DN2菌降解烟碱的动力学及其应用研究

研究了菌株DN2降解烟碱的特性和对烟草废弃物中烟碱的降解情况。结果表明,该菌降解烟碱的最适条件为接种量为5 %,温度30 ℃,初始pH值为6.5。在该条件下,对初始烟碱浓度为500 mg/L的降解过程进行考察。结果表明,未经烟碱诱导的降解曲线呈倒S曲线,半衰期为17.43 h;经烟碱诱导的降解曲线符合Eckenfelder动力学模型,半衰期为4.10 h。添加0.1 %(质量分数)葡萄糖,可提高菌株DN2的烟碱耐受浓度,达5000 mg/L。菌株DN2能够降解烟草废弃物水提液中的烟碱（烟碱含量约为2220 mg/L）,60 h时烟碱的降解率为95.22 %,表明该菌在治理烟碱污染环境方面具有应用价值。     

菌株DN2对烟草薄片制备液中烟碱的降解

使用O.intermedium DN2降解烟草薄片制备液中的烟碱。研究了各种工艺参数对烟碱降解的影响,单因素考察结果表明烟草薄片制备液中烟碱降解的最适条件是:添加0.1%的酵母膏,使用氨水将pH调节到7.0,接种15%种子液,培养温度30oC。在上述条件下,采用30L发酵罐对烟草薄片制备液进行3个批次的半连续发酵,烟碱的平均降解速率为140.55mg/L/h,高于其他烟碱降解菌株。该结果表明菌株DN2可以用来降低烟草薄片中的烟碱含量。     

Optimizing conditions for the growth of Lactobacillus casei YIT 9018 in tryptone-yeast extract-glucose medium by using response surface methodology.

This study was undertaken to find optimum conditions of tryptone, yeast extract, glucose, Tween 80, and incubation temperature for the growth of Lactobacillus casei YIT 9018 and to assess the effects of these factors by use of response surface methodology. A central composite design was used as an experimental design for allocation of treatment combinations. A second-order polynomial regression model, which was used at first for analysis of the experiment, had a significant lack of fit. Therefore, cubic and quartic terms were incorporated into the regression model through variable selection procedures. Effects involving incubation temperature, yeast extract, glucose, and tryptone were significant, whereas the only significant effect involving Tween 80 was the interaction effect between temperature and Tween 80. It turned out that growth of L. casei YIT 9018 was most strongly affected by the incubation temperature. Estimated optimum conditions of the factors for growth of L. casei YIT 9018 are as follows: tryptone, 3.04%; yeast extract, 0.892%; glucose, 1.58%; Tween 80, 0%; incubation temperature, 35 degrees C.     

Screening and optimization of nutritional factors for higher dextransucrase production by Leuconostocmesenteroides NRRL B-640 using statistical approach

To improve dextransucrase production from Leuconostocmesenteroides NRRL B-640 culture medium was screened and optimized using the statistical design techniques of Plackett-Burman and response surface methodology (RSM). Plackett-Burman design with six variables viz. sucrose, yeast extract, K2HPO4, peptone, beef extract and Tween 80 was performed to screen the nutrients that were significantly affecting dextransucrase production. The variables sucrose, K2HPO4, yeast extract and beef extract showed above 90% confidence levels for dextransucrase production and were considered as significant factors for optimization using response surface methodology. 2(4)-central composite design was used for RSM optimization. The experimental results were fitted to a second-order polynomial model which gave a coefficient of determination R2=0.95. The optimized composition of 30g/l sucrose, 18.9g/l yeast extract, 19.4g/l K2HPO4 and 15g/l beef extract gave an experimental value of dextransucrase activity of 10.7U/ml which corresponded well with the predicted value of 10.9U/ml by the model.     

