acid yields are between 60 and more than 95% of theoretical yields.
The amounts of ethanol, acetate, and formate formed varied between 0 and 0.4, 0 and 0.1, and 0 and 0.5, respectively (mol/mol
glucose). All byproducts are valuable and may be separated easily by rectification of the fermentation broth. Complete cell
retention enables high volumetric productivity (5 g/Lh), and a minimum of growth supplements. The high temperature of 65°C
allows the autoselective fermentation without problems with contamination. 相似文献
20.
Baumler DJ Hung KF Bose JL Vykhodets BM Cheng CM Jeong KC Kaspar CW 《Applied biochemistry and biotechnology》2006,134(1):15-26
A portion of the cbpA gene from Escherichia coli K-12 encoding a 24 amino acid proton-buffering peptide (Pbp) was cloned via the shuttle vector pJB99 into E. coli JM105 and subsequently into Zymomonas mobilis CP4. Expression of Pbp was confirmed in both JM105 and CP4 by HPLC. Z. mobilis CP4 carrying pJB99-2 (Pbp) exhibited increased acid tolerance (p<0.05) in acidified TSB (HCl [pH 3.0] or acetic acid [pH 3.5]), glycine-HCl buffer (pH 3.0), and sodium acetate-acetic acid
buffer (pH 3.5) in comparison to the parent strain (CP4) and CP4 with pJB99 (control plasmid). Although the expression of
Pbp influenced survival at a low pH, the minimum growth pH was unaffected. Growth of Z. mobilis in the presence of ampicillin also significantly increased acid tolerance by an unknown mechanism. Results from this study
demonstrate that the production of a peptide with a high proportion of basic amino acids can contribute to protection from
low pH and weak organic acids such as acetic acid. 相似文献