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1.
《Process Biochemistry》2014,49(8):1245-1250
This work describes the development of a novel integrated system for lactic acid production by Actinobacillus succinogenes. Fermentation and separation were integrated with the use of a microfiltration (MF) membrane, and lactic acid was recovered by resin adsorption following MF. The fermentation broth containing residual sugar and nutrients was then recycled back into the fermenter after lactic acid adsorption. This novel approach overcame the problem of product inhibition and extended the cell growth period from 41 h to 120 h. Production of lactic acid was improved by 23% to 183.4 g L−1. The overall yield and productivity for glucose were 0.97 g g−1 and 1.53 g L−1 h−1, respectively. These experimental results indicate that the integrated system could benefit continuous production of lactic acid at high levels.  相似文献   

2.
《Process Biochemistry》2007,42(1):77-82
The production of C595 diabody fragment (dbFv) in Escherichia coli (E. coli) HB2151 clone has been explored. The comparison of fermentation processes mode demonstrated that a higher biomass inoculum operation enhanced C595 dbFv production. It was demonstrated that a concentration of 12.1 mg l−1 broth of dbFv and a cell concentration of 23.6 g l−1 broth were achieved at the end of 75 l fermentation.  相似文献   

3.
There are currently few successful examples of using straw hemicellulose as a carbon source in the fermentation industry. In this paper, hemicellulose hydrolysates were recovered from steam-exploded wheat straw (SEWS) and used to produce microbial oil. The effects of the steam explosion treatment conditions, the elution temperature and the ratio of elution water to SEWS on sugar recovery were examined. A broth with 3.8 g l?1 of reducing sugar and 22.3 g l?1 of total soluble sugars was obtained with a 10-fold excess (w/w) of water at 40 °C to wash the SEWS treated under steam explosion conditions at 200 °C for 5 min. This broth was used to produce microbial oil by the oleaginous fungus Microsphaeropsis sp., which was able to secrete xylanase to degrade oligosaccharides from straw hemicellulose and accumulate microbial oil. Under optimized conditions, the oil concentration was 2.6 g l?1. The yield of oil from sugar consumed was 0.14 g g?1. The microbial oil produced by this research could be used as feedstock for biodiesel production because the microbial oil was primarily composed of neutral lipids. This research establishes a novel protocol for microbial oil production from straw hemicellulose.  相似文献   

4.
A perfluoropolymer (PFP) membrane has been prepared for use in vapor permeation to separate aqueous ethanol mixtures produced from rice straw with xylose-assimilating recombinant Saccharomyces cerevisiae. PFP membranes commonly have been used for dehydration process and possess good selectivity and high permeances. The effects of by-products during dilute acid pretreatment, addition of yeast extract, and ethanol fermentation on PFP membrane performance were investigated. While feeding mixtures of ethanol (90 wt%) in water, to which individual by-products (0.1–2 g/L) were added, the PFP membrane demonstrated no clear change in permeation rate (439–507 g m−2 h−1) or separation factor (14.9–23.5) from 2 to 4 h of the process. The PFP membrane also showed no clear change in permeation rate (751–859 g m−2 h−1) or separation factor (12.5–13.8) while feeding the mixture (final ethanol conc.: 61 wt%) of ethanol and distillation of the fermentation broth using a suspended fraction of dilute acid-pretreated rice straw for 20 h. These results suggest that the PFP membrane can tolerate actual distillation liquids from ethanol fermentation broth obtained from lignocellulosic biomass pretreated with dilute acid.  相似文献   