Influence of growth conditions on the production of lactocin 705, a bacteriocin produced by Lactobacillus casei CRL 705

G.M. VIGNOLO, M.N. DE KAIRUZ, A.P. DE RUIZ HOLGADO AND G. OLIVER. 1995. The effect of growth parameters on the production of lactocin 705 by Lactobacillus casei CRL 705 isolated from dry sausages was studied. The antimicrobial compound was produced during the growth cycle at temperatures between 15 and 30°C. Maximal activity in MRS broth was achieved at pH 6.5-7.5. Investigation into the influence of supplementation and/or replacement of nutrients on lactocin 705 production demonstrated that large quantities of the bacteriocin could be obtained by addition of Tween 80 (0.5-2.0%), glucose (2.0%), tryptone (1.0%) and yeast extract (2.0%). Bacteriocin production did not decrease in the presence of (w/v) 3% NaC1 and 0.02% NaNO₂ in the culture medium. High titres of the antimicrobial compound were obtained in whey permeate supplemented with 2.0% yeast extract and 1.0% Tween 80. Lactocin 705, proved to be stable to pH and temperature at ripening conditions (pH 5.0-6.0 and 15°C) of dry cured sausages.     

Effect of surfactants and identification of metabolites on the biodegradation of fluoranthene by basidiomycetes fungal isolate Armillaria sp. F022

The effects of structure and concentration of surfactants on the biodegradation of fluoranthene, a three rings polycyclic aromatic hydrocarbon in the aqueous phase, as well as their effects on the biodegradation and enzyme activity were investigated. The toxicity ranking of studied surfactants is: non-ionic Tween 80 <anionic sodium dodecyl sulfate <cationic Tetradecyltrimethylammonium bromide. The maximum growth of Armillaria sp. F022 (>4,500 mg/L) was showed by Tween 80 (10 mg/L) culture, manifesting that the non-ionic surfactant present in the culture were beneficial to the fungal growth. Laccase showed the highest enzymes activity in all surfactants culture. Non-ionic Tween 80 showed a significant result for laccase activity (1,902 U/L) in the Armillaria sp. F022 culture. The increased enzymes cumulative activity may stem directly from the rising fluoranthene biodegradability as addition of appropriate surfactants. The biotransformation of fluoranthene was greatly improved by Tween 80, and totally fluoranthene degradation was obtained as Tween 80 was 10 mg/L. Two fluoranthene metabolites were isolated from the culture medium and analyzed by a thin layer chromatography, UV visible spectrometer and gas chromatography–mass spectrometry (GC–MS). The oxidation of fluoranthene is initiated by oxygenation at the C-2,3 positions resulting 9-fluorenone. At the end of experiment, one metabolite was detected in the culture extract and identified as phthalic acid. Evidently, Armillaria sp. F022 seems efficient, high effective and deserves further application on the enhanced bioremediation technologies for the treatment of fluoranthene-contaminated soil.     

Effect of Medium Components on Bacteriocin Production by Lactobacillus Pentosus ST151BR,a Strain Isolated from Beer Produced by the Fermentation of Maize,Barley and Soy Flour

Lactobacillus pentosus ST151BR, isolated from home-brewed beer, produces a 3.0 kDa antibacterial peptide (bacteriocin ST151BR) active against Lactobacillus casei, Lactobacillus sakei, Pseudomonas aeruginosa, Enterococcus faecalis and Escherichia coli. Treatment with Proteinase K or Pronase resulted in loss of activity. Bacteriocin levels of 6400 AU/ml were recorded in MRSbb (De Man-Rogosa-Sharpe broth without Tween 80) at pH 5.5, 6.0 and 6.5. The same growth conditions at pH 4.5 yielded only 1600 AU/ml bacteriocin. Inclusion of Tween 80 in the growth medium reduced bacteriocin production by more than 50%. Growth in the presence of tryptone or tryptone plus meat extract stimulated bacteriocin production, whereas much lower activity was recorded when the bacteria were grown in the presence of meat extract, yeast extract, tryptone plus yeast extract, meat extract plus yeast extract, or a combination of tryptone, meat extract and yeast extract. MRSbb supplemented with maltose, lactose or mannose (2.0%, w/v) yielded bacteriocin levels of 6400 AU/ml. Sucrose or fructose at these concentrations reduced the activity by 50 and 75%, respectively. Growth in the presence of 4.0%(w/v) glucose resulted in 50% activity loss. Glycerol levels as low as 0.1%(w/v) repressed bacteriocin production. Addition of cyanocobalamin, ascorbic acid, thiamine and thioctic acid (1.0 mg/l) to the growth medium did not lead to an increase in bacteriocin production. This revised version was published online in July 2006 with corrections to the Cover Date.     

