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1.
Lovastatin production by Aspergillus terreus ATCC 20542 in solid-state fermentation (SSF) was studied. Various substrates were used to evaluate the ability of A. terreus to produce lovastatin. The results showed that either rice or wheat bran was suitable substrate for lovastatin production in SSF. The maximum yield of lovastatin (2.9 mg/g dry substrate) using rice as substrate was achieved after incubating for 11 d at the following optimized process parameters: 50%～60% initial moisture content,pH 5.5,incubation temperature 28 °C.  相似文献   

2.
Sequential methodology based on the application of three types of experimental designs was used to optimize the fermentation conditions for elastase production from mutant strain ZJUEL31410 of Bacillus licheniformis in shaking flask cul- tures. The optimal cultivation conditions stimulating the maximal elastase production consist of 220 r/min shaking speed, 25 h fermentation time, 5% (v/v) inoculums volume, 25 ml medium volume in 250 ml Erlenmeyer flask and 18 h seed age. Under the optimized conditions, the predicted maximal elastase activity was 495 U/ml. The application of response surface methodology resulted in a significant enhancement in elastase production. The effects of other factors such as elastin and the growth factor (corn steep flour) on elastase production and cell growth were also investigated in the current study. The elastin had no significant effect on enzyme-improved production. It is still not clear whether the elastin plays a role as a nitrogen source or not. Corn steep flour was verified to be the best and required factor for elastase production and cell growth by Bacillus licheniformis ZJUEL31410.  相似文献   

3.
The optimization of cultural conditions for β-glucanase production by Bacillus subtilis ZJF-1A5 was investigated in flask trials. Temperature had gre at effect on β-glucanase production which maximized at optimal temperature of 37 ℃ and decreased significantly when temperature was over 37℃.Charge quantity af fected β-glucanase production significantly. Adding oxygen vector N-dodec ane or acetic ether benefited β-glucanase production, but it depended on the conc entrat ion and charge quantity. The results of fractional factorial design showed that age and size of inoculum and shaking speed were the key factors affecting β -gluc anase production and the cultivation time span to reach the highest β-gluc anase activity. The optimal cultural conditions for β-glucanase production obtai ned wi th CCD were as follows: inoculum age and size (16 h, 3.82%(v/v)), shaking speed 2 10 r/min, charge quantity of 30 mL in 250 mL flask and initial pH 7.0, cultured at 37℃ for 50 h. Repeated experimental results accorded with those predicted b y a second-order polynomial model. The amount of β-glucanase, α-amylase and neut ral protease produced by B subtilis ZJF-1A5 was associated partially with c ell g rowth. Those three enzymes' activities increased following the cell growth and i ncreased significantly when cells entered the stationary phase.  相似文献   

4.
The glutaraldehyde cross-linked chitosan beads were prepared under microwave irradiation and urease was immobilized onto the beads. The activity and the yield of enzyme activity of the immobilized urease were 10.83 U/g carrier and 47.7%, respectively. The optimum conditions of immobilization were 1% of glutaraldehyde volume fraction, 10 mg/g of urease/beads weight ratio, 24 h of the processing time and pH 6.5 of the reaction medium for immobilization. The properties of the immobilized urease were investigated and compared with those of the free enzyme. The optimum pH values were 6.5 and 7.0 for the immobilized and free urease, respectively. The optimum temperature was 60℃ for the free urease, while it shifted to 65 ℃ for the immobilized enzyme. The Michaelis constant Kr, was 9.1 mmol/L for the immobilized and 12.5 mmol/L for the free urease. The immobilized urease retained 40% of its initial enzyme activity even after 10 repeated uses. The immobilized urease stored at 4 ℃ retained 46% of its initial activity even after 35 d.  相似文献   

5.
The production of elastase by Bacillus sp. EL31410 at various temperatures was investigated. In order to study the effect of temperature on elastase fermentation, different cultivation temperatures, ranging from 39 ℃ to 28 ℃, were evaluated in shake flask. The result indicated that 37 ℃ was best for cell growth at earlier stage; while maximum elastase activity was obtained when the cells were cultivated at 30 ℃. This result was verified by batch fermentation in 5-L bio-reactor under 37 ℃ and 30 ℃ temperature, respectively. The specific cell growth rate at 37 ℃ was higher than that at 30 ℃ during earlier stage of cultivation. The maximum value [5.5 U/(h-g DCW)] of elastase formation rate occurred at 24 h at 30 ℃ compared to 4.6 U/(h-g DCW) at 30 h at 37 ℃. Based on these results, two-stage temperature shift strategy and oscillatory temperature cultivation mode were evaluated in the next study. When compared to single temperature of 37 ℃ or 30 ℃, both two-stage temperature shift strategy and os  相似文献   