5.
A new bioprocess for the synthesis of lactosucrose was studied using a covalently immobilized β-galactosidase on macrospheres of chitosan. The effects of temperature and pH on the production of lactosucrose and other oligosaccharides were evaluated. At 30 °C and pH 7.0, the maximum concentration of lactosucrose reached to 79 g L−1. The change of the reaction conditions allowed to modify the qualitative profile of the final products without quantitative change in the total of oligosaccharides produced. At pH 7 and 30 °C, products profile was 79 g L−1 of lactosucrose, 37 g L−1 of galactooligosaccharides and 250 g L−1 of total oligosaccharides, while at pH 5 and 64 °C the concentrations for the same compounds were 40, 62 and 250 g L−1, respectively. The immobilization increased the thermal stability up to 260-fold. Using 300 g L−1 of sucrose and 300 g L−1 of lactose, and 8.5 mg of chitosan mL−1, 30 cycles of reuse were performed and the biocatalyst kept the maximal lactosucrose synthesis. These results fulfill some important aspects for the enzyme immobilization and oligosaccharides synthesis: the simplicity of the protocols, the high operational stability of the enzyme and the possibility of driving the final products.  相似文献   

6.
Conidiation and lytic enzyme production by Trichoderma viride at different solids concentration of pre-treated municipal wastewater sludge was examined in a 15-L fermenter. The maximum conidia concentration (5.94 × 107 CFU mL−1 at 96 h) was obtained at 30 g L−1 suspended solids. The maximum lytic enzyme activities were achieved around 12–30 h of fermentation. Bioassay against a fungal phytopathogen, Fusarium sp. showed maximum activity in the sample drawn around 96 h of fermentation at 30 g L−1 suspended solids concentration. Entomotoxicity against spruce budworm larvae showed maximum value ≈17290 SBU μL−1 at 30 g L−1 suspended solids concentration at the end of fermentation (96 h). Plant bioassay showed dual action of T. viride, i.e., disease prevention and growth promotion. The rheological analyses of fermentation sludges showed the pseudoplastic behaviour. In order to maintain required dissolved oxygen concentration ≥30%, the agitation and aeration requirements significantly increased at 35 g L−1 compared to 30 and 25 g L−1. The oxygen uptake rate and volumetric oxygen mass transfer coefficient, kLa at 35 g L−1 did not increase in comparison to 30 g L−1 due to rheological complexity of the broth during fermentation. Thus, the successful fermentation operation of the biocontrol fungus T. viride is a rational indication of its potential for mass-scale production for agriculture and forest sector as a biocontrol agent.  相似文献   

7.
Methanol biofiltration using methylotrophic microorganisms has been previously reported by various authors. In a previous study, a modified strain of Pichia pastoris was tested for the ability to produce endochitinase (Ech42) when coupled with methanol vapor biodegradation in batch tests. The next challenge was to validate the process in a continuous system. Thus, in the present study, a biofilter packed with perlite and inoculated with P. pastoris transformed with the plasmid pPIC-ech42 was used for methanol vapor biofiltration and the continuous production of recombinant endochitinase (Ech42) for 60 days. The maximum elimination capacity (EC) of methanol obtained was 1320 g m?3 h?1 at a loading rate of 1465 g m?3 h?1. The extracellular protein production rate in the leachate was 2360 μg h?1 with a chitinase enzymatic activity of 123 U L?1. The protein content on the biofilm samples was negligible, indicating the effectiveness of the overall process and of P. pastoris to excrete proteins. The carbon balance indicated that 81% of the consumed methanol was mineralized and 5.8% was incorporated into biomass. The results of this study and the economic balance underscore the promising application of linking methanol vapor biofiltration to the continuous production of recombinant proteins.  相似文献   

8.
 Enzymatic hydrolysis of corncob and ethanol fermentation from cellulosic hydrolysate were investigated. After corncob was pretreated by 1% H2SO4 at 108 °C for 3 h, the cellulosic residue was hydrolyzed by cellulase from Trichoderma reesei ZU-02 and the hydrolysis yield was 67.5%. Poor cellobiase activity in T. reesei cellulase restricted the conversion of cellobiose to glucose, and the accumulation of cellobiose caused severe feedback inhibition to the activities of β-1,4-endoglucanase and β-1,4-exoglucanase in cellulase system. Supplementing cellobiase from Aspergillus niger ZU-07 greatly reduced the inhibitory effect caused by cellobiose, and the hydrolysis yield was improved to 83.9% with enhanced cellobiase activity of 6.5 CBU g−1 substrate. Fed-batch hydrolysis process was started with a batch hydrolysis containing 100 g l−1 substrate, with cellulosic residue added at 6 and 12 h twice to get a final substrate concentration of 200 g l−1. After 60 h of reaction, the reducing sugar concentration reached 116.3 g l−1 with a hydrolysis yield of 79.5%. Further fermentation of cellulosic hydrolysate containing 95.3 g l−1 glucose was performed using Saccharomyces cerevisiae 316, and 45.7 g l−1 ethanol was obtained within 18 h. The research results are meaningful in fuel ethanol production from agricultural residue instead of grain starch.  相似文献   