A comparison of factors affecting the production of two bacteriocins from lactic acid bacteria

The effect of tryptone, yeast extract, Tween 80 and initial pH on the production of enterocin 1146 and lactocin D, two bacteriocins produced by lactic acid bacteria, was studied in a basal buffered medium (tryptone-yeast extract-tween, TYT) using factorial experiments and empirical modelling. Production of enterocin 1146 was affected by pH, yeast extract and Tween 80 and to a lesser degree, by the initial pH of the medium. On the basis of the predictions of the models developed, three TYT media (TYT10, TYT11 and TYT30) were designed to maximize bacteriocin production while minimizing the amount of peptides in the medium. Growth and bacteriocin production by Enterococcus faecium DPC 1146 (enterocin 1146), Lactococcus lactis subsp. lactis biovar diacetylactis DPC 3286 (lactocin D) and Lact. lactis subsp. cremoris LMG2130 (lactococcin A) was compared in TYT media and seven other culture media (Elliker lactic broth, M17, M17 dialysate, MRS, tryptose phosphate, tryptone yeast extract broth, yeast glucose Lemco broth). Bacteriocin production in TYT media was comparable with that in M17 and MRS, which had a higher peptide content. TYT30 allowed good production of enterocin 1146 and lactocin D while TYT11 proved acceptable for all the strains tested.     

Statistical optimization of the medium composition by response surface methodology to enhance schizophyllan production by Schizophyllum commune

The response surface methodology (RSM) involving central composite design (CCD) was employed to optimize the fermentation medium for the cell growth and schizophllan production by Schizophyllum commune CGMCC 5.113 in submerged culture at pH 6.5 and 26 degrees C. The four variables involved in this study were glucose, yeast extract, ammonium nitrate, and magnesium sulfate. The statistical analysis of the results showed that, in the range studied, glucose and yeast extract had a highly significant effect on schizophyllan production. The optimal medium for schizophyllan production calculated from the regression model of RSM was as follows: glucose, 18 g/l; yeast extract, 0.5 g/l; NH4NO3, 0.48 g/l; and MgSO4, 0.05 g/l, with a predicted maximum schizophyllan production of 11.74 g/l. These predicted values were experimentally validated. The excellent correlation between predicted and measured values justifies the validity of the response model. The results of bioreactor fermentation also show that the optimized medium enhanced schizophyllan production (12.80 g/l) by S. commune in a 5-1 fermenter.     

响应面法优化毛霉菌发酵培养基

采用响应面分析方法优化毛霉菌B的发酵培养基,首先通过单因素试验筛选出葡萄糖为最适碳源,酵母膏和玉米浆为最适氮源,用Plackett—Burman试验对葡萄糖、酵母膏、玉米浆、MgSO4、FeSO4、NILCl/、HPO4进行评估并筛选出具有显著效应的3个因素：葡萄糖、酵母膏、玉米浆,再通过最陡爬坡试验逼近其最大响应区域,最后采用Box—Behnken试验对其用量进行优化,得到毛霉菌最佳发酵培养基（g/L）：葡萄糖51．54,酵母膏5．22,玉米浆14．31,MgSO40．5,FeSO40．1,NH4Cl3,k2HPO43,pH6．0～6．5。培养基优化后,毛霉生物量由23．51g／L提高至31．13g/L,比对照组提高32．41％,腺嘌呤转化率由53．59％提高至59．97％,ATP产率由6．56g／L提高至7．34g／L,比对照组提高11．89％。     

Optimized growth kinetics of Pichia pastoris and recombinant Candida rugosa LIP1 production by RSM