6.
A new feather-degrading bacterium was isolated from a local feather waste site and identified as Bacillus subtilis based on morphological, physiochemical, and phylogenetic characteristics. Screening for mutants with elevated keratinolytic activity using N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis resulted in a mutant strain KD-N2 producing keratinolytic activity about 2.5 times that of the wild-type strain. The mutant strain produced inducible keratinase in different substrates of feathers, hair, wool and silk under submerged cultivation. Scanning electron microscopy studies showed the degradation of feathers, hair and silk by the keratinase. The optimal conditions for keratinase production include initial pH of 7.5, inoculum size of 2% (v/v), age of inoculum of 16 h, and cultivation at 23 ℃. The maximum keratinolytic activity of KD-N2 was achieved after 30 h. Essential amino acids like threonine, valine, methionine as well as ammonia were produced when feathers were used as substrates. Strain KD-N2,therefore, shows great promise of finding potential applications in keratin hydrolysis and keratinase production.  相似文献   

7.
Beer fermentation is a dynamic process that must be guided along a temperature profile to obtain the desired results. Ant colony system algorithm was applied to optimize the kinetic model of this process. During a fixed period of fermentation time, a series of different temperature profiles of the mixture were constructed. An optimal one was chosen at last. Optimal temperature profile maximized the final ethanol production and minimized the byproducts concentration and spoilage risk. The satisfactory results obtained did not require much computation effort.  相似文献   

8.
The production of elastase by Bacillus sp. EL31410 at various temperatures was investigated. In order to study the effect of temperature on elastase fermentation, different cultivation temperatures, ranging from 39 ℃ to 28 ℃, were evaluated in shake flask. The result indicated that 37 ℃ was best for cell growth at earlier stage; while maximum elastase activity was obtained when the cells were cultivated at 30 ℃. This result was verified by batch fermentation in 5-L bioreactor under 37 ℃ and 30 ℃ temperature, respectively. The specific cell growth rate at 37 ℃ was higher than that at 30 ℃ latory temperature cultivation mode were evaluated in the next study. When compared to single temperature of 37 ℃ or 30 ℃, both two-stage temperature shift strategy and oscillatory temperature strategy improved biomass but did not yield the same result as expected for elastase production. The maximum biomass (both 8.6 g/L) was achieved at 30 h at 37 ℃, but at 42 h using two-stage temperature cultivation strategy. The highest elastase production (652 U/ml) was observed at 30 ℃ in batch process. It was concluded that cultivation at constant temperature of 30 ℃ was appropriate for elastase production by Bacillus sp. EL31410.  相似文献   

9.
The production of butyric acid by Clostridium butyricum ZJUCB at various pH values was investigated. In order to study the effect of pH on cell growth, butyric acid biosynthesis and reducing sugar consumption, different cultivation pH values ranging from 6.0 to 7.5 were evaluated in 5-L bioreactor. In controlled pH batch fermentation, the optimum pH for cell growth and butyric acid production was 6.5 with a cell yield of 3.65 g/L and butyric acid yield of 12.25 g/L. Based on these results, this study then compared batch and fed-batch fermentation of butyric acid production at pH 6.5. Maximum value （16.74 g/L） of butyric acid concentration was obtained in fed-batch fermentation compared to 12.25 g/L in batch fermentation. It was concluded that cultivation under fed-batch fermentation mode could enhance butyric acid production significantly （P〈0.01） by C. butyricum ZJUCB.  相似文献   

10.
Response surface methodology （RSM） was used to optimize the fermentation medium for enhancing pyruvic acid production by Torulopsis glabrata TP19. In the first step of optimization, with Plackett-Burman design, ammonium sulfate, glucose and nicotinic acid were found to be the important factors affecting pyruvic acid production significantly. In the second step, a 23 full factorial central composite design and RSM were applied to determine the optimal concentration of each significant variable. A second-order polynomial was determined by the multiple regression analysis of the experimental data. The optimum values for the critical components were obtained as follows： ammonium sulfate 0.7498 （10.75 g/L）, glucose 0.9383 （109.38 g/L） and nicotinic acid 0.3633 （7.86 mg/L） with a predicted value of maximum pyruvic acid production of 42.2 g/L. Under the optimal conditions, the practical pyruvic acid production was 42.4 g/L. The determination coefficient （R^2） was 0.9483, which ensures adequate credibility of the model. By scaling up fermentation from flask to jar fermentor, we obtained promising results.  相似文献   