9.
The perennial herbaceous crop Arundo donax is a potential feedstock for second-generation bioethanol production. In the present work, two different process options were investigated for the conversion of two differently steam-pretreated batches of A. donax. The pretreated raw material was converted to ethanol with a xylose-consuming Saccharomyces cerevisiae strain, VTT C-10880, by applying either separate hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF). The highest overall ethanol yield and final ethanol concentration were achieved using SHF (0.27 g g?1 and 20.6 g L?1 compared to 0.24 g g?1 and 19.0 g L?1 when SSF was used). The performance of both SHF and SSF was improved by complementing the cellulolytic enzymes with hemicellulases. The higher amount of acetic acid in one of the batches was shown to strongly affect xylose consumption in the fermentation. Only half of the xylose was consumed when batch 1 (high acetic acid) was fermented, compared to that 94% of the xylose was consumed in fermentation of batch 2 (lower acetic acid). Furthermore, the high amount of xylooligomers present in the pretreated materials considerably inhibited the enzymatic hydrolysis. Both the formation of xylooligomers and acetic acid thus need to be considered in the pretreatment process in order to achieve efficient conversion of A. donax to ethanol.  相似文献   

10.
《Process Biochemistry》2007,42(6):925-933
The influence of organic acids on growth and dithiolopyrrolone antibiotic production by Saccharothrix algeriensis NRRL B-24137 was studied. The production of dithiolopyrrolones depends upon the nature and concentration of the organic acids in the culture medium. Study of the nature of organic acids showed that the most effective organic acids for thiolutin specific production were maleic, 4-hydroxybenzoic, benzentetracarboxylic, pantothenic, pivalic and pyruvic acids (which yielded almost five-fold over the starting medium) and pimelic acid (more than three-fold). 4-Bromobenzoic acid showed the best production of senecioyl-pyrrothine (59 mg g−1 DCW). Tiglic acid showed the best production of tigloyl-pyrrothine (22 mg g−1 DCW). The highest yield of isobutyryl-pyrrothine (7.6 mg g−1 DCW) was observed in the presence of crotonic acid. Sorbic acid yielded the best production of butanoyl-pyrrothine (26 mg g−1 DCW). Methacrylic, butyric, pyruvic and 4-bromobenzoic acids also exhibited the best production of butanoyl-pyrrothine (27–11-fold).Study of organic acid concentration showed that among the selected organic acids, pimelic acid yielded the highest specific production of thiolutin (91 mg g−1 DCW) at 7.5 mM; and senecioyl-pyrrothine (11 mg g−1 DCW), tigloyl-pyrrothine (9 mg g−1 DCW) and butanoyl-pyrrothine (3.5 mg g−1 DCW) at 5 mM. Pyruvic acid at 1.25 mM enhanced the production of senecioyl-pyrrothine (4.3 mg g−1 DCW). The maximum production of tigloyl-pyrrothine (18.6 mg g−1 DCW) was observed in the presence of tiglic acid at 2.5 mM. Maximum production of isobutyryl-pyrrothine was observed in the presence of 7.5 mM tiglic acid. In addition, methacrylic acid (at 5 mM) and butyric acid (at 2.5 mM) enhanced the production of butanoyl-pyrrothine (26 and 20 times, respectively).The above results can be employed in the optimisation of the culture medium for the production of dithiolopyrrolone in higher quantities.  相似文献   