A predictive model for Pichia pastoris expression of highly active recombinant Candida rugosa LIP1 was developed by combining the Gompertz function and response surface methodology (RSM) to evaluate the effect of yeast extract concentration, glucose concentration, temperature, and pH on specific responses. Each of the responses (maximum population densities, specific growth rate (mumax), protein concentration, and minimum lag phase duration) was determined using the modified Gompertz function. RSM and 4-factor-5-level central composite rotatable design (CCRD) were adopted to evaluate the effects of growth parameters, such as temperature (21.6-38.4 degrees C), glucose concentration (0.3-3.7%), yeast extract (0.16-1.84%), and pH (5.3-8.7) on the responses of P. pastoris growth kinetics.Based on ridge maximum analysis, the optimum population density conditions were: temperature 24.4 degrees C, glucose concentration 2.0%, yeast extract 1.5%, and pH 7.6. The optimum specific growth rate conditions were: temperature 28.9 degrees C, glucose concentration 2.0%, yeast extract 1.1%, and pH 6.9. The optimum protein concentration conditions were: temperature 24.2 degrees C, glucose concentration 1.9%, yeast extract 1.5%, and pH 7.6. Based on ridge minimum analysis, the minimal lag phase conditions were: temperature 32.3 degrees C, glucose concentration 2.1%, yeast extract 1.1%, and pH 5.4. For the predicted value, the maximum population density, specific growth rate, protein concentration, and minimum lag phase duration were 15.7 mg/ml, 3.4 h(-1), 0.78 mg/ml, and 4.2 h, and the actual values were 14.3 +/- 3.5 mg/ml, 3.6 +/- 0.6 h(-1), 0.72 +/- 0.2 mg/ml, and 4.4 +/- 1.6 h, respectively.     

Growth optimization of a probiotic candidate,<Emphasis Type="Italic">Bifidobacterium pseudocatenulatum</Emphasis> G4, in milk medium using response surface methodology

Bifidobacterium pseudocatenulatum G4, a wild strain isolated from infant stools that has previously exhibited probiotic characteristics, was used in this study. The aim of this research was to improve the growth potential of this strain in milk-based medium. An initial screening study using a 2³ full factorial design was carried out to identify the impact on biomass production of the various components of the medium which were skim milk, yeast extract, and glucose. Statistical analysis suggested that yeast extract had a significant positive effect on viable cell count whereas glucose had a negative effect. Response surface methodology (RSM) was then applied to optimize the use of skim milk and yeast extract. A quadratic model was derived using a 3² face-centered central composite design to represent cell mass as a function of the two variables. The optimized medium composition was found to be 2.8% skim milk and 2.2% yeast extract, w/v. The optimized medium allowed a maximum biomass of 9.129 log₁₀ cfu/mL, 3.329 log units higher than that achieved with 10% skim milk, which is the amount commonly used. The application of RSM resulted in an improvement in the biomass production of this strain in a more cost-effective milk medium, in which skim milk use was reduced by 71.8%.     

Solid-state fermentation of cornmeal with the basidiomycete Ganoderma lucidum for degrading starch and upgrading nutritional value