11.
Biotransformation of phytosterol(PS) by a newly isolated mutant Mycobacterium neoaurum ZJUVN-08 to produce androstenedione has been investigated in this paper.The parameters of the biotransformation process were optimized using fractional factorial design and response surface methodology.Androstenedione was the sole product in the fermentation broth catalyzed by the mutant M.neoaurum ZJUVN-08 strain.Results showed that molar ratio of hydroxypropyl-β-cyclodextrin(HP-β-CD) to PS and substrate concentrations were the two most significant factors affecting androstenedione production.By analyzing the statistical model of three-dimensional surface plot,the optimal process conditions were observed at 0.1 g/L inducer,pH 7.0,molar ratio of HP-β-CD to PS 1.92:1,8.98 g/L PS,and at 120 h of incubation time.Under these conditions,the maximum androstenedione yield was 5.96 g/L and nearly the same with the non-optimized(5.99 g/L),while the maximum PS conversion rate was 94.69% which increased by 10.66% compared with the non-optimized(84.03%).The predicted optimum conditions from the mathematical model were in agreement with the verification experimental results.It is considered that response surface methodology was a powerful and efficient method to optimize the parameters of PS biotransformation process.  相似文献   

12.
A number of dry bridges have been built to substitute for the roadbed on the Qinghai-Tibet Railway, China. The aim of this study was to investigate the exothermic process of cast-in-place （CIP） pile foundation of a dry bridge and its harm to the stability of nearby frozen ground. We present 3D heat conduction functions of a concrete pile and of frozen ground with related boundaries. Our analysis is based on the theory of heat conduction and the exponent law describing the adiabatic temperature rise caused by hydration heat. Results under continuous and initial conditions were combined to establish a finite element model of a CIP pile-frozen ground system for a dry bridge under actual field conditions in cold regions. Numerical results indicated that the process could effectively simulate the exothermic process of CIP pile foundation. Thermal disturbance to frozen ground under a long dry bridge caused by the casting temperature and hydration heat of CIP piles was substantial and long-lasting. The simulated thermal analysis results agreed with field measurements and some significant rules relating to the problem were deduced and conclusions reached.  相似文献   

13.
Using carbon tetrachloride （CCl4） as extraction agent, the activated sludge from Tianjin Jizhuangzi Sewage Treatment Plant as inoculum, the test study on biodegradability of lubricants was carried out. The test flasks containing the mineral medium, the test oil and the inoculum were placed in incubation together with flasks containing poisoned blanks for periods of 0 and 21 days, respectively. Flasks containing the reference materials in place of the test oil were run in parallel. At the end of the incubation period, the contents of the flasks were subjected to sonic vibration, and were acidified and extracted by using CCI4. The extracts were then analysed by infra-red （IR） spectrometer to measure the maximum absorption of the C-H stretch of CH2-CH3 band at wavelength of 2 930 cm^-1. The absorption values were used to calculate the residual oil contents of the poisoned and test flasks. Consequently the biodegradability of the test oil was calculated. The test results indicate that the differences in the biodegradability of test materials in different tests are within 5.5%, and consistent with the data described in Coordinating European Council （CEC） L-33- A-93. The biodegradability of lubricants can be evaluated by this method effectively.  相似文献   

14.
The phyAm gene encoding acid phytase and optimized neutral phytase phyCs gene were inserted into expression vector pPIC9K in correct orientation and transformed into Pichiapastoris in order to expand the pH profile of phytase and decrease the cost of production. The fusion phytase phyAm-phyCs gene was successfully overexpressed in P. pastoris as an active and ex-tracellular phytase. The yield of total extracellular fusion phytase activity is (25.4±0.53) U/ml at the flask scale and (159.1±2.92) U/ml for high cell-density fermentation, respectively. Purified fusion phytase exhibits an optimal temperature at 55 ℃ and an optimal pH at 5.5～6.0 and its relative activity remains at a relatively high level of above 70% in the range of pH 2.0 to 7.0. About 51% to 63% of its original activity remains after incubation at 75 ℃ to 95 ℃ for 10 min. Due to heavy glycosylation, the expressed fusion phytase shows a broad and diffuse band in SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis). After deglycosylation by endoglycosidase H (EndoHf), the enzyme has an apparent molecular size of 95 kDa. The characterization of the fusion phytase was compared with those of phyCs and phyAm.  相似文献   

15.
Response surface methodology was used to optimize the medium for antifungal active substance production from Streptomyces lydicus E12 in flask cultivation.Initially,the component factors,which influence antifungal substance production,were studied by varying one factor at a time.Starch,soybean cake powder,K_2HPO_4·3H_2O and MgSO_4·7H_2O were found to have a significant effect on the production of antifungal substances by the traditional design.Then,a Box-Behnken design was applied for further optimization.A quadratic model was found to fit antifungal active substance production.The analysis revealed that the optimum values of the tested variable were starch 84.96 g/L,soybean cake powder 4.13 g/L,glucose 5 g/L,MgSO_4·7H_2O 1.23 g/L,K_2HPO_4·3H_2O2.14 g/L and NaCl 0.5 g/L.The test result of 67.44%antifungal inhibition agreed with the prediction and increased by 14.28%in comparison with the basal medium.  相似文献   