11.
Fermentation kinetics of growth and β-carotene production by Rhodotorula glutinis DM28 in batch and continuous cultures using fermented radish brine, a waste generated from fermented vegetable industry, as a cultivation medium were investigated. The suitable brine concentration for β-carotene production by R. glutinis DM28 was 30 g l?1. Its growth and β-carotene production obtained by batch culture in shake flasks were 2.2 g l?1 and 87 μg l?1, respectively, while, in a bioreactor were 2.6 g l?1 and 186 μg l?1, respectively. Furthermore, its maximum growth rate and β-carotene productivity in continuous culture obtained at the dilution rate of 0.24 h?1 were 0.3 g l?1 h?1 and 19 μg l?1 h?1, respectively, which were significantly higher than those in the batch. Therefore, improved growth rate and β-carotene productivity of R. glutinis in fermented radish brine could be accomplished by continuous cultivation.  相似文献   

12.
Yeast immobilization offers operational advantages such as high cell concentration, and some drawbacks related to cell leaking and restricted mass transfer inside particles. The influence of bead size, chitosan, bead charge, volume of liquid media, and the use of corncob hydrolyzates and vinasses as culture medium were analyzed on xylitol production by Debaryomyces hansenii immobilized in alginate beads. The results showed a profuse growth of free cells, accounting 75–95% of total biomass, but electron micrographs revealed the generation of a dense biofilm with hyphal morphology at the bead surface and a very low intraparticular growth. Xylitol production was not affected by the size of particle; however chitosan had a negative effect. The use of corn cob as carbon source and twofold diluted vinasses as economic nutrients incremented xylitol concentration to 13.7 g L?1 (YP/S = 0.56 g g?1; QP = 0.29 g L?1 h?1). The best conditions corresponded to high bead charges and intermediate liquid volumes (44 g Na-alginate and 110 mL liquid medium). These results showed the feasibility of employing these cheap substrates, reflected the importance of the microaerobical conditions, and pointed to the favorable effect of cell immobilization on the metabolism of xylitol production.  相似文献   

13.
Recently, a bubbleless membrane bioreactor (BMBR) has been successfully developed for biosurfactant production by Bacillus subtilis [1]. In this study, for the first time, continuous culture were carried out for the production of surfactin in a BMBR, both with or without a coupled microfiltration membrane. Results from continuous culture showed that a significant part of biomass was immobilized onto the air/liquid membrane contactor. Immobilized biomass activity onto the air/liquid membrane contactor was monitored using a respirometric analysis. Kinetics of growth, surfactin and primary metabolites production were investigated. Planktonic biomass, immobilized biomass and surfactin production and productivity obtained in batch culture (3 L) of 1.5 days of culture were 4.5 g DW, 1.3 g DW, 1.8 g and 17.4 mg L?1 h?1, respectively. In continuous culture without total cell recycling (TCR), the planktonic biomass was leached, but immobilized biomass reached a steady state at an estimated 6.6 g DW. 11.5 g of surfactin was produced after 3 days of culture, this gave an average surfactin productivity of 54.7 mg L?1 h?1 for the continuous culture, which presented a surfactin productivity of 30 mg L?1 h?1 at the steady state. TCR was then investigated for the continuous production, extraction and purification of surfactin using a coupled ultrafiltration step. In continuous culture with TCR at a dilution rate of 0.1 h?1, planktonic biomass, immobilized biomass, surfactin production and productivity reached 7.5 g DW, 5.5 g DW, 7.1 g and 41.6 mg L?1 h?1 respectively, after 2 days of culture. After this time, biomass and surfactin productions stopped. Increasing dilution rate to 0.2 h?1 led to the resumption of biomass and surfactin production and these values reached 11.1 g DW, 10.5 g DW, 7.9 g and 110.1 mg L?1 h?1, respectively, after 3 days of culture. This study has therefore shown that with this new integrated bioprocess, it was possible to continuously extract and purify several grams of biosurfactant, with purity up to 95%.  相似文献   