AIMS: The objective of this research was to study the ability of the basidiomycete Ganoderma lucidum to degrade starch and upgrade nutritional value of cornmeal during solid-state fermentation (SSF). METHODS AND RESULTS: On the basal medium that consisted of cornmeal and salt solution, alpha-amylase activity of G. lucidum reached its maximum value of 267 U g(-1) of culture on day 20 after inoculation. Prolongation of fermentation time from 10 to 25 days increased significantly the degradation rate of starch and ergosterol yield (a kind of physiologically active substances of G. lucidum, also as an indicator of mycelial biomass) (P < 0.01). Supplementation of glucose, sucrose or maltose to the basal medium also caused a significant increase in either the degradation rate of starch or the ergosterol yield as compared with control (P < 0.01). Among five kinds of nitrogen sources supplemented, yeast extract, casamino acid and peptone were more effective than (NH4)2SO4 and NH4NO3, and yeast extract gave the highest degradation rate of starch and ergosterol yield, followed by peptone. Through orthogonal experiments, the theoretical optimum culture medium for SSF of this fungus was the following: 100 g cornmeal, ground to 30-mesh powder, moistened with 67 ml of nutrient salt solution supplemented with 3 g yeast extract and 7.5 g glucose per litre. CONCLUSIONS: Under the optimum culture condition, the degradation rate of starch reached its maximum values of 70.4%; the starch content of the fermented product decreased from 64.5 to 25.3%, while the reducing sugar content increased from 4.2 to 20.6%. SSF also produced a significant increase (P < 0.01) from 11.0 to 16.5% in protein content. SIGNIFICANCE AND IMPACT OF THE STUDY: After SSF by G. lucidum, the digesting and absorbing ratio of cornmeal was strikingly increased and some active substances originated from G. lucidum remained in the fermented product. This implied that cornmeal could be processed into many kinds of special functional foods by SSF of G. lucidum.     

Comparison of various media and various methods for the growth and isolation of Pityrosporum pachydermatis

The pathogenic role of Pityrosporum pachydermatis in otitis externa of dogs and the related diagnostic problems are emphasized. We report results related to isolation, cultivation and identification of yeast. Agar nutritive glucosate with 1,5% of yeast extract has been showed as the best medium permitting identification in 24 hrs, associated with morfological test. Tween 80 integration (1%) to the medium permits to isolate lipolitic yeasts also.     

Optimization of medium composition for actinorhodin production by Streptomyces coelicolor A3(2) with response surface methodology

Optimization of the fermentation medium for maximization of actinorhodin production by Streptomyces coelicolor A3(2) was carried out. Response surface methodology (RSM) was applied to optimize the medium constituents. A 2⁴ full-factorial central composite design (CCD) was chosen to explain the combined effects of the four medium constituents, viz. sucrose, glucose, yeast extract (YE) and peptone, and to design a minimum number of experiments. The P-values of the coefficients for linear, quadratic and cross-product effect of sucrose and glucose concentration were <0.0001, suggesting that these were critical variables having the greatest effect on the production of actinorhodin in the complex medium. The optimized medium consisting of 339 g/l sucrose, 1 g/l glucose, 1.95 g/l YE and 2.72 g/l peptone predicted 195 mg/l of actinorhodin which was 32% higher than that of the unoptimized medium. The amounts of glucose, YE and peptone required were also reduced with RSM.     

Studies on the isolation,growth and maintenance of Malassezia pachydermatis

Results related to the isolation, cultivation, culture and maintenance of the opportunistic pathogen Malassezia pachydermatis are reported. A dextrose nutrient medium with 1.5% yeast extract turned out to be the most favourable medium for its development. It permitted identification in 24 hours and maintenance of isolates for three months without subculturing. Addition of Tween 80 (1%) significantly enhanced the isolation of this yeast from clinical materials.     

Evidence that RDX biodegradation by Rhodococcus strain DN22 is plasmid-borne and involves a cytochrome p-450

AIMS: To investigate the biodegradation of the explosive compound RDX in Rhodococcus strain DN22, a bacterium previously isolated for its ability to grow on RDX as sole nitrogen source. METHODS AND RESULTS: Analysis of the rates of RDX degradation and nitrite production indicated that 2 mol nitrite were produced per mole RDX degraded. Cells of strain DN22 had the highest activity against RDX during the exponential phase and low activity in the stationary phase. Nitrite production from RDX was inhibited by metyrapone, menadione, piperonyl butoxide, n-octylamine and carbon monoxide and inducible by pyrrolidine, pyridine and atrazine. Acridine orange treatment yielded RDX-minus derivatives of strain DN22 at a curing rate of 1.5% and all of the cured derivatives had lost a large plasmid. CONCLUSIONS: RDX biodegradation in strain DN22 appears to involve a plasmid-encoded cytochrome p-450 enzyme. SIGNIFICANCE AND IMPACT OF THE STUDY: Plasmid-borne RDX degradation genes could potentially be transferred between bacteria. Our research into RDX metabolism in strain DN22 will facilitate future applications of this bacterium for bioremediation.     