16.
A mixed bacterial flora was isolated from the soil of two petroleum-contaminated sites, then cultivated and domesticated in an open environment. The bacteria were used to degrade engine oil in wastewater. The optimum biodegradation conditions for all engine oil concentrations of respectively 489 mg L-1, 1 075 mg L-1 and 2 088 mg L-1 are bacterial inoculum concentration of 0.1%, temperature at 30 °C to 35 °C, pH 7.0 to 7.5, and rotation at 190 r min-1 to 240 r min-1. The second-order kinetic model proposed by Quiroga and Sales describes the characteristics of the biodegradation of the engine oil very well. Engine oil concentration barely changes the growth rate of the bacterial consortium. The mixed bacterial flora has a high biodegrading capability for engine oil.  相似文献   

17.
In order to obtain anatase TiO2/expanded graphite with high expansion volume, titania gel was introduced to expandable graphite surface by sol-gel process, and then the composite was expanded and calcined at high temperature. The samples were analysed by using scanning electron microscope (SEM), X-ray diffraction(XRD), energy disperse spectroscopy(EDS), and differential scanning calorimetry(DSC). The optimal conditions for preparation are as follows: the molar ratio of tetrabutyl orthotitanate to triethanolamine is 1∶0.4, and the calcination and expansion temperature is in the range of 650-750 °C. Under such conditions, the expansion volume of composites could reach 98 mL/g, and the mass loss ratio is less than 5%. The analysis shows that lower temperature and smaller particle size of graphite are helpful to the formation of anatase-type of TiO2, but larger particle size will lead to lower mass loss ratio, and higher temperature and larger particle size will lead to higher expansion volume.  相似文献   

18.
The characteristics of the start-up period of single-step autotrophic nitrogen removal process were investigated. The autotrophic nitrogen removal process used a sequencing batch reactor to treat wastewater of medium to low ammonia-nitrogen concentration, with dissolved oxygen （DO）, hydraulic retention time （HRT） and temperature controlled. The experimental conditions were temperature at （30±2） ℃, ammonia concentration of （60 to 120） mg/L, DO of （0.8 to 1.0） mg/L, pH from 7.8 to 8.5 and HRT of 24 h. The rates of nitrification and nitrogen removal turn out to be 77% and 40%, respectively, after a start up period going through three stages divided according to nitrite accumulation： sludge domestication, nitrifying bacteria selection and sludge adaptation, It is demonstrated that dissolved oxygen is critical to nitrite accumulation and elastic YJZH soft compound packing is superior to polyhedral hollow balls in helping the bacteria adhere to the membrane.  相似文献   

19.
Boron-doped diamond (BDD) film electrodes using Ta as substrates were employed for anodic oxidation of salicylic acid (SA). The effects of operational variables including initial concentration,current density,temperature and pH were examined. The results showed that BDD films deposited on the Ta substrates had high electrocatalytic activity for SA degradation. There was little effect of pH on SA degradation. The current efficiency (CE) was found to be dependent mainly on the initial SA concentration,current density and temperature. Chemical oxygen demand (COD) was reduced from 830 mg/L to 42 mg/L under a current density of 200 A/m2 at 30 °C.  相似文献   

20.
The urea nitrogen adsorbent of complex type, which consists of chitosan coated dialdehyde cellulose （CDAC） and immobilized urease in gelatin membrane （IE）, was prepared. The cellulose, the dialdehyde cellulose （DAC） and the CDAC were characterized by scanning electronic microscope. The results indicate that the cellulose C2-C3 bond was broken under the oxidation of periodate and it was oxidated to DAC. The DAC was coated with chitosan and the CDAC was obtained. The adsorption of urea nitrogen onto the adsorbent in Na2HPO4-NaH2PO4 buffer solution was studied in batch system. The effects of the experiment parameters, including degree of oxidation of CDAC, initial urea nitrogen concentration, pH and temperature, on the adsorption capacity of urea nitrogen onto the adsorbent at CDAC/IE weight ratio 10：1 were investigated. The results indicate that these parameters affected significantly the adsorption capacity. The adsorption capacity of urea nitrogen onto the adsorbent was 36.7 mg/g at the degree of oxidation of CDAC 88%, initial urea nitrogen concentration 600 mg/L, pH 7.4 and temperature 37℃.  相似文献   

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