14.
We previously reported a metabolic engineering strategy to develop an isopropanol producing strain of Cupriavidus necator leading to production of 3.4 g L−1 isopropanol. In order to reach higher titers, isopropanol toxicity to the cells has to be considered. A toxic effect of isopropanol on the growth of C. necator has been indeed observed above a critical value of 15 g L−1. GroESL chaperones were first searched and identified in the genome of C. necator. Native groEL and groES genes from C. necator were over-expressed in a strain deleted for PHA synthesis. We demonstrated that over-expressing groESL genes led to a better tolerance of the strain towards exogenous isopropanol. GroESL genes were then over-expressed within the best engineered isopropanol producing strain. A final isopropanol concentration of 9.8 g L−1 was achieved in fed-batch culture on fructose as the sole carbon source (equivalent to 16 g L−1 after taking into account evaporation). Cell viability was slightly improved by the chaperone over-expression, particularly at the end of the fermentation when the isopropanol concentration was the highest. Moreover, the strain over-expressing the chaperones showed higher enzyme activity levels of the 2 heterologous enzymes (acetoacetate carboxylase and alcohol dehydrogenase) of the isopropanol synthetic operon, translating to a higher specific production rate of isopropanol at the expense of the specific production rate of acetone. Over-expressing the native chaperones led to a 9–18% increase in the isopropanol yield on fructose.  相似文献   

15.
Protocorm cultures of Dendrobium candidum were established in balloon type bubble bioreactors using Murashige and Skoog (MS) medium with 0.5 mg l−1 α-naphthaleneacetic acid (NAA), 2.5% (w/v) sucrose, 5:25 mM NH4:NO3 and 1% (v/v) banana homogenate for the production of biomass and bioactive compounds. In 3 l bioreactor containing 2 l medium, a maximum protocorm biomass (21.0 g l−1 dry biomass) and also optimum quantities of total polysaccharides (389.3 mg g−1 DW), coumarins (18.0 mg g−1 DW), polyphenolics (11.9 mg g−1 DW), and flavonoids (4.5 mg g−1 DW) were achieved after 7 weeks of culture. Based on these studies, 5 and 10 l bioreactor cultures were established to harvest 80 g and 160 g dry biomass. In 10 l bioreactors, the protocorms grown were accumulated with optimal levels of polysaccharides (424.1 mg g−1 DW), coumarins (15.8 mg g−1 DW), polyphenols (9.03 mg g−1 DW) and flavonoids (4.7 mg g−1 DW). The bioreactor technology developed here will be useful for the production of important bioactive compounds from D. candidum.  相似文献   

16.
《Process Biochemistry》2007,42(1):112-117
A simple fed-batch process was developed using a modified variable specific growth rate feeding strategy for high cell density cultivation of Escherichia coli BL21 (DE3) expressing human interferon-gamma (hIFN-γ). The feeding rate was adjusted to achieve the maximum attainable specific growth rate during fed-batch cultivation. In this method, specific growth rate was changed from a maximum value of 0.55 h−1 at the beginning of feeding and then it was reduced to 0.4 h−1 at induction time.The final concentration of biomass and IFN-γ was reached to ∼115 g l−1 (DCW) and 42.5 g(hIFN-γ) l−1 after 16.5 h, also the final specific yield and overall productivity of recombinant hIFN-γ (rhIFN-γ) were obtained 0.37 g(hIFN-γ) g−1 DCW and 2.57 g(hIFN-γ) l−1 h−1, respectively. According to available data this is the highest specific yield and productivity that has been reported for recombinant proteins production yet.  相似文献   