THE ENUMERATION OF LACTOBACILLI ON GRASS AND IN SILAGE

SUMMARY: For the enumeration of lactobacilli on grass and in silage the following medium has shown promise: peptone, meat extract and glucose, 10 g. each; tomato extract, 200 ml.; yeast autolysate, 50 ml.; Tween 80, 0.5 ml.; agar, 15 g., in a final volume of 1 1. and containing acetic acid/sodium acetate buffer in 0.2M concentration; pH 5–4. The medium was adjusted to pH 5–4 before sterilization and the requisite amount of concentrated pH 5.4 acetate buffer added just before plating. Double laver plates were used.
The only other silage organisms which in this medium formed colonies comparable in size with those of lactobacilli were heterofermentative streptococci and a micrococcus.     

Enhancing the intrinsic bioremediation of PAH-contaminated anoxic estuarine sediments with biostimulating agents

Estuarine sediments are frequently polluted with hydrocarbons from fuel spills and industrial wastes. Polycyclic aromatic hydrocarbons (PAHs) are components of these contaminants that tend to accumulate in the sediment due to their low aqueous solubility, low volatility, and high affinity for particulate matter. The toxic, recalcitrant, mutagenic, and carcinogenic nature of these compounds may require aggressive treatment to remediate polluted sites effectively. In petroleum-contaminated sediments near a petrochemical industry in Gwangyang Bay, Korea, in situ PAH concentrations ranged from 10 to 2,900 microg/kg dry sediment. To enhance the biodegradation rate of PAHs under anaerobic conditions, sediment samples were amended with biostimulating agents alone or in combination: nitrogen and phosphorus in the form of slow-release fertilizer (SRF), lactate, yeast extract (YE), and Tween 80. When added to the sediment individually, all tested agents enhanced the degradation of PAHs, including naphthalene, acenaphthene, anthracene, fluorene, phenanthrene, fluoranthene, pyrene, chrysene, and benzo[a]pyrene. Moreover, the combination of SRF, Tween 80, and lactate increased the PAH degradation rate 1.2-8.2 times above that of untreated sediment (0.01-10 microg PAH/kg dry sediment/day). Our results indicated that in situ contaminant PAHs in anoxic sediment, including high molecular weight PAHs, were degraded biologically and that the addition of stimulators increased the biodegradation potential of the intrinsic microbial populations. Our results will contribute to the development of new strategies for in situ treatment of PAH-contaminated anoxic sediments.     

Biodegradation of endocrine-disrupting bisphenol A by white rot fungus Irpex lacteus

Biodegradation of endocrine-disrupting bisphenol A was investigated with several white rot fungi (Irpex lacteus, Trametes versicolor, Ganoderma lucidum, Polyporellus brumalis, Pleurotus eryngii, Schizophyllum commune) isolated in Korea and two transformants of T versicolor (strains MrP 1 and MrP 13). I. lacteus degraded 99.4% of 50 mg/l bisphenol A in 3 h incubation and 100% in 12 h incubation. which was the highest degradation rate among the fungal strains tested. T. versicolor degraded 98.2% of 50 mg/l bisphenol A in 12 h incubation. Unexpectedly, the transformant of the Mn-repressed peroxidase gene of T. versicolor, strain MrP 1, degraded 76.5% of 50 mg/l bisphenol A in 12 h incubation, which was a lower degradation rate than wild-type T. versicolor. The removal of bisphenol A by I. lacteus occurred mainly by biodegradation rather than adsorption. Optimum carbon sources for biodegradation of bisphenol A by I. lacteus were glucose and starch, and optimum nitrogen sources were yeast extract and tryptone in a minimal salts medium; however, bisphenol A degradation was higher in nutrient-rich YMG medium than that in a minimal salts medium. The initial degradation of endocrine disruptors was accompanied by the activities of manganese peroxidase and laccase in the culture