17.
Natamycin is an important tetraene (polyene) antibiotic produced in submerged culture by different strains of Streptomyces sp. In the present work, the effects of the addition of short-chain carboxylic acids (acetic, propionic and butyric) on cell growth and the kinetics of natamycin production were investigated during submerged cultivation of Streptomyces natalensis. The addition of acetic and propionic acids showed stimulatory effects on natamycin production when added to the fermentation medium at concentrations below 2 g L?1 at the beginning of cultivation. In addition, when acetic and propionic acids were added in a mixture (7:1) at a total concentration of 2 g L?1, antibiotic production increased significantly, reaching 3.0 g L?1 (approximately 223% and 250% increases in volumetric and specific antibiotic production, respectively, compared with the control culture). Moreover, the addition of carboxylic acids not only increased the antibiotic yield but also decreased the production time from 96 h to only 84 h in shake-flask cultures. A further enhancement in natamycin production was achieved by cultivation in a 2-L stirred-tank bioreactor under controlled pH conditions. The maximum volumetric production of 3.98 g L?1 was achieved after 84 h in carboxylic acid-supplemented culture (acetate and propionate in a ratio of 7:1).  相似文献   

18.
The aim of this study was to develop a bioprocess for l- and d-lactic acid production from raw sweet potato through simultaneous saccharification and fermentation by Lactobacillus paracasei and Lactobacillus coryniformis, respectively. The effects of enzyme and nitrogen source concentrations as well as of the ratio of raw material to medium were investigated. At dried material concentrations of 136.36–219.51 g L−1, yields of 90.13–91.17% (w/w) and productivities of 3.41–3.83 g L−1 h−1 were obtained with lactic acid concentrations as high as 198.32 g L−1 for l-lactic acid production. In addition, d-lactic acid was produced with yields of 90.11–84.92% (w/w) and productivities of 2.55–3.11 g L−1 h−1 with a maximum concentration of 186.40 g L−1 at the same concentrations of dried material. The simple and efficient process described in this study will benefit the tuber and root-based lactic acid industries without requiring alterations in plant equipment.  相似文献   

19.
In this work, straw hydrolysates were used to produce succinic acid by Actinobacillus succinogenes CGMCC1593 for the first time. Results indicated that both glucose and xylose in the straw hydrolysates were utilized in succinic acid production, and the hydrolysates of corn straw was better than that of rice or wheat straw in anaerobic fermentation of succinic acid. However, cell growth and succinic acid production were inhibited when the initial concentration of sugar, which was from corn straw hydrolysate (CSH), was higher than 60 g l?1. In batch fermentation, 45.5 g l?1 succinic acid concentration and 80.7% yield were attained after 48 h incubation with 58 g l?1 of initial sugar from corn straw hydrolysate in a 5-l stirred bioreactor. While in fed-batch fermentation, concentration of succinic acid achieved 53.2 g l?1 at a rate of 1.21 g l?1 h?1 after 44 h of fermentation. Our work suggested that corn straw could be utilized for the economical production of succinic acid by A. succinogenes.  相似文献   

20.
Polyamides are important industrial polymers. Currently, they are produced exclusively from petrochemical monomers. Herein, we report the production of a novel bio-nylon, PA5.10 through an integration of biological and chemical approaches. First, systems metabolic engineering of Corynebacterium glutamicum was used to create an effective microbial cell factory for the production of diaminopentane as the polymer building block. In this way, a hyper-producer, with a high diaminopentane yield of 41% in shake flask culture, was generated. Subsequent fed-batch production of C. glutamicum DAP-16 allowed a molar yield of 50%, a productivity of 2.2 g L−1 h−1, and a final titer of 88 g L−1. The streamlined producer accumulated diaminopentane without generating any by-products. Solvent extraction from alkalized broth and two-step distillation provided highly pure diaminopentane (99.8%), which was then directly accessible for poly-condensation. Chemical polymerization with sebacic acid, a ten-carbon dicarboxylic acid derived from castor plant oil, yielded the bio-nylon, PA5.10. In pure form and reinforced with glass fibers, the novel 100% bio-polyamide achieved an excellent melting temperature and the mechanical strength of the well-established petrochemical polymers, PA6 and PA6.6. It even outperformed the oil-based products in terms of having a 6% lower density. It thus holds high promise for applications in energy-friendly transportation. The demonstration of a novel route for generation of bio-based nylon from renewable sources opens the way to production of sustainable bio-polymers with enhanced material properties and represents a milestone in industrial production.  相似文献   

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